Usage related issues

What kind of situation may lead to stripped thread?
There may be several reasons to cause the stripped thread 1. A screw is with or without a lead point. 2. Lock attached to what thickness of board is. 3. The pounds of electric screw driver lock attached to. 4. Screws to do the heat treatment or not.
What difference is between machine screw and self-tapping screw?
Machine Screw The mating parts must have the corresponding female thread. Self-tapping screw The mating parts do not need to have the corresponding internal thread, and the screw itself can be with a pre-drilling hole or rely on screws to lock into a fixed drilling.
What is the useful life of a screw?
Normally, there is no deadline. It accords with user's using method and preservation and these will decide the period of use toward a screw.