Help! Stuck rear cap- any ideas?

[Bob Miller]

I have an old 50 mm f1.8 lens that I cannot get the rear cap off no matter how hard i try. Anyone have any ideas?

[Cal Walters]

I'm assuming a plastic lens cap on a metal bayonet? Wedged on or does it look like the plastic had bonded to the metal? If wedged, try applying a warm/hot pad to expand the plastic. There are cold packs that can be microwaved. Short of that a pipe wrench!