Sharpening Part 21 – The Bulging Bevel

This is what a flat bevel looks like. So sweet.

For everybody in their busy lives, you need to invest in sharpening your tools, and you need to invest in longevity.

Ryan Holmes

In the previous post in this series about sharpening tools we looked at why and how to true the ura, the hollow-ground area on Japanese chisel and plane blades. This post will focus on the opposite side of the wedge that is a cutting edge: the bevel. This discussion is relevant to all plane and chisel blades, not just Japanese tools.

Preface

Before we dive in, I need to clarify something.

Some of our Gentle Readers have been blessed with the opportunity to learn about tools from accomplished Japanese craftsmen, as was I, or have figured them out on their own. If you find this or other posts boring, please remember this blog’s primary purpose is to provide instruction to our Beloved Customers who have not had similar opportunities.

These Beloved Customers are located in many countries and range in experience from newbies to professional woodworkers, so I try to include both advanced information for the professionals, and detailed explanations so newbies can keep up. Consequently, these articles are sometimes long and wordy. I humbly request your kind indulgence on behalf of those who may benefit.

Investing in Longevity

The quote above by Mr Holmes is applicable to the all the principles of sharpening I have described in this series of posts so far. He is a computer dude, not a contractor, joiner or furniture maker, but it is no coincidence he chose to use handtool terminology: it is encoded in human DNA.

His first point is a self-evident admonition, but what about this “investing in longevity” stuff? By definition, an investment is an expenditure of time, resources and/or effort intended to produce a return greater in value than the expenditure. Then how do we go about investing in the longevity of our chisels and planes, and what return should we expect?

While simply grinding sharp edges on our tools helps with making things from wood, I don’t see it as an investment in tools. Rather, if we train ourselves in professional sharpening techniques, and use those techniques to maintain our tools so they function more efficiently and last longer, we can hope to obtain a real-world return we can quantify financially. The investment I encourage you to make is not in things, therefore, but in your own skills.

The Pros and Cons of the Bulging Bevel

The “bulging bevel,” as I call it, is a deformation too frequently seen in plane, chisel and knife blades. It is simply a cutting edge bevel that is protruding and convex instead of flat. In most cases a bulging bevel can make it difficult to properly sharpen a blade adequately, so it deserves our attention. Most bulging bevels are born unintentionally and are harmful, but some are hatched with a purpose in mind. Let’s examine the pros and cons, and throw in some scientific results just for fun. 

The geometry of the bulging bevel is clearly superior in a few applications such as carving chisels and knives used in a gouging, scooping motion where a rounded bevel provides better control. Another is chisels used for cutting large and deep mortises where a rounded bevel helps pop out waste easier. Only timber framers cut these kind of mortises, however, and most of them use machines to at least rough out the mortises.

Hidari no Ichihiro 42mm Oiirenomi. Nothing obese about this sweetheart.

Our Beloved Customers are, without exception, extremely intelligent people, so right now some of you are no doubt saying to yourself: “Self,” (that’s what they call themselves when they silently cogitate profound matters) does a rotund bevel make my blades sharper or duller?” Let us consider some scientific results.

When I was a grad student in Japan, a fellow student wrote his thesis on the efficacy in plane blades of the bulging bevel versus the flat bevel. He developed experiments, fabricated testing apparatus, and used scientific methodology and microscopic photography yielding indisputable results. We repeated some of his experiments, discussed his research, and pored over photographs and fondled shavings late into the evenings at his lab in Building 11 at University of Tokyo Hongo campus as I drank coke and he drank sake. I’m not sure he made it home some evenings.

The conclusion he reached was that, from the viewpoint of the wood, and based on the classic sharpness test of cutting rag typing paper, there is no difference in the cutting performance between flat and bulging bevels, so long as two conditions are met: (1) Both types are sharpened to the same bevel angle and same degree of sharpness; and (2) The bulge is not so large as to interfere with the cut. The “same degree of sharpness” condition in proviso 1 is critical to this discussion.

Let’s examine the cutting edge closely. It’s effective scope is only the last few microns (μ) or so of the blade’s width at the extreme edge. 1μ=one millionth of a meter. A human hair is 90μ in diameter. We need to precisely repair and polish this narrow strip of steel using our sharpening stones, but remember that working anything beyond this strip contributes nothing to making the blade sharp.

Here’s an important point we can learn from a careful examination: Given the same number of strokes to the same blade on the same stones over the same amount of time, it is difficult to make a bulging bevel as sharp as a flat bevel, unless one spends the time to use a sharpening machine and jigs as my grad school friend did in his research room.

But the most important point, and one I want you to grasp with both hands and feet and all your teeth is that the time expended and amount of stone consumed when sharpening by hand to a set level of sharpness at the last critical microns of a bulging bevel’s cutting edge is huge compared to a flat bevel. Sharpening using machines and/or honing jigs takes even longer.

In addition to time and cost, another factor we need to consider is certainty, because if we are going to invest the time and stones to sharpen a tool, we need to be sure it will consistently achieve the same level of sharpness every time. Unfortunately, the sharpness of the bulging bevel is uncertain because, instead of guiding the blade to ensure consistent contact between steel and stone at the critical location on the cutting edge, the shape of the bulging bevel causes a significant number of strokes to be wasted on polishing a mound of metal that does nothing to make the blade sharper, but is simply in the way. Not convinced? 

Consider the undeniable fact that, despite your best efforts, this irrelevant lump causes the blade to rock around on the stone’s surface like a boat over ocean swells, with the result that, given a fixed number of strokes, a high percentage of those strokes end up polishing the bulge instead of the cutting edge. This is important because, once again, the last micron of the blade is the only part that actually does any cutting, not the bulge. 

Please don’t misunderstand. I’m not saying that you can’t create a fiendishly sharp edge on a blade with a bulging bevel. I’m also not saying that, within reasonable parameters, a convex bevel cuts less efficiently or dulls quicker than the same blade with a flat bevel. It absolutely doesn’t, as my colleague’s research showed. Allow me to restate and summarize the facts so there is no confusion.

  1. It takes longer to create a given level of sharpness at the extreme cutting edge of a bulging bevel than a flat bevel, all else equal;
  2. It consumes more sharpening stone to achieve a given level of sharpness at the extreme cutting edge of a bulging bevel compared to a flat bevel, all else equal; and  
  3. There is greater uncertainty about the actual degree of sharpness achieved at the blade’s extreme cutting edge when sharpening a bulging bevel by hand compared to a flat bevel, all else equal. 

If you doubt these statements, you must find the truth yourself. Buy or borrow a quality loupe or microscope with enough magnification to detect the scratches left by your usual finishing stone. Start with a dull blade with a truly flat bevel, sharpen it freehand using a set number of strokes, and observe the scratches at the last few microns of the cutting edge with your microscope. Then test the blade’s sharpness with your skin or fingernail. Next, repeat this test with a dull blade with a rounded bevel using the exact same sharpening tools and procedures and the same number of strokes. Once again, observe the scratches and test the sharpness. My grad school friend and I performed this side-by-side experiment at the University of Tokyo several times, with consistent results. Actually, it was a bet and I won. He had to buy the drinks and snacks for a month.

The Causes of Bevel Obesity

Besides pernicious pixies, the most common cause of bevel bulge is simple carelessness, which you can take steps to avoid once you realize the causes.

It is human tendency to try to stabilize the blade’s bevel on the stone while sharpening by applying more pressure on the rear half of the bevel, resulting in the rear half of the bevel (which is all soft jigane in the case of plane blades, and mostly soft jigane in the case of chisels) being abraded quicker than the front half (which contains the harder steel lamination), causing the bevel angle to gradually decrease or even become rounded. Even the best craftsmen make this mistake sometimes.

To avoid this tendency, train yourself to focus pressure on the front half of the bevel closest to the cutting edge. At first, you may overbalance and dig the cutting edge into the stone a few times, but with practice and attention, it will become second nature. It is almost a meditative process. Every professional woodworker worth his salt must learn this skill.

There is nothing wrong with making mistakes when learning a muscle memory skill like freehand sharpening, but too many people can’t be bothered to learn, and then become frustrated when their skills don’t improve immediately. In the end, they become defensive, and twist themselves into knots defending their inadequate techniques. Patience, grasshopper.

BTW, don’t forget to use your handy dandy brass bevel gauge to both check the bevel angle while sharpening and to keep those piratical pixies away.

Hidari no Ichihiro 30mm Atsunomi. What ignorant savage would grind multiple bevels on this?

Another cause of the tumescent bevel is the use of secondary bevels or micro-bevels. We’ll look at these aberrations in the next post in this series.

To make multiple bevels work one almost must use a sharpening or honing jig of some sort. Many allow sharpening jigs to become a substitute for real sharpening skills they didn’t bother to learn. Such jigs can become, in effect, training wheels those who rely on them never grow out of. So sad.

Conclusion

I encourage you to “invest in longevity” with regards to your tools in three ways:

  1. First setup your planes and chisels properly so they will provide you with long, reliable and efficient service. Setting up chisels improves not only their longevity but in many case their performance too, strange though it may seem. I will post articles about setting up and maintaining Japanese planes in the future.
  2. Second, true the ura of your plane and chisel blades efficiently without reducing their useful lifespan needlessly, as described in previous posts; and
  3. Third, invest in yourself by developing and honing the hand skills necessary to sharpen your blades quickly and efficiently while wasting only the absolute minimum of valuable time, steel and stone.
Image result for image of mandalorian helmet

Please master the ancient and bedrock-basic skill of freehand sharpening. All it takes is an understanding of correct principles, followed by concentration and practice; The rest will follow. I promise. “This is the way.”

We will look at other causes of bevel obesity in the next post in this series.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 20 – Flattening and Polishing the Ura

A mind needs books as a sword needs a whetstone, if it is to keep its edge.

