should i avoid using a grinding wheel on Japanese chisels

[Phil Pascoe]

Down to misquotes now?

 

[woodbrains]

Hello,

For the same effective cutting angle, convexity must remove steel behind the cutting tip, exactly where it is required in a Japanese tool. If we are being true to the nature of the tools. Jacob's rounding under method relies on the fact, otherwise the cutting angle would increase; a condition that he denies happens in his tools. The soft backing steel is there for a purpose, so removing it defeats the object.

Hollow grinding, if one measures the angle the tool makes with the stone, also removes steel in the supporting area, though it should be noted that this will produce an angle on the tool somewhat lower than measured at the tool rest. A bit of experimentation will correct the tool angle and results in more steel in the tools bevel.

Mike

 

[James-1986]

Hello,

Japanese chisels and plane irons are not HSS (there are a few modern and not particularly good exceptions) and the steel is much harder and more brittle than spindle knives etc. so the comparison does not hold up. The softer back of Japanese tools is meant to support the very hard steel cutting edge and should be honed with a flat single bevel to maximise strength.

Mike.

Seems like a good comparison to me, hard metal laminated onto soft metal! Decent HSS is 60 to 65 on the rockwell scale so hardly soft, and you know when you have a hard bit as glue lines etc don't chip it. How much hardness increases as the numbers go up on that scale I don't know. I also have a big pair of blank moulder knives which are TCT laminated to tool steel which are hollow ground, harder than white steel. Its hard to say which is more brittle unless you know the exact blend.

As the tool has a bevel on the end, the softer steel is no where near the cutting edge to support it anyway. Unless we're talking about a big chunk snapping off?!

 

[richarnold]

Hi Toby.
If this helps I have been using Japanese chisels on a daily basis for over 30 years, and have always ground them (carefully) on a 6" bench grinder, and have never had any problems. I do grind all the way to the edge. One important thing for me is to be constantly dressing the grind stone. This is a great help in keeping the heat down.
Cheers, Richard.

 

[woodbrains]

Seems like a good comparison to me, hard metal laminated onto soft metal! Decent HSS is 60 to 65 on the rockwell scale so hardly soft, and you know when you have a hard bit as glue lines etc don't chip it. How much hardness increases as the numbers go up on that scale I don't know. I also have a big pair of blank moulder knives which are TCT laminated to tool steel which are hollow ground, harder than white steel. Its hard to say which is more brittle unless you know the exact blend.

As the tool has a bevel on the end, the softer steel is no where near the cutting edge to support it anyway. Unless we're talking about a big chunk snapping off?!

Hello,

There is a difference between hardness, brittleness, toughness, wear resistance etc, etc. also, HSS is resistant to losing its temper during grinding; high carbon, low alloy steels are not. There is little in common with machine knives and handtools, even grinding angles are different. Planer knives might be 35 degrees, japanese tools less than 25 . The comparison is really non existent.

Regarding the backing steel being nowhere near the edge in Japanese tools, we have to consider the ura, which makes the hard steel much thinner and needs the support of the softer backing, and the shock absorbing effect of the whole mass of the thing, which damps vibration at the tool tip preventing micro fractures that lead to edge failure. It is a complex system, that, if we choose to deviate from prescribed methods of use, can lead to disappointment, or at least a compromise should be expected. Frankly, it is no hardship,just following tradition, and preparing the bevels flat, or as close to flat as humanly possible and enjoying the tools and methods for what they are.

Mike.

 

[Jacob]

Hello,

For the same effective cutting angle, convexity must remove steel behind the cutting tip, exactly where it is required in a Japanese tool. If we are being true to the nature of the tools. Jacob's rounding under method relies on the fact, otherwise the cutting angle would increase; a condition that he denies happens in his tools. The soft backing steel is there for a purpose, so removing it defeats the object.

Hollow grinding, if one measures the angle the tool makes with the stone, also removes steel in the supporting area, though it should be noted that this will produce an angle on the tool somewhat lower than measured at the tool rest. A bit of experimentation will correct the tool angle and results in more steel in the tools bevel.

Mike

You don't seem to understand what I'm saying Mike. Steel is required behind the edge in any tool, not just the Japs. The slightly convex bevel which is the accidental result of my lazy but quick sharpening will remove steel from the heel of the bevel to some extent. Better than hollow ground where the tool is thinned nearer to the edge..

 

[David C]

I have never found a problem with hollow grind, Though Tormek has 10" wheel so hollow not very great.

I can't remember a faliure in use in the last 35 years

David

 

[G S Haydon]

"Hello,

There is a difference between hardness, brittleness, toughness, wear resistance etc, etc. also, HSS is resistant to losing its temper during grinding; high carbon, low alloy steels are not. There is little in common with machine knives and handtools, even grinding angles are different. Planer knives might be 35 degrees, japanese tools less than 25 . The comparison is really non existent."

but not so long ago we were discussing where we were discussing edges we said

"I still don't see why a spindle cutter will dull any differently than anything else. Perhaps a variation in degree, but a completely different mechanism altogether is not likely. Micro fractures in the grain structure of metals exist, the wood is the same, the colossal forces at the cutter tip are of similar order. Why do we feel that hand tools will behave differently? And if so, someone else prove it, I have read what I have read."

