Any makers working with CPM M4?

[theonew]

I finally got my Spyderco Mule in CPM M4 out for the first time last weekend. I didn't do any batoning but did whittle and notch a good bit of wood. And at the end of the day I couldn't discern any loss of sharpness I was very impressed. Now I've heard this steel is also pretty tough, similar to 3V. It seems like it would be a fantastic steel for a medium sized fixed blade knife geared for woods use.

There's always a lot of discussion here about new designs but to be honest I'm really not that picky about design, my Aurora has kept me happy for well over a year. But a higher performing steel would definitely be of interest Any makers here working with or planning to work with CPM M4?

 

[James_Terrio]

What little I've heard about it matches what you've said. Sounds like a great candidate for any very tough knife that must keep its edge a long time. Probably not going to be embraced by folks who prefer 1095, etc. for ease of sharpening. I'm one of those odd ducks who likes knives made from both types of steel.

I've never worked with or used M4, but I'm sure interested in hearing from folks who have. Great idea for a thread!

 

[zhangmaster12]

I doubt many will work with it, and if they do, there will be quite a premium. Which is to be expected, CPM M4 is supposed to eat through belts like mad.

BUT, I there is no doubt that I really want an M4 camp knife


BTW, forgive my tangent, but how does the M4 compare to S30V? Or S90V?

Its my understanding the 90 hold a better edge than 30, but 30 is tougher.

 

[mcjhrobinson]

i hear lots of the competition knives are in M4...there was a good article in BLADE a lil while ago about CPM steels

 

[Jeremy Horton]

i am going to be doin some chopper stuff in cpm m2 soon,,, i know its not the Rex.. but,, might give a good base

 

[sodak]

Tom Krein works in it.

 

[theonew]

Probably not going to be embraced by folks who prefer 1095, etc. for ease of sharpening. I'm one of those odd ducks who likes knives made from both types of steel.

I'm still undecided regarding the faster to sharpen but dulls quicker vs. slower to sharpen but dulls slower debate, but this last weekend with the Mule has definitely nudged me more towards the latter. I'm someone who very much enjoys freehand sharpening and am fairly proficient and efficient at it, i.e., can quickly get a hair splitting edge (literally) on every steel I've used. I enjoy sitting by a fire and touching up a knife's edge at the end of the day but, if a lot a work needs to be done, stopping to sharpen or continuing to use a dull knife just isn't very appealing to me. I'm also very fussy about using a dull knife and though it may still cut but with more force involved, it just doesn't make me happy :grumpy: I also find it to be the opposite of what is commonly espoused, that harder, more wear resistant steels are harder to sharpen. They burr less and with just a couple of strokes at a slightly more elevated angle than the bevel itself form a beautiful edge, whereas with the softer steels it can be much trickier to remove the burr and leave a crisp edge.

Mr. Horton I'll be keeping my eye on your work :thumbup:

 

[sodak]

Good observations. If the grind and geometry are done correctly, there's no reason at all why CPM M4, or any other "super" steel is harder to sharpen. I usually find that they are easier to sharpen when done correctly. Anyone who owns a Krein or Dozier can confirm that. As you've noted, burring is not nearly the problem with the higher end steels, especially with knives above 62 HRC.

 

[Jason B.]

CPM-M4 is a amazing steel that almost never wants to go dull, even when the edge looks flat and damaged it still feels sharp for some reason. Its edge retention is on par with S90V but seems to withstand abuse much better. I use diamond stones so these hard steels don't hold me back but I still think M4 is easier to sharpen than S90V or ZDP.

If it was my choice every knife would be made out of M4 or S90V but then it would be a perfect world. S90 for a short blade and M4 for the bigger stuff is how I would like it.

It would be great if some of our knifemakers would use M4 but I don't think any of us would like the price tag

 

[fujita yuji]

I've been using mainly M2 for these twenty years.
What theonew says about sharpening is also definitely true for M2.

Both M2 and M4 are well established steels for cutting job.
Above all good features, the best thing for me is that heat-treatment guys
know very well about these steels that they do what they should do without no mistakes.

 

[haggismonger]

who heat treats it?

I heard Paul doesn't

 

[cotdt]

who heat treats it?

