How to Properly Use Anti-Seize

[jcslocum]

Anti-seize is not just for 2 different metals to avoid corrosion/galvanic effects. It's used on nearly all fasteners where a torque value is needed. Bolts should be cleaned and the paste reapplied to the THREADS and UNDER the HEAD of the bolt or the bearing surfaces of the nut. There is actually more friction under the bolt-head/nut than in the threads; 55% to 45%.

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 can 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.

Once a fastener is properly torqued, it should never come loose. The clamp load applied is calculated to be above the loads the joint will see in service usually by about a 2:1 safety factor.