Sharpening Part 20 – Flattening and Polishing the Ura

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.

Important General Principles

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 insane) 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, and is easily obtained over multiple sharpening sessions with patience.

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 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 the ura’s lands are 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 of the hard steel (square millimeters) encompassed within the lands at the ura that we need to eventually make planar can be divided into three areas:

  1. The larger steel land immediately adjacent the cutting edge;
  2. The land where the neck meets the blade;
  3. 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.

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 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 key 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 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.

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 30 of 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.

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 meet 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 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’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 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 light radiating from my gigantic brain (ツ). Thank goodness for my aluminum foil skull cap with its artfully protruding copper wires or the 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, 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 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 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.

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. Please observe that 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. In the meantime, keep yer stick on the ice, and I will the honor of remaining,

YMHOS

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Links to Other Posts in the “Sharpening” Series

13 thoughts on “Sharpening Part 20 – Flattening and Polishing the Ura

    1. Hi Stan

      Yes that too Stan haha!

      The important point was to measure the flatness of the back of the chisel/plain first and make a plan.

      I had up until now only flattened the first inch or so of the back using the black marker method.

      Regards,

      James

      Like

      1. James:

        Now I understand.

        Yes, measuring beforehand is often overlooked, and I find few people think to make a plan. It’s human nature: I know I’ve failed to do it too many times. So many times, in fact, that I decided long ago to take pity on the poor chisels and check and plan before grinding. It feels counterproductive but saves time and effort and valuable steel in the final analysis.

        I have had customers buy nice chisels that were entirely usable, although not perfect, and instead of gradually truing the ura over multiple sharpening sessions as I suggested, they decided they would grind! grind!! grind!!! to try to make them perfect before even using them. Then they complain about it being soooo much work that took soooo much time. Looking at their results, Its obvious they entirely ignored my advice, made no plan, and didn’t improve anything. Instead they wasted their time (and my time) only making things worse, practically ruining the chisel in the process.

        We all learn a little more everyday. We all mistakes, especially me. Ergo the coffee cup method of applying medicine. I hope this post will help our Beloved Customers (sacred in every way!) learn a little faster/sooner and make fewer mistakes. Tools need love to, donchano.

        Regards,

        Stan

        Like

  1. Oh boy. Now we get to the meat and potatoes.

    This is some excellent advice. Much better to learn this way, rather than trial and error (don’t ask me how I know).

    It is interesting that you suggest to work the chisel back and forth rather than side to side. It makes sense to me but I don’t see many people suggesting it. I might have to go back to that approach.

    I’ve got some chisels that I have flattened as best I can. But I’m guessing there is no harm reassessing them and, if needed, following your advice – even though they are not new.

    Please keep the posts coming.

    Like

    1. B.

      Thanks for the kind words.

      Are the chisels behaving themselves? Give them a kiss for me (on the handle!)

      Working the blade on and off the stone lengthwise is not the only way, of course, but I find it works quickest, with the least number of strokes, when truing the ura, while minimizing the tendency to dig “notches” in the narrow and delicate side lands and wear out the ura prematurely. Even when I move the blade’s ura side to side on the stone, as in the case of plane blades, I still move the blade on and off the stone/plate. It turns into an elliptical movement sorta, kinda, almost, hardly.

      The anal retentive types focused on making the ura uniform and maximizing the blade’s beauty will apply thin tape over the side lands so they don’t even touch the stone. I think they stole the idea from sword sharpeners. Much too fussy for me, but it works.

      Meat and potatoes indeed. The next post in this series will be heaped with Death Adder chili peppers that will cause brain damage in a lot of people. I can imagine their heads popping like zits as they read it! Gotta get my 4k video camera ready.

      Like

      1. Yes, but I am not of a mind to kiss them. I just hold them. Lovingly. When I’m not even working.

        I have used tape on a kanna blade but not on a chisel.

        I have also seen wax (ibota?) used to prevent the lands wearing on the stone. I’m somewhat obsessive so that appeals to me. But I’m trying to fight it.

        Like

      2. Not sure how to reply to your comment below. I think the wax does gum up the stone’s surface and then it’s removed with a flattening stone. But I’m working with a google translation. I can’t speak to its efficacy. But it is interesting.

        Like

  2. That must have taken days. How much hagne would be left? Oh well, at least the bevel would have been quick to work on.

    Like

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