Fastener SuperStore, Inc. Thumb Screw 236427

5/16-18 X 1/2 Thumb Screws / Type P / No Shoulder / Steel / Zinc A cold headed, one-piece screw with rolled threads and a flattened head designed for manual turning without a driver or wrench. They are available in two varieties--with and without a shoulder under the head. The shoulder flares to a circular shape of a diameter slightly less than the head diameter of the screw. For use in applications where the fastener is frequently adjusted and where tightening torque greater than that achieved with finger pressure is not required. A shoulder-pattern allows the head of the screw to seat flush against the mating surface and helps avoid over-tightening of the fastener which could result in stripped mating threads.