I hope I'm not the only builder here who seems to be making three parts to get one good one. For example, the threaded female part of the stabilizer jackscrew. Using my mini-lathe, I turned 1" aluminum barstock to the correct dimensions and form, drilled the .421" ID bore, and then hand threaded it. Got the tap off-axis and was rewarded with a wobbly pulley. No good. Try #2 got it much better, but the thread has to be on the same axis as the OD.
After growling all the right words and working up a thought, the solution finally became obvious. I switched to 1-1/4" barstock. First, I bored the .421 ID on the lathe, then used a tap guide to keep the tap square to the bore. Then I screwed a length of 1/2" threaded rod into the blank and secured it with a nut on each end. I chucked the assembly into the jaws on the threaded rod. With a live center on the free end, I turned the OD dimensions. I took the finished assembly out of the lathe, rested the threaded rod ends on V blocks, and set a dial indicator to the large OD. This third part displayed a TIR (Total Indicated Runout) of .0015", and about 1/2 of that number is in the normal sideplay between the male and female threads. Finally, a good part.
Tom
After growling all the right words and working up a thought, the solution finally became obvious. I switched to 1-1/4" barstock. First, I bored the .421 ID on the lathe, then used a tap guide to keep the tap square to the bore. Then I screwed a length of 1/2" threaded rod into the blank and secured it with a nut on each end. I chucked the assembly into the jaws on the threaded rod. With a live center on the free end, I turned the OD dimensions. I took the finished assembly out of the lathe, rested the threaded rod ends on V blocks, and set a dial indicator to the large OD. This third part displayed a TIR (Total Indicated Runout) of .0015", and about 1/2 of that number is in the normal sideplay between the male and female threads. Finally, a good part.
Tom