should i avoid using a grinding wheel on Japanese chisels

[tobytools]

as stated i was wondering can i sharpen japanese chisels using a grinder like a record power? i ask as i have one or two that are in a bad way, to sharpen using stones or papers put me off, i know that its soft steel laminated to white paper steel (the good stuff) but even so im curious to know has anyone used a grinding when??

ive found this.. basically say NO
http://www.fine-tools.com/G10007.htm

because of the face being hollow ground, making the bevel would seriously weaken it...

so how would one get a perfect straight bevel on the darn thing? i have a mortice jap chisel that is to big to fit in a jig so thats out of the question so would have to be free hand if not ground on wheel..,. any advice or help would be appreciated,

ill hold off on any grinding until some sound advice is thrown my way.

thanks.
TT

 

[Phil Pascoe]

Belt sander or alox stuck on a flat disc on a lathe would do it. If badly damaged, take the worst off carefully on a wheel first.

 

[David C]

I have (carefully) ground my Japanese chisels for about 30 years. Not right to the edge.

David Charlesworth

 

[tobytools]

thanks for the alternatives phil.
and thanks also david, i use your sharpening method currently and ill take your advice now. so i should grind almost to the edge and then use flat stones?
i have to say the bevel angles on the chisels i have are all completely different and no way near 25 0r 30.

maby the belt sander would be my best choose or would grinding new 30 degree angles on all of them be my best option. i want to get these working so i can tryout before i decide to either sell on or keep,
ive begun to sell off the tools i don't use ect

TT

 

[Vann]

Hi Toby. I don't have any Japaneese chisels, so this is not the voice of experience...

I grind my non-Japanese chisels on an 8" bench grinder (hand powered - puff, puff), so the hollow is not as great as with a 6" wheel. Anyways, I sometimes find I completely eliminate the hollow at the next stage, on my 1200g waterstone. I don't do this on purpose, and it usually only happens on finer (less thick) chisels. But even if you heavily reduce the hollow (without eliminating it completely) you should end up with enough metal behind the cutting edge to give it enough strength.

My 2d worth...

Cheers, Vann.

 

[Corneel]

I hollow grind on 6" high speed grinder being carefull not to overheat them. They don't seem to mind at all.

 

[matthewwh]

Tempering is the process of warming hardened steel to draw out some of the hardness. On a western chisel the aim is to get it right on the balance point between hard and tough, so you get both qualities simultaneously. Once tempered, the steel can be heated to anything less than the tempering temperature without changing anything. When done intentionally, the blade is soaked at a given temperature for an hour or more to allow the changes time to occur throughout.

The danger with grinding is causing localised damage to the heat treatment by momentarily cooking the tip of the blade.

Japanese chisels use laminated construction to give them strength - therefore the hagane (edge steel) layer can be left harder, so logically the heat treatment may begin to be affected at a lower temperature than a western chisel - which may be the root of the advice against grinding them.

As long as you avoid getting them warm you should be fine, the part that forms the cutting edge is directly under your fingertips, which have a much lower tolerance for heat than the steel, so if you can't feel any warmth you won't be doing any damage.

As DC suggests staying well back from the very thin section at the edge would be prudent. If the edge is very badly damaged it is safer to square it off, then take the bevel back.

 

[bugbear]

I know that its soft steel laminated to white paper steel (the good stuff)

Unless you know the particular maker's technique, all you can really say is that it's soft steel laminated to hard steel.

"White" is a particular type, but there are many others used.

BugBear

 

[David C]

For hardwoods, I would grind them all at 25 degrees and then vary the honing according to use.

Paring, coarse stone 800, 0r 1,000 grit to get a wire edge at 30 degrees, and then polish at 32 degrees. This is done by shortening Eclipse type guide projection by a couple of mm.

Chopping, coarse 33 degrees, polish 35 degrees.

There is no point in grinding right up to the edge, unless you have big chip. It just shortens the life of the tool and probably loses the squareness of the edge.

Just leave a small sliver of previous honing.

My 3 stage sharpening does not reflect Japanese tradition, but has always worked for me.

David

 

[Jacob]

belt sander (or a Sorby Proedge) runs cooler than typical bench grinder and also gives a nice flat bevel (for stronger edge) or even a rounded bevel if you want to emulate the common Japanese way if done by hand power only.

 

[Phil Pascoe]

Here we go again. I've seen loads of Japanese chisels, but I've yet to see one with a round bevel. I've not been to Japan to observe the common way, though.

