Restoring Japanese chisel

[Mike Holbrook]

I just got the Japanese Tataki Nomi I won at auction. It is a heavier, larger version of the typical Ore-Nomi, 30 years old but still in good shape except, there is a small piece missing from one corner of the cutting edge. It looks like I may have to grind off half the distance (1/16 - 1/8") of the remaining portion of the flat area on the back side.

As I understand how these chisels are made from Toshio Odate's book Japanese Woodworking tools, the hollow in the backs of these chisels are not ground into the blades but hammered out during forging. I am in the process of grinding a new edge and bevel in the chisel which I think is fairly straight forward. I am not sure about removing the burr and flattening the back though. I am trying to avoid any unnecessary work on the back as I do not want to abrade away any more of the hollowed area than completely necessary. I have read about tapping this area out on plane blades but do not recall having read anything regarding dealing with this same issue on a chisel?

[David Weaver]

Do not tap it. Use a diamond hone or an aggressive stone after you get the bevel where you want it and flatten the back by hand.

I don't know how the hollow is put into the chisel, but it is definitely finish ground (it is not strictly introduced via dai, and perhaps it was historically scraped - it really doesn't matter, though - knowing how it's done is for trivia buffs and japanophiles - it's important only that the hollow is shallow unlike the one in plane irons).

Tapping is a potentially catastrophic process that is saved for plane irons. Lap the backs of the chisels.

It is not unacceptable to do most of the rough removal on your chisel with a coarse belt sander, the only thing to know is that the temper temperature is likely something like 250-300 degrees instead of 350-400 or so that O1 tools might have, so you don't really want to heat things much. Still, you wouldn't catch me hand grinding off an 8th of an inch on any of my japanese chisels by hand, I'd grind them or belt sand them, and I have dry ground and belt sand them before with no loss of performance. If I dropped the kiyotada, I would belt sand it, too, and then finish with stones for cosmetic reasons.

[Stuart Tierney]

Just before someone says it's a good idea to tap out a chisel...

Some folks I am lead to believe do actually tap out chisels. Some of them speak with authority that they can be tapped out.

I've yet to speak to a single chisel maker that condones it, and I've yet to read anything from over here that says it's acceptable. I have read that it should never EVER be done, and written by some folks who have more authority than anyone you could possibly conjure up that says it's ok to tap out a chisel.

So don't do it. Ever. Doesn't matter who says it's ok or how much experience they might have, because they're wrong.

I don't often say something is flat out wrong, because once it's your tool you're allowed to do whatever you want to it. But in this case, tapping out a chisel is flat out wrong, incorrect, unacceptable and simply a really Bad Idea.

(I saw a video of someone tapping out a Tasai chisel, and I bet folks saw it and thought that it was a good idea because the source carried some authority. I saw another video where someone taps out a chisel, and again they are considered to be some kind of knowledgeable person on these matters. It's their chisel, they can do as they please. Just don't you dare do it.)

As for using a grinder, you're welcome to do that. I don't, and I find it's not really necessary and not a particularly good idea (folks who make them won't touch them to a grinder once they've been heat treated, and they're better on the grinder than you are) but it's your chisel and you can do what you want to.

I hope that helps,

Stu.

[David Weaver]

If I were making them, I wouldn't either. The friable wheels that are out there now can grind them safely, though. I haven't ground anything yet on a pink wheel that I couldn't place directly in my palm and find any heat, certainly nowhere near boiling. The bleeding edge of the tool could possibly be heated a fraction deep, but it's a fraction that would come off with a medium stone.

A cheap belt sander with poor tension and no really hard platen contact should run even cooler (thus the suggestion).

I'm sure the makers could do the same thing I do without ever harming the temper on a chisel, but the bevel would still need to be finished on something, and I have no idea what they use short of a cutlery style large wet wheel setup. They're definitely not always particularly flat (across various brands), sometimes they have a bit of a hump in the middle of a bevel.

That said, anyone who doesn't feel confident grinding a vintage US made tool shouldn't grind a japanese tool, and any dry wheel should always have a fresh surface.