I hate to be a "tool" and mention the above but sometimes we all make this a heap more confusing than it needs to be (or quite possibly I'm to dim to keep up ). Mike, I like your posts a lot so forgive me if this seems personal, it was just an example.

I think Richard Jones has good take on the situation and I don't think Jacob has any issue with maining angles with a rounded bevel. I'll hold my hands up and say I was less than convinced his was the most legit way but that's the problem. Thinking something has to be "legit" and relying only on the text and not on experience at the coal face. Equally Mike your approach is proven and works. The only evidence required is how skilled folks get results. What we can take from this thread is that Japanese Chisels can be hollow ground, flat ground, secondary bevelled or convexed and still turn out great work!

 

[Trafalgar]

The more interesting question is why Japanese craftsmen are so utterly opposed to hollow grinding.

"I've done it and I don't think I broke anything...," far less interesting.

It may be that there is no real reason, but that in itself conveys a lot and might inform how we interpret other 'edicts' (codswallop?) from the Asian traditions.

Is it possible to demonstrate 1) a perfectly flat bevel 2) and whether it cuts better than any other kind of bevel.

I personally doubt it but have no dog in the fight, per se, since I don't own or plan to own Japanese tools in the future.

 

[woodbrains]

"Hello,

There is a difference between hardness, brittleness, toughness, wear resistance etc, etc. also, HSS is resistant to losing its temper during grinding; high carbon, low alloy steels are not. There is little in common with machine knives and handtools, even grinding angles are different. Planer knives might be 35 degrees, japanese tools less than 25 . The comparison is really non existent."

but not so long ago we were discussing where we were discussing edges we said

"I still don't see why a spindle cutter will dull any differently than anything else. Perhaps a variation in degree, but a completely different mechanism altogether is not likely. Micro fractures in the grain structure of metals exist, the wood is the same, the colossal forces at the cutter tip are of similar order. Why do we feel that hand tools will behave differently? And if so, someone else prove it, I have read what I have read."

I hate to be a "tool" and mention the above but sometimes we all make this a heap more confusing than it needs to be (or quite possibly I'm to dim to keep up ). Mike, I like your posts a lot so forgive me if this seems personal, it was just an example.

I think Richard Jones has good take on the situation and I don't think Jacob has any issue with maining angles with a rounded bevel. I'll hold my hands up and say I was less than convinced his was the most legit way but that's the problem. Thinking something has to be "legit" and relying only on the text and not on experience at the coal face. Equally Mike your approach is proven and works. The only evidence required is how skilled folks get results. What we can take from this thread is that Japanese Chisels can be hollow ground, flat ground, secondary bevelled or convexed and still turn out great work!

Hello,

We were talking about abrasion in this instance though. And if I recall, I did not introduce the comparison between edge tools and machine knives, here, either. If I recall it was the contention someone had that machine tools somehow remove more material in a single pass (3mm is often quoted as max material removed) whereas I was proposing tht machines remove similar thickness chips to hand tools, to a thickness of 3 mm. It was also about power required to push tools compared to the power of machines. There is little context between these 2 threads, and it would get too complicated explaining the differences here.

So now Jacob is not intentionally arm flapping to get a convex bevel anymore, but accidentally doing it whilst trying to hone a flat? His bitchin all these years about rounding under has just disappeared into the ether then! Is it because he cannot find all those rounded bevels on Japanese tools he keeps promising us exist.

Mike.

 

[G S Haydon]

Hi Mike, you are of course right, there was an epic amount of context here and on the other thread

I do agree with you that from what little I know it is a tradition that Japanese tools have a "flat bevel" and again with what little I know the tradition with Western is pretty much Primary & Secondary. However it's clear that a bunch of other methods work and work well including a bit of convex and they will work on both Japanese & Western tools. Folks can split hairs on best if they feel so inclined but as long as he edge is good enough for the task at hand why worry?

 

[Jacob]

....
So now Jacob is not intentionally arm flapping to get a convex bevel anymore, but accidentally doing it whilst trying to hone a flat? His bitchin all these years about rounding under has just disappeared into the ether then! ....

You just don't pay attention Mike.
I've been saying over and over again right from the beginning that there is no value in a rounded bevel as such - it's just that if you don't struggle for perfect flatness you can do a relaxed and speedy form of hand sharpening which incidentally results in a rounded bevel but can be repeated indefinitely without having to reshape the bevel with grinding. Happy Christmas!

 

[gwr]

http://www.oobject.com/12-knife-bikes/a ... nder/4444/

Anyone of these will do the job and some even on your way to work ccasion5:

 

[Derek Cohen (Perth Oz)]

I have never found a problem with hollow grind, Though Tormek has 10" wheel so hollow not very great.

