I used this die grinder from Harbor Freight:
http://www.harborfreight.com/electric-die-grinder-with-long-shaft-44141.html
It's around $30 and a few dollars for the bits or, if you have an air compressor, you can pick up the pneumatic version for aobut $10, I think.
Grind it out till you can slip it in, making sure the ground out diameter is a little bigger than the compressor shaft will make it easier on you when you go to remove it.
Once you have the shaft down in there, you'll need a long extension (or a couple connnected) to reach down in and wrench at it to tighten it up. Get as many coils between your plates as possible. The plates don't alway just slide right in either, sometimes you have to use mallet to band them in there.