When Do We Need Torque Values Most?

The right torque for the bolts holding the wheels of your car to the car is pretty important. I've seen 0 ft-lbs and 200 ft-lbs, both with disastrous results (spec is 70). The latter irreparably warping the brake disc and the former nearly killing me on an entrance ramp.

That's certainly one good example which caught me by surprise because this old sick mindlessly wandering fool was thinking only from a mechanics stand point. I am surprised the 9/16" or 14mm stud didn't break at that torque value, sure bears using a wrench to double check the shops instrument eh?

http://www.google.co.uk/search?q=what+are+torque+settings&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8&rlz=1I7GPCK_enGB411&redir_esc=&ei=N94oTeSkBIeohAelkN3iAQ

did you follow the link?

Yes, it's a very good help for those who likes to self repair/maintain its own vehicles.

Anyway, remember that bolted unions are intended to keep some compression stress between the two bolted parts. This is accomplished by tensioning the bolt. Even nowadays exist wrenches with ultrasonic sensors to measure the bolt elongation and give the corresponding stress (if you know the bolt material), most applications still rely in the bolting torque, that isn't bad... but one's must know that the real need is bolt tensile stress. Torque is converted partially to tensile stress in the threads. the factor which correlates torque/force (usually with dimensions in ft or mm) depends on the thread geometry, which is usually considered constant (even it isn't) and the coefficient of friction (COF) between bolt and nut and as applicable between nut/bolt face and piece.

This COF may vary a lot depending on the materials, lubrication.... Thus, the same torque can easily result in forces/stresses half or double of supposed, with the results already commented.

Happy New Year

When you have a job you would rather not do twice.