Hex Head Machine Screws
Indented hex machine screws have an indented top surface, six flat sides, and a flat bearing surface. They are preferred in high-volume assembly applications where pneumatic equipment is used to drive the screw. The indented hex style can transmit higher tightening torque levels than other head styles. The heads may be slotted for driving with a screw driver or unslotted for driving with a socket or wrench.
Indented hex washer machine screws have an indented top surface, six flat sides, and a flat washer which protrudes beyond the sides and provides a flat bearing surface. The washer and hex head are formed together as one piece. Indented hex washer machine screws offer greater protection to the mating surface than a standard indented hex head. The heads may be slotted for driving with a screw driver or unslotted for driving with a socket or wrench.