Advice on Japanese chisels

[Steve Kang]

Okay, so call me narrow minded, but what's the big deal about laminated blade chisels? Has anyone here tried the newest offerings from Veritas with the PM V11 steel? They sharpen and hone very easily and hold a great edge. Is there some mystique about them which I'm unaware of?

Hi Marty,

I prefer LV PMV-11 chisels. I had a set of Koyamaichi but found them difficult to sharpen. Couldn't be happier making the switch to a western chisels. Perhaps if my sharpening skills were better I would have stuck with them...

[Kees Heiden]

4. The better Japanese chisels are hand-forged, at least twice, which modifies the crystalline structure of the hard-steel steel cutting edge breaking up, making finer, and more evenly distributing critical carbides. This makes the blade stay sharper, longer, and much less likely to chip. To someone that knows the "flavour" of steel when cutting, this is a big deal all by itself. Perhaps like the difference between a good sipping whiskey and rotgut, or a Porsche and a Lada.

Not really disagreeing with any you wrote Stanley, but I have my doubts about this one. I think that all difference the forging would have made is wiped out in the heat treatment.

Forging is done at very high temperatures, otherwise you don't get much work done on each heat. A good smith finishes his work in as few heats as possible, because every heat leads to the formation of scale (an iron oxide) which is just loss of steel and with the steel some carbons are gone forever too. In an ideal situation the carbs dissapear at the same rate as the iron, but forging is not a very controlled environment. After forging the smith will do a few normalising cycles. First normalising cycle is heating up well above the critical temperature, this distributes the carbons but leads to large grains. The next and maybe even another normalising cycle is done just above critical temperature and creates the much loved small grains. Then the steel is heated up above critical and quenched.

Above critical temperature (which depends on the type of steel) austenite is formed which is a completely new crystal. Longer time at higher heat leads to larger grains because that is a lower energy state. On each heat above critical the grain structure is thrown over. After these heat cycles the memory of the steel about the forging is vague and distinct.

Forging does have one very distinct advantage. It leads to much nicer tools then just grinding them out of a standard bar of steel, that's about the most ugly way to make a chisel. Manufacturers like Narex use something like a drop forge process, which looks better, but still doesn't come close to forging.

And of course I could be wrong too. I am just repeating information I found in metallurgy books.

[Steve Voigt]

Above critical temperature (which depends on the type of steel) austenite is formed which is a completely new crystal. Longer time at higher heat leads to larger grains because that is a lower energy state. On each heat above critical the grain structure is thrown over. After these heat cycles the memory of the steel about the forging is vague and distinct.

Kees,

I am no expert either, but from what I know the above is an over-simplification. If you want to get deep into the weeds on this, Google one of my all-time favorite WC threads:

"verhoeven steel forging wood central" (just google that and you'll find the thread)

and read the ensuing discussion. Especially read Wiley's posts. If you really want to dive deep, read the manuscript by Verhoeven that he links to (I did, I have no life). Brief summaries are crap, but I'll give one anyway: the way the new molecular structure forms is influenced by the old structure. The new grains, or crystals, form along boundaries, stress points, and deformations present in the old lattice. So forging really does (or can, when done right) make a difference.

Another thing mentioned in the thread is the bogus "packing" hypothesis--that forging reduces grain size by packing the grains more tightly. That is false, but the effect of forging is real; it's just more complicated.

Anyway, I think you'll enjoy reading that stuff, since you're as big a nerd as I am.

[Kees Heiden]

Verhoeven is my bed time lecture at the moment. A great teacher, but it remains a dark art!

In fact, forging is being done big scale at the mill. After casting the large ingott it is being drawn out with roller mills. When it finally reaches the 4mm thick bar we need when making a cisel, it is as heavilly worked as it is ever going to be. And then the first thing the bladesmiths are doing is forge welding it to some low carbon steel. Forge welding! That's heating the steel until it almost burns away! When you really want to make a fine chisel you should take the steel as delivered, file a bevel on one end and harden it.

