Is there a metalurgist in the house?

a-yup, I'm a metallurgist.

Andrew F in Australia

>Hi Bill,

It depends upon the gross size of the carbides.

I'd say that they all can be sharpened to the same level of sharpness, but a Vanadium Carbide (at HRC85) can not be thoroughly sharpened by silicon Carbide (at HRC~80 from memory.)

Note that the thing in steel that gives it it's hardness is also a brittle ceramic carbide (Fe3C.) The rest of the hardness comes from how the Fe3C stops the soft iron in between the carbide from moving and what else is in the steel.

So, it's not the carbide, but it's relative size and hardness that give the steel it's ability to hold a sharp edge. The size of the iron carbide in an O1 steel is minute. From memory, there's chromium carbide in there as well in small quantites.

In a HSS, the carbides are a lot bigger and there's a higher proportion of carbide by weight. The exception to the grain size route here is if the steel's made by Powder Metallurgy techniques (one of PM's big advantages.)

While it is possible to polish carbides (through abrading), it's difficult. You'll find that the steel between each carbide particle wears preferentially to the carbide both during sharpening/honing/stropping and during wear, having the potential to create a minute scalloped edge like a bread knife, which is still sharp, but uneven.

As well, the carbides are brittle and friable, and create small gaps in the edge the first time the load on the edge of the tool is aat the critical point, so they crumble and fall away easily.

Now, how much of a problem is this? It depends upon how large the carbide size distribution is, so it varies from steel to steel and the prior thermal history as well as the manufacturing process and the grade.

How's that for a straight answer.

CHeers,

Andrew

(A degree metallurgist/materials engineer, as well as a trade cabinetmaker who uses M2 in plane blades)

Re: Is there a metalurgist in the house?

Chicago Bob

>Bill �

After polishing, you have to etch (picric acid, HCl, and / or nital or et al, depending upon the substrate you are trying to etch) the surface to differentiate and reveal the grain structure and various carbides, transition metals, impurities and carbon precipitated at the grain boundaries. After polishing, a suitable acid etch followed by DI H2O rinse should reveal grain structure visible from approx 200 to 400X magnification. ASTM and ASME have standards and handbooks on measuring grain size and interpretation of the results.

Chicago Bob

A2 cryo

David Charlesworth

>Bill,

I do detect a very slight difference of feel between a chisel of A2 cryo and a Japanese chisel but the difference is very slight indeed.

When it comes to plane blades I find the extended use obtainable from A2 cryo is fantastically helpful, particularly in hardwoods.

I sense there is some minute difference but am more than happy with the A2 edges for fine cabinetmaking. I examine these under 50X magnification and can detect no discernable difference.

It seems likely from the research of others that Carbon steel may hold up slightly better at low sharpening angles, but I am perfectly happy with the results I get from waterstones. It seems that oil stone users have more difficulty with A2 than waterstone users and I found that powder metallurgy blades seemed to need diamond paste lapping to achieve their potential.

David Charlesworth

Re: a-yup, I'm a metallurgist.

thomd

>Interesting response.

Tough problem since presumably we would need to know the cutting action of all the stones on all the steels, and the cutting action of all the steels on all the woods. The overwellming field response is that a lot of these things vary. There isn't just one set of model parameters.

I'm sympathetic to Bill in one respect. I have heard all the same things said about carbide router bits, how they couldn't be sharpened as sharp as tool steel. I did once get a Japanese bit with a router that was very razor sharp. The only one I have seen before or since. Based on that one bit I found the whole pro or con discussion of carbides was seemingly based on just a shoddy stock of tools.

sage advice

bill tindall, E. TN

>the last sentence said all one needs to know.

What is "fracture grain size"?

bill tindall, E. TN

>I found literature values of 9 for O1 and M2 and 8.5 for A2 but no definition of the term

Also found that the stainless steel used in razon blades is about 12% chromium demonstrating that there is no relation between amount of alloying elements and ability to sharpen.