I'll bet some of the anti grinding sentiment (aside from the fact that it doesn't need to be done at production) is superstition, too - a tool would be unsaleable to some craftsmen who still hold odd superstitions. I can't remember if it was stanley, but someone mentioned to me that they had worked along side a cabinetmaker or templemaker who claimed that if a japanese chisel touches a synthetic stone, it is permanently ruined and is useless. I got a giggle out of that. I don't doubt that sharp abrasives can cause microfractures, but those microfractures certainly don't go very deep and wouldn't even "ruin" a chisel past the next sharpening.

Tapping out a chisel, anyway, gives a false sense of something done. It would be easier and more appropriate and miles less risky to lap the back of any tool needing it, and the shallow hollow doesn't really provide a great sense of what working a deeper hollow on a plane is like, either (which is also a high risk activity, anyway - I've seen several irons that were shortened to get past a crack that appeared when an iron was tapped out by someone who is experienced tapping plane irons out).

[Mike Holbrook]

Thanks again David. I will post pictures when I get it reworked. I have a DMT Dia-Flat Lapping Plate that I am testing out on regrinding the bevel. I thought about the belt sander and Trizact (low heat) sanding belts but I was still concerned about heat. The work seems to be going relatively fast on the Lapping Plate.

I was not thinking about tapping out the back of any chisel. The little I have read and seen regarding tapping out plane blades convinced me I did not even want to try it on a plane blade. I found reference to "Maintaining the Flat Backs of Chisel Blades", a short topic under sharpening in Odate's book on Japanese tools. Odate says chisels under 2" usually are not tapped out, but ground out on the uraoshi (steel plate). Odate mentions even the Japanese Shokunin (trained experts) have trouble tapping out hollowed backs, although he says he does tap out even small chisels. Apparently at the time Odate wrote his book there were commercially available mechanical hand devices for tapping. There are even pictures in his book. Odate apparently tapped against a hardwood corner with a hammer, which was not the common method, so I am not sure what he was doing is exactly what we might think of as "tapping" today. Apparently even at the time Odate's book was written Shokunin used a variety of methods for tapping and were known to ruin, crack, blades by trying to tap them out.

So it sounds like David, Stuart and Odate all agree that it is safest, especially for someone who is not an expert, to hand flatten chisel backs on stones or lapping plates, maybe a cool grinding devise. The back of the chisel I have actually seems to be in good shape. It still has some hollow in it and defined smooth edges. My only concern was whether or not a short flat area behind the tip of my chisel might weaken the edge? I think the answer is, although a short flat area might not be ideal attempting to increase it might make a small issue a big one.

[David Wong]

This past weekend, I spent a long time restoring an Ouichi 42mm bench chisel that was ground approximately 3/32" into the hollow. Since it was a wide-ish blade, my first thought was to tap it out. I remembered reading somewhere that this was ok, but I cannot remember the source. After pounding on it for more than 50 blows, I ended up lapping the back to re-establish the flat behind the edge. It seemed to me, that the hard steel layer was too thick to be "tapped out". Now of course my technique was probably not the best, but towards the end of my effort I was hammering "with authority".

I started with a #220 stone to lap the back. I tried to pay special attention to lapping mostly towards the edge, but every now and then, taking a few passes over the entire blade to prevent "steps" from forming. Here is a picture with the back honed up through my aoto (~#3K - #4K). I am sorry I did not take a before picture.

[David Weaver]

Thanks again David. I will post pictures when I get it reworked. I have a DMT Dia-Flat Lapping Plate that I am testing out on regrinding the bevel. I thought about the belt sander and Trizact (low heat) sanding belts but I was still concerned about heat. The work seems to be going relatively fast on the Lapping Plate.

