If you do not change direction, you may end up where you are heading.
When using the rough stones, and especially when learning basic sharpening skills, it is best to sharpen the bevel in one direction only, lifting the blade off the stone, or at least removing all downward pressure, on the return stroke. The reason for this seemingly inefficient movement is simply that, at least for most people, trying to abrade the blade on both push and pull strokes is extremely likely to cause the blade to rock creating the dreaded bulging bevel.
There are certainly many exceptions to this rule, and we actively encourage you to try to develop the concentration and muscle control required to sharpen in both directions on rough and medium stones, but be aware it may take some years. In the meantime, remember the ancient adage and imperial moto: festina lente, which we chose to translate as “Slow is smooth; Smooth is fast. “
Part of the difficulty of sharpening in both directions is the resulting loss of concentration: the swing of the thing is hard to sense. Perhaps another part of it is due to the difficulty of controlling the complicated and constantly-changing angles of bone and tendon. Both of these natural mental and physical tendencies can be overcome by talented and determined people given time and daily practice, but in the case of everyone I have ever talked with on the subject, it takes many years of focused on-the-job practice, and extreme concentration at first to overcome pre-existing bad habits and avoid developing bad muscle memory.
At this point you need to make a decision, unless you have already made it inadvertently. That is, to sharpen on either the push stroke (pushing the blade away from you) or the pull stroke (pulling the blade towards you). Most people choose the push stroke, as do I, but in reality the pull stroke is actually a little more efficient because the pressure tends to focus closer to the bevel’s front instead of back, and rocking is reduced. Whichever direction you choose, use it consistently.
However, and this is critically important, when it comes to the final finishing stone, work the blade back and forth in both directions. The finishing stone is not abrasive enough to change the bevel’s shape, and since you need to polish the last few microns width of blade’s cutting edge, a very tiny amount of unintentional rocking is actually helpful, as mentioned in a previous post.
If you decide you want to develop the ability to sharpen on both push and pull strokes, I can share some helpful guidance that was given to me many years ago by a sword polisher.
The first step in training yourself is to begin by lifting the blade on the return stroke (either push or pull depending on your preferred direction). All the things mentioned above apply. Becoming proficient with this technique is foundational. Strive to project your senses into the blade traveling over the stone, indeed right down to the last few microns of the cutting edge.
When you are able to create a sharp edge while maintaining a flat bevel consistently and without much concentration using this “one-way” technique, then move on to the second step, which is to keep the blade in contact with the stone on the return stroke, but relieve all downward pressure. Begin slowly with full concentration and and seek for smooth motion. It’s at the transition from one direction to the other where those nasty iron pixies cast their spells of confusion.
And finally, when you have mastered the “light-touch” technique, try applying downward pressure in both directions, beginning slowly at first and with full concentration striving for smooth motion.
Remember, don’t grip the blade like a thrashing snapping turtle, but hold it lightly in your hands like a small bird: too tightly and it will be crushed; too loosely and it will fly away. Don’t lock your wrists or elbows, but actively and consciously rotate them to keep the blade’s bevel always perfectly flat on the stone (your stone is flat right, right?). And don’t forget to use your small, thin stainless steel straightedge and brass bevel gauge to frequently check the bevel for flatness and proper angle.
And as always, brutally crush bad habits, and don’t allow new bad ones to take root.
Sadly, this is a skill that, once learned, tends to deteriorate with time unless practiced frequently. As with cherry blossoms, muscles, tendons and eyes are neither static nor eternal. Setsunai, desu ne.
If you have questions or would like to learn more about our tools, please use the questions 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 or incompetent facebook and so won’t sell, share, or profitably “misplace” your information.
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.
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.
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.
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.
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.
If you have questions or would like to learn more about our tools, please use the questions 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 or incompetent facebook and so won’t sell, share, or profitably “misplace” your information. Honest Injun.
Ideally, a tool blade will have absolutely uniform dimensions: the right thickness and taper, perfect cross-sections, uniform curvature, and straight edges and surfaces. However, professional grade Japanese tools are not made on CNC machines, but are hand forged, and have dimensional imperfections. Indeed, imperfections are part and parcel of all human endeavors. Most imperfections don’t matter; Sometimes they make the tool better; Other times they need to be remedied.
You, Gentle Reader, may not notice that the blade or cutting edge of one of your chisels or planes is “skewampus,” and consequently the cutting results are less than ideal. You may blame those poor results on your technique in using the tool or the irregular wood grain, when the real problem is the shape of the blade’s cross-section, or your unintentionally sharpening the blade with a skew. We will examine this problem in this post.
We will also look at the curved or “cambered” cutting edge profile in plane blades, the benefits and undesirable results it can produce, and how to incorporate this blade profile intelligently into your woodworking repertoire.
