STR said:
Even two same knives from the same pattern won't be exactly alike in handmades so the only way to really know the destruction point of any one knife would be to destroy each and every one you made.
The performance variation should be slight, of course they won't be exact, even productions are not exactly alike, however you should quickly bound expected performance with a few tests, otherwise it means your QC is really low.
Most are using patterns long established in knife making anyway so further testing is redundant.
You don't do destructive testing just to see where the blade breaks, you do it to see how it breaks, plus to confirm aspects like heat treatment which can't be evaluated any other way.
I gave my brother a SOG folder awhile ago, almost instantly he came back to me with the clip mangled. The knife got caught up and put a lot of stress on the clip which he didn't notice while he was working.
Now as a maker you have to ask yourself here what is th amount of strength you want in the clip, but also what do you want to break, the clip, the screws, the handle, the guys pants, etc. .
Alvin Johnson recently made a small paring knife out of 1095 for me, completely hand made, and by hand made I mean with actual hand tools, he even made his knife grinder himself out of the motor of a washing machine.
He also broke a piece of the 1095 he heat treated and sent it to me so he could show me the grain structure, he breaks his steel all the time to check the heat treatment and steel quality. It was the same piece the knife was ground out of.
Not only do you have to examine your own heat treatment, but you would also want to do it with each large batch of steel to check for variations there. In this case you would not need to do a full blade grind, just a rough primary and an edge.
It is not just the steel either, lets assume you make a knife with a lot of wood inlays, or a small folder so you do a extended corrosion soak to see what happens to the internals and the wood.
Now you could ask why would you do this, isn't it abusive, what kind of user would do this to a knife, maybe not intentionally, but it isn't difficult to see how this could happen accidentally plus just poor luck with weather.
Accidents will happen on regular use to hard use knives, by hard use I don't simple mean choppers either, but simply knives which are not used with extreme care, the kind that will cut used and possibly dirty materials.
Not to mention problems with method & manufacturing, there was an issue with Sebenza's awhile back with blades breaking because of thumb studs overstressing the blades which caused them to fail under really low stress, same sample destructive testing would have caught this readily.
I have loaned axes to carpenter friends for example and they will hit nails on a semi-regular basis, not every day, but get the axe back after a month and it has a couple of nail notches. Get a knife back and it has nicks in the edge from hitting a staple in a box, or running across some poly or stryofoam on the form and running over a nail.
Back to Alvin, he makes pure cutting tools, full hardness steels on light stock (1/16") with full hollow grinds and edges which run to the spine, so <10 degrees per side. Awhile back one of his knives got the edge damaged cutting I think some kind of hard poly when the guy was removing a window.
Alvin played with his heat treatment, didn't adjust the hardness down, went to multiple tempers and gave the guy another blade to see if the toughness was there, it was.
Now as for Busse and other manufacturers who make extreme use knives, they are making general use tools, blades which are expected to see heavy prying and hammering, you need to know where these knives fail and how they because their scope of work includes that which could damage them.
-Cliff
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