George R.R. Martin

Now that we are geared-up and our sharpening stones are flat, let’s make our blade sharp. The first step in sharpening a new blade is truing the ura. So let’s get to it.

General

All standard chisel blades and plane blades, whether Japanese or Western, need to have a planar flat or ura that it will be in contact with the sharpening stones its full width, and ideally, full length. Perfection is not necessary, however, so don’t let yourself get obsessive. If the ura is arched (concave), for instance, so it is in contact with a flat sharpening stone near the neck of a chisel, or head of a plane blade, and the cutting edge, that may be workable, but it must be in complete contact right behind the cutting edge. I cannot stress this importance of this point too strongly.

Once the ura of your chisel is flat and true, you should not need to true it again unless the blade needs major repairs. Japanese plane blades, on the other hand, are a little more complicated because repeated sharpenings tend to gradually wear out the land right in front of the cutting edge, called the “ito ura,” and the bevel must be tapped-out to compensate, and the ura re-flattened. I won’t delve into the subject of “tapping out” the ura of plane blades in this post but will save it for future discussions about Japanese planes.

Evaluate the Ura

The first step in flattening or truing an ura is to evaluate its condition. Don’t start grinding away willy nilly without first checking it and making a plan. If you find you cannot stop yourself, don’t walk but run to the nearest pharmacy and buy a bucket of the medicine discussed in part 19 in this series about maintaining sharpening stones.

There are several ways to check the ura’s condition. A narrow straightedge works well in most cases. Place the edge on top of the full length of the shiny land at one side of the ura all the way to the cutting edge. Keep the straightedge touching the land; Don’t let it span the hollow- ground urasuki. Hold the straightedge and blade up to a strong light source and look for light passing between them. This technique is quick and dirty and will suffice in most cases, but does not tell you a lot about twist.

Use a straightedge to check the right and left lands for flatness. It doesn’t do any good to span the hollow-ground urasuki, so don’t bother. These photos are taken from above for clarity, but you want to hold the blade and straightedge together up to a strong light to observe any light showing between them that will indicate a gap. I am using a small square, but a simple small straightedge is more convenient. This takes a bit of coordination so be careful not to drop a chisel on your toe. I’ve done this once or twice before. Monkey-football.
This is a 30mm Sukemaru atsunomi, a famous brand and an excellent and powerful chisel hand-forged by Mr. Usui from Shirogami No.1 Steel. It’s in pretty good shape, but can benefit from a little truing as can most new chisels and plane blades.

Another method to check the ura for planar is to paint the shiny lands with dark marking pen ink or Dykem liquid, apply a bit of fine sharpening stone mud to a piece of flat glass, like the piece mentioned in Part 17, and rub the blade’s flat or ura over the glass. The high spots will become obvious. If the ura is banana shaped (convex), mark the high spot with your marking pen. More often than not, the ura of chisels will be generally flat, but the last 6mm or so of the cutting edge will be curved upwards towards the chisel’s face.

I learned two things from my examination of this Sukemaru brand atsunomi. First, there is a high spot (convex) at the skinny land on one side located approximately 1/2 to 5/8 the blades’s distance from the cutting edge. The land on the other side seems a little low. Hmm, curious. This is a bit unusual, but it happens when a blade warps during heat treat, which Shirogami steels tends to do frequently.

The second problem I observed was that the last 3~4mm of the land right behind the cutting edge curves downward away from the ura just a tiny bit, enough to cause problems.

I next need a plan to resolve these problems with a minimum of time and effort and without making things worse.

Make a Plan

The temptation to start grinding away immediately will be powerful. If it becomes too much, take a coffee cup or three of the medicine mentioned above and slather it on your head forcefully. Don’t hold back, for Pete’s sake, rub it in really good now. Some say my excessive use of this medicine is why I am as bald as an egg, but I prefer to believe it is caused by the light radiating from my gigantic brain (ツ). Thank goodness for my aluminum foil skull cap with its protruding copper wires!

Any plan needs goals and objectives. In this case the goal is a perfectly planar ura, but if this goal is difficult to achieve quickly there is an objective you should plan to achieve immediately in any case, one that may make it possible to achieve the larger goal over multiple routine sharpening sessions without any special effort.

As I keep harping, to make a chisel or plane work well, you need a flat area right at the cutting edge. This is where the cutting occurs and the area I need to keep sharp, so I will make creating this flat area the first objective in my plan, and then determine the steps to achieve it. Make certain every step in your plan and every stroke on the stones gets you closer to this objective, not further away. This means working smart.

If the blade is arched (concave), touching at two points, one near the neck of the chisel blade, or head of the plane blade, and at the other at the cutting edge, and not in between, all is well. I recommend you leave a blade like this as-is because after a few sharpening sessions the ura will become flat and twist-free without any special effort, and the blade will become very sharp and be entirely functional.

If the blade is wavy (rare) or banana-shaped (convex), your plan needs to take those details into account.

I located the highest point of the bulging area at the ura and marked a line across it with my marking pen. I then measured halfway between this line and the cutting edge and made another line. This area we will call the “focus line.” It is here where I need to focus the most pressure when grinding down the ura, not the entire length of the blade.

The purpose of doing all this prissy planning and layout work is to protect the right and left side lands from being wasted unnecessarily. Newbies try to work the entire length of the blade, but this is illogical and ignores three points. The first point is that the majority of the metal I need to waste is usually located to the right and left of the land nearest the cutting edge, not the full length of the blade, so there is little benefit to grinding the entire ura. The second point is that the side lands are thin as a blade of grass and will abrade very quickly with almost no effort. Besides, without using large plates and stones, it is very difficult to work the blade’s full length accurately without wearing notches in the side lands anyway. The third point is it makes no sense to try to grind down the land nearest the neck since the plane of the ura hinges on this land. Best to leave it alone and focus my efforts where they will make a difference.

Plane blades don’t even have a land near the head, so the futility of working the entire ura on plane blades is even more obvious than for a chisel.

Work the Plan

The traditional Japanese tool used to flatten and/or correct ura is a smooth steel lapping plate called a kanaban, meaning “metal plate.” To use it, carborundum powder and water are placed on the plate, and the blade is lapped. This is not a difficult process at all, but there is a tendency for the blade’s perimeter to be ground more than the interior areas as the grit is forced in between the kanaban and the blade’s perimeter. To avoid this tendency, and to speed the process up, I prefer to use diamond plates instead of kanaban.

Whatever plan you developed, and whichever tool you selected for this job, the time has come to work the plan. Do you need more medicine? A bigger coffee cup?

First, color the ura’s perimeter lands with a marking pen or Dykem to help you see where the ura is being ground down. Don’t ever guess.

Place the most pressure on the focus line selected above. Move the blade back and forth (not side to side) onto and off of the diamond plate or kanaban with the cutting edge and the focus line always touching the diamond plate or kanaban. Don’t go past the high point for now. Be careful to not grind a notch into the narrow side lands where they meet the edge of the diamond plate or kanaban. Most people make this mistake at first.

Grind the ura down so the line at the highest point and the cutting edge is fairly flat.

Work the blade on and off the edge of the diamond plate using short strokes and without going much past the highest point marked earlier. This works because the right and left side lands are thin and can be abraded in just a few strokes. I have moved my fingers to reveal the lines, but in actuality my fingers will press down hard on the focus line while working the blade.
Using a stick to apply more pressure to the blade. I am holding the end of the stick and the chisel’s handle together in my right hand. This is simply illustrating a technique. This chisel did not actually require this sort of aggressive attention.
The same stick technique works even better for plane blades and makes it easier to apply pressure right behind the cutting edge. When doing this, however, be sure to work the blade both forward and backward while moving it right and left on and off the plate’s edge to avoid digging a trench in the narrow side lands.

Remember, the narrow lands at the sides of the hollow-ground urasuki will abrade down quickly. And the rest of the ura can be gradually flattened during subsequent sharpening sessions using regular sharpening stones. It doesn’t need to be made perfect immediately. What matters most is the steel on the land right at the cutting edge.

The high spot on the land near the top of the photo has been relieved after a few passes on the #400 diamond plate. The side lands are in fair condition, and the land behind the cutting edge (itoura) needs just a little more work.
After a few more passes on the diamond plate, the ura is in good shape. Note the land at the photo’s bottom is not in full contact, but the opposite side is. This is will not impact the blade’s performance, and will work itself out during future sharpening sessions without special attention.
Flattening my stones before using them. Notice I am using two 1,000 grit stones to save time and stones. Don’t neglect flattening your stones, whether you use waterstones, novaculite stones, coticule, or even sandpaper.
Working the ura on the flat 1000 grit waterstone. Did I mention it is flat? Notice that I am working on and off the stone, not side to side, to save the right and left lands. Some but not all strokes are full length. The goal is simply to remove the deep scratches left by the diamond plate.
The ura after polishing on the flat 1000 grit waterstone. At this point the ura is in good shape. Notice how the land at the photo’s left is wider that elsewhere. This increase in width developed because this location was the high spot on this convex ura. Notice how the land on the left side is not even touching the plane in one area. What you should take away from this photo is the realization that if I had focused my efforts on this high location first and ignored the downward curvature of the land nearest the cutting edge, I would have wasted a lot more time and valuable metal only to shorten the useful life of this excellent chisel. Do you see the benefit of carefully checking the ura’s condition, making a plan with clear goals and objectives, and then working the plan? Did the medicine work? Next, we’ll work on the bevel, make a tiny burr, polish it off by making a few strokes alternating from bevel to ura, and be ready for the finishing stone.
Working the bevel on the flat 1,000 grit waterstone. Notice the mud piling up in front of the blade indicating the extreme cutting edge is in contact with the stone. I am applying pressure only on the push stroke to prevent the stone from rocking and developing a “bulging bevel,” A honing jig is not necessary.
The bevel after working on the 1,000 grit waterstone. No jigs were used. No “tricks” involving rulers were used. A silly, inefficient “micro-bevel” was neither wanted nor needed. The bevel is perfectly flat. Flattening the ura and polishing both ura and bevel to this level took less than ten minutes. When the purchaser of this blade eventually dulls the edge, he should not need to spend more than 2~3 minutes to sharpen this blade once his gear is ready, assuming he is able to sharpen freehand.

