Torque Tolerance

[jcslocum]

Most bolting is a +/- 10% of indicated torque. So 50 Ft. lbs gives you a 45 to 55 window. This typically induces a load of 50% of the yield strength of the fastener.

When torquing, even with a really good torque wrench that has been calibrated, you will still get a 25% scatter of load on the bolts. This has to do with the friction in the fasteners which is impossible to predict. Engineers take all of this into account when they design the joint and fasteners to make it all work.

There is much written on the subject and you can go blind reading it all. Lots of it contradictory.

The best advise has been given; buy the best you can afford and use it properly. If all you can afford is a cheap one, then plan on upgrading as you go.

Archemedes invented the screw 2000 years ago and it's still going strong.