Friends forgive my ignorance but I have a question about psi and foot pounds as used with a torque wrench. I have a craftsman 150psi compressor with an impact gun and air ratchet that the instructions recommend not using above 90psi. I guess what I am asking is how many foot pounds are these tools putting out at 90 psi? Since the lug nuts on my wheels need to be tightened to 90 foot pounds are their psi conversions, or are they not related?
Speaking from my nether regions, I would say that the 90 ft-lb torque recommendation for your lug nuts and the 90 psi rating for your tools just happen to be coincidence. I don’t think it’s how much torque the tools put out, its a matter of how much air pressure they are designed to take * in*.
Surely, you can regulate your compressor to deliver no more than 90 psi, can’t you?
Air operated tools cannot be simply rated by psig input. Impact gun x will deliver y foot/pounds only when supplied with z psig air, delivered at a rate of w CFM.
Example: my big shop compressor does a dandy job for everday tasks, until I want it to bust loose wheel lugs that have been untouched for 6 months or longer. If I use a smaller diameter hose, nothing is gonna happen. Haul out the large diameter hose, and lugs are coming off quickly. Same compressor, air gun, and vehicle.
Torque wrenches aren’t pneumatically operated. They are calibrated tools used to observe a manufacturer mandated level of tightness when assembling rotary fasteners.
AFAIK, you’re never, ever, ever supposed to use an impact wrench to tighten lug nuts or anything else with a critical torque rating. Use a proper torque wrench and some elbow grease.
They are only indirectly related so there is no conversion. Generally, using more psi would have to increase the torque an air powered tool can produce, but mechanical advantage means that you could have a lower psi tool that put out more torque, an vice versa