Helicoil is a last ditch repair after the threads have been destroyed and requires a “kit” consisting of an oversize drill, a special tap, the insert, and an install tool. Usually the most economical method is to give it to someone who has a machine shown in the link. Call a few machine shops and ask them where they send parts to have taps removed as I think at least one shop in every larger town has one.
http://www.electroarc.com/
