On 10/09/2009 02:39 PM, -MIKE- wrote:

Drive a common 16d nail 2/3 into a 2x4.
Do the same with a common screw of the same diameter shaft.

Take sledge hammer and swing it directly down on the nail. It will bend.
Do the same to the screw. It will "shear" right off.

That's why I specified "properly heat-treated". The heat treatment
keeps it from being brittle due to work-hardening from rolling the threads.

Just for fun, I tried your experiment with a #10 Spax brand exterior
screw. (Lee Valley carries them.) The screw bent. I then pounded it
back straight and removed it with a power driver.

I then tried it with a #10 "Precision" brand decking screw from Home
Depot. The screw snapped.

Chris