Many people, like monkeys in trees, learn bad habits from their friends and teachers. We hope this post will help you understand what is going on with your woodworking blades, and how to shape and sharpen them intelligently instead of just monkeying around. Please be sure to BYOB (bring your own bananas).
Dealing With SkewampusBlades
Skewampus is an interesting word I learned from my mother. I am told it is a combination of the word “Cattywampus” meaning “in disarray,” and “askew.” I think it is the perfect word for describing the ailments some blades suffer.
While less than ideal, it is not unusual for the thickness of a chisel blade’s cross section to vary slightly across its width, with one side being thicker than the other, forming an irregular quadrilateral cross section. This irregularity is found in plane blades too, but it is not typically a problem. Since there is more steel on the thicker side, the cutting edge will tend to develop a skew during sharpening.
Japanese plane and chisel blades are formed by laminating a layer of hard steel to a much softer body made of extremely low-carbon steel or iron. If the lamination exposed at the cutting edge is not uniform, the area of the blade with more hard steel touching the sharpening stone will abrade slower than areas with less exposed hard steel such that the cutting edge will tend to become skewed during sharpening. Perfection is not required, but the uniformity of the lamination is an important detail to observe when purchasing Japanese tools.
Likewise, Western plane and chisel blades that are not uniformly heat-treated, and that exhibit differential hardening across the bevel’s width, will also tend to become skewed during sharpening as one side of the bevel abrades quicker than the other. This problem is more common than you might imagine, especially in the case of inexpensive tools where appearance and low price are given higher priority than quality.
Anyone that has experience bidding high-dollar construction projects will understand the statement “the most profitable job may be the one you lose.” Cheap tools are much the same way: that low-cost chisel or plane may look good on paper, but if you count your time worth anything, if you dislike headaches, and real-world performance matters to your bottom line, then such a tool is often disastrous. Caveat emptor, baby.
A chisel or plane blade that has an irregular cross section or a skewed cutting edge may not be a problem for many cutting operations. However, when cutting mortises, a chisel blade with a skewed cutting edge or irregular cross section will tend to drift to the side gouging the mortise’s walls and ruining tolerances. If you find that your mortise walls are gouged, or that tolerances are poor, check your chisel blade’s shape, and correct any deformities.
Like all human work spaces, Japan’s smithies are not immune from pixie infestation despite annual blessings by Shinto priests and periodic offerings of rice, salt and wine to the spirits. In a previous post we discussed supernatural predators, so I will refer you to it for antidotes to pernicious pixie pox. But the deformities we are examining in this post are more often the natural result of the human eye misjudging hammer blows or non-judicious use of grinder wheels rather than precocious pixies at play.
If your blade’s deformity is not excessive, you can compensate by applying a little extra pressure on the blade’s thicker side while sharpening it.
It is interesting how a little off-center pressure on a blade being sharpened over many strokes can change its shape. Many people unintentionally deform their cutting edges by not paying attention to the amount and location of the pressure their fingers apply. A word to the wise.
Another potential solution is to skew the blade in relation to the direction of travel when sharpening the bevel. This works because the leading corner of a skewed blade is abraded quicker than the trailing corner. But once again, inattention causes many people to skew their blades when moving them around on their sharpening stones unintentionally creating, instead of intentionally correcting, skewed cutting edges. There is nothing wrong with skewing the blade when sharpening so long as you are aware of the distortion this practice can produce and compensate accordingly. Another word to the wise.
If these methods don’t compensate adequately, you may want to grind and lap a chisel blade to a more uniform cross-sectional shape. A chemical bluing solution used afterwards will help conceal the shiny metal exposed by this operation if your chisel objects to the shiny spots. Some of them can be quite vain, you know.
Cutting Edge Profiles
Many people have access to electrical jointers and planers, but relatively few have industrial equipment with the capacity to dimension wide boards such as tabletops. And of course architectural beams and columns are typically too long or too heavy to dimension with most stationary electrical equipment.
The choices available to most people for dimensioning such materials therefore are either handheld electrical power planers and/or sanders, or axes, adzes and hand planes. Powerplaners, sanders, axes and adzes are beyond the scope of this article, but we will look at hand planes.
Although the very idea gives some woodworkers vapors (I don’t mean gas), an efficient craftsman will have multiple planes with cutting edges honed to profiles matched to specific operations.
Everyone that dimensions larger pieces of lumber by hand needs a plane with a wide mouth and a curved or “cambered,” cutting edge called a “scrub plane” in the West, and “arashiko kanna” in Japan.
This variety of plane excels at hogging a lot of wood quickly when the craftsman needs to significantly reduce the thickness of his lumber. If the blade is narrow and curvature is deep, this plane will hog wood quickly, but leave a deeply rippled surface, often with bad tearout.