Polish a blade’s ura up to the level of your finest finishing stone once, and don’t touch it with rougher stones again unless it is absolutely necessary, or further gradual flattening is required. This means that in normal sharpening sessions you must remove all the damage at the cutting edge by abrading the bevel with the rougher stones, and only when the bevel is ready for the finish stone, do you work on the flat or ura, alternating from bevel to flat/ura until all defects, burrs, and even visible scratches are polished away.

If you condition the flat (ura) side of the blade correctly, and keep it polished, you should not need to work it on anything but your finish stone until it is time to tap out and grind the ura or back in the case of plane blades. Therefore, the bevel side of the blade is where we spend most of our time and effort.

Now that the ura is in good shape, we will look at sharpening the other side of the wedge, the blade’s bevel, in the next post in the series.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 19 – Maintaining Sharpening Stones

砥石の面直しについて :鑿研ぎ練習 番外編_e0248405_17182931.jpg

Give me six hours to chop down a tree and I will spend the first four sharpening the axe.

Abraham Lincoln

Sharpening stones must be maintained if they are to perform effectively. Abe Lincoln’s quote above is especially relevant to this subject.

There is a lot of hogwash taught as holy gospel on this subject, so in this post I will suggest some more or less traditional methods that I know both work well, and are cost-effective. Do with them as you will.

Key Principles

Let’s begin with a few basic but critical principles for sharpening:

  1. For the majority, but not all, applications, your blades need to meet the following standards:
    • Flat back/ura: perfection is not necessary but it must be flat enough for you to be able to consistently work the steel directly behind the cutting edge on your finishing stone;
    • Flat bevel, for same reason mentioned above;
    • Straight cutting edge (except when a curved cutting edge is required).
  2. All Stones get out of tolerance with use. Working a steel blade on a sharpening stone of any kind, whether waterstone, novaculite, coticule or carborundum, wears the stone a little bit with each stroke, creating a dished-out, twisted surface to one degree or another, even if you can’t detect the distortion with Mark-1 eyeball. Therefore, you need to frequently check and periodically true your stones;
  3. Despite what many imagine, a hollowed-out stone cannot reliably maintain a blade with a planar ura, a flat bevel, and a straight cutting edge, but it can damage the blade being sharpened.

The Rule of Seven applies, so reread these three critical points three times, click your heels three times, and ask the gods of handsaws to help you remember them.

Albrecht Dürer - Melencolia I - Google Art Project ( AGDdr3EHmNGyA).jpg
Melencolia I by Albrecht Dürer 1514
What is the angel pondering? Sharpening, no doubt.

Pretty simple stuff, right? I apologize if you already know these things, but you would be surprised how many people know them but still ignore them, and then wonder why their blades won’t behave. Iron Pixies? Nah. Perhaps Mifune Toshiro said it best in Akira Kurosawa’s movie Yojimbo when he quoted the old Japanese proverb: “There’s no medicine for foolishness” (馬鹿に付ける薬はない).

Toshirô Mifune in Yôjinbô (1961)
A scene from Akira Kurosawa’s classic movie Yojimbo (1961), the inspiration for the later spaghetti westerns beginning in 1964 and even the more recent TV show The Mandalorian. In this scene, the nameless loner anti-hero is warning off some ruffians who have bragged about their tattoos and the death sentences hanging over their heads and informed him they aren’t afraid of him or the pain of being cut. The hero responds with the proverb “There’s no medicine for a fool,” then tests their resolve by cutting 3 of them. Ouch! A hard lesson easily avoided. BTW, if you have tattoos and visit Japan, best to keep them covered since they have an old and indelible association with criminal organizations and judicial branding.

Here’s the scene on YouTube. Please don’t watch it if you are squeamish. Never call the Man With No Name’s bluff.

Yôjinbô (1961)
The Man With No Name (aka Kawabatake Sanjuro played by Mifune Toshiro) pondering the interesting financial opportunities awaiting him in the troubled little post town. His older swordsmith friend (Tono Eijiro) bitterly objects. He was right.

Although it has only happened once or twice in my recollection (my saintly wife of the jaundiced eye may disagree (ツ)), on those few occasions when I have made a stupid mistake I have been known to ask subordinates to go buy a large bucket of “Idiot Salve” for me at the drugstore. The jury is still out on the effectiveness of this ointment, but I would like some credit for writing this entire article without using it.

But I digress.

Obviously, if every stroke wears the stone a little, then we must constantly check our stones with a stainless steel straightedge for flatness (length and width) and wind (diagonals) as we use them. It takes 5 seconds. Even if your stones are brand new, you may find distortions. Time spent checking is not wasted if it results in improvement. This is the heart of quality control, and is applicable to everything in life.

Truing Stones

When your check reveals the stone is out of tolerance, you need to flatten/true it. Don’t put it off. There are many ways to get this job done. Some people advocate using diamond plates to flatten stones. Others insist that sandpaper is best. And then there are the specialty flattening stones. It ain’t rocket surgery. All these methods work, but are unnecessarily costly and time consuming in my opinion. The following is the procedure I use and recommend. Give it a try, Gentle Reader, before you dismiss it.

  • Always have two of each of your rougher stones soaked and ready to go when you start sharpening. This means 2 – 1,000 grit stones, and 2 – 2,000 grit stones in my case. If you use your tools, owning these extra stones is never wasted money.
  • If the blade is damaged, for instance chipped or dinged, begin with a rougher stone or diamond plate, whatever you have that will waste metal quickly and easily while keeping the blade’s bevel flat.
  • If your blade is not damaged, begin the sharpening process with a fresh, flat stone, for instance 1,000 grit. Turn the stone end-for-end halfway through the estimated number of required strokes and continue sharpening. Yes, you need to keep track of your strokes, at least approximately. This will become second nature with practice.
  • Occasionally check the stone for dishing and wind using your stainless steel straightedge. With practice you will develop a sense of the stone’s condition without the need to use a straightedge. Stop using the stone when the distortion becomes noticeable. 
  • Switch the distorted stone with your flat stone of the same grit and continue sharpening. 
  • When both stones become distorted to the same degree, cross-hatch the faces of both with a carpenter’s pencil, then rub them against each other under running water if possible, or while frequently adding water if not. Make short strokes and be careful to apply even pressure to the stones . This requires self-control and is more difficult than it sounds until you get used to doing it. The friction and water will wear the high spots down.
  • Switch the stones end-for-end frequently to ensure the stones wear evenly. Monitor the pencil marks to track progress.
  • Check with a straightedge frequently, and stop when both stones are flat, or maybe even a tiny bit convex. 

With practice, and if you don’t let your stone’s condition get out of hand, this process should take only a few seconds, but it will ensure you are always working on flat stones.

If you think this technique is slower than using a diamond plate, specialty flattening stone, or sandpaper, you are overlooking a key point, namely, that it makes it possible to flatten two stones at the same time with the same hand movements. It may be slower than flattening a single stone with a diamond plate, but it is definitely quicker than using the same diamond plate to true two stones one at a time. Think about it.

It’s also cheaper because diamond plates are costly, and wear out. The specialty flattening stones are not cheap, and they too wear out. Both methods can contaminate stones, in my experience. And sandpaper wears out quickest of all and is the most expensive method long-term.

Now you have two stones of the same grit on-hand that are flat, free of contamination, and ready to rock-n-roll without wasting time or money on diamond plates, sandpaper, or special flattening tools. This means you have four fresh, flat surfaces at the beginning of the work day to use before you need to take time away from your paying job. And if you pay attention when sharpening, and take care to use each stone’s entire face, the time between sharpenings can be increased while saving significant amounts of cashy money.

Finishing stones seldom require flattening, but the same procedure can be used. A better solution is to the use the float-glass lapping plate described next.

If you need to get a stone extra flat, rub the stone on the  ⅜~1/2” (10~12mm) or thicker plate glass mentioned in the previous post. You can often bum scrap pieces of glass from glass stores or contractors. Dumpster diving behind a glazing shop may prove useful if you are careful and don’t cut your arm off. Don’t forget to remove the sharp corners and edges with a carborundum stone or you might end up like the annoying guy in the video linked to above.

To turn the plate glass into a lapping plate, aggressively roughen one side with a carborundum stone, and clean it thoroughly with a scrub brush, soap and running water to remove every trace of glass and stone particles. Then clean your brush and scrub the glass again. These scratches you just made will turn it into an inexpensive and efficient lapping plate. Trust me. Just wet the glass and rub the stone on it while rinsing frequently. Try to use the entire surface of the plate, not just the center.

If a stone becomes grossly distorted, you can use a rougher stone or diamond plate to true it. Even a concrete sidewalk and garden hose will do the job. However, if you do this, remember that there is no way to avoid contaminating the finer stone with embedded grit from the rougher stone or concrete.

To remove the offending stone particles, scrub the stone’s faces, sides and ends with a rough bristle brush under running water. Finish by polishing the stone’s face with a nagura stone, and rinsing well.

You should also use your nagura stone frequently to dress and true the faces of your finishing stones.

Don’t forget to maintain the edge chamfers on your stones and keep them free of contamination too.

As with all things, moderation is best. A perfectly flat stone is expensive to maintain and not especially better for general woodworking than a pretty-flat stone. Beware! For this rabbit-hole is not only deep, but sleepless nights and gibbering insanity afflict many who strive to reach its darkest depths.

Rough Stone vs. Finer Stone

Here is an important factoid you should remember: A stone trued using a rougher stone or diamond plate will be effectively of rougher grit than its designation until its surface is worn smooth again. And it will wear faster too. But if you use identical grit stones (same brand is best) to true each other, the effective grit of each will remain unchanged.

