6-20X3/8 Slotted Indent Hex Washer Serrated  Self Tap Screw Type AB Full Thread Zinc (Pack Qty 10,000) BC-0606ABSWS

Slotted Indent Hex Washer Serrated Self Tap Screw Type AB Full Thread Zinc

The serrations on the underside of the washer face allow this part to perform two main functions: (1) act as a locking fastener, and (2) break drive torque during installation which lessens the chance of reaming out the mating hole in the bearing surface. The torque-breaking feature slows the rotation of the screw when it meets the mating surface.