The fool doth think he is wise, but the wise man knows himself to be a fool.
William Shakespeare, As You Like It
In the previous post in this series about sharpening Japanese tools, we looked at philosophical points such as making tools a long-term investment, as well as the upsides, downsides and causes of the beastly bulging bevel. In this post, your humble servant would like to touch on a subject that will make thoughtful people think and befuddled folks lucid: The Double Bevel.
Some people advocate creating double-bevels (primary and secondary bevels), or what is sometimes called “micro-bevels” on plane and chisel blades. Multiple bevels have three useful applications in your most humble and obedient servant’s opinion:
The first useful application is to repair a tool’s blade in the field when there is not enough time to do a proper sharpening job. If a blade dulls or chips in the course of a job, we can quickly add a secondary bevel at a steeper angle to the blade’s primary bevel in a few seconds and get right back to work, but never forget there will be a price to pay later over many sharpening sessions to restore the proper bevel, so it is only a temporary solution at best, and certainly not a useful long-term solution;
The second application is to quickly adjust a plane blade’s angle to reduce tearout immediately when proper sharpening is not possible. Once again, a lot of remedial sharpening becomes necessary afterwards. This application is usually restricted to the primary bevel, but we will look at a more esoteric and risky application below.
The third application is to efficiently restore a blade’s bevel to the correct angle in the case where pixies or our inattention has made the blade angle too shallow.
Case 3 above often goes like this: A blade that had cut well suddenly starts dulling quickly, maybe even chipping. Whiskey tango foxtrot!?!
When this happens, our Beloved Customers, being of exceptionally high intelligence, use the bevel angle gauge described in Part 11 of this series to check the bevel angle. They may discover the bevel angle has become too shallow for the wood it is being asked to cut.
We could increase the bevel angle by welding metal to the bevel and regrinding it, but such barbaric behavior would ruin the blade, so the most expedient way to correct the bevel is to add a steeper secondary bevel at the desired angle. We can grind this new bevel by hand, or by using a honing jig like the Lie-Nielson widget. I find I can apply more downward pressure using this jig to get the job done sooner and more precisely.
Honing jigs are undeniably useful, but they too often become an impediment to learning professional sharpening skills, and they are more time-consuming to use than freehand sharpening. Jigs can certainly make the sneaky snake of multiple bevels workable, but please don’t ignore the inescapable fact that if one uses a jig properly, over multiple sharpening sessions the result will be… let me think about it…. wait a second while I make a little sketch here…. oh yea, a flat bevel. Hmmm….
Hey, I’ve got a crazy idea: When performing routine sharpening (not the 3 cases listed above), instead of taking shortcuts and adding micro-bevels which turn into secondary bevels and maybe even bulging bevels, why not start with a flat bevel and keep it flat? And then just maybe we could take advantage of the natural indexing properties of that flat bevel to sharpen freehand and save a lot of time NOT polishing skinny secondary bevels or fat bulging bevels? You know what, it just might work!
A honing jig is very helpful for making big angle corrections. I own several, but the Lie-Nielson model is my favorite: I use it every third blue moon. If you decide to use one, however, reserve it for emergency or drastic measures. Don’t let it become training wheels, kiddies.
In this and previous posts we discussed bulging bevels, which are convex bevels on plane or chisel blades; secondary bevels and double bevels, which are additional bevels; and micro-bevels, which are a tiny secondary bevel. But there is another type of secondary bevel a clever Beloved Customer called a “nano-bevel.” I like this term and so will use it, but I caution you that, like all secondary bevels, you should employ this bevel judiciously.
We will go into freehand sharpening techniques in greater detail in future posts, but to avoid confusion when discussing the nano-bevel, we need to touch on some of those techniques now.
You may have noticed that, when sharpening freehand on every stone but the finish stone, most, but not all people do a better job by applying downward pressure on the blade only on either the push stroke away from their body or the pull stroke back towards their body, but not in both directions. This is because placing downward pressure in both directions tends to make the blade rock resulting in a less-than-flat bevel, or Saints preserve us, the barbaric bulging bevel. As you can imagine, if this rocking motion gets out of hand on the rougher stones the bevel angle can get out of control quickly.
