Why no secondary bevels on Japanese chisels?

Re: Why no secondary bevels on Japanese chisels?

Joel

>Easier to sharpen consistently without it.

don't have to eventually regrind the secondary bevel out of the chisel.

Re: Why no secondary bevels on Japanese chisels?

wilbur

>I guess you could just as easily ask, "Why go through the bother of trying to establish a secondary bevel?"

Here's my (probably uninformed take) on it.

With steel, the laws of nature seem to be that you can have hardness and edge durability, or chip resistance, but not both. So, you could have a chisel that takes a sharp edge and keeps the edge for a long time, but will chip easily, or a chisel that takes a sharp edge that won't chip too easily, but will need to be resharpened often.

A micro bevel has the result of strengthening the steel at the very edge of the chisel, which is one way of dealing with this issue. It also makes resharpening faster, since all you have to do is deal with the micro bevel.

But if you laminate two pieces of steel together, as in a Japanese plane, the hard steel will keep the edge, while the soft steel layer will provide the strength and support, so that the hard layer will be less likely to chip. I don't think it's a coincidence that in a Japanese chisel (or plane) the hard steel layer is relatively thin, while the soft steel layer is thicker.

Toshio Odate states in his book that a secondary bevel is a disadvantage because you'll wind up removing more of the soft layer, which leads to an increased chance of fracturing the blade when tapping out the hollow. During the tapping out process, the soft layer distributes the force of the hammer taps. With a thinner soft layer, the hard layer is more prone to fracture during this process.

Re: Why no secondary bevels on Japanese chisels?

Pam Niedermayer - Austin, TX

>Basically, what Wilbur and Joel said, and because a secondary bevel leaves the edge steel hanging all on its own without sufficient soft steel support.

Pam

Re: Why no secondary bevels on Japanese chisels?

Warren in Lancaster, PA

>I think I was rereading Odate while you were posting, Wilbur. He mentions that sometimes you want to ride on the bevel while you work, not so good with a bevel that is somewhat convex.

He also mentions the idea that the wide flat bevel makes it easier to hold a consistant angle on all the stones. If you maintain your tools entirely without grinding or jigs as I do and I think the traditional Japanese does, then I think a flat bevel is the most accurate and efficient (there are tools that I've used for more than 30 years without ever grinding).

I always use the same routine and spend not much more time on the 800 stone than it takes to set up a jig. This is the coarsest stone I use. I think when you do not use a jig, you can use a much larger surface of the stone, keeping it flatter. Odate says "Commonly, 1200X is coarse enough to hone dull blades, so if it does not seem to be, perhaps you went too long without sharpening." He is talking about honing the entire bevel, not just a narrow strip.

There are plenty of workers who get fine results with grind and freehand or grind and jig. The system I use demands consistant sharpening and a practiced hand to work well.

Re: Why no secondary bevels on Japanese chisels?

ThomD

>"The idea that a secondary bevel will eat faster into the chisel and lead into the hollow in the back doesn't fly logically."

I don't know for sure that I know what you mean here exactly. I do have a theory that the Japanese blade is designed to be more or less as easy to sharpen one side as the other. The theoretical reason published for the hollows has often been that it made the chisels easier to flatten. For a variety of reasons, this is not fully satisfying/true (we could go into that separately). A better reason would be one that contributed to the tool being better in use, not merely set-up. My take on that is that the hollowed back comes up while sharpening roughly as fast as the front, the front is smaller, but has some iron, and the back is larger but not much surface area. I'm not claiming an exact 1-1 ratio, but on a western tool it might be 1000-1, so at least we are a lot closer with the hollows. What that means is that one can establish a routine of maintenance, of working similar amounts on each side so that the geometry remains clean, and the polish comes up equally, stone wear is better. If you accept that position, or any other starting point that says that the blade has been optimized for correct use from the beginning then obviously the micro bevel will generally be a bad idea.

Re: Why no secondary bevels on Japanese chisels?

Dave Burnard

>"He mentions that sometimes you want to ride on the bevel while you work, not so good with a bevel that is somewhat convex"

I often do this when morticing, letting my chisel "ride on the bevel". Not gonna work with a secondary bevel.

