In August of ’98, my friend Dave came over with a problem: he was trying to remove his Ultegra cranks with a standard crankarm remover, but the remover stripped the threads. (I.e., after he screwed in the crankarm remover and turned it, instead of extracting the crankarms, it extracted the threads.)
My first idea was to use a pulley extractor. I got a 3-armed one from Sears. This was totally ineffective. It just could not grip the crankarms well enough.
We also tried other brute force methods; e.g., hammer. No luck.
Finally, out of desperation (by this point, Dave did not care whether the cranks were reusable or not), we busted out my Dremel and its rotary cutting tool. The rotary cutting tool cut it like butter! We made a slit in the crankarm all the way to the bottom bracket spindle, and then inserted a screwdriver in the slit to “wedge” it open (like a crowbar). Some gentle taps on the crankarms were able to get them off.
See the picture above. If you are wondering why the main crankarm (the one with chainrings) was also cut on one of it’s “spider arms”, it was so we could get a better grip with the pulley extractor (which still was totally ineffective.)
A few months later it became time for me to remove my Shimano RX100 crankarms so I could install my new Campagnolo Racing T cranks. Same thing happened: my crankarm remover stripped its threads. I had to resort to the same Dremel cutting method.
Incidentally, with the Campy cranks, I’ve never ever had the same stripping problem upon removal. I’d recommend anyone who has to install cranks to use antiseize compound on the BB spindle. This is controversial, but in my experience not only does it help keep the cranks quiet, it prevents the crank from becoming stuck on the BB spindle (just tighten the crankarm bolts really tight and use either teflon tape or Locktite to prevent the cranks from loosening).