What will make a brittle blade?

N

nevarmore

Joined
Mar 20, 2003
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Hey I'm helping one of my friends whos a film major do some special effects research. What he's looking for is a very brittle knife (and other assorted bolts and things). Both of us think that if we heat whatever we want to be brittle with a torch and then dunk it into a bucket of ice water for a few cycles we'll end up with a piece of metal that is more easily broken.

Any ideas? Don't worry, I made sure he's only using crappy knockoff, generic, and junk knives for the shots hes trying. The rough effect he wants is for a charachter to take the blade from another one and just simply bending it and having it break, although something that breaks when a bit of force is applied to it by standing on it or breaking it off on a curb would do as well.

Thanks guys.
 
depends on the steel used in the blade. Some of the exotic steels are technically brittle in the full hard state but still pretty tough. If you're doing a movie stunt where the blade has to snap while prying or some such thing, use a cheapo to begin with, torch it at the point you want it to snap and get it at least glowing, cherry red hot. move it around in the water to chill it faster, it should work but be careful of possible splinters in the eyes. BOB
 
The rough effect he wants is for a charachter to take the blade from another one and just simply bending it and having it break, although something that breaks when a bit of force is applied to it by standing on it or breaking it off on a curb would do as well.

This sounds like a pretty dangerous effect. The better way to do it would be to cut the blade and put it back together with epoxy. That way you know exactly where it will break and there is little danger of generating dangerous chards.*

n2s

p.s. take the edge off while you are at it.
 
What not2sharp said. Acually breaking a piece of steel during a shot? Not very wise. The other alternative is to make the knife blade out of plastic and prebreak and glue it as above.
 
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