Gauge R&R on pre-set torque wrench

[Rush2608]

can anyone tell me how to do Gauge R&R on pre set torque wrench. We use (39NM) pre set torque wrench on our assembly cell to ensure that the nut does not torque BEFORE customer spec which in our case is 39NM. This is part of our customer specific requirement that we use torque wrench to ensure that the nut meets specific torque after we do projection welding. Any help will be greatly appreciated.

 

[John Predmore]

With fastener joints, you will get a different torque value in the tightening direction than in the loosening direction. I don't know whether direction is a factor when you test welds. I think one operator who applies torque slowly could get different results than an operator who applies torque abruptly. Differences between operators is identified as reproducibility in a GR&R, but reproducibility could include differences in how the part is fixtured or how the jaws are clamped to the part. In a classic GR&R, the same joints are tested multiple times by different operators with the assumption that the true value you are measuring does not change. That assumption may not be true as you approach the torque at which the joint yields. You should read about GR&R for a destructive test, where the same joint is not tested more than once.

When you say pre-set torque wrench, I think you are saying a pass/fail torque test. There are distinct formats to conduct a GR&R with pass/fail results. To start, you need many more parts or trials than a textbook GR&R study (10 parts x 3 operators x 3 repetitions). Minitab, for one, has instructions on two approaches for an Attribute GR&R study .

 

[dwperron]

A very common method is to have torque testers / analyzers on the factory floor. The practice is to exercise the tool then test it at the beginning and end of the shift. This gives confidence that the tool operated within tolerances during the shift.