Quote Originally Posted by McDesign View Post
I dunno'. I think the cross-section is so reduced at the "cup" for the indicator that the bolt is essentially useless for a given diameter.

All the elongation will be in that area before the bolt shank starts to load.

Maybe if your trick indicator half-inch bolt was only supposed to replace a normal 5/16" bolt . . .

Forrest
I kind of agree. Elongation can occur at any place in the bolt and not necessarily linearly, usually just above the threaded section or at the base of the head or nut would be starting points. With the head and upper shank compromised by counterbore and a sight window added I would question any real accuracy of readings on that scale. I would however guess these are not used on any bolt <1".

The Abstract of the Patent is full of good details about the complexity of a threaded fastener systems but a few key factors are left out imho, like Quality control (1/100, 1/1k or 1/10k and always the Monday/Friday rule), metallurgic consistency, Grading, and Thread quality. It does however point out a LOT of other patents for this type of fasteners world wide.

The only thing I would think this is good for is a rough, visual thumb to eye rule, during initial installation torquing. Personally If something is critical, Torque Standards have been around a long time and if it needs torquing for critical reason...Use a well maintained and "Calibrated" torque wrench, in proper fashion!

PJ