I was not thinking about tapping out the back of any chisel. The little I have read and seen regarding tapping out plane blades convinced me I did not even want to try it on a plane blade. I found reference to "Maintaining the Flat Backs of Chisel Blades", a short topic under sharpening in Odate's book on Japanese tools. Odate says chisels under 2" usually are not tapped out, but ground out on the uraoshi (steel plate). Odate mentions even the Japanese Shokunin (trained experts) have trouble tapping out hollowed backs, although he says he does tap out even small chisels. Apparently at the time Odate wrote his book there were commercially available mechanical hand devices for tapping. There are even pictures in his book. Odate apparently tapped against a hardwood corner with a hammer, which was not the common method, so I am not sure what he was doing is exactly what we might think of as "tapping" today. Apparently even at the time Odate's book was written Shokunin used a variety of methods for tapping and were known to ruin, crack, blades by trying to tap them out.

So it sounds like David, Stuart and Odate all agree that it is safest, especially for someone who is not an expert, to hand flatten chisel backs on stones or lapping plates, maybe a cool grinding devise. The back of the chisel I have actually seems to be in good shape. It still has some hollow in it and defined smooth edges. My only concern was whether or not a short flat area behind the tip of my chisel might weaken the edge? I think the answer is, although a short flat area might not be ideal attempting to increase it might make things even worse.

Yeah, I wouldn't use a trizact. If it's backed by a platen, it will burn steel pretty fast. If it's not, it cuts slowly. I was thinking more along the lines of 60 or 80 grit paper with a light touch / slack belt, etc. A short flat area is fine, even if it's something like 1/2 inch. Just make sure that as you lap it if you do that, that you don't hang the chisel over the edge of the lapping plate where the middle of the hollow is over the edge of the lapping plate. The area with less steel in contact will quickly get worn and you'll end up with a back that's concave along its length, and that's bad.

[Andrew Hughes]

Looks good David, nice and square to the sides and that's a pretty piece of Doug fir one of my favorite woods.
I lost a corner couple years ago on my tasai mortise chisel. Completely my fault I choose to keep using it till I caught up to the rest of the edge from normal sharpenings.The steel is just too nice to see it wash away from the stone.with out some service.

[David Weaver]

This past weekend, I spent a long time restoring an Ouichi 42mm bench chisel that was ground approximately 3/32" into the hollow. Since it was a wide-ish blade, my first thought was to tap it out. I remembered reading somewhere that this was ok, but I cannot remember the source. After pounding on it for more than 50 blows, I ended up lapping the back to re-establish the flat behind the edge. It seemed to me, that the hard steel layer was too thick to be "tapped out". Now of course my technique was probably not the best, but towards the end of my effort I was hammering "with authority".

I started with a #220 stone to lap the back. I tried to pay special attention to lapping mostly towards the edge, but every now and then, taking a few passes over the entire blade to prevent "steps" from forming. Here is a picture with the back honed up through my aoto (~#3K - #4K). I am sorry I did not take a before picture.

Looks great to me, David!

Somewhere, I read someone say that tapping out the back (on a plane iron) requires about 5000 tiny taps. I bought an iron a long while ago (one of those $10 specials on ebay) with the intention of tapping it out, but I still haven't had to tap out the back of a plane iron - they just don't wear very fast, and like a lot of folks, having several planes and using other types a lot of the time slows the wear even more.

[David Wong]

I have tapped out plane blades on 4 occasions. For initial setups and to restore my own sharpening screw ups. I was never able to get light taps to work for me. I use a 575g hammer and an anvil I picked up at Hida tools. The force I use is the weight of the hammer plus a little wrist action thrown in. I am careful to find a spot on the anvil that gives me a dull thud sound, instead of a hollow clang.

The Douglas fir is the bottom of a chisel tray I am working on for my toolbox. The hard late wood layers make any end grain work a pain. I will sometimes use camilla oil to soften the end grain so I can pare cleanly.

[Mike Holbrook]

Odate has a picture of him tapping out a plane blade. He has the back, hollow side against the end grain corner of a large hardwood block. The corner of the block of wood appears to be shaped so that it will create the desired hollow. He is tapping the flat side of the plane blade with a small plane hammer. He says "Depending on the thickness of the blade, 20 to 30 taps should push out the hollow in the back enough to create a flat at the edge after the blade has been ground on the uraoshi, which is the next step." He provides more information on exactly how to set up the blade and where to tap it too, but too lengthy to mention here.

