"Mark & Juanita" wrote in message
s.com...
In article ,
says...
On Sun, 16 Nov 2003 07:01:24 GMT, Larry Jaques
wrote:


I've had failures in drywall screws, but it was from a
racking/bending force, not shear force. Have you had a
failure from shear?

Overtightening a drywall screw, which is common with power-driven
screws into wood/wood interfaces, will twist the head right off.

Barry


But that's a torsional force, not shear force.

Lots of armchair engineers in the audience lately. The primary failure mode
of a circular member in torsion is by shear stress. There's a difference in
a shear force and a shear stress.

todd