What a great and important topic with loads of spot on information concerning the wonderful world of torque. One thing I would like to expand upon is about the clean threads on the bolt AND INSIDE THE TAPPED HOLE is extremely important... meaning that chasing those internal threads is a must. About 40% of the effort turning the torque wrench is consumed by friction across the threads and another 50% is consumed by friction under the bolt head as tightening occurs. That only leaves about 10% of your effort available to stretch that bolt to provide your clamping force. That is on a good day. Dirty thread interfaces rob more effort from your 10% so those foot pounds you dialed in are not making it to clamp your load. Your wrench clicks or" beeps" but your preload you need is not there. Pretty important for all those head bolts as you want the same clamping load over your head.
Also when I am done using a "clicker" type torque wrench I dial it back to zero as you don't want it sitting in your tool box with load on the internal spring... putting it out of calibration for next time.
I agree in that I cringe when I see somebody hit lug nuts full on with an impact gun putting full torque on each lug nut. You need to creep up on clamping that wheel. Half torque then full torque. Same goes for cylinder heads.
