Quote Originally Posted by darkosaric View Post
Agfa Isolette is not expensive camera, so you can try with ...

http://en.wikipedia.org/wiki/WD-40

NO--HELL NO!!!!!! Do NOT ever put this $h!t on anything photographic. Use a couple of drops of lighter fluid on the edge of the helical and wait a bit. Then wiggle the focus with a rubber pad for added grip. Repeat as needed to un-stick.