Had problems with a cheapo 67>77mm step ring. Used it to mount a big Mamiya 77mm polarizer on 67mm Bronica glass. Damn thing would jam--and I mean like welded--tight on the polarizer. Finally wised up that it was the unhappy marriage of aluminum ring to the brass threads of the polarizer. Simply wrapped thumb and index finger around the step ring, warmed it up for 30sec or so, and off it came--easily. Won't detail the embarrassing--and futile--efforts that preceded this simple solution.