SHARPINING JAPANESE CHISELS

Re: SHARPINING JAPANESE CHISELS

Wiley Horne--Glendora CA

>Yes, you do "flatten" the backs. This is made easier by the hollow--it is only the thin periphery around the hollow that you make flat. Whereas on a western chisel you flatten the entire back surface. You will keep the hollow intact on your chisels (more on this below).

When you're ready to sharpen, just work the back on the first stone until the periphery is showing a uniform scratch pattern. Then the back is 'flat'. As you proceed through the stones, you will remove the initial scratches until the back is polished. In my experience, not much metal will need to be removed, so starting with a 1000grit stone, say, will probably be plenty. YMMV.

You may wonder if sharpening the chisel will, over time, cause the blade edge to retreat back into the hollow. What happens is this: If you work the back a little each time you sharpen, say, on the middle stone, the hollow will recede a little with each sharpening. So even though you're taking metal off the edge, the hollow is receding too, and you will always have useable edge remaining. You'll be able to judge over time how much the back will need to be worked in order to maintain the little flat.

Congratulations!! Wiley

Very curious Wiley

Christopher Schwarz

>When David Charlesworth was in Indiana recently he mentioned that Japanese chisels are wonderful when sharpened at the proper bevel angle. And he said that most Westerners get it wrong. The conversation moved quickly on to another topic and I didn't get a chance to revisit it.

Any thoughts on this topic? I'm uber-curious.

cms

Here ya go!... *LINK*

Scott Burr in Ben Lomond CA

>Here's a good primer on the subject.


Sharpening details

Re: Very curious Wiley

Scott Burr in Ben Lomond CA

>I was talking to the owner of Hida tools the last visit to his store. He said a lot has to do with how the chisels are heat treated. Specifically that they get harder as the chisel wears down.

I, being way to impatient to wait for this to occur naturally went about it in a different way that he suggested. Slowly start to bring the bevel angle up.

Most of my DT chisels started out at 25 (or so) deg. I'm up to about 30 deg. now and they have stopped the occasional chipped blade that sometimes happened (probably do to my chisel handling). They pare just as nice and hold an edge longer.

Re: Charlesworth on Japanese Chisel Sharpening

Rick Hoppe (Los Angeles)

>To paraphrase from David Charlesworth�s first book Furniture-Making Techniques, he says that working hardwoods with Japanese chisels requires the blade to be sharpened at about 5 degrees more than for a softer chisel. He says that he finishes his paring chisels at 30 degrees, chopping chisels at 35, and heavy mortice chisels at 45 or 50.

For paring chisels he grinds at 25 degrees on the Tormek, produces a slight wire edge on the 800 grit stone at 28 degrees and polishes the tip of the bevel on the 8000 stone at 30 degrees. He recommends that if one does not have a Tormek grinder, he could use a very coarse waterstone such as a 220 grit.

Re: Very curious Wiley

Moses Yoder in White Pigeon, MI

>His book I think recommends 30 degrees as the lowest angle for Japanese chisels. A nice book, but not really a necessity I think for a shop, but if you are in a book store with money burning a hole in your pocket it will solve the problem. It makes sense, as a harder steel is more apt to chip as the angle lowers. I like the looks of the chisel with a very long handle on it for paring, but I spent all my money on his books.

Re: Very curious Wiley

Wiley Horne--Glendora CA

>Chris,

Perhaps David will enlighten us. I think I am one of the ones who get it 'wrong'. Here's why. My recall of Mr. Charlesworth's sharpening angles for Japanese chisels follows along the lines of what Rick Hoppe states.

What I have evolved to personally is to use the most acute angle that the chisel steel will take without failing by microchipping. I am using Miyanaga blue steel mortise chisels; Imai sword steel bench and dovetail chisels; Imai sword steel and Tasai blue steel paring chisels; and Funahiro genju paring chisels (super blue steel). I am finding that all of these chisels will dull without microchipping at less than 30 degrees. Including the MIyanaga mortise chisels, which I wail on hard with a 13-oz. steel daruma hammer. All these chisels are hollow ground, and then honed by eye to the ballpark of 27 to 30 degrees. I can't recall about the Miyanaga's, but the Tasai's, Imai's, and Funahiro's were all delivered at about 28 degrees, give or take a degree.

