5/16-18 x 6 Slotted Round Machine Screw Zinc Plated . A straight shank fastener with external threads designed to go through a hole or nut that is pre-tapped to form a mating thread for the screws. Machine screws form a fastening superior in strength to spaced thread screws. These machine screws are manufactured from AISI 1006-1022 or equivalent steel with a hardness of Rockwell B70-B100 and a *60,000 psi minimum tensile strength.
*Steel machine screws which have a nominal diameter smaller than #4 are not subject to tensile testing. #4 and #5 machine screws which are shorter than 1/2 inch are not subject to tensile testing. Steel machine screws of diameters #6 to 1/2 inch inclusive, which are shorter than 1/2 inch are not subject to tensile testing.