Any DIY thread dial indicator mod?

Hello all. I recently purchased my first lathe, the BV25B chinesse piece of masterwork. Well it isnt that bad, at least I wont be turning in my drill press anymore. The lathe is acceptable for me but there is a little shortcoming, it does not have a thread dial indicator, you see, I want to make some nuts for my 3mm pitch two flutes leadscrew and I do not have a certain method to engage the halfnut in position for the second pass. There is also a possibility to make the dual V cutter and make both flutes in one pass, but I d rather have a thread dial indicator. Is there any plans or mods for thread dials? I dont even know how it works, I know that the dial turns but nothing else.

Thoughts?

Thanks. Konstantin

Reply to
konstantin.neo
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You could try turning the compound 90 degrees to the infeed, or in line with the longitudinal axis. After cutting the first of the two leads, turn the compound the correct amount to cut the second thread. I have cut four (4) lead threads this way.

Dixon

Reply to
Dixon

One method of doing this is to set the compound parallel to the ways and then offset the cutting tool by the difference in the thread pitch.

Jack

Reply to
Jack Hayes

Home Shop Machinist has had a number of construction articles over the years:

See

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Randy

Reply to
R. O'Brian

But you don't need that. Cut the first pass withou disengaging the halfnut (to go back, use the reverse). The second pass is done by advancing the compound by the pitch. Of course, you can't swivel the compound. Well, you can, if you have a pocket calculator. :-)

Nick

Reply to
Nick Müller

Thank you very much for the ideas and the HSM article. It cleared things in my head.

Konstantin.

Reply to
konstantin.neo

The way this was done in the old days was to turn between centers with the stock driven by a lathe dog. If the faceplate has two slots 180 degrees apart, you unmount the part and index the dog to the other slot to cut the second thread form.

Jim

Reply to
jim rozen

I've done it that way, works well. One thing one book suggested was to drill and tap a faceplate at 90 degree intervals(or whatever spacing you'd need for the number of thread starts), then just use a regular machine bolt for a dog driver. The article detailed a making fancier dog that forked around the bolt.

One thing I've done with chucked work is to leave the half-nuts engaged on the last pass of the first thread, mark the tumbler and the spindle gears where they're engaged with a Sharpie, then disengage the tumbler and flip the spindle 180 degrees and re-engage the tumbler. It worked, no extra muss or fuss, saves removing the work and possibly screwing up positioning. If I was doing multi-start screws for money, I'd make up the faceplate and driver dog, though. Lots of other ways of doing the same thing. I'm not in favor of positioning the compound parallel with the bed travel and offsetting for the second thread, that way you're back to plunge cutting with the threading tool and that's never given me any good results with threading, lots of chatter and a rough thread. If it gives you good results, go with it, though. You can probably get away with it if you've got a lot heavier lathe than I've got currently.

Stan

Reply to
stans4

But you can swivel the compound and still offset for the second pass. It requires just a bit of trigonometry (hint: tangens).

Nick

Reply to
Nick Müller

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