Phillips Vs Posi Drive????

[Chris Friesen]

On a philips screw the edges of each "blade" are not parallel. They're designed to cam out under torque to prevent over-tightening. On a posi-drive the edges of each blade are parallel, so there is no tendency to cam out under torque.

Do note that there are multiple sizes of both philips and posi-drive....at least three of each. The smaller the number, the smaller the bit.

[John Sanford]

There are three "common" cross head screw patterns. Phillips, Posi-Drive, and JIS. Using the proper tip matched to the screw is the best course of action. JIS is commonly found on products from Japan, especially motor vehicles.