Sharpening CPM M4

D

Dr. Cornwallis

Joined
Feb 11, 2014
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Hey guys, I've got an 810 Contego with the CPM M4 blade, it seems like a lot of people use DMT stones but is it possible to sharpen CPM M4 with a strop and compound? I already have the knives ship free strop and compound from when I purchased my Bravo A2.
 
As long as the edge is not too far gone, it is certainly possible to touch up M4 on a strop.
 
Stropping an edge can and should be used to refine an edge rather than to sharpen it. Stropping pushes metal back into place and lightly polishes the edge, but if an edge has actual wear on it, you're going to have a tough time actually removing metal - in fact, you're probably going to compensate for this by applying too much pressure, which can have a negative effect on edge retention.
 
You may be able to retouch or refine the edge with a strop and compound but not resharpen.

Plus the a amount of time it would take with a non diamond/cbn compound will probably round the edge
 
Ok awesome. I'm new to knives in general but it's a growing interest for me. I think I'll pick up a set of the DMT whetstones unless there is something better out there?
 
You can sharpen a knife start to finish on a strop if you feel so inclined. There is high quality stropping compound available as coarse as 80u (160 grit)

I would start off with a 3 piece stone set and go from there though.
 
Dr. Cornwallis said:
Ok awesome. I'm new to knives in general but it's a growing interest for me. I think I'll pick up a set of the DMT whetstones unless there is something better out there?
Click to expand...

I use DMT hones (C, F, EF), and they've been handling just about any steel I've thrown at them, including S30V, ZDP-189, M390, and M4. They're not the cheapest but they work very well.
 
The CPM-M4 Contego I've used for a few months touches-up best on a 325 grit Smith's diamond bench block. Bought the diamond block at the big chain sporting goods store headquartered in Nebraska. They also sell the 750 grit Smith's diamond block; I suggest the larger 11.5" size.
 
It's not that you can't it's the abrasive that you are using that will be lacking in ability.

For stropping you will NEED diamond sprays or pastes.

My personal favorite is a fine diamond followed by 1 micron diamond on balsa wood.

CPM M4 also responded very well to being microbeveled with a spyderco Ultra Fine Ceramic.
 
Thanks guys! I messed around with it a little yesterday on my strop using the knives ship free black and green compound and while I haven't gotten it razor sharp yet, I've got it where it will cleanly drop cut paper again. I'm new to sharpening though and just going off the directions.
 
The Bark River black compound is approximately 3000 grit. If you want a finer edge especially on abrasion resistant steels. select 4 micron CBN. Two micron is finer and 8 and 16 will help quickly restore the edge. These are all available on KSF.

---
Ken
 
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