Anyone tried to sharpen a Japanese plane blade?

[Rimu]

I know this may be sacrilegious to many, but has anyone tried using a Tormek to sharpen a Japanese plane blade? Interested to hear about what worked or didn't...

There are multiple videos on YouTube that show Japanese black smiths using big, wet, stone wheels during the the production of plane blades.

I would be interested to also hear about  experiences with Japanese chisels on the Tormek as well.

[RichColvin]

I have read of people starting the sharpening of their Japanese chisels on the Tormek, and finishing on water stones.  Apparently it works well.  Haven't read about anyone doing so with Japanese plane blades though.   Try contacting Andrew Hunter.  He is big in the Japanese techniques. 

[jhood]

You really don't want a hollow grind on a Japanese kanna blade (or Japanese chisel blades either...)  The blades of Japanese tools are made from two different types of steels...  there is a very hard steel that is brittle (the cutting edge...) laminated to a much thicker and softer iron...  the thicker iron keeps the more brittle cutting edge supported, and if you use a Tormek to hollow grind the bevel, you will be significantly reducing the thickness of the supporting iron...  mostly because of the thickness of the overall blade, and the length of the bevel...  (most of my kanna blades are around 25 deg. or so, and almost a half inch of bevel...)  Same goes for Japanese chisels... 

On western blades, the whole blade is the same type of steel, so hollow grinding isn't a problem...  but I would think that if and when you go to tap out the blade (which you will have to do at some point...) it's stressful enough to do it with the full support of the softer iron, but I would think that the possibility of cracking the hard steel would go up many times with a hollow grind...

Also, the main advantages of a hollow grind being to keep a narrower bevel "stable" when honing and not needing to hone as much steel on each sharpening pretty much go away with Japanese blades...  I've found that the wide bevel makes it very easy to keep the blade flat on the stones, and the softer iron hones so easily that they are much easier to sharpen on stones than western blades...

I use my Tormek all the time for western blades and knives...  but wouldn't touch one of my good kanna blades on it...

Also, no micro bevels or ruler trick bevels on the back on Japanese blades... 

Hope this helps...

JH

[jvh]

You really don't want a hollow grind on a Japanese kanna blade (or Japanese chisel blades either...)  The blades of Japanese tools are made from two different types of steels...  there is a very hard steel that is brittle (the cutting edge...) laminated to a much thicker and softer iron...  the thicker iron keeps the more brittle cutting edge supported, and if you use a Tormek to hollow grind the bevel, you will be significantly reducing the thickness of the supporting iron...  mostly because of the thickness of the overall blade, and the length of the bevel...  (most of my kanna blades are around 25 deg. or so, and almost a half inch of bevel...)  Same goes for Japanese chisels...

On western blades, the whole blade is the same type of steel, so hollow grinding isn't a problem...  but I would think that if and when you go to tap out the blade (which you will have to do at some point...) it's stressful enough to do it with the full support of the softer iron, but I would think that the possibility of cracking the hard steel would go up many times with a hollow grind...

Also, the main advantages of a hollow grind being to keep a narrower bevel "stable" when honing and not needing to hone as much steel on each sharpening pretty much go away with Japanese blades...  I've found that the wide bevel makes it very easy to keep the blade flat on the stones, and the softer iron hones so easily that they are much easier to sharpen on stones than western blades...

I use my Tormek all the time for western blades and knives...  but wouldn't touch one of my good kanna blades on it...

Also, no micro bevels or ruler trick bevels on the back on Japanese blades... 

Hope this helps...

JH

Hello,

no, that's not true. If you will have 25° at the apex you will have more material at the edge heel due to hollow grind. You can see what's happening during flat and hollow grinding in this video.

In example below are calculations for chisel with edge heel thickness 5 mm, chisel (single bevel) grind, angle 25°, wheel diameter 240 mm. Hollow grind depth is in that case 0,122 mm, but there is no reducing the thickness of the supporting iron.

The problem with the hollow grind is that the apex angle is 25°, but the angle between the apex and the edge heel is 27,579°. Compared to flat grinding there is "unground" material on the edge heel (due to the rounding of the wheel), which does not allow the blade to be tilted below 27,579°, because it would not cut as the apex does not touch the material. This makes the cut more aggressive because the edge is directed more into the material. This also affects the subsequent re-sharpening on a flat stone, where the minimum angle 27,579° is also ground (if the apex and the edge heel are touching the stone).

