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Electronic Leadscrew for the New Lathe

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S. Heslop:
Image from lathes.co.uk http://www.lathes.co.uk/boxford/page2.html



The leadscrew itself has the spline in it, instead of it being a leadscrew and a separate splined shaft for the autofeed.

Can't quite see how it's all connected in this image though. But the worm reduction would probably help bring threading leadscrew speeds down to something slower for autofeed, and at least save the need of switching gears back and forth except for when you need to cut threads.

There's alot of popular videos on the topic of worm hobbing using taps, and it looks like it works fairly well (even though I've only seen one video where the guy bothered to include a scene of the thing actually meshing with a worm).

Fergus OMore:
Again, might I suggest that you look at the Pools Major? OK, the first lot of pictures are pretty basic- perhaps a dog clutch but follow on until you look at the tailstock stock end and see what appears to be something different. Then you see a non- threaded leadscrew.

I'l let you enjoy the rest but with a bit of fiddling with the feed screw dials, you get some interesting developments- which I haven't seen later.

Enjoy- it's different

Norman

Manxmodder:
Simon, the free hobbing process works best with a spiral flute tap,certainly when small diameter taps are being used.....OZ.

vtsteam:
Simon, thanks, so you were just mentioning a way to separate functions of autofeed and threading without using two leadscrews. That's the part I didn't quite get. What the purpose was. (btw, the Craftsman also has a single, grooved leadscrew.)

Well, looking at that drawing, it may be interesting as a historical mechanism, but two leadscrews and/or making a single grooved leadscrew plus a lot of complexity in the apron isn't something I'll be doing on my own lathe. There won't be any gears in the apron, and no rack and pinion either. The only thing in the apron will be a half nut, and if I go with chase threading, a clamp for the pushrod, as outlined earlier.

To me, complex apron gearing makes sense for large lathes with very heavy carriages and long traverses, but for something like a 9x12 lathe it doesn't serve a purpose. On the Gingery, I release the half nut and slide the carriage toward the headstock instantly to position it. It's a lot faster than cranking the carriage handwheel on the craftsman.

For hand feed on the Gingery, you close the half nut and use the crank at the tailstock end of the leadscrew. It's a lot finer control than the rack and pinion on the Craftsman apron.

For autofeed on the Gingery you slip a round belt onto the leadscrew pulley at the headstock end, and the leadscrew turns. Very simple and straightforward. The Craftsman is cumbersome on all counts by comparison.

Will_D:
May I suggest that first we set down some requirements:

1. Cut threads accurately and quickly

2. Use fine feeds both longitudeanly (and cross slide (if supported)) to quickly machine some parts.


Req 1:

Requirement 1 can be satisfied by simple (conventional) gear trains and the leadscrew and the TDI as implemented on most lathes
or
A pseudo cnc system as mentioned in this thread that picks off headstock rotation and converts this into a digital input to software that then ouputs control signals to leadscrew stepper motor drive.

Consider this:

Thread cutting is a slow process. To set up the gear train on a conventional lathe may take 5 minutes or less. To cut the thread can take 30 minutes. That's for imperial threads on an imperial lathe (Longer for Imp on Metric)

So on balance I would favour the traditional aproach!


Req 2:

Requirement 2 can be satisfied by simple gear trains and the leadscrew or by applying a separate digital/cnc feed to the lead screw.

On my ML7 I have just one FF available using the gears and lead screw.

Using a simple digital lead-screw drive would give infinite feed rates. Just think of a controllable rechargeable drill applied to the leadscrew hand wheel on a ML7

BTW: Guess what I am working on!

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