Calibrating Master Gages   

    Over the past 6 years that I have conducted workshops at and consulted with dozens of companies and hundreds of personnel. I often receive feedback regarding Master Gages.

 There seems to be some confusion regarding the definition of Master Gages. In particular, there is often a question regarding Master Gage Blocks.

 I have found, in particular, 2 scenarios regarding Master Gage Blocks.

1. Company Personnel have interpreted auditors as stating that Master Gage Blocks can only be used for Calibration of Gages.
2. Company Personnel have interpreted auditors as stating that Master gage Blocks refers to a specific Grade or Material of Gage Block.

In examining the Standards, we find that neither of these statements are exactly correct.

• ISO 9001/2000 (7.6) "Where necessary to ensure valid results, measuring equipment shall a) 'be calibrated or verified at specified intervals, or prior to use, against measurement standards traceable to international or national standards'
• ISO/TS 16949:2002 (7.6.2) "Records of the calibration/verification activity for all gauges, measuring and test equipment, needed to provide evidence of conformity of product to determined requirements, including employee- and customer-owned equipment, shall include -equipment identification, including the measurement standard against which the equipment is calibrated..."
• ISO 10012 "A check Standard should only be used as a check standard"

 ISO 10012 defines Masters as "Check Standards".

Regarding item 1 above- The standard allows using the gage Blocks for other purposes. However, the standard alos states that the Master Gage should only be used as a master gage. Using the gage blocks as check standards only reduces the uncertainty of the blocks and also prevents wear or damage from other operations. We recommend using master gages or check standards as check standards only.

 Regarding item 2 above- The topic of this discussion comes back to Traceability. The "Check Standards" used to Confirm or calibrate your gages are referred to as the Masters for that gage or piece of test equipment. Thus, the Gage Blocks become the Masters for calibrating gages of lesser Tolerance or higher uncertainty. The masters or "Check Standards" create your traceability to international or national standards. So the master is defined as a gage of tighter tolerance and lower uncertainty than the gage being calibrated.