Tightening of NPTF threads in production

We are an OEM of industrial hose reels. Each reel we build gets a swivel tightened into a main shaft that have NPTF threads. With the tolerances on threads we can barely get the correct amount of threads tightened after hand engagement. We would like to use a pneumatic gun to tighten these in prodcution. We have tried an impact wrench, but we can not calibrate an impact wrench. We would like to use a wrench we can set a torque on but we cannot figure what torque to set it at. Does anyone have any ideas?

 

[Hush]

NPTF is based on thread makeup. Torque will vary considerably based on material, thread finish and thread dope. I would try torquing a few of your actual product to the correct makeup and using that value as your standard. Also, using impact wrenches on tapered sealing threads usually isn't a good idea, very easy to cause damage.