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Old 10-03-2017, 05:42 PM   #1
djohnson
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Default Cryo treated knife blade question

New to knifemaking. Bought one of those Cryo treated blades and wanted to drill a 1/4" hole in the end of it for a lanyard. I couldn't believe how hard this stuff is. Try as a I might I'm barely making progress in the thing. Is there some trick to drilling this stuff? And what exactly is Cryo treatment anyway?
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Old 10-03-2017, 09:29 PM   #2
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You should be able to use an all purpose bit slowly with cutting oil but generally you would drill your holes before heat treat for that reason.
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Old 10-04-2017, 11:21 AM   #3
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I'n no knife maker by any means, but would it be possible to simply heat the end of the tang with a torch to allow the metal to soften enough to drill. How risky is this to not impact the blades hardness?
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Old 10-04-2017, 01:32 PM   #4
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Quote:
Originally Posted by canny View Post
I'n no knife maker by any means, but would it be possible to simply heat the end of the tang with a torch to allow the metal to soften enough to drill. How risky is this to not impact the blades hardness?
It may soften a bit and worth trying - if you use a torch and don't get near the blade, you'll be fine but I don't think it will back down super much with using a limited time/torch process - just going to be hard to drill but possible.
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Old 10-04-2017, 01:35 PM   #5
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Thanks! I've been looking at ordering a couple damascus blades and building the scales our of some antler from a buck my grandfather killed, but I was concerned about drilling the tang for pins, if they weren't drilled already.
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Old 10-04-2017, 02:22 PM   #6
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So what exactly is cryo treatment in a knife blade? I'll try heating it next.
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Old 10-04-2017, 04:19 PM   #7
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So what exactly is cryo treatment in a knife blade? I'll try heating it next.
according to the webopedias: Cryogenic hardening is a cryogenic treatment process where the material is cooled to approximately −185 °C (−301 °F), usually using liquid nitrogen. It can have a profound effect on the mechanical properties of certain steels, provided their composition and prior heat treatment are such that they retain some austenite at room temperature. It is designed to increase the amount of martensite in the steel's crystal structure, increasing its strength and hardness, sometimes at the cost of toughness. Presently this treatment is being practiced over tool steels, high-carbon, and high-chromium steels to obtain excellent wear resistance. Recent research shows that there is precipitation of fine carbides (eta carbides) in the matrix during this treatment which imparts very high wear resistance to the steels.[1]

The transformation from austenite to martensite is mostly accomplished through quenching, but in general it is driven farther and farther toward completion as temperature decreases. In higher-alloy steels such as austenitic stainless steel, the onset of transformation can require temperatures much lower than room temperature. More commonly, an incomplete transformation occurs in the initial quench, so that cryogenic treatments merely enhance the effects of prior quenching. However, since martensite is a non-equilibrium phase on the iron-iron carbide phase diagram, it has not been shown that warming the part after the cryogenic treatment results in the re-transformation of the induced martensite back to austenite or to ferrite plus cementite, negating the hardening effect.

The transformation between these phases is instantaneous and not dependent upon diffusion, and also that this treatment causes more complete hardening rather than moderating extreme hardness, both of which make the term "cryogenic tempering" technically incorrect.

Hardening need not be due to martensitic transformation, but can also be accomplished by cold work at cryogenic temperatures. The defects introduced by plastic deformation at these low temperatures are often quite different from the dislocations that usually form at room temperature, and produce materials changes that in some ways resemble the effects of shock hardening. While this process is more effective than traditional cold work, it serves mainly as a theoretical test bed for more economical processes such as explosive forging.

Many alloys that do not undergo martensitic transformation have been subjected to the same treatments as steels—that is, cooled with no provisions for cold work. If any benefit is seen from such a process, one plausible explanation is that thermal expansion causes minor but permanent deformation of the material.
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Old 10-04-2017, 04:54 PM   #8
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So it's cold hard huh?
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Old 10-04-2017, 04:56 PM   #9
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Quote:
Originally Posted by djohnson View Post
New to knifemaking. Bought one of those Cryo treated blades and wanted to drill a 1/4" hole in the end of it for a lanyard. I couldn't believe how hard this stuff is. Try as a I might I'm barely making progress in the thing. Is there some trick to drilling this stuff? And what exactly is Cryo treatment anyway?
Carbide if you have it.
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