Great pictures David. I see that the flat area at the front of the back of your chisel is very small. Andrew it had occurred to me to leave the front bevel like it was and remove it over future sharpening. The entire bevel was in sad shape though so I decided to lap it back enough to restore a more serviceable edge generally. I gave it a rest to think about how much more to do and decided to start the thread for more info. Glad I did as I certainly have a better idea of the better options now.

[Jack Curtis]

I just got the Japanese Tataki Nomi I won at auction. It is a heavier, larger version of the typical Ore-Nomi, 30 years old but still in good shape except, there is a small piece missing from one corner of the cutting edge. It looks like I may have to grind off half the distance (1/16 - 1/8") of the remaining portion of the flat area on the back side.

As I understand how these chisels are made from Toshio Odate's book Japanese Woodworking tools, the hollow in the backs of these chisels are not ground into the blades but hammered out during forging. I am in the process of grinding a new edge and bevel in the chisel which I think is fairly straight forward. I am not sure about removing the burr and flattening the back though. I am trying to avoid any unnecessary work on the back as I do not want to abrade away any more of the hollowed area than completely necessary. I have read about tapping this area out on plane blades but do not recall having read anything regarding dealing with this same issue on a chisel?

I don't really recommend that anyone new to Japanese chisels make their first purchases on ebay, although there are a couple or three sellers who are absolutely reliable, but it takes a while to figure out who they are.

Instead, it's just dirt simple to buy a couple or three tataki from Stu, brand new, no chips or otherwise mangled hollows and edges. They probably aren't even all that much more expensive than used. And the new user gets a properly set up chisel that needs only honing. Plus, he can help recommend the proper tataki for your job.

And people wonder why so many seem to have so many problems with Japanese edges. Fairly predictable when we buy the cheapest ones we can find without knowing how to prepare them for use. Then they go out and trash Japanese edge tools. Oh, no, they can't be faster and crisper.

[David Weaver]

It would be far more prudent to actually try the chisel and see if it's acceptable than to draw conclusions that are likely untrue.

[Stanley Covington]

The hard layer of high-carbon steel is wrapped at least partway up the sides of blade on decent Japanese chisels providing necessary rigidity. Any attempt to tap out narrow blades will fail because of this. Very wide blades can be tapped out with great care as a measure of last resort.

I hit an embedded stone in some burl redwood with a wide tataki nomi once chipping it so badly that the ura would have disappeared entirely before I could have ground out the damage. The only choice was to tap it out. It worked, but I attempted it on another chisel later with disastrous results.

Realize that a chisel blade, while laminated, is structural different and typically has harder jigane than a plane blade. Tapping out will only work on very wide chisels, it must be done very carefully, and should only be attempted when destroying the chisel is no worse than leaving it as-is.

[Mike Holbrook]

I took a couple pictures to try to show the end result of my work to restore this chisel. Unfortunately I was not able to get a picture that really illustrated much. I did get the bad corner removed and did not loose as much of the leading edge as I was afraid I might. I have about 1/8" of flat surface remaining at the leading edge. The corner that needed to be ground back is not quite square with the side of the chisel, but it is hard to see the issue without an engineer's square. I plan to use this chisel to make 5/8" mortises in the legs of a workbench, so I thought I would not worry about the slight error for now. I suspect it will get sharpened a few times during my project and I will have the opportunity to square it up during that process.

The steel in the cutting edge of the chisel is very hard and it took a good while on the DMT Dia-Flat to remove enough steel to restore the edge but I think the result is a very serviceable heavy duty chisel. The chisel has the number 2, engraved both in the top side of the chisel and the handle. I think it may have been designed for use in a framing or architectural capacity. It is 11 1/4" long and quite heavy. I think it will serve me well for making mortises for bench and table legs, larger frames and carcasses. Thanks for all the good input and sorry I was not able to get an illustrative picture.