This gage was one thast I was taking care of for one of my QS9000 Customers. They used the gage to be relatively sure of the metal thickness before stamping it into parts.
They have decided that since they measure the final part with micrometers, calipers, dial indicators, etc, that they do not need to have a perfect measurement of the initial metal thickness. THis could lead to some scrap, but is perfectly acceptable for their QS9000.
We had calibrated this in the past using gage blocks on a surface plate which worked quite well. The point which was brought up about verifying disc masters with a micrometer is valid, but I would still have to have Ultrasonic thickness testers listed specifically on my ISO/IEC 17025 Accredited Scope for Calibration.
When we initially became Guide 25 accredited (about four years ago), parameters were listed in a very general way, "Length" for example. At some point (I can't remember when since I have been through so many scope changes in the pat three years), they switched to listing Calipers, micrometers, height gages, dial indicators, etc... When the scope listed length, verifying the ultrasonic thickness tester with gage blocks was OK, but since they have required us to list specific items, I would need this to be listed separately.
Thank you again for your input.