Counting the horse's teeth

Wiley Horne

>Bill,

If you can resolve blade edges to 1 micron, let's just look at a couple of them, and see what we can see. F'rinstance, take a high alloy blade, sharpen it to a known level, photograph the edge. Then take an O1 blade, sharpen it to the same level, photograph its edge. Put the photographs side by side and see if any differences are apparent at the 1 micron level. If differences appear to be there, repeat and see if the same result obtains.

But don't miss deer season to do this. First things first.

Wiley....whose anecdotal observation is that diamond sharpening (through 1/4 micron) brings O1, A2, CPM3V, and M2 to the same edge, as tested by how the blade slides through an edge of newsprint. Jury is still out on Japanese steel--it may get a hair sharper, but a tougher test than newsprint will be needed to find out.

Re: Is there a metalurgist in the house?

Paul Kierstead

>all the tool steels sharpen to the same refinement, if done right.

Helluva if, now isn't it?

Fancy tool holders

Phil Smith

>I have not posted much on WC lately but have been following this thread and the one below on edge wear with interest.

My observations over the last several years is that there a lot of energy spent on making tool holders. By that I mean we have commerical companies making very high quality replicas of old Stanley planes, we see changes in the plane bodies to make them easier to use, and we have specialty tool makers making exquisite infill planes and we have specialty tool makers making high quality wooden planes. Almost all of the energy has been focused on the plane body, with discussions around fit, and finish, and overall quality of the plane body. BUT AT THE END OF THE DAY THESE ARE JUST TOOL HOLDERS.

The real work done by planes is with the iron and here we have seen almost no innovation. The two big innovations we have seen is the introduction a A2 and cryo treating. In the scheme of things these are small steps that you can likely measure with carefully desigend experiments but may not be worth the effort.

There are numerous tool steels that potentially have significantly better properties than either O1 or A2 for our woodworking needs. I started making tools with Bill Tindall only after we could find no tool makers offering tools with the edge holding properties we desired. We started with CPM 3V because we were looking for a very tough steel for mortise chisels and in this application it is impressive. Because we had the steel we also made bench chisels, plane irons and other tools and here it also has significantly improved wear properties over O1 and A2 as shown by the work by Steve Elliott. In my opinon Steve's use test is first rate and exactly what is needed for an end use test.

What we need is a sereening test that would allow us to rapidly screen a series of tool steels and geometries with various species of wood to allow choice of the optium steel for different applications.

Just imagine what Stanley or other tool makers would have done if they had acess to the powdered metals that we have today and readily available diamond powder with which to sharpen the tools. When you look for an old tools you will often find the words warrented cast steel and an indication that they were using the best steel available at the time.

Re: Fancy tool holders

Joel

>I think you are making an assumption that longer edge retention is the be-all and end-all. This isn't a universally held view.

Bill Jones the ivory turner, wrote that he much preferred easy to sharpen, inexpensive files to purpose made turning tools of High speed or other alloys because he would rather have a tool that he could trivally sharpen to his specifciations as he worked a job, and have dozens of inexpensive tools all perfect for one application of another, than having fewer, much more expensive tool that wasn't so easy to sharpen.

a question

Larry Williams

>In part you said, "The two big innovations we have seen is the introduction a A2 and cryo treating."

I've spent a little time digging into cryo and can find no documentation of any real improvement in the steel. It simply completes the heat treating which would occur naturally anyway. Every thing I've found agrees with the following from Machinery's Handbook:



Changes Resulting From Subzero Treatment.--When Steel is at the hardening temperature it contains a solid solution of carbon and iron known as austenite, which is relatively soft, tough, and ductile even at room temperatures, is transformed into martensite, a hard and strong constituent. If all the austenite were changed to martensite upon reaching room temperature,, this process would be an ideal hardening operation, but many steels retain some austenite. In general, the higher the carbon and alloy contents and the higher the hardening temperature, the greater the tendency to retain austenite. When steel is cooled to subzero temperatures, the stability of the retained austenite is reduced so that it is more readily transformed. To obtain more complete transformation, the subzero treatment may be repeated. The ultimate transformation of austenite to martensite may take place in carbon steel without the aid of subzero treatment, but this natural transformation might require 6 months or longer, whereas by refrigeration this change occurs in a few hours.

