Setting Masters

Obtaining precise quantitative dimensional data requires the combination of the air gage readout instrument and gaging member to be mastered with one or two setting masters. Western’s master rings, plugs and discs are fabricated from heat-treated and stabilized chrome alloy steel blanks conforming to Gage Design standard A.N.S.I. B47.1. After heat treat and stabilization cycles, these masters are custom finished by grinding and lapping to the precise dimensions specified. Final calibration is done in a special, temperature-controlled, gage calibration lab using electronic comparator instruments and laboratory grade reference standards.

Master Rings are used to set air probes and other types of bore gages to a known size.

Master Plugs are used with air rings and other external diameter measuring instruments as setting standards. Depending on whether single or dual masters are required, single or double-ended aluminum handles are utilized.

Master Discs are used for the same purpose as master plugs, except that these members incorporate plastic grips on each end, rather than aluminum handles.

Manufacture and Certification. Western Gage’s setting masters are manufactured on-site in our state-of-the-art, environmentally controlled gage finishing and calibration laboratory. Calibration is done by transfer measurement with standards that are traceable to the National Institute of Standards & Technology (N.I.S.T.). Western Gage is accredited in accordance with the recognized international Standard ISO/IEC 17025:2005 and conforms to ANSI/NCSL Z540-1-1994.


  • Master Rings
  • Master Plug with Trilock Handle
  • Reversible Plug Master
  • Master Disc