Reread the last paragraph three times, click your heels three times, and do that prayer thing again. Namu Amida Butsu.

In this post we looked at inexpensive traditional ways to effectively flatten and maintain our sharpening stones long-term. Now that our stones are looking good, in the next post to this little theatre of gleeful mayhem and hogwash refutation we will be ready to consider how to use them to flatten and polish the ura of our blades. Y’all come back now y’hear.

YMHOS

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I don’t want to hear no more of your cracks about hogwash. You said to clean the stones, didn’cha!?

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 18 – The Nagura Stone

In the previous post we listed some of the tools and accouterments necessary for sharpening Japanese tools using waterstones. In this post we will examine one especially useful stone mentioned previously: the Nagura. I know, it sounds like the name of some smelly, creepy thing that crawled out of a mountain cave in Angmar in LOTR, but if you don’t have this Nagura, you should get one.

The Nagura Stone

Nagura stones have been used in Japan for millennia, but they are not unique to Japan. For instance, the Coticule stones of Northern European have been used with nagura-equivalent stones since before Roman times. And I would not be surprised if the same tradition existed elsewhere too, they are so useful.

A Tsushima Black Nagura stone 55x55x55mm

There are several varieties of Nagura stones mined in Japan, the two most popular being the grey/black Tsushima stone pictured above and the softer white Mikawa stone pictured below. I use a soft white Mikawa Nagura stone for my straight razor.

Mikawa Nagura Stone

The black Tsushima variety is cut from sedimentary stone on the ocean floor near Tsushima in Nagasaki Prefecture, located midway between Japan’s Kyushu island and South Korea. I believe it to be the best for general usage so I will discuss this stone in particular.

Like all Japanese natural stones, Tsushima Black Nagura Stones are sedimentary deposits created by airborne volcanic ash being sifted by distance and wind and filtered by waves and tides by the time they reach the ocean floor. But they have not been subjected to the metamorphic weight and heat that makes harder sedimentary stones, and are relatively soft and permeable. They also tend to crack in the same plane they were laid down to in, especially if subjected to wet/dry and/ or freeze/ thaw cycles, so special measures are necessary to protect them.

The Job of the Nagura Stone

The Nagura stone is typically used to perform five tasks.

1. Cleaning Finishing Stones: Finishing stones become contaminated with pixie dust and grit from rougher stones. A 10,000 grit stone with 1,000 grit particles mixed in is much less than 10,000 grit effective. If you think a stone is contaminated, wash it well with a scrub brush and clean water then work the surface with the Nagura stone to loosen and float up the contaminate particles, then wash off the slurry. The stone will be clean.

2. Removing Clogging: Similar to 1 above, the Nagura stone is effective at unclogging dried slurry and metal swarth from the sharpening stone’s surface helping it get back to work sooner.

3. Truing Stone Surfaces: Finishing Stones need to be trued occasionally, usually the corners and edges. Use the Nagura periodically to knock these high spots down. The resulting slurry can be used for your normal sharpening process without it all going to waste.

4. Reducing Startup Time: Time is money. Waterstones abrade most efficiently when they have a slurry worked up, but it can take time to get decent slurry started on some stones, especially hard ones, and with some blades, especially those with soft jigane. Use the Nagura to quickly develop this necessary slurry saving time and money. If you focus on the corners of the stones, which tend to be high anyway, it will contribute to truing the stone as mentioned in 2 above.

5. Reducing the Average Particle Size in the Slurry: Nagura grit is quite fine. You can add Nagura slurry to a stone (by rubbing the stone to create slurry at corners and edges, BTW) to reduce the average grit size of the slurry making a stone create finer scratches and a better polish. For instance, adding Nagura slurry to a 8,000 grit stone makes it polish more like a 9,000-10,000 grit natural stone.

Using the Nagura Stone

Nagura stones are just as useful when sharpening with synthetic sharpening stones as they are with natural stones. In fact, they may be even more useful with synthetic stones since synthetic stone slurry containing nagura particles more closely approximates the positive aspects of natural stones.

Nagura stones are easy to use. Simply wet the large stone and rub the small stone on its surface. You may need to add additional drops of clean water while doing this. The goal is to wear down the high spots on the large stone while at the same time producing a slurry mixture from both stones to use when sharpening blades.

The key is to pay attention, use your handy dandy stainless steel ruler to identify the high spots, and use the nagura on those areas first. Don’t be a ninny and rub the nagura all over the place willy nilly. Make a plan. Work the plan. Develop good habits and speed will follow.

If the large stone is already perfectly flat, and you need to produce a starting slurry, work the ends and corners of the large stone with the nagura in anticipation of those areas becoming high in the near future. That’s a good boy.

Protecting the Tsushima Nagura Stone

Nagura stones are fragile. To avoid water penetration and cracking, it is wise to use the side of the stone that was in a horizontal plane when it was formed. It is also wisdom to use only one surface of the stone and to coat the stone’s other 5 sides with paint to prevent water infiltration and cracking, and to keep skin oils from penetrating. Traditionally, natural urushi lacquer made from a poisonous tree sap has been in Japan used for this purpose, but any high-solids urethane will do the job.

The Nagura stone is a subtle tool. As your skill using natural sharpening stones improves the value of this tool will become apparent.

In the next article in this depraved series of sex and scandal we will discuss ways to maintain sharpening stones. Some people will be miffed. Others will be thrilled. What about you?

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 17 – Gear

Do what you can, with what you have, where you are.

Theodore Roosevelt

Sharpening can be a stuff-intensive process, so I want to reduce the number of accoutrement to the barest minimum especially since portability is always a factor in my case. The following is a list of some gear, besides sharpening stones, that I am confident will prove useful whether in your workshop or the jobsite.

I will first list the gear needed for general sharpening either in the workshop or the field. At the end of this article that I have listed a minimal set of gear for use specifically in the field where space and weight might make it inconvenient to carry the heavier/bulkier general set of sharpening gear.

General Set of Sharpening Gear

The following is a list of tools and equipment I think are indispensable for sharpening Japanese woodworking tools in general and in many, but not all, circumstances. I have not included some tools that may be necessary for doing “uradashi,” i.e. “tapping out” the hollow-ground urasuki of Japanese plane blades. So here we go.

  1. Stone Base or Holder: A wooden base with a wedge to secure stones is the old standby, but repeated wetting and drying and the resulting expansion and contraction may compromise a wooden base over time. For my synthetic stones I have come to prefer the commercial bases with twin metal rods and rubber feet. They are unromantic, but are durable, stable, non-slip, grip the stone tightly without breaking it, and work well anywhere. If you decide to make and use a wooden base, I highly recommend Ipe wood because it is stable, unaffected by water, won’t rot, and bugs hate it.
Washing powder storage square plastic buckets in 2L 5L 8L 10L 15L 18L 20L

2. Soaking Bucket for stones: A medium size plastic or steel mop bucket (not the heavy industrial unit with rollers) is best for soaking stones because they are durable, and their more or less rectangular shape is superior to round buckets for leaning stones on end against the inside walls. You don’t want to stack the stones on top of each other if you can avoid it. Any durable bucket that doesn’t leak will work, but a tightly-fitting lid is a big advantage. You will need to soak all but your diamond plate and finishing stones in this bucket before use. 

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I soak my synthetic stones 365 days a year. I close the lid to prevent evaporation and keep out mosquitoes, journalists and tax collectors, and add either washing soda, borax or a few drops of Simple Green ProD5 concentrate to the water to prevent bugs and algae from growing when I won’t be using the stones for a while. Simple Green is a better bug/algae killer, but Borax has the advantage of making the water slightly alkali which helps prevent rust in my blades during sharpening.

Some stones use a magnesium-based binder that can dissolve and weaken them if left soaking for long periods of time. Please refer to the manufacturer’s instructions.

3. Glass Plate: 9mm~12mm thick float glass. This is used to true the faces of waterstones when they become distorted through use. The piece I use is 60mm x 30mm x 10mm. This plate can be used for many other purposes including checking the fettle of your plane’s soles. I leave this in my workshop. We will discuss how to use this in future posts in this series, God willing and the creek don’t rise.

4. Working Surface: If working outside, a Japanese craftsman will place his stone holder directly on the ground or concrete slab. A craftsman that works inside a shop will often have a wooden or plastic box with a board spanning the narrowest dimension forming a bridge. The stone rests on this bridge, often with a wet towel between board and stone to prevent slipping. This box, called a pond, catches water and mud dripping from the stones. The ideal situation is a board spanning a sink with a faucet of running water. When away from the workshop, I prefer to place a piece of fiberglass-reinforced rubber roofing membrane on a truck’s tailgate or stack of boards or gypboard at a jobsite. I can roll-up this lightweight, tough, and absolutely waterproof mat and stuff it into my toolbox for easy transport. In my workshop, I use a large plastic cutting mat on my workbench, but any waterproof non-slip surface will work. No need to get fancy. My stones and sharpening gear are stored under my workbench close at hand. 

5. Water Source: While sharpening, you will frequently need water to wet your stones and rinse blades. If you work at a sink, use the faucet. If you work outside, a garden hose works great. Some people, mostly knife sharpeners who seldom use stones finer than medium grit, will scoop water from their pond or bucket to wet their stones. However, since stone slurry drips into the pond, or washes off the surface of stones soaked in the bucket, this water will always contaminate stones with the grit from rougher stones, making it difficult to remove all the scratches left by the previous stone. To avoid this contamination, always use clean water for wetting and rinsing. 

Some people prefer a spray bottle to add water, but spray bottles wet things I prefer to keep dry, so a better choice, in my opinion, is a plastic bottle such as a dishwashing soap bottle or a plastic lab wash bottle with a bent tube coming out the top. Almost any plastic squeeze bottle will work.

Tap water contains chlorine in all but backward countries, and chlorine accumulates and accelerates rust, so I use distilled water in my wash bottle, and add washing soda or borax to adjust the water’s PH, a technique I learned from sword sharpeners. 

