Help with choosing Rockwell Hardness

T

Theo988

Joined
Dec 20, 2013
Messages
19
I made 3 knives out of cpm 3v one usuba and two kiritsuke and sent them out to be heat treated to 62. I don't see people taking it that high. The charpy values on crucibles data sheet seem to be good at 62. Did I mess up or will it be ok? Second question, is it ok to not have a distile taper on the knives I made? I don't think I can do it and make everything crisp. The full flat grind has a distill taper. 20151103_164855-480x853.jpg20151103_191934-480x853.jpg
Thank you for your time. First time asking for advice been too shy to ask before. Will be really grateful for any feedback back:)
 
CPM 3V at 62HRC in usuba and kiritsuke should be A-OK! Especially if the user really understands how to use these knives properly. Sure, it is OK to not have distal taper. I don't suppose there is any set rule on that....go with what you want to accomplish. If in the future you want to try it out, give it a go!
 
62 is no problem. I've had mine done at 64 and had no issues with a general use outdoor knife.
 
I have a small custom from a maker here on BF in 3V at 62hrc. Works great the maker sent me some info stating benefits of running it hard in a smaller knife and he was spot on. Good luck with your cutlery. Russ
 
I think these numbers are from crucible, at least they match the crucible datasheets I've seen IIRC. I pulled them from a post from another member:

Charpy C notch, ft. lbs.

CPM-15V......@Rc60..........10
CPM-10V......@Rc60..........20

CPM-3V.......@Rc58..........85
CPM-3V.......@Rc60..........60
CPM-3V.......@Rc62..........40

CPM-4V.......@Rc60..........50
CPM-4V.......@Rc62..........36

CPM-M4.......@Rc65.5.......20
CPM-M4.......@Rc63.5.......28
CPM-M4.......@Rc62.........32

CPM-S90V......@Rc56..........20
CPM-S90V.....@Rc58...........19

CPM-S60V.....@Rc56...........16

CPM-S30V.....@Rc58...........28

CPM-S35VN....@58Rc...........32

CPM-154......@60Rc............30
154CM..........@Rc58...........28

440C............@Rc56...........26
440C............@Rc58...........16

420HC...........@Rc58...........24

M390............@Rc60...........22


Even at 62 for 3V there's a lot of toughness there, relatively speaking. Hell, at 60 RC 10V and M390 are three times more likely to fracture and CPM154 is twice as likely. If guys are generally happy with most properties of these steels I'd assume they'd be even happier with 3V at 62 unless they wanted higher stain resistance or only needed the carbides to do the cutting.
 
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Just one suggestion. Don't grind knives wearing flip-flops. Drop that blade and it may end up standing up vertically with the point thru your toe.

Tim
 
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