If you count with this you can start grinding with a sharper angle to get the angle between the apex and the edge heel equal to 25°. Second picture shows that you have to set initial grinding angle to 22,17° (= apex angle) and this slighly reduce thickness thickness of the supporting iron - hollow grind depth will be 0,146 mm. Is it too much?
But this is not the end, now you can continue on the flat stone - when the apex and the edge heel are touching the stone you will grind 25° angle + you will reduce also hollow grind depth while grinding. Other possibility is to grind 25° microbevel on Tormek too. 

Personally, I see no reason why Japanese chisels could not be sharpened on the Tormek. It will only be better to use advanced grinding techniques...

jvh

[jhood]

My main point was that between what you call the apex and the edge heel, the soft iron layer will be thinner...  that's all...   And if you have experience with Japanese blades (especially high quality ones, not the junk that is generally sold through the western tool dealers...) you would know that the wrought iron layer is integral to the support of the thin blue or white steel layer...  and the risk of tapping out a Japanese kanna blade is high enough without thinning out the layer...  (and if you never tapped out a blade, you aren't using the plane very much, or have one of the junk blades that has a huge flat on the edge of the ura...)  You don't tap out a blade at the edge heel, you tap it in the middle, between the apex and the edge heel...  where it would be thinned out...

I'm not saying that you -can't- grind a Japanese blade on a Tormek...  just that I wouldn't (and neither would any of the guys that I know that use high quality Japanese tools...) ever grind a $600 hand made blade, and wouldn't see any reason to grind a cheap one either...  a hollow grind would structurally change the blade, and not for the better...

JH

[jvh]

My main point was that between what you call the apex and the edge heel, the soft iron layer will be thinner...  that's all...   And if you have experience with Japanese blades (especially high quality ones, not the junk that is generally sold through the western tool dealers...) you would know that the wrought iron layer is integral to the support of the thin blue or white steel layer...  and the risk of tapping out a Japanese kanna blade is high enough without thinning out the layer...  (and if you never tapped out a blade, you aren't using the plane very much, or have one of the junk blades that has a huge flat on the edge of the ura...)  You don't tap out a blade at the edge heel, you tap it in the middle, between the apex and the edge heel...  where it would be thinned out...

I'm not saying that you -can't- grind a Japanese blade on a Tormek...  just that I wouldn't (and neither would any of the guys that I know that use high quality Japanese tools...) ever grind a $600 hand made blade, and wouldn't see any reason to grind a cheap one either...  a hollow grind would structurally change the blade, and not for the better...

JH

Hello,

I must repeat that the soft iron layer will be thicker after hollow grinding (for the same apex angle). And for a thin layer of blue or white steel the rounding of the hollow grind is negligible, even if you grind a sharper angle as shown in Example 2 in my previous post. Other possible problems are described here too.

Please look at the enclosed picture what is difference between flat and hollow grind in higher zoom.

Can you explain how a hollow grind would structurally change the blade?

My post is not meant to be offensive, I'm just trying to verify if the information makes sense and if it's not another myth about grinding...

jvh

[micha]

Jan,
I think both assumptions are correct, depending on where you start grinding.
If you have a very wide existing bevel, like on a chisel/scandi grind and want to grind / polish over the complete height  of the bevel, you'd have to start grinding in the center of the existing bevel, not from the apex. This way you would get more concavity within the bevel, thus thinning the material more, I guess that is what jhood meant.

If you can apply a new bevel like in your drawing, then your statement is also true. But you would not get the complete existing bevel without more hollow grinding.

I'm aware that the apex angle would be more acute then, of course, but that's the general problem with chisel grinds - either you just add a secondary bevel, ignore the existing flat ground bevel or establish a new angle.

Does that make any sense?
Mike

[jvh]

Hello Mike,

I have no problem with this. I understand what is the problem and therefore I mentioned "sharper angle grinding" option in my previous post. All deviations caused by hollow grind are calculable and if you take them in account you can eliminate their impact, eg. you can grind microbevel on the flat stone or directly on the Tormek.

A brittle edge indicates a problem with the bevel angle being too sharp. But it's not the fault of grinding - there you can set what angle you want to grind - this is due to the rather inappropriate use on too hard material/wood...

