Hollow grinding japanese chisels

[Edwin Santos]

It has been my workflow to hollow grind western chisels and then freehand hone them. Freehand honing a hollow bevel is fast, accurate and easy.

I recently acquired some japanese chisels and have been advised not to hollow grind them. Any other opinions on this? What are the reasons for the advice, and what am I risking by hollow grinding?

Does the no-hollow grind advice apply even if the grinder is a Tormek, which is a large diameter wheel (thus a shallower hollow)? Plus the Tormek is as gentle as a grinder can be due to the slow speed and the water.

If I must stay with a flat bevel, I just see it taking more time than my usual routine, and possibly more reliance on a honing jig.

Thanks,
Edwin

[Howard Pollack]

My understanding is that Krenov used to hollow grind his Japanese chisels. I've tried it on occasion and have found no bad results, but people do warn against it.
-Howard

[brian zawatsky]

Hollow grinding isn't necessary on a japanese chisel because of the laminated construction. The majority of the steel in the tool is very soft and abrades quickly. Only the bottom lamination (~2mm thick or so) is hardened, so honing a flat bevel is not a time consuming process. In fact, the jigane (japanese name for the soft iron or steel backing) is so soft that you need to be careful not to lay the angle of the bevel back too far when setting up the chisels. Keep your finger pressure right at the cutting edge, but be sure the whole bevel is touching the stone. One of the really nice things about Japanese chisels is that microbevels are totally unnecessary so the honing jig stays in the drawer where it belongs lol

Since these are your first nomi, I would recommend using your jig to do the initial flattening and trueing of the bevels, and then work on your freehand honing once you know you have a flat true bevel to use as a reference point. This cut the learning curve way down for me.

Here is a good video for your reference: https://youtu.be/MhgzGI4vlkY

In the video, he flattens the back using a kanaban (steel plate) but I use a 1k grit synthetic stone. The Shapton pro stones are hard enough to use for flattening since they don't wear hollow as fast as some of the softer synthetics. Hope this helped

Oh yeah, almost forgot. As far as the time factor, once the chisels are set up properly sharpening is quick. It takes me 3 or 4 minutes to go from 1k (if needed) to a final polish that you can shave with.

[Robert Hazelwood]

I suspect you will be ok to hollow grind. None of the die hard J-tool aficionados seem to recommend it, but there are several western woodworkers I can think of who do it. The biggest danger in grinding would be overheating, they are more sensitive than the typical western blade in this respect, but you should be fine with the water cooled tormek.

However, you may just be creating extra work. If the edge geometry on your chisels is good and does not need major correction, just sharpen them (freehand). Keep the pressure on the cutting edge, just on the verge of tipping it, to avoid removing more steel from the soft part and lowering the angle over time (eventually causing the steel to chip in use). They do not take long to sharpen if there is no major damage to remove. If you need to change the bevel angle or remove a chip, then work it over on the tormek and then return to freehand maintenance. That's what I'd do anyways.

[david charlesworth]

I have used Tormek hollow grind for many years with no ill effects.

Best wishes,
David

[brian zawatsky]

While I’m sure a Tormek would do no harm to a Japanese chisel, I just don’t see the value in it. Allow me to elucidate.

I like Japanese nomi for 3 main reasons: 1 - The steel. Well-tempered white steel is super hard and fine grained so it is capable of taking and holding a very keen edge, which brings me to, 2 - The cut quality. That very hard, very keen edge is a joy to use, they will leave end grain glassy and do it for quite some time between sharpenings. 3 - Aesthetics. I find a high quality, well executed nomi to be a thing of beauty. The appearance of a fine polish on a laminated blade is a magnificent thing that will surely be misunderstood by the uninitiated. On a more practical note, I feel that a highly polished flat bevel reduces resistance while the edge is engaged in the cut.
DC775784-FF46-47F0-ACF3-5CE21234D2B4.jpg
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You wont get a polish like that with a hollow grind off of a tormek

[Andrew Hughes]

That’s looks great Brian. I also don’t hollow grind my Japanese chisels. They sharpen so fast it just seems like a waste of expensive steel.

[Brian Holcombe]

Neatly done, Brian!

Edwin, don’t grind them. Develop a reliance upon yourself to set the angle and maintain it, it’s a worthwhile pursuit.

[Patrick McCarthy]

Brian Z, you have done well on your trip down that rabbit hole. Very nicely done.

Patrick, just starting to go down the rabbit hole. . . . . .

[Warren Mickley]

"On a more practical note, I feel that a highly polished flat bevel reduces resistance while the edge is engaged in the cut."

A chisel is not just a cutting edge, it is also a wedge. It pushes material aside as it penetrates. Both concave and convex bevels make for poor wedging action. One who has never used this type of chisel might not notice this.

[brian zawatsky]

Brian Z, you have done well on your trip down that rabbit hole. Very nicely done.

Patrick, just starting to go down the rabbit hole. . . . . .

It’s deep, VERY deep. And I keep wandering further in. Just ordered my first kanna yesterday...

[Derek Cohen]

As David notes, one can hollow grind (some) laminated blades (only on a Tormek, however). I have done this on Iyoroi, which are beaters for me ...



.. as is a Fujikawa, which is PM HSS (really, really hard and tough!). The reason for this is that the hollow simply speeds up honing. Removing the soft cast iron supporting steel does not weaken the edge in any way. I have never experienced any chipping. It is just faster since balancing the bevel is easier than keeping it flat.



On the other hand, my Kiyohesa and Koyomaichi chisels are all honed on the flat. I take the time to do this, and I respect the traditional honing methods here.



Regards from Perth

Derek

[Nicholas Lawrence]

What do people use to sharpen Japanese chisels? Not the HSS stuff, but the regular white or blue steel versions. Will an Arkansas stone work, or do you need something fancier?

[Robert Hazelwood]

What do people use to sharpen Japanese chisels? Not the HSS stuff, but the regular white or blue steel versions. Will an Arkansas stone work, or do you need something fancier?

People will generally say you cannot use arkansas stones, but I have been using them on J-tools for a couple of years and I think they work fine. I have shaptons, but without a sink in the shop it's more of a hassle to use them than the oilstones.

My tools are mostly white #2. I use a fine india to raise a burr, then soft ark, and finally a translucent. I get a good hazy mirror polish with a nice distinction between hard and soft steel, and the process goes quickly. Edge quality and edge retention seem very good.

I don't have experience sharpening the extremely hard white #1 tools, so can't say about those. I imagine they will go a little slower but produce an even better polish.

The blue steels have more wear resistance so should be tougher to sharpen, but I have a blue #2 gyuto (chef's knife) that comes up very nicely on the arks. Blue #1 or Super Blue might be pushing it, but I can't say.

[Brian Holcombe]

.. as is a Fujikawa, which is PM HSS (really, really hard and tough!). The reason for this is that the hollow simply speeds up honing. Removing the soft cast iron supporting steel does not weaken the edge in any way. I have never experienced any chipping. It is just faster since balancing the bevel is easier than keeping it flat.

There is absolutely a risk that you will damage the chisel with the higher hardness white and swedish steels.