Need brass, aluminum, bronze, or ??? helical threaded sleeves
Hi folks,
Not even sure if this is feasible, but I'm trying to repair the focusing helicoid of an older camera lens. The existing threads are aluminum (from the body of the lens) and they are stripped. I'm thinking that I might be able to machine off the existing threads and replace them with brass or aluminum sleeves with a similar thread pattern. I would install the sleeves with cyanoacrylate or maybe epoxy.
As far as I can tell, the current helical has nine parallel threads, but I think 8 would be OK. They run half a turn over 11mm. They are about .75mm deep. I would need an inner sleeve, smooth on the inside, threaded on the outside, 11mm wide, and 42.85mm ID. The outer sleeve would be smooth on the outside and would need to thread onto the inner sleeve; it would also be 11mm wide, and would need to be 44.85mm OD.
If these dimensions make for too thin of sleeves, I could probably machine off an extra .2mm or so from the lens barrel parts (so, +.4mm OD and -.4mm on ID), but that's really about all the meat there is to work with there. The barrel parts, especially the outer one, are pretty thin. As long as the sleeves thread together well, I would expect that shallower threads would be OK too. As indicated in the post, I am not sure what would be the best metal for this. Aluminum has known issues for helicoids, as it tends to microweld itself. I would think brass would be good, but if you have other ideas, please let me know.
I have a mini-lathe I can use to machine off the threads and oversize the barrel parts if neccessary, but making the sleeves is definitely beyond my skills and probably beyond the capabilities of the lathe (it's a Sieg).
I'd only need one set (assuming I don't mess things up installing them). What do you think?
Cheers,
Paul
