Sharpening Japanese chisels - the irritating part

Re: Ten minutes "moves" hollow 3 mm

Pam Niedermayer - Austin, TX

>But if you take off a bit more metal on the edge, even if the back somehow, by magic, stays flat, won't the thickness of the blade be diminished?

Pam

Re: Ten minutes "moves" hollow 3 mm

Frank D. in Montreal

>Yes it will, but much more so toward the cutting edge (and almost not at all at the heel), so the hollow at the rear end of the blade will be preserved because you're not lapping it out.

Hard to explain...my chisel vocab. isn't the best...

Re: Ten minutes "moves" hollow 3 mm

Pam Niedermayer - Austin, TX

>I understand, Frank, truly. I just think you're all cracked. :)

Just kidding.

Pam

:)

Frank D. in Montreal

>

Re: Ten minutes "moves" hollow 3 mm

Dave Burnard

>Nothing wrong with this technique. Traditionally it might have been a little faster to do on one of those kanaban soft iron plates with powdered grit added that are often used traditionally to (re)flatten the backs of tools. I'd rather just use a waterstone, never cared much for loose grit sharpening.

I effectively do the same thing when flattening the back during routine sharpening, but only use my middle and polishing stones when I can get away with it. The hollow still retreats more slowly than the bevel eats into the land. When they meet on a large chisel or a favorite one I choose to spend my ten minutes tapping out. Call it a personal preference.

Tapping out a chisel is always inherently riskier than just reflattening. Good sharpening is intimidating enough for newcomers without having to worry about cracking their $50 chisel about the time they've figured out how to sharpen it well. I don't recommend that everyone learn to tap out their chisels, even though the smiths in Japan could sell a lot more chisels that way. ;) Just wanted to point out that there is another way to solve the "running out of land (the flat part between the hollow and the edge)" problem that isn't very obvious, or mentioned much in the west as applied to anything other than plane blades. (Hey is this nut saying you could similarly tap out kogatana, single bevel kitchen knives, carving tools, anything with an ura-side hollow? Yup, that's what I'm saying.)

I don't think the effect is a practical issue, but preferentially flattening a chisel back this way (I do it too) even though the entire back stays planar - will cumulatively affect the geometry of the chisel. Might be good since it would eventually elevate the handle a bit which might make paring easier. Or, it might be less than optimal for a striking chisel to have the handle go out of line with the chisel back. One could simulate or correct either by just bending the iron shank a little one way or the other. Theoreticallly if one never worked the back of the chisel near the shank, then when the chisel got really short the geometry offset could be pretty extreme, but in practice you just wouldn't let this happen. I haven't heard or registered any complaints about this so the everyday effects are likely just not noticeable.

Re: Ten minutes "moves" hollow 3 mm

david charlesworth

>There are only two methods of moving the hollow.

Tapping out or hard steel removal.

The removal can either be done a little at every sharpening or every year or two!

Rate of hard metal removal is a function of pressure on stone, so heavy at the bevel and light near the shaft does slope the back very very slightly.

If you do not slope, the hollow is likely to be lost long before the chisel gets short?

Buying a soft steel plate & grits today!

best wishes,

David Charlesworth

Re: Ten minutes "moves" hollow 3 mm

paul womack

>Tapping out a chisel is always inherently riskier than just reflattening. Good sharpening is intimidating enough for newcomers without having to worry about cracking their $50 chisel about the time they've figured out how to sharpen it well. I don't recommend that everyone learn to tap out their chisels, even though the smiths in Japan could sell a lot more chisels that way. ;)

I seem to remember Odate illustrating a "tapping jig".

On a loosely related note, it always amuses me to be told (repeatedly, and with emphasis) about the pragmatic and highly skilled Japanese craftsman always sharpening by hand.

Every report I've seen of a planing contest (Kezurou-Kai) where Japanese competitors are present mentions their use of jigs, either commercial or self-made.

