Re: The glory of the air impact wrench

Posted by Fish'n Jim On 2015/5/9 20:22:47

That model creates 600 ftlbs in reverse and has a working range up to 350. For most auto applications that's twice as much as the most you'll ever need to torque anything.
So it's fine for snapping off bolts and stripping studs/threads. Not the precise tool you'll want for assembly. Even if you adjust it to deliver proper torque, I'd recommend to check with a torque wrench. Don't just go by the air settings. Some have a torque sequence that starts low and ramps up so it's not much use for those.
With alot of speed comes alot of heat and that can harm special tensile studs or bolts. Use a penetrating lubricant before breaking and oil on threads before tightening and adjust the torque spec for "wet" torque. Leave the impact on the shelf for tightening. Ok to run them up, but finish with a torque wrench.
Even lug nuts/bolts only need at most 120-150 ftlbs. Yeah, you can crank 'em on to max for a few cycles but eventually... Plus, on the road you have to loosen with a "wrench". So you don't want to hit 'em up full for that.
Most tire shops hire unskilled help and turn them loose with impact tools for speed. I had a flat on my trailer while on the road and I took it to the nearest branded tire dealer for a new tire since it was covered they rotated/balanced too. The tire jockey put the big dog on the alloy wheel lugnuts and stripped all the studs. Spec is a meager 75 ftlbs. I didn't find it out till I got home. I carry a torque wrench for wheel tightening when traveling.