CPM 440V (yet another Q): WHY so brittle?

JoHnYKwSt · Dec 9, 1999

OD's denting was on a very small scale. All it managed to accomplish was dulling the edge faster than his cheaper steels. But cutting normal everyday things, 440V's edge will last longer.

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Johnny
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Bladeandbarrel · Dec 10, 1999

Anybody who has ever used a Spyderco knife in 440V can easily explain why they frequently chip-they are only sharpened with a single bevel...this creates a very acute (thin) edge that is prone to deformation.

Simply resharpening both sides of the ground blade a conventional edge (with correspondingly more metal behind it) will increase toughness in ANY knife edge.

I blame Spyderco chips on the method of sharpening, not the steel, although 440V's toughness has been questioned by others.

tom mayo · Dec 10, 1999

to make myself perfectly clear...i have always sent my knives to paul bos....i have NEVER changed the hardness...i tried to get him to but he said no...that lowering the rockwell below 56c would make the corrosion resistance go out the window.....heat treat is not an exact science....440v is heat treated similarly to 440c, and the goal it to end up with Rc between 56-58. It matters not where....as long as it is in those boundaries...then you know you did everything right...if not...you either have been sent the wrong steel (ive done that plenty of times believe me) or something went wrong..ie...your gauges are off...as for the edge bevel....the steeper the bevel, the better the steel cuts....the blunter the bevel, the worse it cuts...so changing the sharpening bevel is not a cure all for getting rid of edge chipping...id rather have a knife like a razor that might chip than one that didnt cut nearly as well...my opinion//obviously.

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[This message has been edited by tom mayo (edited 10 December 1999).]

storyville · Dec 10, 1999

Thanks all for this latest round of feedback -- I believe Im finally getting a more informed picture of 440V now! (Slowly but surely...!)

Tom, I was certainly NOT referring to your posts, which (as always) have been very clear -- thanks for tolerating my thick-headedness and sharing your wisdom and experience.

...Same for all -- apologies for my long, not carefully thought-out questions, and thanks for replying. Sometimes Im not sure quite what Im getting at till I get some responses first, unfortunately. My stubborn persistence is simply a reflection of my very slow learning curve...

Glen

Jeff Clark · Dec 11, 1999

I forgot to mention a significant factor that influences Spyderco's priorities for heat treatment--serrations. Spyderco is deeply tied to producing serrated blades (and blades with big round holes). If harder 440V tended to chip the tips of their serrations I would expect them to go softer. This is not an issue with a lot of custom knife makers.

My edge rolling was under direct impact to rabbit neck bones. I had a smooth-edged blade that I had thinned slightly. My son was doing some of the work and it was dark. I'm not sure how we rolled the edge, but at 55.5 RC the 440V sure wasn't brittle. I think that 57-58 would have worked better for me. At the same time we were using a little folding knife made from BG42 at RC61, I couldn't see any real signs of use on that blade.

CPM 440V (yet another Q): WHY so brittle?

JoHnYKwSt

Bladeandbarrel

tom mayo

storyville

Jeff Clark