BugBeae

Re: Ten minutes "moves" hollow 3 mm

Pam Niedermayer - Austin, TX

>Many have said the hollow is there only to make sharpening easier. Therefore, what's the worst that can happen if/when the hollow disappears? I say it takes a little more work to sharpen, nothing more, so there should be no problem using a chisel right up to the shannk as long as the tool steep is still present. What's wrong with this picture?

Have fun with your plate and grits.

Pam

Re: Ten minutes "moves" hollow 3 mm

Miles

>Tapping out could presumably leave some additional tensile stress on the lower surface of the chisel, where the steel has been distorted by the blows to bring it down to the target level. It is probably only a small distortion, but if the steel is hard, the stress associated may be large. This is the opposite of what happens in prestressed beams etc where a stress is engineered in to oppose the normal load in use.

I would wonder about the risk of promoting edge fracture when tapping out, as the resulting stresses in the lower surface should be tending to promote cracking at any scratch or grain boundary.

There's a reason why annealing is important after forging (or hardening) - I'm not a metallurgist, though, and it would be interesting to see if any here can comment.

I'd go with grinding, myself, to get that hollow moved back. The comments above about tapping helping to sell more chisels does rather suggest that it is a risky approach, and I cannot see any significant advantage.

Miles

Re: Ten minutes "moves" hollow 3 mm

Dave Burnard

>"Every report I've seen of a planing contest (Kezurou-Kai) where Japanese competitors are present mentions their use of jigs, either commercial or self-made."

Remember who most of those competitors are though - amateur woodworkers like us looking for an "edge". So they're using all sorts of things including stereo microscopes, etc. When you visit a real craftsman, you'll rarely see sharpening jigs. You see some amazing natural stones, too.

Re: Ten minutes "moves" hollow 3 mm

Dave Burnard

>One thing to remember is that when your plane blade or chisel arrives new, it is often in this "tapped out" state. Fairly safe to say that all japanese plane blades arrive this way (and are maintained this way throughout their lifetime). Laminated tools in general tend to warp a bit during heat treatment and they are straightened cold, essentially by tapping out. A fair number of chisels also get trued up by tapping out during the factory sharpening.

OK, I promise I'll never mention tapping out a chisel again. ;) (Unless I'm talking to tool makers)

Re: Ten minutes "moves" hollow 3 mm

Dave Burnard

>Let us know what you think of the iron plate with carborundum powder.

For those who don't know, it came into being back before diamond stones, diamond pastes, or even decent coarse sharpening stones. The key being that the lapping plate stays flat as the abrasive wears away.

Re: Sharpening Japanese chisels - lifespan?

thomd

>I have to confess that I have so many different chisels sets, I am unlikely to really wear any of them out. Not a boast, not really the best way to go, but a bit of curiosity combined with having started all this early enough I couldn't afford to buy the best, and that's where I am.

I did have this Ouchii chisel with ebony handle and about a 1.25" blade, that I left out on a bench when some guys came to remove an oil furnace. They used it as a cold chisel and chipped it badly, and I rehabed it by taping it out. Not only would I have lost a lot of the hollow and affected sharpening, but I would have had a more shrunken looking chisel if I hadn't tapped it out.

I do have a couple of anvils, still, with or without one, tapping out blades is not difficult. It surprises me that it seems to be the kind of thing that takes less force than one would imagine rather than way more. Which means control isn't such an issue.

Re: Ten minutes "moves" hollow 3 mm

Frank D. in Montreal

>Dave,

I'm glad you brought it up. I like to make tools amd I'm settimg up my own forge right now, although I'd never call myself a "tool maker". While there is a lot of great info on metallurgy and forge work as well as forges, I've never seen much on tapping out or cold work on hardened steel. Would you have a link of some sort with any info on this?

Re: Ten minutes "moves" hollow 3 mm

david charlesworth

>Dave,

I wish the chisels which I have bought over the last 25 years or so had been correctly tapped out!

Large bellies in the length of the back have been present in at least 30% I would estimate. Small belly in most of the rest. Are the badly ground and prepared 'seconds' dumped on unsuspecting craftsmen in the west, like the unsuitable Macassar handles on striking chisels?

The oddest to me was a reasonably expensive Suminagashi one from Nishiki, as sold by Dick fine tools.

