Special Features:

Bearing surface of head 0.375 in. Diameter and 4-40 unc 2b thd 0.375 in. Deep concentric hole in thd end and medium diamond knurl portion of head 0.188 in. Wide and 0.031 in. By 45.0 degrees chamfer on both sides of knurled portion

Properties:

An externally threaded fastener whose threaded portion is of one nominal diameter. It may have an unthreaded portion with a diameter less than, equal to, or greater than the diameter of the threaded portion. It has either a vertically flattened, circular knurled, or wing type head, all of which are designed for rotation by the thumb and fingers. For items having wrenching facilities such as socket recess, multiple spline or slot heads, use screw (as modified) or bolt (as modified).