I don't understand the use of secondary bevels in the first place. ;) But that's just me. I always figured secondary bevels were a shortcut invented with solid steel chisels in mind, where it takes longer to sharpen because the whole bevel is hardened - unlike on a laminated chisel?

So maybe in a pinch if you run into some nasty wood and want to quickly steepen up your normal bevel angle, but not as a regular practice.

Re: Why no secondary bevels on Japanese chisels?

ThomD

>I can say from experience in hardwood, that lack of iron support isn't any problem. I have a set done in the Krenov style (yuck, I was being experimental, they do work great though) where the bevel is really ground away and there is a tiny micro bevel, and they don't break as long as they are not pried. Perception wise though, youa re probably right on.

Picking up on a separate point, Odate seems to have mostly believed one shouldn't tap out chisels (p155 hadback edition from '84). I have seen sets that had been tapped out, where they look flat front and back and the center in a missing line. So it isn't black and white, but if you aren't tapping then this isn't a problem either.

Terminology?

Wiley Horne

>Denis,

Some of the respondents are speaking to secondary bevel being a steeper facet at the bottom of the primary bevel. Others are speaking to hollow grinding. Which were you asking about?

Wiley

Re: Terminology?

Denis Ch�nard, Orl�ans, Ont.

>I'm talking about a "steeper facet at the bottom of the primary bevel". No hollow grind.

Thnx,

DC

Re: Why no secondary bevels on Japanese chisels?

Pam Niedermayer - Austin, TX

>I don't understand the use of secondary bevels in the first place.

Me, neither, except in strengthening a heavy duty chisel for things like plane mouth mortising.

Pam

Yabut...

Denis Ch�nard, Orl�ans, Ont.

>Your statement doesn't refer to Japanese chisels per se, what you say is applicable to all chisels.

What would make a Japanese chisel different?

DC

Yes. Why not? *LINK*

Friedrich Kollenrott

>in my opinion, there is absolutely no reason not to apply a secondary bevel to any chisel, whether european or japanese style. I don't see any disadvantages.

I grind the bevel (freehand on a 800 grid waterstoone) at 25 degrees, then hone (freehand on a 8000 grid waterstone)a 30 degrees secondary bevel. These are the angles on any kind of standard chisels, the heavy duty ones like mortise chisels get 30/35 degrees.

Advantages are: Firstly, honing the bevel is done in just a few seconds. Five strokes for the secondary bevel, then five for the back, then three for the secondary bevel again and three for the back. Overall time: say thirty seonds. Secondly, the quality of the narrow secondary bevel is remarkably good which means you get a perfectly sharp edge.

As for japanese chisels: Their hollow back is easily kept in good, scratch- free condition, far easier than the overall flat back of western type ones. A well honed secondary bevel harmonizes perfectly.

There ist not more loss of tool length per sharpenig compared to the entire-bevel-honig. And I do not see a lack of edge support.

Me, I haven't sharpened any chisel or straight plane blade without a secondary bevel for years.

Just my two (Euro-)cents. If You are interested, look at my sharpenig totorial (see link). Sorry, its not in English.

Friedrich Kollenrott, Extertal (Germany)


http://www.woodworking.de/schaerfprojekt/schaerf2.html

Re: Why no secondary bevels on Japanese chisels?

paul womack

>I don't understand the use of secondary bevels in the first place.

The secondary bevel can be worked with REALLY coarse abarasives.

This means that the primary (or "actual" bevel) is small, and can be honed (more) quickly.

(other pros and cons are mentioned in this thread, so I won't repeat them).

BugBear

My bad...

Pam Niedermayer - Austin, TX

>First, as Wiley says, I completely misread the question, but I basically agree with Dave on the real question, I don't see that the advantages of microbevels, secondary bevels, or back bevels outweigh the ostensible benefits.

Thom, I've heard repeatedly that one shouldn't tap out chisels and it makes very little sense to me, probably because I'm too ignorant to believe it, so I'll quote Dave, a true authority in his June 2004 response to my question about the hollow being essentially a repository of hard steel:

For a plane blade you essentially do treat the hollow back as a "repository" of edge steel. You try to avoid flattening the back of the blade much and so end up tapping the hollow out to form the new cutting edge for the life of the blade. Is that what you meant? For a chisel I tend to use that repository only when I need to correct a small problem. We all find out that you can't move it very far or very fast without cracking in the hard steel - and the crack is usually far worse than whatever problem the tool started out with (DAMHIKT). It is amazing how much metal you can move, but sometimes there are unpleasant surprises.