Some people add just a bit of liquid lye to their water to adjust the PH. This chemical can be purchased from industrial cleaning supply companies. Too much will damage your skin, so be careful. Also good for keeping Iron Pixies in the shadows.

6. Sharpening Station and/or Sharpening Pond: I don’t use a sharpening pond, and don’t believe them to be essential, but several practical options are illustrated below.

余暇のある時や休日だけに出現するものであるにせよ、専用の研ぎ場があるというのは工作をするものにとって幸せなことです。自分なりに工夫を重ねながら研究を深めてゆくのは、何よりも楽しみを感じさせてくれるでしょう。
A bridge placed over a sink forms the ideal sharpening station. Professional workshops frequently use this classic arrangement. Flush the drain well. You may need to remove the sinks’s P trap and clean sharpening stone mud out of it every couple of years.
Plastic boxes placed inside a wooden box make a portable sharpening pond and stone storage box. There are dozens of variations on this theme possible.
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Perhaps the best solution in my experience (short of a dedicated sink) is a plastic box to catch water, with another plastic box nested inside containing sharpening accoutrements such as a wash bottle, brush, abrasive powders, an oiler, and nagura stone. This equipment, along with the sharpening stones, 2 bases and stainless steel straightedge pictured, can be stored inside the box and the lid closed for ease of transport and to keep out pixie dust. This is an inexpensive and extremely practical solution, but be sure to use a high-quality box made of high-impact plastic.
Another plastic box used as a sharpening pond with a simpler bridge.
Image result for straightedge

7. Stainless steel straightedge: Use this to check stones for flatness and wind, and cutting edges for straightness. Don’t use a plain steel one unless you want to give the iron pixies skulking under your workbench great joy. The thinner the better. The thick blades used in combo squares are difficult to use in less than ideal light

8. Wiping materials: You will need something to clean and dry your blades during sharpening sessions. Rags work well for wiping and drying blades, and can be washed and reused, but be careful to avoid cross-contamination. Paper towels are most effective and convenient in my experience, but they cost money and make garbage. Decisions decisions.

The classic Japanese “Baby Turtle” brush with palm-fibre bristles.

9. Scrub brush: A clean stone is a happy stone, as are bases, buckets and glass plates, all of which have grooves and scratches and holes where grit can hide. Scrub brushes are great for digging out this contaminating grit. Palm fiber brushes are ideal because the bristles are finer and grit does not get embedded into the bristles as much as plastic brushes.

Lie-Nielson Honing Guide. An excellent if expensive tool.

10. Honing Guide: This tool is optional. I hesitate to recommend these jigs because they can easily become a crutch preventing you from becoming proficient at freehand sharpening. However, jigs make it much easier and quicker to shape blades to the desired angle on rough stones, especially when correcting a double-bevel or bulging bevel to a more useful single, flat bevel. Eclipse-style honing guides work well. The die-cast versions are inexpensive. Lie-Nielson makes a terribly expensive version machined from stainless steel that I am fond of. Jigs won’t work for all blades, but it is worth having one.

tzushimanagura8_4
A Tsushima Nagura Stone

11. Nagura Stone: More details will be included in next post in this series.

Minimal Set of Sharpening Gear

Sometimes, especially when working at remote jobsites, weight and/or space may impose physical limits on the tools we can carry with us. The following is a list of the minimal set of sharpening tools I bring in these situations.

1. Stone Base: At the jobsite the stability this tool provides becomes more critical than ever, but if an ultra-light set of tools is needed, then it can be eliminated by placing the stone directly on the rubber sheet I use as a portable working surface.

2. Soaking Container: There are many potential solutions for soaking stones in a minimalist or ultra-light situation. I will describe just a few here. If I need to able to move wet waterstones to and from the jobsite during the workday, but a bucket full of water is not convenient to haul around without a truck. If clean water is available at the jobsite (water coming from newly-installed pre-flush plumbing may not be clean, BTW, and immediately post-flush it may contain lots of chlorine used to sterilize the pipes and fittings), then the minimalist solution I employ is to use a dry plastic bucket to carry tools, including sharpening gear, to and from the jobsite. I then add water before beginning the work day. Depending on the other tools I will need during the workday, this is often a good choice. Another option is to scrounge a joint compound bucket or paint bucket and leave it at the jobsite. But unless I have a gang box or other trustworthy tool lockup available at the jobsite, I still may need to transport at least one wet sharpening stone to and from the jobsite each day. The ultra-light solution I sometimes employ is to carry my waterstone(s) in a durable plastic container with a watertight lid, such as the thinner (6cm) rectangular containers by Tupperware. Water can be added at the jobsite to keep the stone(s) soaked and ready to rock-n-roll. And with the lid closed, dirt and dust can’t get in. An even lighter option is a heavy plastic bag. I place the stone(s) in the bag and carry it in my tool bag. At the jobsite, I can add water and close the bag with a thick rubber band to soak the stone(s). But be forewarned that these bags will not protect the stones, and the stones will make holes in the bag at the worst possible time.

3. Working Surface: I use the fiberglass-reinforced rubbber roofing membrane described in item 4 above. This is invaluable for many applications.

4. Water Source: Clean water is necessary even in the field to add to the stones and to wash mud off tools. To save space, I use a small plastic squeeze bottle with a tightly closing lid that originally contained ketchup. If clean water is available at the jobsite, I carry it in my toolbag empty.

5. Stainless Steel Straightedge: See Item 7 above. I use a thin, flexible, lightweight one in the field.

6. Wiping Materials: A clean face towel and a some folded paper towels work well.

7. Scrub Brush: I always bring my “Baby Turtle” scrub brush. It’s lighter in weight than a plastic brush and comes in handy for tasks beyond sharpening too.

8. Nagura Stone: Just in case I need to get an extra-fine finish.

The selection of stones I use at the jobsite will depend on the work planned for that particular day, but the minimal set is a 400 grit diamond plate, a 1,000 grit synthetic waterstone, and a 6,000 or 8,000 grit synthetic finishing stone. If I anticipate a lot of sharpening, and if weight is not critical, I will bring two 1,000 grit stones to provide 4 flat sharpening surfaces thereby reducing the need to spend time flattening stones at work. I can also use them to flatten each other. If I need to do some fine finish planing, such as when doing door modifications/installations, I will bring a 10,000 grit synthetic waterstone. And of course I always carry a Tsushima Nagura stone.

In the next post in this romantic series of adventures in sharpening will focus on the important Nagura stone. Stay tuned for muscled thews and busted bodices!

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 16 – Pixie Dust

Ashes to ashes, dust to dust, if the women don’t get you then the whiskey must.

Carl Sandburg
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In the previous post we examined sharpening stones, the minimum set I recommend, those I typically use, and the most important stone in any set. In this post we will shift our focus to things that can go wrong when sharpening, including supernatural influences.

Dust Contamination

As I mentioned in the previous post in this series I almost never take a 10,000+ grit synthetic finishing stone or natural finishing stone to jobsites. This decision is based on observation under practical conditions: Jobsites are rough and dirty places, and stones are fragile. 

Iron Pixies are rabid fans of Lingerie Football. Don’t hang posters or watch games in your workshop if you want to avoid crowds of the tiny beer-drinking fiends.

Even if Murphy is drunk and the Iron Pixies are distracted watching Lingerie Football on the boob tube (pun intended), airborne dust at the jobsite will always instantly degrade an expensive 12,000 grit rated stone to an effective 4,000 grit or less in an instant, making a fragile, expensive, ultra fine-grit stone pointless. How clean is your workplace? Something to think about. Seriously.

This is not just a theory that sprouted from my overactive imagination like a dandelion on a dung pile, but is scientifically verifiable. Give it try.

Get out your microscope or high-power loupe. Place a clean glass slide near where you will be sharpening. 60 minutes later, examine the slide and count the dust specks. How did they get there? Dust is in the air quite naturally, but vehicular and foot traffic kick up lots more.

Most of those dust specs are larger and harder than the grit that makes up your finishing stone. Imagine what happens to your blade when those pieces of relatively large, hard grit get mixed into the stone slurry, or become embedded into the stone’s surface. Not a pleasant thought.

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Dust contamination even has historical precedence. Japanese sword sharpeners traditionally do their best work during the rainy season when there is less dust in the air to contaminate their stones. 

Professionals that polish pianos, stone, glass and jewels are also sticklers for eliminating dust contamination.

Just design and build a few cleanrooms for picky customers with SEMs (scanning electron microscopes), or with lens coating equipment, or who make pharmaceuticals and you will get an education about dust and the problems it creates quickly.

What dust do we find at construction job sites or workshops? First, assuming we are working at a building project, there are exterior sources of dust. Unlike a house, the doors and windows are usually open to gain maximum circulation, even when dusty landscaping operations are ongoing and trucks carrying materials and garbage are running everywhere kicking up clouds of dust.

effects of dust on lungs

Second, unless you have the jobsite entirely to yourself, there are usually other trades inside the building grinding, sanding, cutting and walking around kicking dust into the air too. The most pernicious dust on the jobsite is drywall and joint compound. This white fluffy dust appears harmless, but it contains tiny granite silica particles harder than steel, that float around and settle on everything. They are a health hazard that has put more than one person in the hospital with respiratory problems. They will contaminate your sharpening stones.

Sandpaper, sanding discs, grinders and angle grinders also spray millions of tiny hard particles everywhere, many of which float in the air and can travel some distance before settling, especially inside an enclosed building or workshop.

dangers of dust on site

Does your business or home workshop have a large door facing a public road with cars and trucks going back and forth? Do people with muddy boots come in and out? Are dirty pallets with piles of dirt hidden on the bottom boards offloaded inside? Do you use sanders or grinders in your workshop?

