Attaching alm pulley to acme rod

[Jkountz]

If one were to attach an aluminum pulley w/set screw to this acme rod McMaster-Carr should the rod be machined smooth first or is it ok to tighten the set screw directly to the threaded rod?

[Markwind]

you need to machine the threads off

[CarveOne]

This assumes that the pulley hole is the same diameter as the lead screw.

You can just drill into the thread where the set screw contacts the lead screw with an end mill that is the same size as the set screw. Drill down to the bottom of the thread only. You may need to get a longer set screw that reaches that far and still has plenty of threads left inside the pulley hub. If the pulley has a 1/4-20 set screw, drill with a 1/4" end mill. Be sure that you use a vise that is securely to the securely tightened table if you are using a drill press. The end mill will grab and jump sideways if the setup is too loose. You can also pre-drill with a drill bit and then flatten the bottom of the drilled hole with the end mill. The drilled hole walls will help support the set screw if this is done correctly.

Another way is to just mill, file, or carefully grind a flat across the side of the lead screw down to the bottom of the thread. Don't remove any more metal than you need to to get a flat surface for the set screw to contact.

These methods aren't the best way but it doesn't require much in the way of tooling to get it done. Turning the end on a lathe is best.

CarveOne