No argument with anyone else--just my preference and experience. Like you, I'm curious what others are doing.

Wiley

Re: Very curious Wiley

Manny Hernandez - Livermore, CA

>That's an interesting commment by Mr. Charlesworth. I was under the impression that the "correct way" was specific to each chisel, it's intended use and could also be dictated by the preferences of the craftsman. I've noticed that the performance and edge holding ability will vary among makers that use the same steel, blue or white. Just out of habit I increase the bevels to 30 degrees from the start. Although there are similarities in philosophies among users, I've met some Japanese craftsmen that have their own preferences when it comes to "tuning" their chisels. In fact, if I recall correctly, way back when I first started buying Japanese tools, the chisels came with blunt edges. Almost as if someone had chopped off the tip. It was up to the craftsman to put whatever bevel angle he wanted.

It would be interesting to find out what Mr. Charlesworth meant by his comment.

BTW, as someone mentioned, I found the chisels characteristics to change as the bevel moves back after repeated sharpenings. Usually the edge holding improves.

Lung oil !!

Rich Glisson (Durham, NC)

>Kind of turns my stomach just thinking about it. But then, I don't really like sushi either.

Re: Very curious Wiley

Pam Niedermayer - Austin, TX

>BTW, as someone mentioned, I found the chisels characteristics to change as the bevel moves back after repeated sharpenings. Usually the edge holding improves.

Yeah, me, too, work hardening seems effective.

Pam

Most chisels don't get harder as they wear

Ludger Hentschel

>Several posts have stated that Japanese chisels hold their edge better after a few sharpenings because they get harder.

I believe the first part is correct. Some Japanese chisels hold their edge better after a few sharpenings.

I believe the reason for this, however, is that repeated sharpening removes the hardest and most brittle steel from the original edge. The chisel then holds a better edge because it chips less. But the edge is actually softer.

During heat treating, the chisel edge is likely to get hotter and then cool faster than the rest of the chisel. This can make the chisel edge extremely hard and brittle. Grinding the chisel back even a small amount can expose softer and more resilient steel from the thicker chisel body.

Ludger

Re: Charlesworth on Japanese Chisel Sharpening

david charlesworth

>Thank you Moses for buying my books, I hope you enjoy them. The long paring chisels are great.

Also thank you, Rick for quoting me so accurately.

My thoughts are that most woodwork done in Japan is in softwood. Most of the Japanese chisels I have, came with a single bevel at around 27 degrees.

The hardwoods we use here are very variable in density and hardness. I like to introduce small exotic details, and some exotics are extremely hard. I would prefer that my students are not unduly disheartened by large chips in their chisels, so my polishing angles may be a little conservative. I do not sugest they are "right", just a general guide of what works for us.

I agree that the most efficient angle would be the lowest that does not chip in the timber you are working, and accounting for the way you work. This would require experiments for different operations in each timber.

I have also noticed that a scooping, or levering cut, as opposed to a nice straight one, will often lead to chipping, so the technique of the user is also relevant.

I am certain there are no "right" honing angles, just those that work for you!

David Charlesworth.

OK, thanks.

Pam Niedermayer - Austin, TX

>

Metalhead question

Christopher Schwarz

>OK, we all know how much voodoo there is to metalwork -- almost as much as there is in woodworking.

That said, I've heard repeated a few times that a reason some tools get better as they age is because the conversion from austenite to martensite continues (albeit slowly) over time. So a tool that was heat-treated well and saw a good conversion to martensite will see even further improvement as the steel moves to the finer grain structure throughout.

Is this bunk?