[Kees Heiden]

BTW, there are (at least) two elementary ways to dress the grain size. One is recrystalisation like you mentioned, the other is through rapid austenisation cycles. Each cycle indeed depends on the former. A good sequence is to martenise the steel first, that's the best starting point. Then heat and cool it quickly, each time above critical temperature, but only just high enough for austenisation.

[Brian Holcombe]

Yes, they're making quite a mess of it arent they...

Here is where I pound a chisel 7/8" into a piece of wood... all in one shot....just pounding away until the wedging forces are overpowered by the wood


Here is what the edge looks like upon extraction


No chips...not even a burr is formed.

[Matthew N. Masail]

that's a nice looking MORTISE . .. . .

[Kees Heiden]

Isn't that what a chisle is supposed to do? Out of curiosity I did the same with one of my vintage Nooitgedagt chisels. It went about 3.5 cm deep. Same result, absolutely no damage to the edge.

BTW, in my posts today i sound as if I know what I am talking about which is far from true. Just sparing some ideas around.

[Brian Holcombe]

It's making for a good discussion of course, we havent had a deep dive steel discussion in quite some time on this board so I'm glad that it's coming up.

I've had alloyed steel mortise chisels that doing such a thing to would have a very ugly looking edge, maybe not after one shot, but a round of cutting mortises would do it.

[Stanley Covington]

Kees:

You bring up some good points, but I urge you to remember that the information in MOST technical books available nowadays on steel is focused on the needs of large-scale commercial manufacturers, such as the automotive, aeronautic, ship-building, structural steel industries, etc., and that forging, with the exception of drop forging, is not a factor they ever consider anymore, because it has not been done commercially on a significant scale since the 1950's. Its simply too expensive, and unecessary for 99.999% of steel products. Face it, the market for handtools of the sort we neanderthals buy is relatively microscopic, consuming insignificant amounts of steel. Therefore, the very high quality, simple high-carbon steel we crave is not worth anyone's time to research or write about anymore.

It can be, and has been, confirmed time and time again prior to the 1960's that forging does improve the crystalline structure of high-carbon tool steel. You just have to dig for the information.

Martensite formations absolutely tend to clump, leaving interstitial spaces between then comprised of relatively softer and weaker unconverted pearlite material. Kind of like icebergs locked into an ocean of pearlite and unconverted iron. All steels wear away and dull first at these softer areas, leaving the harder martensite behind. But soon, as the blade is forced through the workpiece some more, these unsupported martensite clumps are torn off the edge too, further dulling the blade. Draw yourself a picture of how the edge would dull once these icebergs are torn away.

In the case of a sub-standard blade, the steel may measure very hard on average, but it will wear and fracture along these lines, but unlike the better-quality blade, these areas will wear away quicker since the softer pearlite between martensite formations is larger. Such a blade will dull very quickly despite passing all Rockwell tests. In some cases, it will chip badly. When viewed under an SEM, the martensite clumps at the cutting edge can be seen standing out from the cutting edge like the (ragged) prow of a ship, while the softer pearlite around it is worn away.

The physical action of the hammer when forging simply breaks up these martensite formations into smaller clumps, and distributes them more evenly around the steel. Therefore, there are relatively more of them located at the cutting edge, like pickets in a fence, and as the softer pearlite wears away, the worn-away distance between the martensite clumps is less, leaving them relatively better supported, and more durable than larger, but less evenly-distributed martensite clumps. This is not a perfect solution, of course, but it is a very significant improvement.

And you are right that every heat over the critical temperature causes the mass to lose carbon. This is entirely acceptable so long as the blacksmith has allowed for this by maintaining just a bit of excess carbon. Of course, you realise that a skilled blacksmith can and does intentionally add carbon, and remove carbon, as necessary. However, you also know that if he loses control of temperatures, and allows too much carbon to escape, thereby "burning" the steel, it is very difficult to get the carbon levels back up to where they need to be, and the steel is practically ruined. I am not a blacksmith, but I spend a lot of time in their company and ask a lot of pesky questions. The good ones I know use at least 2 heats/forging cycles per blade. Some insist that 3 is necessary. Both types produce good blades.