If you are sharpening outside, or at a dusty jobsite, or inside a dusty workshop, and especially if you regularly use sanders and grinders there, I recommend the following procedures before you use fine-grit stones:

  1. Try to locate your sharpening area away from foot traffic, grinding and sanding operations, and dusty areas;
  2. Sweep the surrounding floors well, since it is the movement of feet that billows settled dust back up into the air, and wait at least 15 minutes after sweeping for the dust to settle before sharpening;
  3. Wet the surrounding ground or floor with water to keep the dust down (this makes a big difference);
  4. Lay a clean cloth or a sheet of clean newspaper over your fine stone when you are not using it for more than a couple of minutes to prevent airborne dust from settling on it;
  5. Keep your fine stone wrapped in a clean cloth or newspaper when you are not using it;
  6. Scrub your fine stone under running water with dishwashing soap (neutral PH) and a clean natural-bristle brush before each use to remove dust and embedded grit.

And for heaven sake, even if you can’t take your benchdogs with you everywhere, at least have a brass bevel angle gauge in your toolkit, and use it everytime you sharpen, to keep the pernicious pixies at bay. I hang mine around my neck from a red string, red because all species of the Little Folk strongly dislike that color. It’s no coincidence that Iron Pixies take great joy at turning valuable tools red.

The following are few references regarding silica and construction dust: Silica-Safe.org Center for Disease Control. Makes you want to wear a respirator in bed.

The legal team hard at work digging up dirt

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form below.

Sharpening Part 15 – The Most Important Stone

Orders are nobody can see the Great Oz! Not nobody, not nohow! 

Gatekeeper, Emerald City

Many people high-center on the question: “What is the best way to sharpen my tools?”

I was hesitant to publish this series of posts about sharpening because, beginning with this post, I must answer this question by writing about tools and techniques that contradict many people’s sharpening religion. Some of those people will doubtless become emotional. As Benny Franklin once famously said: Ça ira, ça ira.

The objective of this post is to help our Beloved Customers properly maintain, sharpen and use the blades they purchase from us. Nothing else.

This post will not be a sharpening tutorial; that will be a future post.

We will examine the process of sharpening woodworking tools using mostly waterstones. We will touch on the motivations, goals and priorities related to sharpening you should consider, the minimum set of sharpening stones I recommend, and my suggestion for the most important stone in your arsenal, one you must be proficient in using.

Motivations

The Great and Powerful Oz has spoken!

You might have noticed from my previous posts that I like to understand motivations. Am I cynical? Perhaps, but where there are smoke and lights presented and money to be made, there is almost always someone behind the curtains spinning dials and pumping pedals. Oooh, pretty lights!

Anyone who does anything has a motive for doing it, and knowing that motive can help us evaluate the validity, and sometimes even the honesty, of what they do, say and write on a particular subject. How can we best ascertain the motivations of those advocating various sharpening methods and related accoutrements? Here are some simple questions you might want to ask: Are the promotions or promoters touting sharpening stones or other stuff they might profit from? Are they selling books on sharpening? Do they teach classes on sharpening? Do they have “sponsors” or “patrons” that supply them, at no cost or with large discounts, stones, diamond paste, sandpaper, sharpening machinery, and/or honing contraptions in exchange for promoting those goods? Are they “influencers” (yes, that’s a real vocation in the YouTube World) who are compensated for clicks? Do they publish reviews on products they receive for free? You see the pattern.

Regardless of their business model or motivations, many people give good advice. But some are shills, while some others are pretenders, and their advice will be colored accordingly. Caveat emptor, baby.

And then there is the most obvious motivation. After all, it doesn’t cost even $20 to make a Mechaultrasuperfine Ninja-purple Gold-dust-infused Musashi Walk-on-Waterstone that retails for $650. And have you calculated the long-term equivalent cost of diamond paste and abrasive films? Somebody’s making serious cash.

Just once I’d like to cross the road without having my motives questioned…

Whatever stones you select, I urge you to find a good balance of performance vs cost vs time vs sustainability, with sustainability referring to both the amount of landfill-stuffing the selected process creates as well as its long-term effect for good or ill on your blades. This 4-variable calculus depends not only on the characteristics of the stones and blades you use, but on your sharpening skills too, so it may take years to find the inflection points if you take a scientific approach. The quadratic formula does not yield useful results, sorry to say.

At one time or another I have tried and tested many popular sharpening “systems” including those that rely on jigs, machinery, sandpaper, plastic films, stick, liquid, paste, and powdered abrasives, buffers, strops and even superflat ceramic plates. I enjoy learning new things. They all get the job done, and all have serious merits, but to reduce the time and brain damage involved in this calculus, a wise man will learn from professionals, people who have been down the road before and actually use tools to feed their families, and who have no conflict of interest, be it stones, books, or clicks. That’s what I finally did, and I think it worked out well. But I need to issue a disclaimer before we go further.

Disclaimer

Here it is in red letters.

I say what I believe and believe what I say, even if it offends the “gurus” of sharpening. I buy their books and DVDs, watch their YouTube videos, and try the sharpening techniques and even the “tricks” they recommend, so I like to think I am not a “frog in a well,” as the Japanese saying goes. If I don’t know something, I will say so. I am not a child to be offended if you disagree with me, but I ask you to not become orcish.

Please note that we do not now and have never received goods, discounts, or financial compensation of any kind from anyone in exchange for modifying our opinion about sharpening tools and techniques.

I have personally taught many people how to sharpen tools over the years, but have never received a red cent for my time and haven’t used those training sessions as an excuse to sell stuff.

I have never done a product review.

I have never written a book or magazine article or even a blog post with advertiser support.

Please note that the document you are currently reading cost you nothing, was written and paid for by C&S Tools alone, and that there are no banners, commercials, or outside links on any of the pages in this blog. No SEO strategy at all. If Evil Google brought you here, it was not at our bidding.

We want to help our Beloved Customers, mostly professional woodworkers who already possess a certain level of skill, to level-up those skills. C&S Tools has no commercial incentive to mislead, and will not do so. But we do have a profit motive.

Remember, we have a 100% guarantee on the materials and workmanship of the tools we sell, so our sole financial motivation, and the very reason for this blog, is to help our Beloved Customers understand the tools we sell, and to become proficient in sharpening, maintaining, and using them so they won’t mistake a lack of skill and/or experience on their part as a problem with the tool. All most professionals really need is a little guidance. We want ecstatic customers because they become repeat customers. And we do hate to disappoint.

Goals, Objectives and Priorities

I mentioned 4 variable calculus above. Actually, it’s more like 5 variable calculus, the fifth variable being your goals and objectives for sharpening. Let’s examine those in more detail.

If satisfying curiosity are among your goals, then by all means try all the stones, sandpaper, films, pastes, jigs, contraptions, and machines available and methodically test them until they turn to dust. It simplifies the calculus, but the cost and time required to reach a final conclusion may become a heavy burden.

If beautiful blades, zen-like sharpening experiences, and improved hand-soul coordination are high among your ojectives (they’re included in mine), then you will want to try natural finishing stones. I heartily recommend them to those who have reached a certain level of skill with synthetic stones and are willing to roll the bones.

The performance of the sharpening system you select, including the following factors, is something should include in your calculations:

  • Time efficiency: How long does it take you to produce an adequately sharp edge starting from a dull/chipped one? How fiddly is the process? For this calculation you will need to determine how much your time is worth. Remember, while you may enjoy sharpening, from the professional’s viewpoint, time spent sharpening is non-productive time because, during the period you are working on tools, your hands, eyes, and mind cannot work on the stuff you contracted to deliver to the Customer;
  • Cost efficiency: How many billable hours and expensive supplies/tools/equipment must you expend to obtain an adequate cutting edge? For this calculation you will need to determine the cost of time, consumables (stones, sandpaper, film, paste, powder, beer) and equipment (grinders, jigs, plates, widgets, etc.) expended in producing an adequate cutting edge long-term. Even if you are not getting paid for your woodworking, your time still has value. And don’t forget to depreciate the cost of stuff. This is where synthetic waterstones shine in comparison to the many other sharpening systems out there.
  • Cutting efficiency: How well and how long does the sharpened blade cut? For this calculation, you need to determine what an “adequate cutting edge” is for you. For instance, given the same abrasives and expending the same amount of time to sharpen two blades, the blade with a rounded bevel, or even multiple bevels, is seldom as sharp as the blade with a simple flat bevel, as can be readily confirmed using a powerful loupe or microscope to examine the last few microns of the blade’s effective cutting edge (more on this subject in Part 21 of this series). Does the sharpening system you are testing tolerate or even promote bulging bevels or multiple bevels? Get out your loupe before your inner troll makes you say things you will regret.

If curiosity, pleasure and beauty are lower priority than practical performance in your list of objectives, then I suggest you focus on synthetic waterstones and the bedrock basics, at least for now:

  1. Obtain a minimum set of basic synthetic stones, or adapt what you already have;
  2. Learn how to use them skillfully;
  3. Practice those skills until they seep into your bones.

It is not an expensive process, but neither is it the instant short-term sort of thing the Gurus of Sharpening offer in their books and DVDs and classes through their tricks and gimmicks. It takes real skills that will serve you and your tools well for your entire life. And it all starts with the minimum set of stones.

The Goldilocks Set

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Oh my goodness, just look at the time! I really must be going.

Sharpening stones are expensive consumables that disappear a little with every stroke. If you need more than 5 minutes to sharpen a plane or chisel blade that was not chipped or damaged, then you may be spending too long, and wasting your time and stones, so it’s important to determine the bare minimum set of stones that work best for you.

The Goldilocks set I recommend includes the following 4~5 stones/plates:

  1. A Rough Stone: 400~800 grit rough diamond plate or two carborundum stones;
  2. Medium Stones: Two 1,000 grit waterstones (I will get into the reasons for having two stones of the same grit in another post);
  3. A Finish Stone: 6,000~8,000 grit waterstone.