Another thing I hear tossed around is that different parts of a tool can be heat-treated to different levels of quality depending on the way it was done. So is it conceivable that a tool could get harder and/or more durable as it's used up and new metal exposed?

Or is this "revenge of bunk?"

More questions than answers these days.

cms

Re: Metalhead question

Dan Donaldson

>I don't know about the change over time, but it is definately possible to have different parts of a tool at different hardness levels. You can harden just the tip of a chisel and leave the rest soft, if you wanted to. By controlling the temperature gradient on a part and the rate of cooling, you could probably get a very sophisticated hardness profile across a tool, although I am not sure it would be worth it.

Re: Most chisels don't get harder as they wear

paul womack

>I believe the reason for this, however, is that repeated sharpening removes the hardest and most brittle steel from the original edge.

IIRC Odate is very clear on this point.

BugBear

Re: universal truth

paul womack

>the most efficient angle would be the lowest that does not chip in the timber you are working, and accounting for the way you work.

That about says it all. Although advice on "typical" answers to this question are also useful :-)

BugBear

Some (late) answers *LINK*

Andrew F in Australia

>It's possible for retained austenite to convert to martensite over time, Chris.

One of the triggers for the transformation is work hardening or bending stress.

When the transformation occurs, there is a 45 volume expansion in the area of freshly formed martensite, as well as the formation of brittle, untempered martensite.

These tend to be detrimental to the performance of the chisel and are the reason for either a good heat treating schedule or cryogenic treatment to bring the transformation to near-complete before tempering occurs.

I'll see if I can dig you up a reasonable reference for this phenomenon via google.

(my first trade is metallurgy/mat'ls engineering at a degree level)

Cheers,

Andrew


Here's one reference - the TTT curve & explanation

Re: Some more good (excellent) links

Andrew F in Australia

>(probably the best link first)

http://www.ime.auc.dk/people/employees/rml/HEATTREATMENT-ENGLISH_99.pdf

(two others that may help in understanding)

http://info.lu.farmingdale.edu/depts/met/met205/cryogenictreatment.html

http://www.crucibleservice.com/eselector/general/generalpart2.html

Chris,

Shoot me an email please to let me know that you've got these (given that the thread's an old one) or if you've got any questions.

Cheers,

Andrew

typo - ..4% volume... , not ...45 volume...

Andrew F in Australia

>

Re: Most chisels don't get harder as they wear

dburnard

>I think the discussion is on the right track, and here is some more to think about...

In a laminated chisel the bevel is put on before hardening so the "initial" cutting edge is not buffered by the soft iron lamination when quenched. However low alloy or plain carbon steels quenched in water don't really "see" much of a buffering effect from steel more than a few mm's away since they tend to jacket harden. Oil hardening steels tend to thru harden so you might see more of an effect with something oil hardened. White *and* blue steel planes and chisels are usually quenched in water. Anyway, I don't think the tip getting harder is the problem.

Instead I think that the effect is more likely due to grain size growth in the "exposed" end of the chisel. This area is thinner, and when properly heated it doesn't get hotter than the rest of the chisel - but it can come up to temperature sooner. And the longer it stays at/above the critical temperature while waiting for the rest of the chisel to catch up - the more the grain size can grow. Coarser grain size can lead to a more brittle edge at the same hardness.

Even if the tip did get too hot somehow, it wouldn't end up harder than the rest of the chisel, unless the rest of the chisel didn't reach the critical temperature or it didn't stay there long enough. Instead, getting the tip too hot will lead to more grain growth.

In an oven, you can try to minimize this when heat treating by soaking at a subcritical temperature to get the entire chisel warmed up, or in a forge you can leave the tip in a cooler part of the fire and let the tip heat by conduction from the rest of the chisel.

Lots of people have made decent RC58-60 chisels out of O1 in a BBQ+hairdryer forge, since luckily for us O1 (or 1095) are pretty forgiving. All the little details start to add up when using 1.25%C steel and aiming for RC64 (and above!) with little or no post quench tempering...