difference between M2 and M4 steel

Re: difference between M2 and M4 steel

John K Jordan

>I notice this:

"Because of their high hardness, vanadium carbides are particularly beneficial for wear resistance. When present in significant amounts, vanadium carbides tend to dominate other types in affecting wear properties. For instance, M4 high speed steel�s chemical content is nearly identical to M2 high speed steel, except M4 contains 4% vanadium instead of 2%. Despite the high levels of molybdenum and tungsten carbides (about 6% tungsten, 5% molybdenum) in each grade, the small difference in vanadium content gives M4 nearly twice the wear life of M2 in many environments." http://www.crucibleservice.com/eselector/general/generalpart1.html

Of course the key phrase here may be "in many environments". Since HHS is widely used for cutting metals instead of wood, the difference in wear they mention may not be as significant for turning.

JKJ in East TN

Re: difference between M2 and M4 steel

Brad Vietje

>M4 is harder, and longer wearing. Most people agree that the softer, more maleable metals can be sharpened to a keener edge, but they won't hold up as long as the harder alloys.

Safe spinning,

Brad Vietje

Thetford, VT

Re: difference between M2 and M4 steel

Fog Tanner

>I have a 9/16" gouge in M4, which I bought from The Cuttingedge. They are local here in Houston. I have never had a problem indealing with Steve. He has the best prices around here for cutting tools and carries all the Henry Taylor tools.

I sharpen the M4 gouge on my Tormek and can get the same edge as I do on my M2 tools. The M4 does hold its edge a little longer than the M2. In talking with one of the professional turners, I asked about the various harder alloys, like 2030 and 2060. He felt that the price could not be justified and uses all M2. And if you want to sharpen them you will need a differnt hardness wheel to get them sharp. The M4 is close enough to M2 to use the same wheel.

Re: difference between M2 and M4 steel

jeff jilg

>re: m2 keeps a keener edge than m4

That seems to be true for my m2 and m4 tools. But I wouldn't want to say that on a witness stand. Does anyone have a metallurgy explanation for why this would be true? Can M2 be sharpened to a finer edge than the PM steels (Powdered Metal)? If so, why?

Re: difference between M2 and M4 steel

Fog Tanner

>I have yet to find anyone that can give a reason that the softer steels can be supposedly be sharpend better than the harder steels. When I was in college I worked in a shop that made carbide cutting tools. We did everything from mixing the powder and fusing it to grinding the finished piece. Among other things I ran the grinder. I could put a razor edge on the cutting tool, but I had the right wheel for the job. It was a diamond wheel, which is the only thing harder than the carbide.

On one of my shop grinders, I have a "green" wheel for sharpening carbide only. I think the stories about getting a sharper edge on the softer steels, is because they are using the wrong wheel for those steel. I get a razor edge on both my M2 and M4 with my Tormek, but would not be able to use the same wheel on the PM tools.

But, as with religon and politics, everyone has an opinion that they will beleive in very strongly. And I'm not even going there about not being able to get a real sharp edge with a 56-80 grit wheel - for the same reason. Just my 6 cents worth (inflation)..

Re: difference between M2 and M4 steel

Brad Vietje

>I'd be happy if a real metalurgist jumped in here, but here's the result of some research I did a few years ago, when I first bought a few powder metal tools.

I was told that the difference was found in the crystaline structure of the alloy. Basically, that softer metals, like carbon steel, had a flatter, more plate-like crystal structure, while powder metals and exotic alloys (2060, V-15, PM, etc...) had a more grainy structure. For some reason, the softer metals were said to be capable of a finer edge, but that they would break down and dull more quickly. It doesn't seem like the difference in sharpness is very large, if it exists at all. The difference in cost, however, is significant.

Sharpening often is only a problem if sharpening is difficult, slow, costly in metal removed, or stressful (can ruin your turning). Seems to me that a sharpening system that is fast, easy, reproducable, and that removes very little steel is the best bet, and people might not spend so much more if they had such a sharpening system.

Safe Spinning,

Brad Vietje

Thetford, VT

Re: difference between M2 and M4 steel

jeff jilg

>I have two Crown gouges. One is M2 HSS, the other is from their PM line. The PM basically is a different compound, and created differently, using more vanadium and other metals. In this particular case I didn't think the PM tool was exhorbitantly more expensive than the M2 HSS version.

Both get sharpened via the same jig on the same wheel. One thing is certain. The edge on the PM tool stays sharper longer. I've turned over 300 pieces and the PM tool is my mainstay.

Brad - your hypothesis on the grain and crystal structure makes sense. But I also agree with your comment that the difference in sharpness (if it exists) would be hard to detect.