Description:

An unslotted hex-washer machine screw, but with a thicker flange and serrations on the bearing surface side.

Advantages:

Designed for use in applications where loosening forces are present, such as vibration.

The serrations grip to the bearing surface so that significantly more torque is needed to loosen than to tighten the screw. Flange provides more strength than a standard
machine screw. Eliminates need for a lockwasher or locknut.