A frequently asked question we receive at Gaging.com is: "What type of certification is offered for thread gages?" Normally gage manufacturers today (PMC Mercury, Hemco, Vermont Gage, Meyer Gage) offer three types of certifications for thread gages:

Certificate of Compliance

A certificate that states that a specific gage or set of gages has been inspected by comparison with master gages that are traceable to NIST (National Institute of Standards & Technology) and found to be within the required tolerance.  This certificate does not give actual measured readings and is normally furnished free of charge with new gage orders.

 Long Form Certificate of Calibration

This type of certificate lists actual measured readings for parameters such as: pitch diameter, major diameter, minor diameter (in the case of thread rings), lead variation and angle measurement.  These certificates are traceable to NIST and list: customer purchase order, gage type/size, and serial number (if one is given).  There is a charge for this type of certification, which varies from manufacturer to manufacturer.

A2LA Long Form Certificate of Calibration

These certs have the same information as Long Form Certifications and are furnished by ISO17025 accredited laboratories.  These labs have been audited, approved, and certified by an A2LA certifying agency and have these certificates maintained and on file.  They are accredited for each type of gage they calibrate and their scope is readily available.  Like the Long Form Certification, there is a charge for this type of certificate.

The Long Form Certificate of Calibration is the starting point for all future calibrations whether done in house or at an outside calibration source.  These certificates are also used when the customer is being audited to prove that they are using gages that are made to the required tolerance.