Cpm rex m-4

[Ocelot85]

Have any of you worked with it before? If so what was your exprience like with it? I was thinking of using it one some future projects.

 

[Kunklec]

I have used on 2 knives. Easy enough to grind annealed. PLate quenched. Very difficult to grind when hardened. Even with ceramic belts, I felt like I was just polishing it. Be sure and get all finishing done before heat treat. I don't have the temps in front of me right now, but I used the numbers from CPM. After temper it was about 62 Rc. Holds the edge forever and then some. It is expensive. The reason I used it was a direct customer request. Did a ferric chloride bath and handles in horse stall mat. One was over 10", no warp problems. He was a very happy customer until he decided he would try to improve the hair shaving edge. After much frustration, he brought it back to me for resharpening on the ceramic belt. He had used a diamond stick and rolled the edge. MAke sure you or your customer really want a knife that is extremely difficult to sharpen.
Chip Kunkle

 

[Nebulae]

Agree with everything above, but I didnt find it too hard to finish after grinding.

 

[Aldo Bruno]

I ground this piece from CPM M-4. It was the drop from a piece that came off the rolling mill at Niagara and was "Pre-Tapered". I was able to remove very little to get to what you see here. I usually work with carbon steels and found I went through a lot more belts to get to this point. I guess it's all perspective. It was heat treated by Peter's to 60RC and holds a wicked edge in spite of the card board shipping tubes we've run it through. I've got a little more work to due on it then it's off to get finished by somebody else or it will never get done.

 

[xmtgx]

Ground a .310 piece into a competition chopper it was fairly easy to grind preheat-treat roughly an hour or so from stock to rough ground blade used up only a single 36grit belt and a single 120grit belt. Post heat treat is another story its such a pita to grind. Performance is worth it however IMO. Holds an edge like no other at around 61RC and cuts like crazy.

 

[Nebulae]

It does perform very well, it is my favorite all round steel, good at high hardness, but also tough enough to make a big chopper. It is tough at high hardness, and has good carbide volume, but it still takes a very fine edge. I agree with aldo though about the perspective. I make most of my knives from pre-hardened T1 stock at about 64 Rc, so I am used to working with supper hard steel.