Why should I grind / hone over the complete height of the chisel bevel if I know that resulting angle will be wrong?

jvh

[micha]

...
Why should I grind / hone over the complete height of the chisel bevel if I know that resulting angle will be wrong?

I agree, of course.
Admittedly it's a merely esthetic problem, not a technical one. In Knives it's perfectly comprehensible, but not an issue with most other applications, I suppose.
Mike

[Rimu]

If you watch this video, you will see the use of round stones at various stages of plane balding making

https://www.youtube.com/watch?v=hQsciiR9-9g

You even see the use of rounded fixed stones.

I was actually more interested if anyone had use the side of the stone for Japanese plane blades... that seems a little more straightforward to me. There is a guy on here (sorry forgot name) who is mounting  the Makita plate-stone wheels which looks promising.

I was also wondering how anyone approached the holding jig for these blades as that always seems to be a challenge.

[WimSpi]

You really don't want a hollow grind on a Japanese kanna blade (or Japanese chisel blades either...)  The blades of Japanese tools are made from two different types of steels...  there is a very hard steel that is brittle (the cutting edge...) laminated to a much thicker and softer iron...  the thicker iron keeps the more brittle cutting edge supported, and if you use a Tormek to hollow grind the bevel, you will be significantly reducing the thickness of the supporting iron...  mostly because of the thickness of the overall blade, and the length of the bevel...  (most of my kanna blades are around 25 deg. or so, and almost a half inch of bevel...)  Same goes for Japanese chisels... 

On western blades, the whole blade is the same type of steel, so hollow grinding isn't a problem...  but I would think that if and when you go to tap out the blade (which you will have to do at some point...) it's stressful enough to do it with the full support of the softer iron, but I would think that the possibility of cracking the hard steel would go up many times with a hollow grind...

Also, the main advantages of a hollow grind being to keep a narrower bevel "stable" when honing and not needing to hone as much steel on each sharpening pretty much go away with Japanese blades...  I've found that the wide bevel makes it very easy to keep the blade flat on the stones, and the softer iron hones so easily that they are much easier to sharpen on stones than western blades...

I use my Tormek all the time for western blades and knives...  but wouldn't touch one of my good kanna blades on it...

Also, no micro bevels or ruler trick bevels on the back on Japanese blades... 

Hope this helps...

JH

The plane iron but also the chisels of the Dutch brand 'Nooitgedagt' were also made of laminated steel until about 1950. I still use these chisels today. Grinding at, say, 25 degrees has never given me any problems.

It is true that the softer steel will grind away faster, but on the other hand the softer steel is also thicker. Theoretically it may be a difference, but in practice I don't notice it.

When I started in 1975 and worked with carpenters who were much older and also worked with the same chisels, I never heard that this was a real problem either.

The sharpening used to be done first on a large sandstone running in a large tank of water, just like Tormek. Then the chisel was honed on a 'Belgium Coticule'.

[Rimu]

Actually, now I see that in the Tormek video for the SE-77 Square Edge, they show it sharpening a Japanese plane blade! 

[RickKrung]

...snip...
There is a guy on here (sorry forgot name) who is mounting  the Makita plate-stone wheels which looks promising.
...snip...

Is this the post/thread you are referring to?  By Arthur. 

Rick

[sharpening_weasel]

Noticed that too- a fascinating idea. Some interesting possibilities: mdf wheels impregnated with successively finer diamond grits for flat sharpening super steels, installing a flat over hollow grind for sloyd knives, possibly even convex edges.

[bicycle freak]

Hi there, in my opinion you are all focussing too much the wrong axis of the plane blades. For a carpenter's usability it's negligible whether the grind is flat or slightly hollow. Some of the best planes, equipped with Aogami steel blades are reversing the position of the blade with the grinded side upwards. Then the only difference is that you have to bend the planing chips with lees than 1/10 mm of thinness about 2 degrees more. Important? I don't think so. However, the difficulty for me when grinding a plane blade on a Tormek is to achieve a really really rectangular edge with the SE-77 jig. I know well how to adjust the jig, and also have the precision square tool to measure, but I only notice any aberration of the edge after having grinded away some of the precious steel. Even worse, this has to be adjusted with every new mount of the blade. For this type of usage, the SE-77 jig alignment appears not to be precise and stiff enough, in my opinion.

Any ideas on this?
Dieter