Cam out

To cam out (or cam-out) is a process by which a screwdriver slips out of the head of a screw being driven once the torque required to turn the screw exceeds a certain amount.

Frequently, camming out damages the screw, and possibly also the screwdriver, and should normally be avoided. However, the Phillips head screw and screwdriver combination was designed specifically to cam-out, as at the time of its invention torque sensing automatic screwdrivers did not exist. The Phillips design is auto-centering, that is, the screw does not slip off the screwdriver, unlike a normal slotted-head screw or flat-head screws, but cams out once the screw has been driven home. These properties were used to speed up automobile production in the USA in the early years of the industry.

In recent years, automated manufacturing insertion tools can now precisely sense fastener torque. Consequently, it is typical for computer parts, automobiles, and other highly-engineered products, to be assembled with Torx head screws, which have been specifically designed not to cam out.