In my plant we use several program-controlled DC torque tools to install bolts. These are tied in to the production system via PLCs, which read the torque value from the tool. The product cannot leave that step in the process until all bolts have the correct torque applied.

To calibrate these tools, we take each tool and use it to apply torque to a test bolt that has a transducer. The transducer will read the torque applied to the bolt and compare it to the value read by the PLC. We can then adjust the tool until the numbers match.

So given this, how do we perform an MSA on the torque tools? Each tool may actually cover several different torque tolerances (i.e. one tool may install x bolts at 25-35 lbft, and another y bolts at 45-55 lbft). In addition, we only know if the value is "right" by comparing it to the transducer value. However the results from the PLC generally show that the torque tools hold very tight spreads compared to the target (many Cpk are greater than 2.00, and some are more than 6.00).

Thanks in advance for all your help!

Hi BenL,

I've had very similar equipment in several facilities I've worked in and I have never considered doing an MSA study on them. You are calibrating them to the tranducer which I assume is calibrated outside and traceable to a National standard, etc. What we did was run capablity studies on the tools at set intervals. Tools used on joints that were SC we did a weekly 30 pc study and tools used on non SC joints we would take a 5 pc sample once a week to insure the tool was operating properly. We would use a joint simulator to run multiple readings or used the transducer in the process as you are doing. We also got similar cpk's of 2.00 or greater.

Performing MSA on a torque meter used to check torque after the nut/bolt has been run down is another story. I debated this with an auditor once as not possible due to the fact that when you check the torque with a torque meter you end up changing the torque value of the joint. When yo go to check it for the 2nd and 3rd the torque would be higher each time (This is due to when checking torque you move the wrench/ meter until the fastner moves).

So it sounds like what you are doing currently is enough.

Torque wrenches and drivers - How to perform MSA (measurement system analysis)http://elsmar.com/Forums/showthread.php?t=14886&highlight=torque+msa

Gage R&R - Digital Torque Wrenches - 5-50 nM range unitshttp://elsmar.com/Forums/showthread.php?t=1031&highlight=torque+msa

MSA - Torque Wrenches - Statistical studies that cover requirements of MSAhttp://elsmar.com/Forums/showthread.php?t=6060&highlight=torque+msa