CPM M4 Hunter

samuraistuart

samuraistuart

Joined
Dec 21, 2006
Messages
3,158
Figured I'd give CPM M4 a go around this year. This was from .106" bar stock, supplied by Chuck Bybee, and the heat treat done by Peter's Heat Treating to 64HRC. Custom HT: no snap temper, straight to the LN, and 3 low temp temper cycles. (thank you Brad) 0.008" before sharpening, full flat grind. Stabilized Walnut Burl from Chuck Bybee, black G10 liners, SS corby bolts. Can't wait to sharpen it tonight, I'll probably do the "usual" 15°DPS edge at 1 micron. Feel free to comment, critique, or place an order! Thank you for stopping by.

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samuraistuart@yahoo.com
www.stuartdavenportknives.com
Facebook: Stuart Davenport Knives
 
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Another beauty, Stuart, I sure like mine. Been using it in the kitchen to get used to it for deer season. The CPM-M4 is terrific.
The new one has a little less drop at the tip than mine does- I like both! And, you changed your blade marking.

SamuraiM4knife_zpswrfyv3wi.jpg~original
 
Very nice and clean!!
Stuart, by 15dps do you mean 30° included? I have never tryied M4, do you think it won't stand lower angles?
Thank you

Stefano
 
Thank you, kind gents! Stefano....yes, sir. 30° included. Forgot to mention that it is at 64HRC....post edited to reflect that. I actually think M4 WILL stand lower angles....for the type of work that knife will see. Due to the CPM process, it's fairly fine grained steel.

I am always looking at opinions on how low an edge can be taken for a given steel/given application. Obviously...a knife like the one above isn't a camp knife, mainly a meat slicing machine, and the edge will not be torqued much. So if someone says, "I use M4 at 64HRC on deer and mine is at 20° inclusive...no issues", my sharpening stones will be drug out again!

Sharpened it last night, and what fun that was! To establish a quick bevel, I had a used 60 grit belt that I cut and laid out. I did not want to apex with that belt, just establish the bevel. Moved to a 400 Naniwa Superstone. Very strange....the metal swarf was clearly visible, but I felt like I was getting NO where with that stone. Kept my eye on how much light was being reflected by the edge, seemed like no change even after some moderate pressure on the stone. Moved to the XC DMT....and that went somewhat faster....almost apexing with the DMT. Back to the 400 Naniwa...apexed....and wow what an edge. Moved up to Naniwa 2000 Green Brick, and that stone took out all the "bite" the edge had. Moved up to 4000 King, and it felt like I was dulling the apex, those two stones maybe too soft? Not sure what was going on. Moved back to the 400 superstone and left it there, finishing with a few light edge trailing passes. VERY aggressive edge.

Anybody with thoughts on CPM M4 performance, or sharpening tips, I'm all ears.
 
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I have not used M4 at that hardness, but would love to try it out. On my fine slicing knives, I like to establish the edge bevel at around 7 or 8 degrees per side- basically just keeping the spine off the stone enough to prevent scuffing the finish. Maybe come back at 10 degrees per side with a microbevel, but only if I can see it's actually needed after using it a while.
 
I asked because i have never worked with that steel and i like to know your opinions that i trust.
When i stumble into very hard edges i'm not afraid going to the apex with the coarse diamond stone, then goin' through the naniwa chosera 600grit. The latter (amazing stone!) has low wear and lowering the pressure as i go i can prepare the edge for the final honing...generally 1000(just few touches)-5000-9000-wet newsprint/smooth leather strop.
I agree, just because there is a just a minimum sliver of light on the edge doesn't mean it would be easy to get rid of!!!!
If possible, i advise against trailing edge on the stones, even if there is the risk of digging/dulling in leading mode if the stones are soft.
 
I had micro-chipping with M4 at 30 degrees inclusive. Working at 34 degrees now and it seems more stable at high hardness. The knife hits walnut a fair bit for use on a cutting board. So far so good. Any issues and i'll try 36. Keep in mind with a full flat grind, if you are using a sharpening system you must increase the angle to account for the grind of the knife :)

Beautiful piece Stuart!
 
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Thanks for the info. I'll keep my eye on the 30° inclusive edge and see how she performs. This knife is a dedicated hunter, and as such will hopefully only be cutting meat. After reading a recent thread here, I bought a Bausch and Lomb 20X loupe. I was amazed at how much detail you can see on a sharpened edge!
No sharpening systems here......although I do use the Razor Edge systems clamp on guide, and adjust the guide's position in order to obtain the angle that I want. I use trig to do so, and then usually verify with my Iphone and the angle app. I take the measurement using the actual center line of the blade....not the bevel itself.

Stefano, I rarely if ever do any trailing edge strokes. I tried it on this one just to see what's what. Just did a few light passes...couldn't tell any difference by touch anyway. What gets me is how the apex felt like it dulled on me when I went to the softer stones. Now if I was freehanding it, I would say that it was improper technique, but with a guide....I am at a loss.
 
You might have been flipping a microscopic burr back and forth. Try increasing the primary bevel angle by 1 degree on the final stone and knock the burr off. A few strokes on a ceramic hone and a strop might help as well.

Alternately, the depth of the final grit stone may be slightly different than the other stones, and you may be missing the apex by a few micrometers when you switch.
 
If your stone is that soft, there is a real possibility that you're actually cutting into the stone and dulling the edge, rather than gliding across the top. I found this out when I tried to use my Norton 4000/8000 razor hone to put a microbevel on pocketknives. The edge was digging into the stone since the binder is so soft.
 
Thanks for the additional input. As the edge sits now I'm pleased. If I get the bug to re try the soft water stones and a more refined finish, I'll post the results.
 
The loupe and the permanent ink marker are indeed a useful add-on to the sharpening toolbox ;)
With softer hones i'm also having troubles avoiding digging into the stone! Grrrr!

Just in case someone had missed it, here is a very interesting insight into sharpening, worth reading every page

https://scienceofsharp.wordpress.com/
 
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