older, US made cranks are cold forged. if all you need is a little clearance, you don't even have to heat them to bend them. just take them off (never try it on the bike. cranks are stronger than mild steel bike frames) wedge them somewhere, put a pipe over them and yank on it.
speaking of broken crank injuries (not those kind, get yer mind outta the gutter
) years ago in my bmx days my buddy landed a huge stair drop, his leading crank arm broke, the bike freewheeled and 4" of broken crank penetrated his calf.
pretty disgusting. his foot was on the ground (which probably stopped the crank from ripping his leg in half) and his bike was stuck to him, using him as a human kickstand.
lucky thing was, we were in the hospital parking lot. we got to watch as the paramedic seperated him from his bike.
he healed up fine, eventually.
i remember this now, because i need to make some wider cranks for my bike, and i was thinking about what could go wrong...