I can't remember a faliure in use in the last 35 years

David

Absolutely.

The OP asks whether a Japanese laminated blade can be hollow ground ..... and we get a bunch of responses that go off on a hobby horse .... what's new?! :lol:

The fact is that a Tormek is perfect for hollow grinding laminated blades as the hollow is shallow and the steel does not overheat. I have done this for years. As David notes, there is no weakening of the edge due to the removal of "backing" iron. I cannot recall a Japanese chisel chipping or breaking as a result of a hollow grind (which I do to the very edge of the blade).

Keep in mind that Japanese chisels are, by the nature of use with a gennou, constantly testing the durability of a hollow grind. What they have proved for me without a shadow of doubt is the effectiveness and reliability of a hollow grind. I am not saying this to convince others that hollow is the best way to sharpen - what ever floats your boat - but it is the way for me.

Regards from Perth

Derek

Edit: Here's link to another David ... http://www.finefurnituremaker.com/news/ ... s-year-49/

 

[sdjp]

The more interesting question is why Japanese craftsmen are so utterly opposed to hollow grinding.

I don't know, but I have a theory; and it's (partly) the same reason they use waterstones, not oilstones.

Firstly, I note that the Japanese have a much stronger history of deferring to tradition then any other cultural groups. Therefore, it requires something to be 'better', to some standard, to effect a noticeable shift - and without that, there will be a strong pointer to keep doing the same. I therefore submit that a historical answer would suffice.

Japan was a metal poor country - in addition to there not being much ore, it was what would have been called 'poor quality' in other places, needing a lot of work to get a good steel. So there was a lot more labour involved in making the tools, hence expensive. Thus using a sharpening process that's slower, but less likely to damage the tool (through overheating) fits with that. Also, the tradition of using them was a bit more 'respectful' of the tools - you were really really not supposed ding the cutting edge; hence less grinding needed to keep them good.

In a counterpart to that; consider the materials that were used for sharpening. Most of the good naturally occurring stones in Japan were softer than western ones, and this leads to two separate effects. Firstly, they are faster cutting - so the point at which you'd want more mechanical assistance is larger. Secondly, these softer stones are not quite as strong - meaning that for a naturally occurring stone, you face two issues. Getting a large enough piece to make a wheel is more difficult; and they are more likely to shatter. Not necessarily a lot more likely, but I submit that it would be enough to discourage this process, relative to other places.

Therefore I would answer the question by a mixture of: More expensive tools, favouring labour over mechanical assistance; and sharpening equipment more suited to flat grinding than hollow.

 

[DTR]

....consider the materials that were used for sharpening. Most of the good naturally occurring stones in Japan were softer than western ones, and this leads to two separate effects. Firstly, they are faster cutting - so the point at which you'd want more mechanical assistance is larger. Secondly, these softer stones are not quite as strong - meaning that for a naturally occurring stone, you face two issues. Getting a large enough piece to make a wheel is more difficult; and they are more likely to shatter. Not necessarily a lot more likely, but I submit that it would be enough to discourage this process, relative to other places.

I was thinking along the same lines.

 

[Derek Cohen (Perth Oz)]

I would offer another reason why a Japanese chisel is not hollow ground.

First of all it is incorrect to state that these blades are not hollow ground by the Japanese blade maker. They are ... just look at the back of the blade. In other words, the Japanese blade maker believes very strongly in hollow grinding! It is the bevel that they choose not to hollow, and probably for two reasons.

The first is that the softer backing is also intended to speed up sharpening.

The second is that there is a value system in the way the hard cutting layer is applied, with good, better and best chisels being determined by the excellence of the steel layer. Honing a flat bevel will show this off to it best.

Regards from Perth

Derek

 

[Jacob]

The main reason for not hollow grinding thick blades is that it makes them effectively thinner. Whatever advantage there is in thickness is thereby reduced.
The main reason for not hollow grinding thin blades is that it could make them too thin with a higher risk of overheating.

The main reason for hollow grinding is that it's quicker than doing it by hand, but no faster than a belt sander, which is a much better option IMHO.

 

[Trafalgar]

Is anybody aware of a book or article, in translation or otherwise, where a professional Japanese craftsman (not a Western hobbyist) states the case for a flat grind? This isn't to say all of you aren't probably right, but do we have anything from a horse's mouth?

 

[bugbear]

Is anybody aware of a book or article, in translation or otherwise, where a professional Japanese craftsman (not a Western hobbyist) states the case for a flat grind? This isn't to say all of you aren't probably right, but do we have anything from a horse's mouth?

"Japanese Woodworking Tools: Their Tradition, Spirit and Use" Toshio Odate, already cited.

The problem is finding a Japanese Craftsman who uses English and publishes.

I've been learning directly from Japanese web pages, but Google translate
(and make my own guesses from pictures) is not a Royal Road.

BugBear