ASTM D668-12 PDF

1.1 These test methods cover the measurement of the dimensions of all rigid rods and tubes used as electrical insulation, the limitations imposed being those of the size range of the more common forms of measuring instruments used.

1.2 Where the number of tests to be made or the specifications covering the rod or tube justify its use, it is acceptable to use an accurately calibrated "go-and-no-go" ring gage of suitable size.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.