Question about destructive testing.

[Heavy]

Hi I'm Paul. Long time knife nut. Newbie knife maker.

Does it make sense to test a knife to destruction? I suppose you can learn a lot by using it but I feel like you can't know everything untill you break it.

I made one and I plan on making more but I find myself wondering how good my heat treat is and if the hollow grind I put on made it to weak. Maybe I should flatgrind this particular model. Things like that.

I tested the tip by pounding it through a few pennys and it held up to that with no damage....is this a stupid test? Maybe this test would be worth more if I used a quarter.

Anyhow, any comments would be appricated.

 

[mete]

For the purpose of learning about and checking HT it's a good idea. You don't have to do it on a blade just use a sample of the steel.

 

[Heavy]

For the purpose of learning about and checking HT it's a good idea. You don't have to do it on a blade just use a sample of the steel.

I see your point but it might not answer the question of "is this blade shape/grind strong in this steel with this heat treat"

Know what I mean?

 

[Guy Thomas]

I feel destructive testing is necessary especially when you are learning a new steel and working on your heat treatments. I feel you should be clear though on just what you are testing. I would expect any knife to be able to be driven through a penny or used to cut a quarter in half. That kind of thing is more of a gimmick than a test. Make a knife, and then put it through what you'd expect it to handle, then put it through even more to see how it takes it. About the only way to "see" how good your heat treat is will be to break it. (Remember though, the amount of energy required to bend a piece is steel is more dependant on it's thickness than on it's heat treatment so bending can be a bit subjective. A 1/4" bar of mild steel requires just as much force to flex as a 1/4" bar of heat treated high carbon steel, the mild steel just reaches a "giving" or bending point sooner than the heat treated steel. Young's Modulus of Elasticity if I remember right.)

Not every knife needs to be tested hard but you should probably be breaking a few on a regular basis to keep yourself on track. Speaking of which I need to take my own advice when I get back into the shop!