Today I used my newly acquired crank puller to remove a steel cotterles chainset off an old bike with a view to putting this on my single speed 'project' frame as it is in very good nick. It came off after a lot of sweat and cursing. When I went to remove the knackered alloy chainset from the aforementioned frame the right crank came off ok but the thread stripped on the chainwheel side crank. What do I do now? I have sprayed loads more WD 40 on it, will it tap off with a hammer? I do not want to damage the bottom bracket or remove it if I can avoid it, as the bottom bracket, like the headset on this frame appear to be in very good condition, and the steel chainset will fit the bb.