Setscrews are used in a number of applications to clamp parts together: end fittings to fiberglass duct rod, fiber optic strength members, and electrical conductors into pulling eyes, for example. They’re a quick, simple and relatively strong connection, so long as you turn the wrench with some care.
 

Duct rodders can be spliced or ends replaced with new fittings – the setscrews can bite right into the fiberglass core to ensure a solid material interlock, or you can apply a redundant coating of glue.
Another application is our multiplex pulling eyes: three setscrews are used to clamp the free end of the each conductor into a pulling eye, for short, straight pulls of moderate tension.
However, the clamping force developed by the setscrews can’t be considered an exact science. The copper strands will shift as the setscrew descends, moving strands aside to fill the remaining bore space. But they may randomly shift to one side as the screw turns down, or they may not shift and just ovalize the conductor.
Fixed torque values are difficult to define for these somewhat random events! Practically speaking, “as hard as you can” works out to be a fairly comprehensive instruction for the guy turning the wrench.