Sharpening Japanese Chisels

[Chris Friesen]

Something I've wondered...why can't you take a japanese chisel and hollow-grind it almost to the edge, then use waterstones to put the final edge on it?

[David Weaver]

You can. There are two reasons for the advice to avoid a hollow ground, but if you have a reasonable radius of wheel (6"+ would be my wild guess), then there's only one reason to avoid it, and that's heat.

The temperature that you draw the temper on a japanese chisels is lower than it is for western tool steel, mostly because of the higher carbon content of the plain japanese steels (blue and white 1 and 2). You have a greater chance of ruining the temper without ever seeing a change in the tempering color. Older western tools were often tempered to a straw color, but japanese tools lose their temper long long before that.

The other reason, I guess, especially if you have a nice backing metal, is that the chisel looks much much more attractive when it's traditionally honed, and if it's taken care of, because the backing metal is soft, it shouldn't be difficult to keep plain japanese steel chisels in good shape without going lower than a medium grit stone.

[Derek Cohen]

I know of one respected woodworker who hollow grinds his Japanese chisels, and that is David Charlesworth. As a non-respected woodworker, I have not hesitated to do so as well with some of my Iyoroi bench chisels, especially the large ones. The only reason I do not do so with my Koyamaichi and Kiyohesi chisels is to offer respect to tradtion. I doubt very much it would harm them if I did do so.

The important qualification here is that dry grinding is out. Definitely out. It creates too much heat for the thin hard steel layer. However all will be well with a wet grinder, such as a Tormek. I also recommend limiting grinding to the 10" wheel version of the Tormek. This creates a shallow hollow, unlike a 6" or 8" wheel, and does not remove much of the iron backing. I have never experienced an edge chip as a result of reduced support from the iron.

It should not be necessary to hollow a Japanese blade since the iron backing is soft and abrades quickly, offering support as one freehands the bevel over a stone. I do recall that JIm Krenov would add a secondary bevel, which is also non-traditional. The advantage of a hollow is that one may support the bevel over the stone when sharpening, and a hollow does speed up sharpening.

One reason not to hollow - and also why I only use this method on a few of the bench chisels - is that it removes that wonderful look you get of the laminations when they are honed together in the same plane.

Regards from Perth

Derek

[Jeff Bartley]

I saw a great tutorial recently on sharpening japanese chisels.....Chris Halls blog 'thecarpentryway dot blogspot dot com'. He goes into great detail the initial preparation of the chisel (setting the hoop) through sharpening. And aside from this particular series on japanese chisels his work in general is incredible; some of the joinery takes a few minutes of study to figure out how all the components come together.
Hope this will help!