However, on the finish stone, it is most efficient to apply light downward pressure in both directions. The advantage is that a teeny tiny bit of unintentional rocking helps to ensure the last few microns of the blade’s cutting edge are thoroughly polished. And because the abrasive power of a finish stone is so small, there is no danger the bevel will become rounded, at least if you don’t get carried away. From the wood-shaving’s eye view, this creates a tiny bevel at the last few microns of the cutting edge. This is one example of a “nano-bevel.” Stropping produces the same result on a larger scale. There is also another type of nano-bevel for emergency use.
When using a finish plane on wood with twisty grain you have no doubt experienced frustrating tearout. The usual litany of solutions is to reduce the blade’s projection for finer depth of cut, skew the plane, oil and adjust the chipbreaker, resharpen the blade, adjust the plane’s sole and mouth, or even slightly dampen the wood with a planing fluid such as water, whiskey, or unicorn wee wee. All these methods can help.
Planing fluid is the term I use for moisture applied to the surface of the wood to reduce tearout when planing by either hand or machine.
The good Lord designed trees to move water from the ground into the sky, so wood loves water. When a tree is cut down it immediately begins to loose cell water making the wood lighter in weight and much harder and stiffer structurally. But it still loves water.
If we apply a little moisture to the surface of a board the wood’s fibers become slightly softer, more flexible and less likely to develop tearout when planed, at least temporarily. The moisture is usually applied with a damp rag. Not too much, now!
Regarding the moisture source, water works well and is priced right, but it may dry slowly and produce inconvenient side effects. Unicorn products are dreadfully expensive nowadays, even on Amazon, so I prefer a smooth, inexpensive, industrial-grade busthead. Please ask Ken Hatch for a demonstration and recommendations for a good planing fluid next time he invites you over to his house for his world-famous tacos.
Please note that I don’t drink any planing fluid other than water. Of course unicorn wee wee is more addictive than OxyContin and drives mortals quite mad. And alcohol is yeast pee pee and deadly, but I prefer whiskey for a number of reasons.
Whiskey has a good water/alcohol ratio that wets the wood about the right amount and then evaporates cleanly. Too wet and it penetrates too deeply and can discolor the wood. Too dry and it evaporates too quickly.
I used Isopropyl alcohol when living in the US where it is dirt cheap, but it is considered a pharmaceutical in Japan and so is very expensive. As with other alcohol products not intended for internal consumption, it contains actual poisonous additives demanded by greedy governments for the sole purpose of maximizing tax revenues. I don’t need those poisons touching my tools or my skin. Cheap whiskey, however, doesn’t contain poisons (other than alcohol, of course), it’s cheaper and smells better.
Emergency Nano-bevel Modification
Another classic solution to reduce tearout of course is to use a plane with a steeper blade bedding angle, but what to do if you don’t have a high-angle plane handy?
A traditional, jobsite-expedient solution used by Japanese woodworkers is to create a nano-bevel on the ura side of the blade. This is accomplished during sharpening while polishing the ura on the finishing stone by lifting the head of the blade just a itsy bitsy teeny weeny nat’s buttfuzz thickness during the final stroke, pulling the blade towards you, of course, creating a “nano-bevel” on the last few microns of the cutting edge at the ura, effectively changing the approach angle of the blade.
Be forewarned that this is only for emergency use, and that if you overdo it, or do it too often, the nano-bevel will become a microbevel in a bad location, your blade will be damaged, efficient sharpening will become impossible, the chipbreaker will cease to function, and the gods of handsaws may curse you so all your hair falls out and your dog will barf on your shoes! Or is it your dog’s hair will fall out and you will barf? I forget.
Now where did I put that jar of planing fluid….?
A wise man will seek to avoid shortcuts that save a bit of time short-term only to waste more of his time and money long-term. If you simply make the effort to invest in basic sharpening skills, pay attention, and keep the bevel flat, time, steel, and stone-wasting monkeyshines such as double bevels will be unnecessary.
We have talked about the cutting edge’s proper shape. Beginning with the next post in this series, we will examine how to use sharpening stones to make it that way.
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may my blade bevels multiply exponentially.
