I never liked the idea of running threads on a bare rod to attach a nut for holding and adjusting length for a clock pendulum bob. This allows rough adjustment anywhere along the rod, and very fine adjustment with the mating part, tweaking the bob location for optimum timing needs.

The cross-section image shows significant clearance between the female and male threads. Thats what I needed to have for the resulting print of parts to assemble and move freely. My print nozzle is 0.4mm dia.

The center hole is designed to fit a shaft of 5/32" dia. You could easily modify the part to fit other shaft diameters.

The set screw holes actually extend into the opposite side surface a bit to allow a little more clearance for the tap end while forming the threads.