On Sat, 20 Mar 2010 01:14:12 +0000, Christopher Tidy
wrote:

Wes wrote:

I've replaced a lot of bits in hex sockets with cut up chunks of Bondhus hex keys, the
Bondhus replacements last far longer. When they do fail, they tend to fail lengthwise.

You mean they split longitudinally like a sausage? I'm just trying to
figure out the stresses in my mind. Probably the corners/ridges are
important too.

Sounds like a textbook torsional fatigue failure.
http://school.mech.uwa.edu.au/~dwrig...e/fatigue.html
http://school.mech.uwa.edu.au/~dwrig...urfaceBIG.jpeg

--
Ned Simmons