One might also have a second arashiko, or jack plane with a wider blade with a shallower curvature for the next steps in the dimensioning process. Such a plane will not hog wood as quickly, but it will produce a surface that is closer to flat and smooth and with less tearout. You can see the advantage of having two arashiko planes, or a scrub plane and a jack plane, with different cutting edge profiles when dimensioning lumber.
Many Gentle Readers use electrical-powered planes to dimension lumber before turning it into furniture, doors, chairs, or sawdust, etc. and are aware that planers always leave tiny ripple-like scallop cuts on the wood’s surface, along with some tearout. This will not do as a final surface. A hand-plane finish is far superior, but it doesn’t make sense to remove any more than the bare minimum of wood necessary to remove the washboard.
A finish plane is the perfect tool for this job on condition that it is sharp, set to a fine cut, the chipbreaker is tuned and set properly, the blade profile is appropriate for the width of the wood to be finished, and the wood does not have too many large knots. In one or two passes such a plane can easily remove the ripples and leave the wood clean and shiny without changing its dimensions much at all.
Assuming the wood is cooperative and one knows how to sharpen and setup their plane properly, blade profile frequently remains a key factor many fail to grasp. Obviously, the curved cutting edge of a scrub plane cannot produce the perfectly flat surfaces required for joining two pieces of wood together. On the other hand, the corners of a perfectly straight blade will leave clearly visible steps or unsightly tracks on the surface of a board wider than the blade, which is not a problem when rough dimensioning a board, but is painful to see if the board’s surface is to be left with just a planed finish.
So how do we solve this conundrum? When finish planing, the professional approach is to use two planes each with a different cutting edge profile. The first type of finish plane has a perfectly straight cutting edge used to plane pieces narrower than the blade’s width. Since the blade’s corners are not riding on the wood while cutting it, they won’t leave tracks and ridges.
The second type of finish plane found in the professional’s toolkit has a curved cutting edge, or more correctly, curved just at the corners to prevent it from leaving tracks and ridges when planing boards wider than the blade. Nearly all the edge is left straight, but creating this tiny amount of curvature at the right and left corners causes it to smoothly disappear into the plane’s mouth so no tracks are made and any ridges are nearly impossible to see or feel. In other words, the corners of the cutting edge never touch the surface of the board, and so don’t leave discernible tracks or ridges. The finer the cut made the smaller any ridges created will be. Indeed, where a high-quality surface is required, the final cut with the finish plane will produce shavings thin enough to see one’s fingerprints through.
You may want to reread the previous two paragraphs to make sure you understand what these two cutting edge profiles are and what they can accomplish before you read further.
Naturally, a professional doing high-quality work needs at least two finish planes, one with a straight cutting edge used to produce flat, precisely-dimensioned surfaces on wood narrower than the blade’s width, and another finish plane with a cutting edge very slightly curved at the corners used to finish wider surfaces.
There are those that advocate using a curved blade, sometimes dramatically “cambered” as some call them, for all applications. Those who teach this sloppy technique twist themselves into knots justifying tricks to approximate flat surfaces using such blades. I have no doubt this is an ancient technique, but I think it is a sad practice that sprung from the carelessness of some craftsmen in flattening their sharpening stones, and with time this bad habit became a tradition in some quarters. I strongly suspect fans of this strange way of doing business habitually sand all visible surfaces anyway so tracks and ridges are not a problem for them. But the fact remains that perfectly flat, track/ridge-free surfaces work best for joinery.
Tradition and “monkey see monkey do” are a useful place to start, but as his skill level increases, the thoughtful and efficient craftsman will eventually seek to confirm the validity of the traditions he has been taught. I urge you to get started early.
Sadly, too many people never notice the strange instruction label pasted to their boot’s sole, nor that smelly stuff sloshing around inside.（ツ)
As we come to the end of this post, my advice to you, Gentle Reader, is to learn two bedrock basic skills to perfection. First, learn how to keep your sharpening stones flat; And second, learn how to sharpen your blades to have a straight cutting edge. Everything else will flow naturally from these skills. Your blades deserve it. We will talk more about these subjects in the future.
In this post, we have discussed 12 serious points about plane and chisel blades and how to use and improve them all but a few woodworkers in the West are unaware of, or ignore, but which are common knowledge among professional Japanese woodworkers in advanced trades. While condensed, it is enough information to fill a book, but we are giving it to you for the price of bananas (BYOB, remember?). We hope you picked up on each point, and test those that are new to you.
The next installment in this simian soap opera of sharpening will focus less on monkeyshines, and more on stones and techniques. Please stay tuned.
If you have questions or would like to learn more about our tools, please use the questions 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 or incompetent facebook and so won’t sell, share, profitably “misplace” your information, or do any other monkeyshines with it.