5/16-18X1 Unslotted Indented Hex Washer Thread Cutting Screw Type 1 Fully Threaded Zinc An 1000 pcs 31161W

5/16-18X1 Unslotted Indented Hex Washer Thread Cutting Screw Type 1 Fully Threaded Zinc. Thread-cutting Type-1 threaded screws are used in steel sheets, sructural shapes, special alloy steels, cast iron, brass or plastics. Stainless steel material into which the screw is to cut threads should have a lower hardness by 10-20 Rockwell hardness. Indented hex washer head offers advantages of hex head, plus greater protection to mating surface.