Just realized I've been handling stuck helicoids two different ways and I'm not sure which is better

Last week in my home shop, a Canon FD 50mm 1.4 came in with a completely seized focus ring. I tried the classic method of soaking the threads in lighter fluid overnight, which usually works. This time, after 12 hours, it only budged a millimeter. So I switched to a 50/50 mix of acetone and automatic transmission fluid, applying it with a needle every hour for three hours. That finally did the trick, but I'm worried the acetone might be too harsh on old plastics inside. Has anyone else compared these methods on vintage lenses? Which do you think is safer long-term?

2 comments

2 Comments

the_henry6d ago

Wait, you put acetone on a lens with plastic parts?

jordan6536d ago

Holy crap, did they actually do that?