View contents. GENERAL (a) This Standard presents screw thread gaging systems suitable for determining the acceptability of UN, UNR, UNJ, M, and MJ screw threads on externally and internally threaded products. It establishes the criteria for screw thread acceptance when a gaging system is used. (b) A screw thread gaging system comprises a list of screw thread characteristics that must be inspected/ evaluated to establish the acceptability of the screw threads on a threaded product and the gage(s) which shall be used when inspecting/evaluating those characteristics. (c) Federal Government Use. This Standard is approved by the Department of Defense and federal agencies, and is incorporated into FED-STD-H28/20, Screw Thread Standards for Federal Services, Section 20. The use of this Standard by the federal government is subject to all the requirements and limitations of FED-STD-H28/20.