heli coil install
I've read several articles on heli coil installation. I have a 1/4" x 28 that has broken off. I'm thinking about heli coiling it. Got some questions for the machinist in this group:
a. The kit I think is for that says I should use a 17/64 drill. This, of course, is bigger than the 1/4" hole. Does this size sound right? If this is right, then it drills out the thread, plus a little material.
b. So, what is the threading device I should use? Sounds to me like it would be slightly bigger than the 1/4" tap I'd normally use for a whole of 1/4".
Is this the way I'd get 1/4" bolt to fit in?
The reason I'm asking is that my 1/4" hole has a broken pice of bolt all the way in there. Let's say my shaft length on it is 6/8", and the broken piece all the way in there is 3/8".
The problem I would have had was how to get the broken part out. One way is to use a drill slightly below 1/4" threads, and drill it. That still would leave a little in the threads.
I might get an easy-out, but not sure if they make one that small or not.
With drilling the full thing out, I would feel much better about it getting everything, and being ready for the heli coil, all in one smooth operation.