Please also note that I don’t take 10,000+ grit synthetic finishing stones or natural fine-finishing stones to jobsites. This decision is based on simple practical experience: Jobsites are rough and dirty places, and stones are fragile. 

But there is an even more important reason: Airborne dust at jobsites will instantly degrade an expensive 10,000 grit rated stone to an effective 4,000 grit or less in an instant, making ultra-fine grit stones pointless. Dust will be the subject of the next post in this series.

The sharpening stones I normally use in the shop include a few beyond the minimum set described above. This set includes more stones, but the idea is that this finer gradation creates a better-quality cutting edge while consuming less of my expensive finishing stones. Natural stones can be pricey:

The packaging is fancier, but the content’s the same.
  1. One 400~800# diamond plate or two rough carborundum stones (only occasionally necessary);
  2. Two 1000# Imanishi waterstones (Bester brand) (usually necessary, but sometimes I skip it);
  3. Two 2000# Bester waterstones;
  4. One 6000# stone (fine enough for quickly finishing chisels and most planes);
  5. Two natural stones for finish planes and push chisels, or just for fun (a 10,000# synthetic stone works just as well).

Which Brand of Synthetic Stone?

I don’t think there is a dime’s worth of difference between the various synthetic stone manufacturers except for their marketing and distribution. I use what works for me and is available locally at the cheapest price. We don’t sell stones and have no relationship with or loyalty to any manufacturer. 

Regardless of manufacturer, I do recommend you avoid the extra-thick variety of synthetic stone because the oven’s heat sometimes does not penetrate deep enough leaving the interior too soft.

The Most Important Stone

Everyone focuses like a laser on the finishing stone, the final stone in the process, but when sharpening a particular blade, the most important stone is really the first stone you use in the series, be it a 400 grit diamond plate or a 2,000 grit waterstone. 

You may find this whole discussion passing strange, so I will explain. The roughest stone (or diamond plate, depending on the amount of steel that must be wasted and your available time and budget) you begin the sharpening process with builds the foundation of your cutting edge by performing the following two critical tasks:

  1. Removing damage at the cutting edge; and
  2. Shaping/flattening the cutting bevel.

Only a rough stone (400~800 grit) can accomplish the first task efficiently. If the truth of this statement is not self-evident, I won’t even try to convince you. Do the comparisons yourself: count strokes, time, and cost, measure angles, and peep at scratches through a high-power loupe.

In addition, your roughest stone or diamond plate is also the most efficient tool for shaping the bevel and cutting edge, if it needs to be adjusted. Until these two critical tasks are completed, none of the subsequent finer stones can accomplish anything efficiently, and the faster and more precisely these two tasks are accomplished the sooner one can stop sharpening and get back to the real job of woodworking.

The role of the finer stones in the sharpening sequence is simply to replace the deeper scratches left by the preceding rougher stone with progressively finer scratches. And since this work is done using more expensive, less-abrasive and slower-working stones, it is most cost/time-efficient to accomplish this task as quickly as possible. If you knock out the two foundational tasks listed above using your rough stone/plate well, then you can accomplish the subsequent polishing work at minimum cost and maximum speed. Screw it up and your blades will hate you.

Please be sure you understand the meaning of the previous 4 paragraphs. They are the heart of this article

So how does this work in real life? If the blade is chipped, dinged, or needs shaping, then I start repairing and reshaping the cutting edge’s foundation with my diamond plate. A carborundum stone, if very flat and kept flat, will work too. If my blade is only dull, but not damaged, and the bevel is in good shape, I start with a flat 1,000 grit stone. If the blade is starting to lose its edge, but is not damaged and still cuts, I start the process with a flat 2,000 grit stone. Notice the word “flat” is used a lot in this paragraph.

The objective, again, is to create an adequately sharp edge in the minimum amount of time and cost by starting the sharpening process with the cheapest, most aggressive stone appropriate to the blade’s condition for the heavy wasting and shaping thereby creating a bevel and cutting edge which you can then quickly polish to the final cutting edge using the more expensive, finer-grit stones. Wow, that’s a mouthful!

I want to make one thing perfectly clear before ending this post. Except for a few special situations, I don’t recommend using secondary bevels or micro-bevels except in special circumstances because, like training wheels on a bicycle, they are not an efficient long-term solution. In fact, they are a short-cut that has stunted many people’s sharpening skills. We will return to this subject later. 

YMHOS

This image has an empty alt attribute; its file name is tenor.gif
The Marketing Department

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 14 – Natural Sharpening Stones

Advice is a dangerous gift, even from the wise to the wise, and all courses may run ill.

J.R.R. Tolkien
The finest, softest natural stone I routinely use. Black Cashew Urethane paint for protection.

We receive a lot of enquiries about natural finishing stones, so I wanted to share some of my thoughts and experiences about them with you. Perhaps they will be useful.

To begin with, natural Japanese stones are a lot of fun, and can create a beautiful, cloudy finish on a blade’s bevel. They make my heart sing, wild thing.

I think blades finished with a natural stone tend to stay sharper a little longer compared to synthetic stones, but can’t prove it. Despite my fondness for them, I want to make it clear that natural stones are not magic, and are not critical to do good work.

It is interesting to note, however, that while top-quality natural stones are expensive, if judged by the amount of steel they can sharpen, they are actually no more costly than the better synthetic stones. But they can be more of a gamble.

Geologists believe that Japanese natural sharpening stones were created when particles of volcanic dust fell from the sky, transported, sorted, and sifted by winds and waves, and settled onto the sea floor eventually becoming sedimentary stone.

Being natural, they carry the inherent and potentially expensive risk of internal defects, such as weakness between sedimentation layers, cracks, and contamination such as hard particles of sand concealed inside. Even if you find one that seems perfect in every way, the bones never stop rolling because you never know what lurks inside.

Medium hardness natural finishing stone I regularly use.
The stone is epoxied to a base made of Ipe wood. The sides are coated with a natural urethane called Cashew, a product of the cashew nut tree, to prevent water from soaking into the stone’s sides potentially causing cracks and separation. The bright orange color is to ensure pesky pixies do not talk the stone into sprouting legs and walking away when outside the workshop.

I erred with my first purchase of a natural stone. It was recommended by the hardware store owner in Sendai where I bought it many years ago, and I fear he intentionally foisted a low-quality stone on me that a person more experienced with natural sharpening stones would have rejected. This stone “drags” steel, a phenomenon where the stone deposits hard clumps on the blade that gouge the stone’s surface and leaves rough spots on the blade. It’s impossible, BTW, to judge a stone’s propensity for this pixieish behavior by eyeball alone. I learned an expensive lesson about both natural stones and salesmen that day. I still use that stone for sharpening axes and gardening tools, but the real reason I keep it around is as a reminder of my foolishness.

After that first disastrous purchase, I became more careful and paid less attention to what people said or write. Instead I learned from people’s mistakes. And I considered motives. Consequently, I don’t give a rodent’s ruddy fundament about most people’s opinions. Too many who claim expertise talk and write about things they only partially understand. Many have a conflict of interest. Still others seek justification of their poor decisions.

Nor I do care about the region or mountain or mine a stone came from, or its designation or color. Even the best mine produces mostly waste.

And because of the impossibility of evaluating stones long-distance, and considering Gildor’s wise words quoted at the top of this post, I don’t give advice about stones, so please don’t ask. But I will tell you what I do when buying a stone:

  1. I examine the stone for cracks and signs of irregularities and impending separation at its sides (not all defects are fatal);
  2. I take the stone in my hand, close my eyes, and feel it;
  3. I flip it with my fingertips and listen to the sound it makes;
  4. I touch it to my teeth (the surest way to detect the fineness and consistency of a stone’s abrasive qualities);
  5. I put a plane blade to the stone and take a few strokes, and like a bow on violin strings I feel the friction and listen to the music;
  6. I examine the scratches it leaves on the blade’s jigane and hagane using a loupe. 

None of these critical tests can be conducted long-distance. BTW, if you think any of them are pointless, then I know where you can get a good deal on some swamp land in North Korea.

I have two natural stones I use regularly nowadays. One is of medium hardness suitable for most every straight blade. The other (see the picture below) is very soft, and easily damaged, but creates a beautiful foggy finish on the steel. 

I love my natural finishing stones, the feel of using them, the smell, and the pretty finish they produce on my blades. They are part of the romance unique to Japanese blades. I believe the stones I use now and their sisters worn to slivers in past decades were worth every penny I paid for them, but I recognize this is an emotional rather than practical viewpoint, and difficult to defend economically.

And just to save you wasting your time with questions, allow me to explain that we don’t sell synthetic sharpening stones because we can’t sell enough to justify procuring enough volume make our prices competitive. Besides, shipping costs would be too high. And we don’t sell natural stones because we cannot provide a warranty on anything so unpredictable, and I really hate disappointing people.

Don’t misunderstand: I am not suggesting you should not try natural sharpening stones, only that you carefully evaluate them in-person beforehand, and buy from a reputable dealer that offers a reliable warranty (please don’t ask for recommendations). And just to prove I am neither troll nor curmudgeon, I will give you the same four points of sound advice about purchasing natural sharpening stones that a wise old man gave me a long time ago, advice that has passed Gildor’s test.

  • First, don’t trust your eyes alone when judging a stone’s origin, designation, appearance, or performance (see the five tests listed above);
  • Second, don’t buy a stone from someone you don’t trust and who won’t give you a reliable 30 day warranty. That gives you time to check the stone carefully for suitability and defects. Remember, the combination of stone and blade is much like a marriage where the softer (but actually granularly harder) stone smooths and polishes the harder blade. If the two don’t work well together, then even lawyers can’t make it right, but a warranty may help reduce the damage;
  • Third, always try a blade on the stone before purchasing it to make sure it works for you and your blade;
  • And fourth, don’t whine if the stone disappoints: roll the dice and smile at the faces they show you. Besides, hoes, axes, and hedge shears need sharpening love too.