Pam

Re: Yabut...

joel -( tools for working wood)

>I am reffering to Japanese chisels. On western chisels a true microbevel allows you to stregthen the chisel but keep a very very low effective angle. by microbevel I mean a flat about .005 across that is removed with every sharpening. But with Japanese chisls which are typecially at a higher angle to begin with the extra strength isn't important.

Clarification (long)

Wiley Horne

>Pam and all,

I had to go back and ask Denis for clarification because I really wasn't sure.

Coupla thoughts on the tapping out matter, and this is just by way of sorting the thing out.

Thought 1. On tapping out chisels....There is a problem with being dogmatic--either yea or nay--on the question of whether chisels should be tapped out. As with so many handtool matters, it all depends. Now in my case, the hollow recedes steadily enough in the course of ordinary sharpening that I don't need to tap out. My anecdotal conversations with several others tells me that it is the same for them. Now if we _were_ to tap out, then instead of maintaining a land at the rear edge, we would actually be growing it and filling in the hollow unnecessarily. Which is not good; you want the hollow. So we only tap out chisels if there is a big chip which requires grinding back into or close to the hollow, and fixing that chip requires reestablishing the land.

On the other hand, if other folks actually need to tap out in order to keep the blade edge out of the hollow, then of course they must do it.

2. Tapping out plane blades. This is a different situation. On a chisel, maintaining a flat back is good. But you don't flatten a Japanese plane blade back--as Dave B. mentions in the quote. The back of a Japanese plane blade is made slightly concave--on purpose. I have mic'ed a half dozen Mosaku, Funahiro, and Ishida plane blades and found that there is consistently a 2 to 4 thousandths amplitude curve in the length of the hard steel back. This curve has a function: As the blade is tapped into the dai, it becomes sprung in the abutments. This is why Japanese planes work well without a subblade--the blade is perfectly secure because it is sprung. You only need the subblade to pretension the main blade edge so it won't deflect under heavy cuts; for finishing cuts the subblade is not usually needed.

Now if the back of the plane blade were to be flattened, you would lose fit in the dai--the blade would get loose. This is why it is always advised to flatten a Japanese plane blade only at the edge--to maintain the curve of the back.

In addition, the hollow on a Japanese plane blade is deeper than on a chisel, and normal flattening of the 1/8" of land on the backside of the blade will not make the hollow recede. So as we sharpen, the plane blade _must_ be tapped out or else the edge will creep back into the hollow.

The above is not to challenge anyone. Just trying to sort a few things out.

Wiley

Thanks, Friedrich

Tom Colligan

>

Re: Clarification (long)

Dave Burnard

>Tapping out a chisel so often/severely that the land on the chisel actually grows so large that it significantly reduces the hollow? You might move the lamination line of the chisel below the plane of the back too, but more likely you'll just crack the chisel.

"So we only tap out chisels if there is a big chip which requires grinding back into or close to the hollow, and fixing that chip requires reestablishing the land."

I'll add "or a significant deformation at the edge" which can happen with large chisels that get hit really hard, say in timberframing. Faster for me to tap out near the deformation when the deformation is away from the back than flatten out the entire remainder of the back of the chisel.

I believe the tapered groove and friction fit underside of the blade are doing most of the work securing the blade

The heel to toe blade curvature varies quite a bit in the new blades I've looked at. From none at all up to 20 thousandths! I can see this might contribute towards securing the blade (when it exists) but the tendency would be for the ears of the blade to scrape away the groove to match the curvature as the blade is hammered into the dai. I've watched that happen. Reflattening after tapping out, especially on a kanaban with SC powder will also remove it. Hmmm. I wonder if the variations in curvature may come from the processes used to create the rough hollow prior to grinding it clean and pretty. I'll ask more about it's purpose and variation when I'm over there again in May.