Do you have any documentation showing any improvement in edge retention, wear resistance or anything else?

Re: a question

Phil Smith

>I agree with you. What I should have said is advertised innovations are.....

The next sentence was " In the scheme of things these are small steps that you can likely measure with carefully desigend experiments but may not be worth the effort."

No I don't have any data and in my opinion it probably isn't worth the effort to get when there are potentially much better steels to look at that have the potential to give very large increases in wear resistance.

Re: Fancy tool holders

Phil Smith

>I agree that edge retention is not the be all end all for tools but for some is a major consideration. For specialty tools that are used infrequently, yes easy to make and sharpen is a key factor. But for work horse tools such as plane irons and bench chisels edge retention becomes more of a factor. I would rather make sawdust than spend time sharpening.

With the right equipment the tool steels are not necessarily harder to sharpen and may actually be easier to sharpen for novice woodworkers. The tool steels are typcially hardened somewhere around a 1000 deg F. This means that someone with relaitvely low skill can grind the tool on a grinder without taking the temper out of the tool. We have shown that if you grind CPM 3V to a wire edge on a grinder that you can go directly to 3 micron diamond powder on a cast iron plate and produce a razor edge. It dosen't get much simpler than this.

Re: What is "fracture grain size"? *LINK*

Andrew F in Australia

>Hi Bill,

I use the M2 because it keeps its edge longer than others - it takes a while to regrind but when you need to regrind the main bevel.

If I was working only the softer US hardwoods such as maple, I would reconsider using it - it lasts a fair while between rehonings.

Fracture grain size - I thought that it was ASTM, but I'm wrong - see attached link.

Cheers,

eddie


http://www.metlabcorp.com/pdf/grainsizebrochure.pdf

Re: What is "fracture grain size"? *LINK*

Andrew F in Australia

>Hi Bill,

I use the M2 because it keeps its edge longer than others - it takes a while to regrind but when you need to regrind the main bevel.

If I was working only the softer US hardwoods such as maple, I would reconsider using it - it lasts a fair while between rehonings. It's more a nice to have, but the timber I routinely use will blunt a standard stanley blade in about 2 good strokes (about 10 linear feet,) so a high hardness blade became more of a necessity.

Fracture grain size - I thought that it was ASTM, but I'm wrong - see attached link.

Cheers,

eddie


http://www.metlabcorp.com/pdf/grainsizebrochure.pdf

Oops, double post, delete this one please.

Andrew F in Australia

>

Cryogenic treating

Andrew F in Australia

>Hi Larry,

It's good to see that some are actually now seeing that Cryogenic treatment is more a panacea for poorly controlled heat treatment - in the higher alloy content steels, the martensite start temperature may be depressed sufficiently to keep the steel austenitic at room temperature (eg: 316 stainless steel that is designed to be austenitic at room temperature)

There is an equilibrium amount of austenite that will remain untransformed at room temperature in the high alloy steels - the only way to get to that is to low-temperature quench. (this is my memory talking from 1988 or so in lectures on the subject here - I may be wrong.)

There is also the austenite that has remained untransformed because the rate of quench was too slow - it is this austenite that will change to martensite after a while. This is bad because usually stress initiates the transformation, and if the (naturally brittle) martensite is formed in-service, the section is now brittle. This results in chipping of a blade if it's a tool, as stress is experienced at the cutting edge.

This is the reason for the subcritical anneal - to completely transform as much austenite as possible, avoiding warranty issues and poor press.

Best regards, and hoping that this makes sense,

Andrew

Re: a question *LINK*

Frank D. in Montreal

>Hi Larry,

This doesn't count as documentation, but there's still some interesting info, especially as pertains to the two types of cryo processing.


Cryo thread on SC

ps: more for others' info than yours

Andrew F in Australia

>I forgot to mention that the brittle but unstable martensite is transformed to the tough stable matrix/phases that make up steel by a process called tempering after the hardening (conversion austenite to martensite) is finished

This is typically a 180 degree C by 90 minute spell in an oven for O1,

or heating in air until polished sections turn light straw for cutting tools - 400C by 10 seconds puts the same amount of thermal energy into the steel to drive the conversion as the spell in the oven.

