Bolt torque discussion

nm9stheham said

Interesting.... Just a wild guess on the thinking behind this, but it sounds like this particular concept of properly torqued is to try to achieve a set amount of stress in the bolt/stud. Are they looking at bolt stretch and trying to get the stretch to be in proportion to the length, or ????

Click to expand...

When you torque a bolt, it has some elastic stretch and some permanent stretch... The elastic stretch goes back when you loosen the bolt, the permanent stretch is just that, permanent...

We used to monitor torque vs angle when we torqued to yield... You stretch the bolt and monitor torque vs angle and when the curve bends over, you stop when the slope of the curve goes 10% past the peak... That is how you get maximum yield and minimal stretch...

That is how you keep from putting too much permanent stretch in a bolt and achieving maximum clamp load... Once you get into the permanent deformation range, you are not getting any more benefit for clamp load....