Shall I compare thee to a summer’s day? Thou art more lovely and more temperate: Rough winds do shake the darling buds of May, And summer’s lease hath all too short a date; Sometime too hot the eye of heaven shines, And often is his gold complexion dimm’d; And every fair from fair sometime declines, By chance or nature’s changing course untrimm’d; But thy eternal summer shall not fade, Nor lose possession of that fair thou ow’st; Nor shall death brag thou wander’st in his shade, When in eternal lines to time thou grow’st: So long as men can breathe or eyes can see, So long lives this, and this gives life to thee.
William Shakespeare, Sonnet 18
Your most humble and obedient servant began this post with the elegant sonnet quoted above, indisputably one of the most beautiful pieces of poetry ever written in the English language, instead of the usual pithy proverbs of Red Green, that Great Canadian Philosopher-Handyman and erudite Leader of Possum Lodge, just to show Gentle Readers how refined we at C&S Tools can be when no one is watching (ツ). But sadly we must now pause all such elegant distractions for a time to focus on the nuts-and-bolts of how to true the ura of a Japanese woodworking blade, the first step in making it sharp.
This tutorial is rather wordy because Beloved Customers sometimes find the task of managing the ura difficult at first. Indeed, while truing the ura of Japanese chisels and planes is a simple task, it’s one many get wrong the first time, occasionally resulting in emotional damage to both blade and it’s owner. I know it almost drove me non compos mentis the first few times I tried, but now that my psychiatric team has stumbled onto the right mix of meds, and Doctor Alonzo has released your humble servant from that unflattering canvas straight jacket, Beloved Customers have the opportunity to learn from my mistakes. Rejoice!
So let’s get to it.
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 become obsessive; That way lies madness.
A few lost souls mistakenly assume (just before they go barking mad) that the ura’s lands must be all planar for the chisel to function, but such is not the case. Granted, it does make it easier to sharpen the blade, but it need not be achieved immediately, especially since a planar ura can be easily obtained gradually over multiple sharpening sessions.
If Beloved Customer’s chisel does not have a fully-planar set of lands surrounding the hollow-ground uratsuki when new, understand that it may be a hand-forged, hand-shaped, hand-sharpened tool with imperfections, and perhaps not a CAD-CAM designed, mass-produced, sharpened Chinese screwdriver. If so, please understand that this is not an aberration but is normal. However, if such natural irregularities distract to the point your eye starts twitching like that of Chief Inspector Dreyfus after spending time with Inspector Clouseau, perhaps hand-forged tools are not your cup of tea.
In any case, the chisel will work just fine as-is if you are aware of the blades tendencies and compensate using your eyes and hands accordingly. After all, the chisel only does what you direct it do, so please pay attention and actually direct the blade instead of just going along for the ride while drinking adult beverages and smokin wacky-tabaccy in the back seat with Murphy. 〜(シ) 〜
If the plane formed by the ura’s lands is concave, the chisel will tend to undercut the end walls of a mortise, not difficult to avoid with some caution of the sort one must always exercise.
On the other hand (the one with 6 fingers) if the plane is convex, the chisel will tend to scoop away from the end walls of a mortise. All things considered, however, concave is far better than convex.
But whether concave or convex, such irregularities always exist to some degree from time to time in all chisels sharpened by hand. It is the craftsman’s job to manage his tools and find efficient ways to maintain them. Of course, this means we must strive to create and maintain a reasonably flat ura, so let’s consider some practical time-proven solutions that avoid wasting a lot of time, stone and steel, and at the same time don’t wear out the hollow at the ura in the process.
Let us begin by observing that the surface area (square millimeters) of the hard steel encompassed within the lands at the ura that we need to eventually make planar can be divided into three areas:
The land immediately adjacent the cutting edge (aka “itoura;)
The land where the neck meets the blade;
The two skinny side lands right and left of the ura.
The area that matters most when sharpening and cutting is the last couple of millimeters immediately behind the cutting edge.
The area near the neck matters not at all. This is an important point to grasp.
The side lands are important bearing surfaces for aligning the chisel in the cut, but they are less important than the cutting edge land. These we want to keep as skinny as possible as long as possible in order to preserve the ura thereby keeping the job of sharpening easier.
