It may appear that the solution for best performance is simply to harden all blades to 60 RC. It is not quite that simple. The higher the hardness the greater the brittleness and greater likelihood of breakage or cracking. For that reason most of the knives do not exceed 57 or 58 RC. Anyway we have seen many knives broken or cracked on its cutting edge.
The test pieces that I hardened with blades, show that my knives do not break without previous deformation. I full guarantee it.

With these and other tests demonstrated again that it is possible to hardened the blade to 60 RC, without risk of breakage.
A good hardened blade must flex (within the limits permitted by its thickness) without risk of breakage and pass the elastic limit to arrive the deformation without breaking (as in the sample picture on the left).
This knife (Mod. 38) is twisted without breaking, by prying nailed on something hard, maybe a bone or a joint, although it is "fully hardened", ie "side by side"
to 61 RC of hardness.

The right photo shows a jagged knife. Says the article published in the journal Blade of August 2000, signed by Ed Fowler, that Schempp, after successfully cutting the ropes, and win the competition in the Oregon Knife Show in 1999, dented knife trying to cut branches a task for which the knife was not prepared. I agree that a knife prepared to cut rope is not suitable for axing branches, not to have the structure and proper angles, but would not rule out that the thermal treatment also has any effect on the result.

In my conference at the Expo Arms 2001, discoursing on the importance of angles and hardness, with this knife cut 30 or 40 times hemp ropes 1 inch and the same number of pieces of sole, few empty cans of soda and without re-sharpening the cutting edge, the blade intact was "shaving". Its blade is extremely thin concave, of SAE 52100 steel, hardened and tempered with a hardness of 61-62 RC. The knife belongs to the private collection of Colonel. J. B. Dagger.

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