Use mini-lathe as dividing head?

I saw a picture of a gadget that was on a myford - looked like a worm that fit the gear on the outboard end of the headstock, with dividing plate etcetera.

So's I got to thinking, I could make that - a mount to fit one of the extra change gears, and a worm wheel on the same shaft, and a worm at right angles, cobble the whole thing so it would turn the spindle (slowly) and then have fun making stuff to fit on the cross-slide.

Then I had a (possibly) bright idea:

I don't need a lot of teeth hitting the worm-wheel, it's not like power transmission is going on. How about a single worm with thread profile to match the headstock gear? I'd have to tilt the worm at some small angle. Maybe there's a source of threaded rod that would fit nicely...

And while I'm posting, I got a quick-change toolpost holder for it and it is not as good in the rigidity department as the one that came with it. This is a cheaper type of qc holder that overhangs the compound and it moves unless I tighten the gibs too much for easy movement-in-the-plane-which-was-intended. Bummer, and I can't return it 'cause I had to modify it to fit the mouunting stud.

Here's a pic of it:

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Without a precision worm and gear, the accuracy and backlash would not improve over just eyeballing divisions scribed on the headstock. So the existing headstock gear won't help, but you do have a "head start" on an improvised rotary dividing plate arrangement.

For all that I would think about a CNC encoder instead of a precision gear.

Reply to
Richard J Kinch

Have a look at this

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Easy, accurate results without having to get all rectal about the price of actual precision worms and worm gears.

Two names worth looking for in books George H. Thomas and Radford (sorry, can't remember his name). Both were frequent contributors to Model Engineer magazine, and both dealt with dividing mechanisms a lot. There are books of the collected wisdom of both these guys out there, and I can give my highest reccomendation to the book Dividing and Graduating by GHT. It contains drawings and detailled instructions for both the versatile dividing head, and the headstock dividing attachment. While they are detailed as for a Myford 7 inch sing lathe, the ideas are adaptable to any that you may have. A big thing to watch for is the tooth count of the bull gear. It helps if it is a conveinient number for a dividing head. If it is not convienient, you are pretty much stuck with a gear on the spindle end. Any lack of precision apparent in the gears you choose, will be well beyond the ability of anyone to find with hobby equipment. It's not like you'll be bidding NASA contracts now, is it? These units have been succesfully built for a great many years.

Get the book I mentioned above. If you are leary about spending the bucks right off, borrow it from the public library through their inter-library loan program. Great book!

Cheers Trevor Jones

Reply to
Trevor Jones

Older bench lathes used to often have indexing holes on the outboard side of the headstock cone pulley. I recall that one of the Lautard books described a more involved indexing setup with worms, gears, etc.


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Reply to
jim rozen

This is used in Sherline's indexing head.

Reply to
Ron Thompson

Thanks! Not original, but not unworkable either.

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Reply to
John Fletcher

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