I heard Paul doesn't

Paul Bos can heat treat M4 up to hrc 63. His oven only goes to 2100 F.

 

[haggismonger]

alright, i thought that was the issue, for an ideal treat on that stuff it's got to soak at some ungodly magmatic temperature, doesn't it?

 

[the possum]

Now I've heard this steel is also pretty tough, similar to 3V.

According to the people who make the steel (Crucible), M4 is no where near as tough as 3V. Comparagraph on 3V spec sheet

But of course with so much success in the cutting comps, it seems like it should have enough toughness to do most normal cutting jobs. I see it more as a steel that would excell in a geometry really meant for cutting rather than bashing. Lots of strength (high hardness), very fine carbides for wear resistance; looks awesome on paper. Would love to try some myself.

 

[dphillips]

I like CPM-M4 alot. All the knives I make, that I carry, are CPM-M4, except for a recently finished S90V one. I compete in the Bladesports competitions, this is where I started using CPM-M4. I now carry a 2.5" caper and a 4" modified wharncliffe everyday at work. My competition knife is of course CPM-M4. I have started carrying the S90V on my belt when I'm not at work since I finished it a couple of weeks ago. I have not had a real good chance to test it out though, that is why I am carrying it instead of the M4. I grind M4 pretty thin and sharpen on diamond. I recently had to use it to cut urethane out of a steel manifold with brass nozzles. The chipping was not that bad but it was so dull from hitting the steel and brass that it would not cut tape. I used a dia-fold sharpener during lunch at work and had it shaving hair in 10 min. Like someone has already said, if it is thin, sharpening is not that bad. And IMHO if you are using a "super steel" and it is not thinner that normal steel then it is a waste. I have seen some amazing things with this steel during the competitions. I can't say enough good about it. The only thing that could be improved is to make it stainless, but for most on this forum that is not a problem. If more information is wanted let me know. I will stop rambling now.

 

[dphillips]

One more thing. Walt2 also has made a couple out of M4, he posted them here. http://www.bladeforums.com/forums/showthread.php?t=667379&page=2

Saw them while cruising Shop Talk.

 

[James_Terrio]

Lots of good points being made here, gentlemen.

Above all good features, the best thing for me is that heat-treatment guys know very well about these steels that they do what they should do without no mistakes.

To me that's a huge plus as well. Being able to find accurate, tested, proven HT information is a big factor when deciding on a steel. I would rather have an ugly grind than a badly HT'ed blade.

 

[cotdt]

According to the people who make the steel (Crucible), M4 is no where near as tough as 3V. Comparagraph on 3V spec sheet

From that same spec sheet, both at 62 rc:

CPM 3V - Impact Toughness: 40 ft-lb, Wear Resistance: 8
CPM M4 - Impact Toughness: 32 ft-lb, Wear Resistance: 20-25

Looks like M4 is just slightly less tough but has vastly superior wear resistance as compared to 3V.

 

[the possum]

I think I'd call that difference significant enough- that's about the same spread in ft-lbs between M4 and the high carbide stainlesses. But either way, yeah, I guess I should have pointed out I wasn't making a perfectly fair comparison. I've always thought of 3V getting its claim to fame for the much greater amount of toughness it can have by tempering down a few points more- it almost doubles by dropping to 60 Rc, which is still pretty hard for a chopper (compared to conventional/traditional wisdom of mid to lower 50's for simpler steels). I would assume Crucible follows the same line of thought considering how much higher they show the line for 3V on the graph.

 

[Mike Carter Custom Knives]

Crucible has been making CPM-M4 for 30 years as a tool steel. It just had never been adapted to cutlery until Warren Osborne and Gayle Bradley started experimenting with it. They literally developed the heat treatment for blades through a lot of research and trial working with Crucible's metalurgist Scott Devanna. You might want to talk to Warren or Gayle about heat treating.

From what Warren has told me, M4 is very difficult to work and it will burn up a lot of belts. He told me "you better have it where you want it before you heat treat".

I have never used it in my own knifemaking but I have been covering the cutting competitions for the last couple of years and learned about it from those who are using it in the competitions. Like Donovan said, you can take it down pretty thin and it will still stand up to very hard use while keeping a fine edge which makes it ideal for the cutting competitions.