Is it possible to tap the rest of the hole that you say was untapped as a defect?-(with the original size threads) Some LBS's may have the proper tap or your local machinist could probably do it. If you don't have one already, get a good crank extractor tool and hopefully it will work with the new threads. Also try pouring some boiling water over the crank to help make it easier to pull off. I'm a little suspicious of that tool and new bolt/extractor setup from above as the aluminum piece may not hold up to a crank that is stuck on the axle. And I may be wrong, but it will be hard to find a 24mm extractor tool to use if it fails. I know my old Shimano bolt/extractor felt a little iffy when I tried to pull my cranks so I just played it safe and used my proper extractor tool.