The critical factors here are temperature control, carbon control, and martensite crystal manipulation. A good blacksmith is an expert at these things. An excellent blacksmith can do this in a dark workshop, without a thermometer, and without wasting any time or effort. Its a wonderful thing to see. I guarantee that your beloved vintage Nooitgedagt chisels were made from what was initially relatively poor-quality steel, and shaped by hand forging, using expert temperature and carbon control, by some blacksmith that knew the secrets of steel.

Before the modern era, ALL steel was very expensive, and ALL steel was forged, whether by hand-wielded hammer, or spring hammer, or trip hammer, simply as a step in the shaping process, and more often than not, as a means to add or remove impurities and excess carbon. Therefore, forging was unavoidable. That is not the case nowadays, and modern, large-scale commercial manufacturers use shaping processes that reduce expensive heats and shaping steps to the absolute minimum. In addition, the raw steel they are buying is very very pure compared to steel available even 70 years ago, so the need for commercial tool makers to remove impurities and/or remove/add carbon is non-existent. What's difference does a little bit of extra silica or phosphorus or unintentional chrome left over from a Ford bumper make in an Estwing hammer bought by the typical fellow at Home Depot? They don't even know how to do these things on a commercial scale anymore.

Sorry if this has become long and rambling, but I don't have time to edit much or condense.

There are more steps in the process, including normalising as you mentioned, which in Japan is accomplished by placing the shaped blade in a box of rice straw ashes for 24 hours. Not sure why rice-straw helps. I will ask next chance I get.

Stan

[Kees Heiden]

Maybe increase the bevel angle a few degrees on those alloyed chisels?

Anyway, I studied the relevant chapter in Verhoeven this morning in the train. Like I wrote there are two methods to manage the grain size in steel. Heat changes and recrystaliation on forging. The book from Verhoeven is very good, but it is no recipe book. Link: http://www.hybridburners.com/documents/verhoeven.pdf

Rapid heat changes work because on each austenising cycle. It works because when the steel is heated above the critical temperature for that steel (720 degree Celcius for a 0.77% C steel), austenite crystals are formed, first on the grain boundaries, then they grow inwards into the old grains. On higher heats larger austenite crystals are formed, just above critical the grains remain small. Long heat cycles promote grain growth too. And a smaller grain when you start results in even smaller grains after the heat cycle. That's why repeated cycles work, the grain gets smaller and smaller on each cycle until after 3 or 4 times you end up with very small stuff.

One caveat. The book writes about very fast heating. They heat the steel in molted lead or molted salt baths. That is typical "do not try at home" stuff. That kind of stuff is extremly dangerous. I don't know if it also works quite as well when you put the steel in a hot oven, wait until it reaches the right temperature throughout and then quench it. Something to be experimented with.

The second method is the recrystalisation. When steel is mechanically deformed, you get small defects in the grain structure. When it is hot enough new crystals form around these defects. That's the idea. There are two variations, static and dynamic recrystalisation.
-Static. The steel is cold formed (for example in a rolling mill). Then it is heated. The amount of recrystalisation depends on the amount of deformation, the temperature and the time. Steel that is 50% deformed can be recrystalised in one hour at 500 degrees. At higher temps it goes faster or you can recrystalise smaller deformations.
- Dynamic. This happens during forging. Forging happens at much higher temperatures. So the recrystalisation goes a lot quicker too. It goes as you work, so to speak. There are two effects going on at the same time. Forging is done at rather high temperatures which promotes grain growth, but the mechanical action causes recrystalisation which shrinks the grains. Lowering the forging temp reduces the grain growing process, but it is much harder to forge colder steel so the deformation is less, resulting also in less recryctalisation. And lower temperatures cause loewer crystalisation rates anyway. So it is all a matter of balance, like everything in life.