As you know, overtempering results in a softer steel.

If you temper but have retained austenite that transforms at a later stage, then you have a mixture of tempered steel (tough) and brittle steel (untempered martensite) that causes the problems and chipping.

As well, Austenite to martensite is an expansive reaction, that results in the steel becoming 4% less dense (as the matrix expands) and therefore induces stress and buckling into thin sections such as plane blades as a result of the transformation. If this occurs post tempering, it affects flatness.

This is the reason that high quality surface plates are also quenched down to -196C (liquid nitrogen) - to avoid subsequent problems with flatness. However, this level of surface flatness isn't really needed in woodwork.

Cheers,

Andrew

(regurgitating physical metallurgy 201 in no set order and hoping that it makes sense.)

Sounds like there's more than one, Bob

Andrew F in Australia

>

Re: a question

thomd

>I have a set of very nice chisels were the four main sizes were chryoed, and the 3 half sizes were not. SO far the only advantage has been that the very beefy ferule of one of the chryoed chisels split. They otherwise are all the same.

I agree about the Bill jones point there are a large number of the real workers who prefer good tools that are easy to sharpen. Over long edge holding, though decent edge holding is certainly a requirement. Whether this is the real truth or not is hard to tell since I think this is the pattern of serious tool users. Just what they grew up with. I feel the same to some extent, that easy to sharpen with decent edge holding is the best bet, but I like a variety of tools so it's hard to tell.

I very much agree with the tool holder, or handle idea. I get a slight, hard to repress feeling of superiority when I see planes where the body is more expensive than the blade. It is fairly hard to find other examples in hand tools where this is the case though I suppose something like prunners might fit the bill. Maybe an appropriate model would be the modern american corporation where the CEO costs 200 times what the guy at the cutting edge does. Anyway I do think better blades are the way to go.

Re: Fancy tool holders

Miles

>I agree - I have a range of old & new chisels some of which show me other reasons than wear resistance to like 'better' steel - some of them have edges that fail in more extensive ways (fold up, crumple) if they are asked to cut something a bit too hard - such as chopping into ordinary oak... whereas a slightly worn but still straight edge can be used, with more effort, a folded/crumpled one is unusable. I can hone them to steeper bevel angles, etc to reduce the occurrence, but what I think we'd all like is an edge that 'fails gracefully' and predictably, instead of going from 'great' to 'useless' with one excessive blow on the mallet.

It's a very good thread... I will try to find some suitable 'wood machining' info to add to what has already been posted on metalworking.

Miles

Very lucid.

woodburnbob

>Andrew, your mini-seminars throughout this thread are much appreciated. I hope you continue to regurgitate what you recall from your education.

dependent variables

bill tindall, E. TN

>I think these people get settled with a sharpening routine and pick steel to fit it. An alternative could be to pick a sharpening routine that works for any steel. It has not been long that abrading steel with diamonds has been economically available. It was quick to be adapted by those with commercial needs to polish tool steels. Diamond will abrade any steel with near equal rate to what ever refinement one can desire. Sharpening can be a quick and easy two step-grind & diamond hone. The link recently posted from the material scientist at Iowa State should dispel any doubt to the accuracy of this claim.

But we have a chicken and egg situation. Woodworking customers won't accept abrasion reistant steels because their sharpening routines won't handle them. Suppliers won't offer diamond based sharpening systems(for example grey iron plates or diamond charged hones) because there are few customers for them. Contributing, we have highly promoted sharpening systems that have become fashionable that won't measure up to the needs of some tool steels. Finally, we have celebrity figures making claims about ability to sharpen that are not supported by data.

Both the knife and lathe crowd were quick to explore and accept advantages modern steels, likely because they had the means to sharpen them. I found a link to a site where it appears that every tools steel ever made has been intensively investigated by knife makers. But, as Phil said, the woodworkers focus on the tool holders. I don't believe that there are no advantages to be gained by woodworkers from modern steels. But it won't happen until people start exploring these steel properties.