If everyone's lost on the torque wrench theory, how about using angle of twist. That's the way we do it on the Shuttle Booster nozzles. OOps, hope I didn't open another can of worms! <img src="/forums/images/graemlins/shocked.gif" alt="" /> <img src="/forums/images/graemlins/nana.gif" alt="" /> <img src="/forums/images/graemlins/smile.gif" alt="" />

If you want to calculate exact preload on the fastener, friction and the nut size will come in to play. But, if you're just applying a torque to a nut or fastener, size doesn't matter. Torque is just a rotational force around a point. Or, how about lubricating everything first to reduce friction. That's why there are usually two different torque values; one for a lubricated fastener and one for a dry one.