On my sawmill I have a boom loader which is motorized to slide in and out. To achieve this, I put a 3/4" threaded rod into a sprocket with 3/4" hole. It was a sloppy fit so I wrapped it with shimstock to tighten the fit, drilled a hole thru the assembly and drove a roll pin thru it. It was makeshit at best and doesn't turn true. I want to redo it with a 5/8" Acme rod (because I have it and 3/4" is gross overkill for this application) but need advice on fastening the rod to the sprocket short of taking it to a machine shop. I have scoured McMaster for Acme fittings and couplings but came up short. Any neat and clever ideas from the top?