We have also had long paring chisels from Iyoroi, not too expensive, where there was clearly stored tension. As the belly is honed away the chisel curls more, resulting in a huge amount of work and complete loss of hollow. I have stopped buying Iyoroi long paring chisels as a result and find Koyamaichi to be much better but about double the price.

As Pam says, completge loss of hollow is not the end of the world but it is irritating and should be unnecessary. A huge amount of work. I believe Japanese craftsmen prefer to maintain it.

As well as tapping the soft area of bevel, how do you rate the chance of tapping along the back, to stretch metal and remove belly?

This technique was posted by a woodworker on UK forum.

best wishes,

David

Re: Ten minutes "moves" hollow 3 mm

Dave Burnard

>Thanks Frank,

I've never found much useful information about it on the web or in print either. I've learned by watching various japanese smiths doing it, at first just by watching videos, but now more by watching in person and then having to do it myself. It's called "hizumi tori", which translates as "to remove distortion". First scrounge yourself something to use as a wooden anvil.

Email me offline if you have other questions.

Re: Ten minutes "moves" hollow 3 mm

Pam Niedermayer - Austin, TX

>OK, I promise I'll never mention tapping out a chisel again. ;) (Unless I'm talking to tool makers)

Geesh, Dave, I wish you'd talk about it more. Then I won't get so admonished every time I talk about it. :)

Pam

Re: Ten minutes "moves" hollow 3 mm

Dave Burnard

>David,

I don't think the toolmakers are quietly dumping their seconds on unsuspecting wholesalers or dealers, rather I suspect some dealers offering bargain prices are selling seconds without saying so. Or thinking of their market, they just import the seconds because it keeps the price down. I suppose it's possible that some funny business goes on when small US dealers deal with wholesalers in Japan. The best solution is to send it back so someone on one or both ends of the transaction gets the message. Sometimes you wait so long for the tool, it is easier just to deal with it...

For plane dai's it's the same thing - ebony dais? Even the daimakers will say that most of their red oak dai's are shipped to collectors or the American market. At the *customers* request. I think the same thing is happening with ebony handled striking chisels - they look great in your catalog, even though it's not a good choice for that type of chisel.

If the chisel back is convex (bellied out) you can straighten it. However if the chisel back is concave you can't very safely straighten it (sometimes you get lucky - depends on how soft the tool was tempered, etc.)

Convex (belly out) curvature is a natural distortion that happens when a laminated tool is hardened, so possibly the maker didn't get it all out in the first place, or it changed during sharpening as you noticed it can. If the maker can wait long enough the curvature created during hardening will often relax at least partially by itself. Since the curve can relax on it's own, concave curvature can sometimes happen if you don't wait long enough after hardening before straightening, a day or two is typically enough, but for some old hard steels Yataiki likes to wait at least a year!

On an (improvised) wooden anvil you place the tool iron side down and hit the steel back of the chisel. You do this with a flat faced steel hammer, which still makes me cringe, but does work. I've also seen it done with a small piece of wood, like a stubby chisel handle, being struck with the hammer (I'd need three hands for this). I suppose the western equivalent would be a rawhide hammer or wooden faced hammer. You have to hit pretty hard, but proceed fairly slowly so you don't overshoot. If the bend is localized - that's where you hit. If it's spread out, that's what you need to do. Failure is pretty expensive by the time you pay retail for a chisel - so proceed with caution. If you've learned to tap out plane blades then this is ultimately the same process applied on a larger scale.

Good Luck!

(The author will not be responsible for broken or cracked tools that occur as the result of someone reading this post and trying the techniques described above. Even in the best of curcumstances life is a gamble, you spin the wheel and you take your chances. There is no such thing as a free lunch. This is not a flying toy.)

Dave, thank you very much;-) NM

david charlesworth

>

Dave, thank you so much

Wiley Horne

>for this most informative thread, and especially the post just above regarding the cold working of forged laminated blades.

Perhaps you or Mike Wenzloff, if he happens by, could post photos here of your recent work.

Wiley