Description : What does "UNC" stand for in a mechanical drawing / drafting context?
Last Answer : It's a screw thread designation: Unified Coarse , which refers to the standard for thread sizes and shape used for machine screws in the US. The .250 is the nominal diameter of the screw that will fit ... , the hole is first drilled with a number 7 drill bit, then tapped using a 1/4-20 tap.