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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #1  
Old 12-14-2006, 12:15 AM
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titaniumdoctor titaniumdoctor is offline
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cpm m-4

We recently built some die steels from cpm m-4 and these steels were hardened to about 64-66 Rc. I was able to obtain a few small pieces from scrap, enough for a dozen or so folder blades. I think this is the alloy that taps and drills are made from and seems like a good choice for a using folder. Anyone ever use this material and if so how does it work compared to say D2.
Thanks, Jeremy


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Old 12-14-2006, 01:17 AM
KLC KLC is offline
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Cpm M4

Titaniumdoctor

Check out the December issue of Blade. There is a good article on CPM M4. It seems to be good for chopping and have high impact strength. Reads like A2 on steroids.

Kevin
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Old 12-14-2006, 04:21 PM
Larrin Larrin is offline
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At 59-61 Rc it has toughness close to that of A2 does at 60 Rc (about 36 ft. lbs. vs. 40), and if you take it to 65.5 Rc you get toughness close to that of D2 at 60 Rc (20 ft. lbs. vs. 22 ft. lbs.) so it can be taken very hard with toughness that is more than adequate, or taken softer for toughness for heavy use blades, or just for a good balance of toughness and wear resistance. There are several makers using it in competition choppers. It is also very wear resistant, somewhere in between 3V and 10V. It is difficult to polish, though.

Edit: It also gets 28 ft. lbs. at 63.5 Rc and 32 ft. lbs. at 62 Rc.

Last edited by Larrin; 12-14-2006 at 05:28 PM.
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Old 12-14-2006, 11:29 PM
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So for overall ease of finishing, would it be in my best intrest to use this steel over D2 on an everyday carry folder? D2 in itself is a pain in the ass to finish, so in the long run if M4 dosen't yield much of an edge holding benifit over D2 is it worth it?

Thanks, Jeremy


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Old 12-15-2006, 01:06 AM
KLC KLC is offline
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Cpm -m4

Titaniumdoctor

The article in Blade suggests that CPM M4 has a higher vanadium content than both D2 and A2 but has A2 like chrome content so it has really good edge holding due to the vanadium but strength from the carbon/chrome ratio similar to A2.

Therefore as I read it it is intended to have better than D2 edge holding along with subsequent resharpening difficulty due to the higher vanadium content and high strength due to the carbon/chrome ratio but of course trades this off against less stain restistance and therefore higher care required than D2.

The Blade article was written from the perspective that CPM M4 would make really great cutting competition blades.

I'm probably preaching to the converted but as with all tool steels you have to trade the various characteristics of toughness, strength, edge holding, sharpenability and degree of maintenance to make the type of blade that suits the job you have in mind for it.


Kevin

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  #6  
Old 12-15-2006, 01:49 PM
Larrin Larrin is offline
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CPM-M4 should have much greater edge retention than D2. Jerry Haffridge (sp?) is a longtime user of D2, and he says M4 cuts much longer, I believe he likes it better overall. CPM-M4 is probably not any easier to finish due to the vanadium carbide, it's probably more difficult even.
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Old 12-15-2006, 06:11 PM
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Thanks for all the info. guys, I may give this stuff a try on a knife or two.
Thanks again, Jeremy


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Old 12-16-2006, 04:31 AM
Jerry Hossom Jerry Hossom is offline
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I have some CPM-M4 but haven't had a chance to use it yet. Talking with people in the chopping competitions it is pretty far beyond anything else they've tried in terms of toughness. They don't really care about edge retention, which based on the composition I'm sure is prettty good. They really care that nothing will chip or roll an edge that has to cut through both empty coke cans and 1" hardwood dowels. That takes a very fine and very tough edge. It also fine edge that won't roll. Getting all those in one steel is pretty tough.

S30V has the same transverse toughness as A2, and about the same wear resistance as D2. CPM-3V is better than most of these, but a fine edge (Rc61) on hard impacts will tend to flatten just a tiny bit (as in difficult to see after cutting through 3" beef bone).

I believe CPM-M4 is probably a very good steel based on some of the recommendations of some of the best knifemakers out there. I do understand it is NO fun to work with. M2 is bad and CPM-M4 is worse.


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Last edited by Jerry Hossom; 12-16-2006 at 04:34 AM.
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