 

[matthewwh]

In fairness (and before we all get carried away) if you are freehanding anything on a larger surface you have to be moving the shape of it towards convexity.

The broad bevel of a Japanese chisel registers well on the stone, so it's reasonably easy to keep it reasonably flat, but there isn't a single variable that could lead to concavity and absolute flatness doesn't exist - so it has to be convex.

 

[bugbear]

In fairness (and before we all get carried away) if you are freehanding anything on a larger surface you have to be moving the shape of it towards convexity.

The broad bevel of a Japanese chisel registers well on the stone, so it's reasonably easy to keep it reasonably flat, but there isn't a single variable that could lead to concavity and absolute flatness doesn't exist - so it has to be convex.

Last time this came up, I posted, from multiple blogs, videos, websites etc, Japanese craftsman showing their very flat bevels holding the entire tool fixed to the stone by suction/capilliary attraction.

The bevel may not be "absolutely" flat, but they're flat enough

BugBear

 

[Trafalgar]

I suppose one can hollow grind them but the more interesting question is why Japanese craftsmen do not. It's my understanding that most are quite adamant about a flat bevel and of course a flat back which the hollow greatly facilitates.

Are we somehow loosing some essence of these tools by hollow grinding fronts and introducing microbevels of all ilks all around?

Matthew wrote above:

"In fairness (and before we all get carried away) if you are freehanding anything on a larger surface you have to be moving the shape of it towards convexity. The broad bevel of a Japanese chisel registers well on the stone, so it's reasonably easy to keep it reasonably flat, but there isn't a single variable that could lead to concavity and absolute flatness doesn't exist - so it has to be convex.."

This is absolutely true and absolutely why "Jacob's method" works as well as any and maybe even better -- at the cutting edge the tool is no different than one honed by a master Japanese craftsman.

 

[bugbear]

This is absolutely true and absolutely why "Jacob's method" works as well as any and maybe even better -- at the cutting edge the tool is no different than one honed by a master Japanese craftsman.

The Japanese craftsman's edge would be polished with circa 1 micron abrasive (8000 JIS polishing stone); Jacob's edge is 43 micron (Norton India fine), so I'm fairly sure they'd be a substantial difference. Further, the Japanese tool is harder steel, so the effect of the abrasive is reduced, leading to an even better finish for a given abrasive.

The Japanese tool also has (as you pointed out) a flat back, which Jacob doesn't really bother with.

BugBear

 

[Jacob]

Here we go again. I've seen loads of Japanese chisels, but I've yet to see one with a round bevel. I've not been to Japan to observe the common way, though.

I've sen a few on here and other forums with rounded bevels usually with the owner crowing on about someone having sharpened them really badly. But I've also seen videos of japs sharpening a la P Sellers (and me) i.e. with a dip.
Basically there's no reason why not. A lot of old tools are done that way - it's easier.

 

[Jacob]

.......
The Japanese tool also has (as you pointed out) a flat back, which Jacob doesn't really bother with.

BugBear

A lot of Japs don't bother either.

 

[bugbear]

But I've also seen videos of Japanese craftsmen sharpening a la P Sellers (and me) i.e. with a dip.

Link to one or two of these please?

Preferably with captions or subtitles, but whatever you've got.

BugBear

 

[Trafalgar]

This is absolutely true and absolutely why "Jacob's method" works as well as any and maybe even better -- at the cutting edge the tool is no different than one honed by a master Japanese craftsman.

The Japanese craftsman's edge would be polished with circa 1 micron abrasive (8000 JIS polishing stone); Jacob's edge is 43 micron (Norton India fine), so I'm fairly sure they'd be a substantial difference. Further, the Japanese tool is harder steel, so the effect of the abrasive is reduced, leading to an even better finish for a given abrasive.

The Japanese tool also has (as you pointed out) a flat back, which Jacob doesn't really bother with.

BugBear

One micron, that's quaint. .05 micron polishing is where it's at. :lol:

I think the only craftsmen honing on one plane (same as 'flat?') are those who hollow grind and then hone directly on the grind polishing heel and toe with no microbevels added.

 

[bugbear]

I think the only craftsmen honing on one plane (same as 'flat?') are those who hollow grind and then hone directly on the grind polishing heel and toe with no microbevels added.

Not so in Japan;

from a previous thread on this topic:

post788026.html?hilit=%20flat%20bevels%20stick#p788026

BugBear