Stop using lighter fluid to free up stuck focus rings, a watchmaker in Toledo showed me the right way
I soaked a Nikon 50mm focus helical in naphtha for 2 days and it still felt like sand, then a watchmaker told me to use a 50/50 mix of ATF and acetone with a syringe and let it sit for 20 minutes. Has anyone else tried this on old Takumars, or am I about to learn an expensive lesson?
I read on a repair forum that the acetone part can eat certain plastics and painted coatings if you're not careful, so maybe test it on a junk lens first. The ATF supposedly stays behind and keeps things slick after the acetone flashes off.