It’s important to realize sooner than later that as we wear out the skinny side lands, the ura will become shallower and the amount of hard steel we will need to sharpen/polish will drastically increase, which is inconvenient in so many ways. Sadly, too many people make their chisel’s side lands fat as a sumo wrestler soon after purchasing a chisel in their quest for the totally flat ura. Makes me wanna cry.
The cost-efficient and time-efficient solution is to make small corrections to the ura over multiple sharpening sessions thereby saving valuable time as well as expensive stones and steel while preserving the ura as long as possible. How to do this? Focus all your attention on the most important area, and patiently plan on accomplishing the job over 5~10 sharpening sessions, using the chisel in the meantime.
Don’t spend any effort correcting/polishing the ura full-length from cutting edge to neck, instead work the area behind the cutting edge on the stones (which must be flat). To do this, focus finger pressure nearest the cutting edge only. An effective approach is press down on the land nearest the cutting edge while moving the blade on the stones, while the rest of the blade hangs off the stone.
In other words, while pressing down with the fingertip(s) on the face of the blade (the surface opposite the ura with the brand on it) as near as possible to the cutting edge, move the last 5~15mm of the blade onto and off of the stone in a back-and-forth diagonal motion concentrating abrasion where it is needed most. This requires the ability to sense the balance of the blade on the stone, and to apply fingertip pressure where it is needed most. Wow, imagine that.. real hand skills. If you don’t have these skills now, they are easy to develop with concentration and practice.
During each subsequent sharpening session, increase the width of the area you work on the stones a tiny bit until the entire ura is flat and can be worked on the stones.
Through this technique and over multiple sharpening sessions, you will notice the ura’s lands will gradually become planar while only the lands nearest the cutting edge increase in width. Honest.
It helps to apply either marking pen ink or machinist’s blue to the blade to confirm whether or not you are applying pressure where it is need most and that abrasion is proceeding as desired.
Please also keep in mind that, when working the ura, in most cases, you should focus hand/finger pressure on the “ito-ura,” the land at the ura located right at the cutting edge, and almost no pressure elsewhere on the ura.
It is human nature to want to rely on the flatness of the ura’s lands to keep the blade flat on the stone, and therefore we tend to apply pressure at the midpoint of the back so that the pressure on the ura’s land is even at all points of contact. This feels good; It feels stable.
But if you consider the narrow width (and small area) of the hard steel exposed at the side lands compared to the lands at the ito-ura cutting edge and the corners of the blade, you will see why this technique will wear the skinny side lands quickly and prematurely.
Allow me to restate an important point: The goal therefore is to focus hand/finger pressure nearest the cutting with much less pressure focused on the sides lands preserving them, and the depth of the ura, as long as possible. This technique will also save time and expensive steel. It is an advanced skill, but one Beloved Customer should aim to perfect.
A detailed example follows.
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 a detailed explanation can be found in Part 30of this series.
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 thin 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.
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 2mm or so of the cutting edge will be curved upwards towards the chisel’s face.
I learned two things from my examination of this atsunomi. First, there is a high spot (convex) at the skinny land on one side located approximately 1/2 to 5/8 the blades’ 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 itoura land right behind the cutting edge curves downward away from the ura just a tiny bit, enough to cause problems.
I next must formulate 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. But… I must… resist… the… stupidity impulse!!
If it becomes too much, I’ll take a coffee cup or three of the medicine mentioned in the previous post and slather it on my 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 high-intensity psychic waves radiating from my gigantic brain (ツ). Thank goodness for my aluminum foil skull cap with its artfully protruding copper wires or the radiating light might blind airline pilots passing overhead!
But getting back to practical matters, 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, ruthlessly subduing the stupidity impulse, and perhaps the occasional dab of ointment…
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 (assuming the faces of your stones are flat).
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 often ignored is that the majority of the metal I need to waste is usually located to the right and left of the itoura 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 steps into the side lands anyway.
The third point often ignored is that 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 or diamond stones 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 idiot-b-gone 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, diamond stone 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. Please don’t you make it more than once.
Grind the ura down so the line at the highest point and the cutting edge is fairly flat.
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 itoura land right at the cutting edge.
This flattening process is seldom required except on new blades. 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. In the meantime, keep yer stick on the ice.
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may an elephant caress me with his toes.