Shear Strength Of Nails,drywall Screws, & Construction Screw

This demonstration is informative about the fasteners, but those are not shear failures.

Quoting the definition found here:

https://secure.wikimedia.org/wikipedia/en/wiki/Shear_strength

"sliding failure on a material along a plane that is parallel to the direction of the force"

A test would be closer to a test of shear strength would be trying to cut each fastener with a pair of snips. It is not the shear strength but the ductility of the nail that allows it to bend back and forth without breaking.

As far as how they work as fasteners, I am no master carpenter but I have assembled and taken apart a fair amount of framing (for pay), and joints rarely fail from shear stress. The fasteners pull out of the wood.

If you were to take each of the fasteners you have tested and use them to attach a 2x4 to the same plank and then try and pull them apart with your hands, the construction screw is going to hold the best. Second is probably the nail, but I have honestly gone in to pull up with hammer and pry bar some sub-floor that had been attached with 1 5/8 drywall screws and wished to heck that it had been put down nails. :-)

Having learned to put everything together with nails when I was young, I personally was slow to adopt screws, but they make stronger joints. Of course you have to comply with code so you can't use them everywhere and as you demonstrated drywall screws are not suitable for structural purposes, but there was a point in time where code did not allow the use of PEX.

It's good advice but when you bend a fastener with a hammer you are testing its resistance to "bending" stress instead of "shear" stress.

to get sheetrock screws for my mother in laws new balcony,she'll get a jump rope for her birthday.....thx

i never knew that before... this was interesting, informative and educational... thanx for posting and keep it up ^_^