In the "Welcome" section of this forum Nikon Ron wrote:
He indicated he would start a thread in a different group so I thought I'd give my answer here instead of continuing on in the Welcome section. So here goes.Soooooo, feeling a little frisky I decided to drill and tap the compound rest on my Compact 8 lathe for a QCTP, which many of you helped me with. Well to make a long story very short, I drilled the hole crooked, very crooked. Which brings up a question and subject for a new post in the group that I haven't joined yet. The best way to right the wrong, or make the wrong right whichever you prefer, should I try repairing the compound or should I try, with your help, to find another one? It seems that if I found another compound I would have the same problem, drilling it correctly. I squared everything up on my drill press before I started but I "still" got it wrong.
Bob replied with one good approach:I have used stud plugs as Bob describes for many different applications. They work particularly well when further machining is not going to occur at the same location as where the hole is being plugged. Of course, a threaded stud requires a threaded hole (which is Nikon Ron's case). In some cases when I just had a round hole, I simply threaded it so I could stud plug it.My thought on the mis-drilled part is to install a threaded stud to completely fill the hole and mill it off so the it is level and square. We used to do this on diesel engine blocks that cracked between the liners and it is a tough and durable fix. When you install the stud, use a bit of green loctite and it is nearly permanent as any other repair.
Stud plugs become a bit more problematic if they are plugging a hole that was drilled close to the correct location, and which will be corrected with a new threaded hole. The problem arises when the new hole drills out a significant portion of the plug. The remaining bits of threads from the stud plug may not hold securely enough to enable clean threads to be made in the new hole. (In this case, the more the first hole missed the mark, the better.)
For holes that have to be moved only slightly (or realigned slightly) filling the hole with weld may be an alternative. Use soft filler material and let the entire piece cool slowly to anneal it. After it is cool, grind off the excess filler to get a smooth surface. Of course, this may not be practical for hardened or precision pieces (such as Nikon Ron's QCTP).
So, in Nikon Ron's situation:
1) Can you stud plug the errant hole and drill and tap in an undisturbed location?
2) Could you disassemble all except the base, weld the hole shut, anneal, re-drill and tap it? (I don't think it has to be hard to function well. You would want to do a little clean-up surface finishing to make it look better and work well.)
3) Can you, as Bob suggests, re manufacture just the base?
Then, Ron, you need to figure out just what went wrong when you drilled and tapped the first time. Why did it come out crooked?