 peteroznewman
Subscriber

The desired nominal preload force in a fastener is typically between 70% and 90% of the Proof Strength of the fastener.

When I look up 316 SS, I find it comes in Class 50 and Class 70, which is more common. I didn't look up 316L, so check on that.

The preload force that is 70% of the Proof Strength for an M5 in 316 SS is 653 lbs or 2.9 kN.

To convert that desired force F into the torque T to tighten the fastener, an engineer can use the simple Nut Factor calculation.

T = K x D x F where T = torque, K = nut factor, D = bolt diameter, F = bolt tension.

Using this formula, the Torque is 3.1 N-m.  The attachment explains Nut Factor.

The last piece is to decide how long the thread engagement must be to prevent stripping the threads of the aluminum. That is based on the shear strength of the nut material. Given the shear strength, one can simply calculate the length of the thread engagement so that the shear stress in that length of a cylinder of the diameter of the fastener is equal to the shear strength of the material. 