Clarifying the clarification

Wiley Horne

>Hi Dave,

I made no mention of tapping out severely etc etc., and that is not what I meant either. What I said was that, for many including myself, the land at the cutting edge is well-maintained by ordinary sharpening alone. Just normal backing off. This is on Imai, Funahiro, and Tasai chisels. If, in addition, I were to tap out--any tapping out at all, moving any amount of metal--it could only result in moving more metal than needed out of the repository (hollow) and creating a larger than necessary land.

The 'significant deformation' occurring away from the edge, or at the edge for that matter, is very informative. And as I said, if there is a need to tap out, then tap out. It's situational.

I have heard heated arguments between experts on the origin of the curvature. The most convincing to me was that it occurs in the first place during the quench. But I personally know only what I have inspected by feeler gauge. Would love to hear Yataiki-san's take on it, if you are able to share that at some point.

Wiley

Regarding the tapered groove and friction fit in the abutments...Yes of course this is right. But there is an interaction with the curvature of the blade. The dai abutments are cut to fit the original state of the blade, which is curved in its length. I pulled out 6 blades--3 Mosaku, 1 Funahiro, and 2 Ishida--and they all had curvature in the same magnitude, a few thousands (by feeler gauge). If the curvature is larger on other blades, OK, but the point remains the same: The blade is sprung in the dai by this curvature. If the user later flattens the back over the extent of the cutting steel (removing the curvature) then the blade will be looser by a few thousandths, i.e., there would be a loss of fit, and you will now be relying more on the subblade to hold the main blade in place. I thought this is what you were referring to in the quote that Pam included above (when you said not to flatten plane blade backs). I don't need to tell you that a number of folks use their Japanese planes without the subblade at all, especially for finishing cuts. So in a well-set-up Japanese plane, the blade is sprung in the dai, and held securely by the fit of the wood acting against the sprung blade.

Re: reclarifying the clarification

Dave Burnard

>The land is well maintained by ordinary sharpening for me too on all sorts of chisels, until something out of the ordinary happens - chip, deformation, etc. Then I think, and YMMV, that it's faster to tap out than to do all the sharpening necessary to restore the land and or flatten it. I think what I originally said was along the lines of - don't tap out unless you need to, and you want to, it's a handy alternative. Maybe revisionist history has clouded my memory, or it appeared I was suggesting routine chisel back flattening be replaced by tapping out. That was not my intent.

Wiley got the essence of my significant deformation picture, but for others I was referring to deforming some portion of the edge, up and away from the plane of the flat back of the chisel - say if one corner was bent up out of alignment. It's rare but even in a hollow backed 48mm timber chisel there's a lot of metal to remove from everywhere but that one corner to get it back into alignment again - and a lot of unnecessary land would be created. So I tapped it back down into alignment instead. Reflattening the back would have worked too. If the corner had bent down instead - tapping out would not have been an option - and I would have reflattened the back, focusing pressure on the corner to return it to the plane of the back.

Wiley, the plane blade curvature discussion is very interesting to me, unfortunately I don't have the time at the moment to hold up my end of the conversation properly. I hope we can continue it offline at a more leisurely pace and one of us can report back if we come up with anything more to add to the general understanding. Sound reasonable? If not, carry on by all means, I'll be rooting from the sidelines.

Question

Denis Ch�nard, Orl�ans, Ont.

>Thanks for all the insight...

But one question remains (for me at least): how do you tap down the edge (or part of it)? I figure you use a hammer (what kind?), but do you put the chisel on a piece of wood, an anvil, anything else? Since we're talking hard steel here I wouldn't want to do something stupid if I ever need to do this...

Thnx,

DC

Dave, thank you for your patience and

Wiley Horne

>for so freely sharing your deep knowledge of Japanese tools and methods.

Wiley

Re: Question

wilbur

>You put the chisel or plane blade on an anvil. One trick is to put a sheet of lead, which is soft, so as to provide the most closely fitting support for your tool. Then you tap at the top of the bevel on the soft iron layer. Not too hard -- about the same force you would use to drive a finish nail into pine.

Re: Question

Denis Ch�nard, Orl�ans, Ont.

>Gotta say it does sound like a scary proposition on a $200 chisel...

DC