I have had success removing the hub by using a thin cut off wheel and cutting the slot over the key. Removing a coil gives you more room. The top is easy. Be careful near the bottom. I have a flexible shaft on my dremel and that helps me get close. Slow and careful does the job. Just a little out of line will break the wheel. After you are down as far as possible, drive a wedge into the top of the slot and add a few drops of penetrating oil. It should pop right off with a little prying. . . 😀