[Fot] Head torquing

[Randall]

> This 
> phenomenon probably has
> a name which has escaped me in the thirty years since college. 

We called it "stiction", a contraction of "static friction".

> In light of this, when re-torquing a head should you just set 
> the torque
> wrench to the desired torque and have at it, or should you loosen the
> bolts/nuts and re-torque to spec?

Definitely loosen and retorque, always.  You should also endeavor to meet
the torque spec with the nut/bolt still turning.  If you let it stop just
slightly short of the torque target, stiction will stop the fastener from
turning to it's correct final position.  I was taught that, if that happens,
you must back off and torque again.  This isn't so much an issue with the
'clicker' type torque wrenches (which BTW should be recalibrated often,
especially if you are having problems), but could be with the beam (or dial)
type torque wrenches where it is sometimes hard to watch the pointer while
also pulling on the wrench.

Randall