CPM M4 sharpening

A

ammo

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May 5, 2009
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I recently got a Benchmade 760. 4" folder, tanto blade. I've read that CPM 4M can be difficult to sharpen. Anyone have experience with it? I am a newbie when it comes to sharpening. I got croc sticks but they seemed ineffective. It's sharp but could be better. Any suggestions? Thanks
 
It's a very wear-resistant steel, so it'll probably take a longer time than other steels to sharpen.

It's probably not a good steel to use to learn the ins and outs of sharpening.
 
I am used to sharpening ZDP, S30V, CPM D2, VG-10, ect and find CPM M4 (as done by Tom Krein) to take an incredible edge whether it be by DMT, Spyderco ceramics, or Shapton Glasstones. It sharpens easily for me and even at coarser grits starts pushcutting extremely well. When finished off on .05 micron lapping film the sharpness is stunning. Then again, I just sharpened my ZDP-189 Stretch 2 the other night and am marveling it sharpness wise. I just remember when sharpening my Krein M4 knife side by side with other steels it was the pretty always the sharpest.

Mike
 
CPM-M4 is easier to sharpen than most other CPM steels, it will also take a very very keen edge. It seems to respond well to ceramic and diamond hones and loves a good stropping. M4 takes a very high polish and seems to have no limit to how sharp it can get and will do all of this at low edge angles.

Re-profile the edge to a nice low angle and polish it to a mirror finish, get rid of the factory edge its causing most of your problems.
 
ammo said:
I recently got a Benchmade 760. 4" folder, tanto blade. I've read that CPM 4M can be difficult to sharpen. Anyone have experience with it? I am a newbie when it comes to sharpening. I got croc sticks but they seemed ineffective. It's sharp but could be better. Any suggestions? Thanks
Click to expand...

Use modern sharpeners - DMT. I fount it is easy to sharpen premium steel then entry level. I consider all this talk about "hard to sharpen" some kind of universal way to downgrade superior steel from lazy for new technology manufacturers. Another one is "too brittle, easy to chip". Every single new high performing steel went through this "claims", which have no real basis when you try to dig to the roots.

Thanks, Vassili.
 
knifenut1013 said:
CPM-M4 is easier to sharpen than most other CPM steels, it will also take a very very keen edge. It seems to respond well to ceramic and diamond hones and loves a good stropping. M4 takes a very high polish and seems to have no limit to how sharp it can get and will do all of this at low edge angles.

Re-profile the edge to a nice low angle and polish it to a mirror finish, get rid of the factory edge its causing most of your problems.
Click to expand...

That pretty much hits the nail on the head. M4 takes very thin and polished edges that are sharper than any other steel I have.

Mike
 
I agree, M4 just loves to get sharp. I too have the 760. It's really, really thick, and has a pretty obtuse grind compared to a lot of other knives. It's a great knife, but untill you thin it out you won't see the really, really sharp edges like Gunmike gets with his Krein knife. The comparison is like a splitting maul compared to a hunting knife.

I want to send my 760 out to get thinned professionally to make it a slicer, which it isn't out of the box IMO. Joe
 
Joe, send the knife to Tom Krein! I am really interested in how Benchmade's M4 is because I may want to get one and send it to Krein for a regrind, but I'm not sure how the Benchmade heat treat is, though I suspect it is very good. It is a shame if M4 is being wasted on really thick edges when the steel works so well on the thin side.

Mike
 
Thanks to all who responded, great info.
When a blade is thinned is that done at the cutting edge or is it done over the entire blade width? ( another newbie question ). Thanks
 
ammo said:
Thanks to all who responded, great info.
When a blade is thinned is that done at the cutting edge or is it done over the entire blade width? ( another newbie question ). Thanks
Click to expand...

Just the edge bevel.
 
knifenut1013 said:
CPM-M4 is easier to sharpen than most other CPM steels, it will also take a very very keen edge. It seems to respond well to ceramic and diamond hones and loves a good stropping. M4 takes a very high polish and seems to have no limit to how sharp it can get and will do all of this at low edge angles.

Re-profile the edge to a nice low angle and polish it to a mirror finish, get rid of the factory edge its causing most of your problems.
Click to expand...

Knifenut, what is your preferred method of re-profiling an edge like the one the OP is referring to? I have an older Lansky system, a Sharpmaker, and various old stones and I am not happy with any of them for re-profiling even D2, much less M4.
 
Gunmike, It's one of 6 knives I have in CPM M4. Benchmade runs it a bit soft for my tastes, so I may need to reheat treat it harder somewhere too. Another BM M4 knife I bought came thinner, and sharper. That was the osborne, with it's strange recurve tanto. It looks weird, but it cuts great. Likewise the Spyderco Mule will really cut as is. The 760 is just another project in a long list. Joe
 
FLymon said:
Knifenut, what is your preferred method of re-profiling an edge like the one the OP is referring to? I have an older Lansky system, a Sharpmaker, and various old stones and I am not happy with any of them for re-profiling even D2, much less M4.
Click to expand...

I use DMT diamond hones and diamond strop spray, makes quick work of any steel.
 
My CPM M4 knives are so easy to sharpen, I can't believe it's not butter.

Easy to mirror polish as well. Scratches are easy to remove. Whenever I try to mirror polish stainless steel there would always be a few scratches that I couldn't get rid of.
 
Love M4! I have had good luck with the edgepro and M4 as well as convexing it. It is a great steel. I wished more maker would use it.
 
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