- Joined
- Mar 18, 2011
- Messages
- 243
That's a good ol' 60 degree V thread which is the most common in the USA. I'm more concerned with the thread in the face plate being that same type and at the proper pitch diameter.
Also, another thing to keep in mind, is that face plates can be purchased "blank" meaning no threads to mount on a spindle so the new owner can thread their own as desired. It is certainly possible that the previous owner threaded this himself and didn't take the thread to full depth for some reason... maybe he fitted it to an under size spindle??? Who knows.
If it is the case where the threads just aren't deep enough, it could be put on a lathe, indicated in, and very carefully line up a internal single point threading tool on the original thread and then taken to depth. That is what I would do if I found myself in this situation. It sounds more difficult than it is if you've never done it before. You'd have a nice large bore and coarse thread to give you a big advantage over a much smaller bore. You run the threading tool in using your half nuts, stop the spindle while the tool is inside and then line the tool up in the thread using your compound and cross feed. Do this over and over a few times making very small adjustments until you just start to make a chip and then go from there. Doing this type of work is a great skill to have in your tool belt. Just go very slow and carefully. One additional word of advice is to make sure your threading tool has sufficient clearance because you will be inside a bore and you don't want it rubbing.
Ted
I just learned that skill yesterday (chasing a thread) as I had something go wrong and I do not fully understand what happened. I don't think I backed out the cross slide enough after taking a bunch of compound cuts and when I moved the carriage to the right the tool bit hit each thread (like click click click click etc) but I just said oops (really said #&*!$@) and just went in for the next cut on the compound. It started to cut and then caught on something and moved the part in the chuck and made it wobble a little. I then said "#&*!$@" again and remembered something I read somewhere about if that happens..."don't worry as it's easy to fix". So I re -chucked the part and got it spinning true and engaged the half nut with the tool away from the part and then stopped the machine with the half nut engaged. I move the cross slide and compound until it looked right and finished the part. I was proud. I do plan on making one more of these adapters as the 3rd time is the charm, right?
I will see if that method above is something I want to tackle but first I am going to buy a few more tools like a Starrett thread gauge that has 8 TPI on it. My cheap set does not go that low. I have thread rods for measuring but didn't use them as I am going to need to practice with those first. I think grease would help or I need an extra hand.
But you are correct. The "who knows" factor is there and is just my luck. The good part is that I somewhat successfully cut the 2 1/4 - 8 TPI threads and they actually feel pretty good as far as fit. The finish, not so much. But when I make the 3rd one I will have experience. And based on that "flat" spot on the entire thread on the faceplate that does not fit, it may be the problem all along that the cut is not deep enough.
Thanks,
schemer