You can get a tap and die set from Harry Higley and Sons for 1/4 - 32. If all you need to do is chase the threads, that's the tool, the tap. I use the die on some plugs if I suspect it might be off a little bit. Anyway, once you have the set, you can use it for a very long time. And no, it will not replace the need for a heli-coil if you need one. That you need to send to Mr. Clarence Lee as reference above.

Cheers,

Chip