SS Bolt torque

Guest,

Most good bolt manufacturers will provide the formula information for torquing their bolts. A rule of thumb often used as a starting point is 75% of tensile strength. Then you just need to know the friction coefficient. And that works OK for black steel.

Stainless is another story because of galling. You have to use consistent thread finishes and probably anti-seize. My experience has been that stainless can only be done by trial-and-error a few times, then making a range based on that. A couple years ago, I found a company over in eastern PA that put a mirror finish on threads and that pretty much eliminated the problems. Lots of $$ though.

Shigley and Mischke Standard Handbook of machine Design has some good information. Look at www.unbrako.com also.

Researching?

Go back to basics.

Cast Iron, Timber,Tool Steel, SS any type , Superstrong alloys- could be any :

Find from tables:Allowable Yield stress σ_0.2 of That material _.

Never exceed that.

Nut tightening Torque directly reflects to axial Tension =σ_0.2 x area of bolt at Minor Dia.-- through helix angle of thread.

And shear stress on thread itself too.

http://www.engineersedge.com/torque.htm

should give you a good starting point

joshua

For really accurate torque I use hydraulic tensioning.

When you torque a bolt, you are really stretching it to a certain linear tension. However the differing resistance from bolt to bolt make it hard to do with a torque wrench, so pretensioning is the answer.