Model: 5/16-18UNC-2A X 3 1/4, TYI

Properties:

An externally threaded fastener designed for insertion through holes in assembled parts and normally intended to be tightened or released by torquing a nut. the threaded and unthreaded portions are both of one nominal diameter of 0.190 inch (5 mm) or larger. The head is not designed to be held or driven with an inserted driver or by the thumb and fingers. a locking feature may be incorporated in the design of the head or threads. head dimensions and sizes of threaded and unthreaded portions shall conform to internationally recognized fastener standards. for items having a grip length portion machined to a tolerance of 0.0015 inch (0.038 mm) or less, bolt, shear. See also screw, cap, hexagon head and screw, machine.