I did some research and have come to the conclusion that I was correct in my statement that a rethreader is not the same as a tap or die.
A
rethreader is for clearing, cleaning, or repairing dirty or damaged threads. It comes as a device that looks like a screwdriver that fixes threads in holes (aka, female threads), or as a
matched pair that looks like a tap and a die but is still for the purpose of clearing, cleaning, or repairing dirty or damaged threads.
A
matched tap and die set cuts new threads. The tap cuts them in a hole, and a die cuts them onto a stud or rod.
What you need is a
thread repair/replacement kit, which I referred to by the brand name of Helicoil, and others referred to by other brand names. That kit does what was described above:
- it removes the stripped or damaged threads using a drill bit
- it cuts new threads into the wood or metal
- it allows you to insert a special set of replacement threads
- it restores the threads so that a fastener of the original size and pitch can be used
A. If you were to use a rethreader, you might be able to restore the original threads, but if too much metal is missing, you'll need to create new threads because the existing ones won't be able to hold the bolt securely.
B. If you were to drill the hole to remove the threads and then use a tap to cut new threads, your original fastener would not fit because the diameter has increased.
C. If you were to use a Helicoil (or other brand) of kit to drill it, tap it, and then install the replacement threads, you'd have a set of threads that would let you use your original bolt to hold down the dizzy.
Method C is what you're after, not methods A or B. (Don't forget to knock that tang off at the bottom before actually using the new threads!)