On the other hand, if you can follow the last rule and don’t mind risking your money, then the previous 3 rules can perhaps be ignored. I grew up in Sin City and know that can be fun too. You pays your money and you takes your chances. Viva Las Vegas!

Ancient Roman or Norse dice in a pose worthy of gambling.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

The Ancient Art of Hand Forging

Those who hammer their guns into plows, will plow for those who do not. 

Thomas Jefferson

Hand forging is an ancient blacksmithing technique that, from the viewpoint of cutting tool performance, has been almost entirely replaced in modern times, but never surpassed. Understanding a little bit about this technique and its history is helpful in understanding what a good blade should be.

Before motor-powered machinery and gas-fired forges, steel was very expensive. It took a lot of expertise, fuel, manpower and endless hammering over long periods of time to turn rocks into useable pieces of steel, an economical reality that shaped civilization for millenia. International economics aside, all steel was of necessity hand-forged back then.

This is not an efficient process compared to drop forging or press shaping. It consumes more time and fuel, and requires more labor, skill and experience. It is contrary to modern mass-production methodology. It’s a job for a trained blacksmith who demands a fair wage, not a seasonal factory worker in Bümfüq Guangzhou intent on earning enough cash to put a new corrugated sheetmetal roof on his family hovel in the countryside.

In the final analysis, hand-forging is both unprofitable for corporations and too expensive for consumers who actively value low cost and appearance above performance. No wonder it’s as Dead as Disco.

You may recall people talking about how they prefer to use hand-forged antique chisels and planes because they are superior. Those old tools certainly don’t look superior to modern tools, and they aren’t cheap. But are they superior? And if so, why?

The essence of hand forging is using hammer, tongs, anvil and forge (charcoal/gas fired) to violently shape the metal during a series of heating and cooling cycles. The combination of hammer impacts and repeated heat cycles (heating, cooling, reheating) breaks the relatively isolated, large clumps of carbide crystals into uncountable small crystals, distributing them more evenly throughout the steel’s matrix, producing the sharper, more durable, and most desirable “fine-grained” steel.

The properties of this steel are what make it valuable.

A “Tatara” furnace in Japan used to create a “bloom” of “Tamahagane” steel from “satetsu” which translates to “sand iron.” This is the traditional steel that was used throughout Japanese history prior to the importation of Western steel from England in the 1860’s
A clump of Tamahagane (“Jewel Steel”) as it is sold from the bloom furnace. It contains lots of voids and impurities that make this material entirely unusable in modern tool-manufacturing processes.
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A clump of Tamahagane early in the forging process. Most of this material will be lost as waste before a useful piece of steel is born.
After the Blacksmith hammers the raw clumps of Tamahagane hundreds of times, he then forms it into numerous small flat steel patties, which he breaks into the pieces shown in this photo in preparation for forge-welding them into a single larger piece of steel that he can then forge into a blade.

Let’s examine some of these coveted properties. The first is is that it is tougher than steel of lesser quality, meaning it is less likely to fracture due to crystalline defects. In the case of swords or knives it means the blade can cut and chop without breaking when subjected to stresses that would destroy a blade made of lower-quality steel.

The second and third ways fine-grained steel is superior is related to the first. The consistent crystalline structure with its finer carbide crystals distributed more uniformly throughout the matrix results in a cutting edge that can be made sharper, and that will retain that sharpness longer than steel of lesser quality. Of course, realizing this performance depends on the quality of the materials employed, and the skill and diligence of the blacksmith.

Many antique tools were made during a time when steel was expensive, and hand-forging was the only way to shape it. In fact, in the case of critical tools such as swords, this process included forging and reforging clumps of impure iron, folding and refolding the resulting mass into itself hundreds of times to remove impurities and adjust the carbon content, typically resulting in the a loss of 75+% of the original material’s mass. That’s a lot of material and manpower tossed onto the ash pile.

I call these tools critical not just because of their important functions but because of the implied warranty that went with them. For instance, if such a blade failed in battle, the blacksmith’s implied warranty went beyond financial compensation and involved the loss of his body parts at the hands of his vindictive customer’s surviving family members. How’s that for an “extended warranty?”

But any decent steel cutting tool was time consuming and expensive to produce. Until quite recently, blacksmiths did not have tools such as infrared temperature gauges, oxygen sensors, or hardness testers. All they had were their hands and Mark 1 Eyeball, so it took many years of training under a master for a blacksmith to learn how to make a good blade and survive.

Quality control was a big problem back then, but the blacksmiths in Scheffield, Philly, Solingen, Fukuoka and elsewhere still managed to make excellent blades of all varieties with fine-grain steel as the customer demanded. Most of those surviving blades are superior to what is manufactured in the West today. Certainly better than anything made in Chinese factories.

Drop-hammer forging parts in China

Unfortunately, it is impossible to judge a piece of steel’s crystalline structure with the naked eye, a fact mass producers exploit nowadays to make huge profits selling low-quality tools made from scrap at relatively high profits based solely on the tool’s appearance as it hangs on the hardware store wall encased in its impermeable armor of clear plastic. Lower-quality tools became widely acceptable once a generation or two of consumers that knew the value of cutting tools hand-forged from high-carbon steel left for the big lumberyard in the sky to be replaced by more urbanized generations that valued low cost and appearance more than performance.

Sadly, while the quality, consistency, and workability of steel as a material has greatly improved, the ancient technique of hand-forging has been abandoned throughout most of the world, skilled blacksmiths are almost extinct, and blade performance has suffered as a direct result.

Hand forging is still practiced by some blacksmiths in Japan, where the greater quality and performance this technique provides are still highly appreciated by craftsman obsessed with performance. Accordingly, our chisel and plane blades are made from modern high-quality high-purity steel produced by Hitachi metals instead of the much more expensive and difficult to work traditional Tamahagane. However, our blacksmiths hand-forge every single blade in their one-man forges through a minimum of three heats to form a fine-grain steel with the characteristics noted above that Japanese professional woodworkers demand.

鉋の製造工程
A composite photo of Nakano Takeo forging a plane blade.

YMHOS

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Sharpening Part 13 – Nitty Gritty

“The true mystery of the world is the visible, not the invisible.” 

Oscar Wilde

In this post we will dig into a few important nitty gritty points about sharpening stones everyone needs to know. Perhaps you already know all these points, but please ready your shovel because there may be at least one buried surprise.

A Flea’s-Eye View

When seen under high-magnification, the surface of a sharpening stone looks like millions of densely-packed stones embedded in a flat field. The smaller the stones, the finer the grit.

As the blade is pushed and pulled over these stones, they scratch and tear metal from the blade’s surface leaving behind scratches corresponding to the size of these small stones. This violence continues until the blade’s ura and bevel form a clean intersection of two planes.

A view of a blade sharpened with 1200 grit diamond plate showing the furrows left by individual pieces of grit

Seen under high-magnification, the cutting edge is jagged where these furrow-like scratches terminate at the cutting edge. To some degree, it may even look like a serrated sawblade. Some blades, like kitchen knives and swords, are used in a slicing motion to cut soft materials like meat and vegetables and enemy arms, and their performance benefits from a serrated cutting edge more than a highly-polished edge, and so do not need to be highly polished on fine-grit sharpening stones. 

Plane and chisel blades, however, are used to cut wood, a material typically harder than foodstuffs, in a straight-on direction, not in a slicing motion, for the most part. In this situation, a rough, serrated cutting edge is weaker than a highly polished edge because the jagged edges are projecting out into space like the teeth of a handsaw blade, and are relatively unsupported and more easily damaged than a highly-polished blade with smaller, more uniform scratches terminating more cleanly at the cutting edge. 

Therefore, in order to produce a sharp durable blade, we must make the microscopic cutting edge smoother and more uniform by using progressively finer grit stones to produce shallower and narrower scratches, and a thin, uniform cutting edge.

But how fine is fine enough? There is a curious phenomenon related to friction that is applicable to cutting edges, and is useful to understand. 

The Friction Paradox

Imagine a cube of heavy stone with its downward flat face resting on the level, flat surface of a larger slab of similar stone. Let’s say it takes some specific measure of force pushing horizontally on the stone cube to overcome the static force of friction between the two stone surfaces in order to make the cube start moving. 

If we gradually increase the degree of polish between the two contact surfaces and measure the force required to start the cube moving at each progressively higher level of polish, we will find the force decreases with each increment of increased polish, for a time. This is at least partially because the irregularities between the two surfaces (asperities) do not interlock as deeply when the surfaces become more polished. 

However, at some point, more polishing brings the surfaces of the two stones into such intimate contact that the molecular attraction between them, and therefore the force necessary to move the cube, actually increases. 

The Inflection Point

The same phenomenon occurs with tool blades. If you sharpen and polish your blades past a particular point, the friction and heat produced between blade and wood will increase, as will the energy that must be expended, while the resulting quality of the cut and durability of the cutting edge will not improve significantly. Of course, the time and money invested in stones spent sharpening past this point will be mostly wasted.

The inflection point where additional polishing yields increased friction with little improvement in cut quality will depend on your tool and the wood you are cutting, but you can gain a pretty good idea of where it is if you pay attention over time. While the sharpening stone manufacturers hate my saying it, in my well-informed opinion there is little practical gain, beyond self-satisfaction, to be had from sharpening chisels or planes past 6,000~8,000 grit, making this range of grit an inflection point in my mind. What about you?

Conclusion

I encourage you to conduct your own experiments to determine the inflection point in the case of your planes and wood you cut. Many who figure this out save themselves significant amounts of time and money sharpening over the long-term.

To those of our Gentle Readers that love sharpening more than woodworking, and enjoy putting money in the pockets of sharpening stone manufacturers more than keeping it for themselves, I apologize for pointing out the floater in the punch bowl. But you probably would have it noticed it eventually anyway, if only from the taste difference.

I will touch more on this important point in the next exciting installment in this scientificish adventure.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

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