White steel from Hitachi is a quality product. I would be surprised if it was anything else then a fine grained steel. The circumstances in the mill are the perfect situation for recrystalisation. The rolling mill is very strong and also vreates very homogenous deformation paterns. Homogenous is something you really want in tool steel! So I think the blacksmith must watch out that he doesn't make the end product worse then the quality he started with. He begins with forge welding which isn't the best way to start when very fine grain is your end goal. I also don't know if hamering on an anvil is what Verhoeven had in mind when he was writing about this recrystalisation process.

[ken hatch]

Thanks Stanley, I would like to know more.

ken

[Kees Heiden]

Hi Stanley, you were posting while I was writing my epistel. It took a bit of time because I had to do some pesky work in between...
I'll read it later when I have some more time.

[Kees Heiden]

If everything is done correctly at the hardening stage then there won't be any perlite in the steel! The quench must be quick enough to prevent formation of perlite. Now, Japanese white steel is mostly iron and Carbon, and steel like that needs a superfast quench. A high carbon rate makes this time a little longer, but I guess it still needs to be past the "perlite nose" within one second. That's fast! Another problem of the very high carbon content is the retained austenite. Iron can only absorb about 0.6% carbon. The rest is a problem, unless you manage to transform it into a carbide. This steel doesn't contain carbide forming alloys, so the only carbide you get is some FexC combination. The number x depending on the circumstances.

So, after quenching you get retained austenite with fine martensite along the grain boundaries. The reatined austenite needs to be converted with the tempering process in things like ferrite and carbides. During the tempering the same happens with the martensite, so you end up, hopefully, with a homogenous distribution of ferrite and carbides, where the ferrite probably is still somewhere halfway between the martensite and the pure alpha iron shaped ferrite. I haven't dissected my Japanese chisels yet, so I don't know what the reality is.

BTW, the process with slow cooling in rice straw is annealing. Heat it up nice and good and let ik cool very slowly. In the west they do it with wood ashes or in a down ramping electrical furnace. I don't know why they use rice straw in Japan, maybe because it is plentifull and cheap?

I don't think you can add much carbon to the steel, not even in a charcoal furnace. This is a very slow process which litteraly takes days. This is how they made blister steel in the past. A few minutes in the fire isn't going to add anything. Losing carbon is much easier. Just heat it up more then neccessary. Burning is something else alltogether. I did that quite a few times last weekend on my beginner course blacksmithing. Loosing your S-hook among the coals before you can grab it is a good way to end up with burned steel. It is a bloomy shaped mess, and I understand it is mostly the iron that burns out, so you end up with something akin to low quality cast iron.

One thing many romantic hand forge fans are forgetting is that ALL steel is forged. The rolling mill is the most perfect forging technique you can think of. Hammering on the anvil doesn't even come close to the amount of deformation the mill can do.

Playing a bit of the devils advocate here, mostly to learn more myself too. So please refute my arguments with reason.

[Allan Speers]

Okay, so call me narrow minded, but what's the big deal about laminated blade chisels? Has anyone here tried the newest offerings from Veritas with the PM V11 steel? They sharpen and hone very easily and hold a great edge. Is there some mystique about them which I'm unaware of?

Marty, I don't think you got a complete answer:

A laminated chisel or blade is a combination of a super-hard steel edge with a soft iron backing. The best use wrought iron, esp old stuff from ship anchors and such, and the ultimate is called "Tamahage" IIRC. Super rare stuff and it's even illegal to bring it out of Japan !

Anyway, the idea is that the ultra-high carbon steel, while very sharp, is also very brittle. The soft iron backing absorbs & diffuses vibration & shock, theoretically making the steel edge last longer. Additionally, this iron is much easier to grind and hone, so less work overall with maintenance.

I have a few 18th & 19th century woody planes, with lovely laminated blades from England, and they are indeed a joy to use and hone. I've never had the pleasure of using a laminated chisel, though.

Regardless, my next set of chisels will almost certainly be PM-V11's. I need to simplify my life more.