Sharpening CPM M4

[theonew]

First let me say, 98% of my sharpening is done with two tools, an 8 inch DMT Duosharp (coarse and extra-fine) and an 8 inch Spyderco ultra-fine benchstone. While I respect all you guys with the .92 micron Shapton stones and 2,000,000 grit diamond dust and love to see pictures of those beautiful edges, I'm happy with my set up as is and haven't encountered a steel yet that I can't put a hair whittling edge on.

Now lots of guys here are able to get a hair whittling edge finishing with DMT extra-fine. Up until now that just hasn't been possible for me, I attribute it to having very thin, fine hair. Sure I can sometimes get an edge that will take off a curl after a few passes using optimal technique, but it's just not really there. Several strokes on the Spyderco ultra-fine and bingo hair splitting goodness.

Well this weekend I finally got my M4 Mule dull, well dull enough so that it shaved leg hair but didn't leave a clean patch behind That took a lot of use, cutting out roots in a hole I was digging, cutting rubber, eating a steak on a china plate, and lots of other tasks. So last night I sharpened it just using the DMT extra-fine. Gave it a good 20 - 30 passes per side and touched the edge and it felt particularly sharp and sure enough it whittled hair beautifully. Running a fingernail down the edge, it didn't feel highly polished but more polished than any other blade I've checked right off the DMT extra-fine hone

So today just to see if this was an aberration, I dulled the blade and re-sharpened it with the DMT extra-fine. Sure enough, hair whittling sharpness again. This is interesting to me. I'm guessing the carbide structure is such that it abrades in a cleaner fashion than other steels, though honestly I don't really know what to attribute it to.

In any case it's a big plus for me since I only bring an extra-fine DMT Mini-sharp when I go hiking and camping and had given up on ever getting a hair splitting edge when sharpening in the woods.

CPM M4 just continues to impress the he11 out of me

 

[cotdt]

My M4 Mule also seems to have finer grain size than some of my other knives, the edge wears more smoothly. Not as smooth as 52100, but smoother than any stainless steel. The grain size also has a lot to do with the heat treat though, so my hats off to Spyderco. You need perfect temperture control and timing to prevent grain growth.

BTW, it's 200,000 grit diamond dust, that's 1 fewer zero. I think the finest available is 400,000 grit but nobody uses it. I used that and got an edge that was so smooth it looked like a straight line under my 200x microscope. It shaves off a thin layer of skin in my shave tests, without cutting into the main skin cells, just got a smoooth clean under-the-skin shave, this knife has a soul of its own.

 

[theonew]

BTW, it's 200,000 grit diamond dust, that's 1 fewer zero. I think the finest available is 400,000 grit but nobody uses it. I used that and got an edge that was so smooth it looked like a straight line under my 200x microscope. It shaves off a thin layer of skin in my shave tests, without cutting into the main skin cells, just got a smoooth clean under-the-skin shave, this knife has a soul of its own.

Yeah I know one of these days I'll kick it up a notch

 

[David Martin]

One, Glad to see your achievement.Probably was just the full moon.Better check it again.
DM

 

[gunmike1]

Good job! I've gotten my Tom Krein Ultimate Caper to start whittling hair with perfect technique at DMT Fine (only on my wife's thicker hairs, not my daughter's thinner hair), and at Spyderco medium it whittles hair very nicely on my microbevels. CPM M4gets sharper than any other steel I own. At .05 micron (300000-400000 grit) it is amazingly sharp. It skinned out a large pig with that finish and was still cutting very nicely at the end after several light bone impacts with no visible denting or rolling on the thin and acute (20-24 degrees included) edge.

Mike

Mike