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Lathe Spindle Speed Reducer Exist?

adh2000

Titanium
Joined
Dec 21, 2005
Location
Waukesha, WI
Would like to reduce the spindle speed without changing the gearbox speed, for cutting super steep threads, spirals really. So I imagine something like a planetary gear arrangement that goes onto a D1-6 spindle and has a faceplate that rotates at something like 1/4 speed. Does such an attachment exist? I know the Monarch 10EE had some crazy thing sort of like that for multi start threading. Not really a speed reducer though.
 
Are there gears in the drive train that can be change for making different ratios, such as those used to change from SAE to metric and vice-versa? If you have a selection of such gears, you might be able to come up with a combination that will create the kind of rapid lateral motion that (I think) you're looking for.

What is the coarsest thread your lathe will cut with standard gear combinations? What pitch do you need?
 
I know both Pratt & Whitney and Monarch made spindle speed reducers in D1-6 the next thing is to find one mite be like finding frog hair or chicken lips ken
 
What an interesting proposal!

Call it a long lead headstock designed for infrequent used as an attachment

Perhaps the housing could be made by modifying a tailstock casting from an identical lathe taper bored as the outer bearing and a spindle whose bearing fits had matching tapers. Radial clearance is easily adjusted by altering the thickness of the thrust washers. This is old technology from a century ago. Add 4:1 or 8:1 ratio countershaft gearing driven from a gear mounted in the lathe's spindle.

Oil lubricated tapered spindles used at low speed are extremely stiff and generate very cylindrical diameters provided the fits are precise and the lubrication is maintained.

If the long lead headstock had some common spindle nose standard spindle tooling could be used on it. It might be nice for the spindle to e hollow so long work may be passed through it. A tapered socket for inserting a spindle center would be essential in any configuration.

Naturally such an attachment would eat bed length.

An arrangement that mounts directly on the spindle would certainly be shorter but I can't see any way to prevent generated cylindricity from being a casualty.

Never in my geologic-epoch length life have I seen a factory set-up for a lathe intended for cutting very long leads There may be shop made solution but I've never seen one or heard of one. I'm quite sure you'll have to make what you need. Hell, that's what us machinists do for a living.
 
Seems like the biggest issue would be the rpm needed on the leadscrew to fly down that steep helix at any reasonable rpm for turning..

Think about a powered side head so that you can cut with an endmill, and keep the leadscrew rpm down. Might power the rig through the leadscrew instead of the spindle, using the gear train in reverse as a reduction instead of a step up.
 
P&W made them too. Get an old K&T or Cincinnati horizontal mill with a low lead gear box and mill whatever thread or lead you want.
 
Right in the Hendey manual - other makes also - like the second thumbnail from the P&W Additional Equipment brochure also showing multiple index face plate

Speed Reducer also often used with Relieving Attachments

Never in my geologic-epoch length life have I seen a factory set-up for a lathe intended for cutting very long leads There may be shop made solution but I've never seen one or heard of one.
 

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VFD would work.

That was my first thought, too, but on reflection I realized that all the VFD would do is change the spindle speed and leadscrew speed at the same time in the same proportion. If you could have separate motors controlling the spindle and leadscrew with a VFD on at least one of them, then I think it would work. But if a lathe is cutting, say, 12 tpi, all a VFD will do is make it cut that 12 tpi thread faster or slower. It will still be 12 tpi.
 
cutting super steep threads, spirals really.

Not a new need, nor even close to one.

CNC goods can do it with ease.

Legacy approach used a (universal) mill with powered and synchronized rotab or Dividing Head.

If you have access to neither?

Might be wisest to farm it out ....before it sucks all the spare time out of your life trying to implement alternatives that do not simply ruin one chunk of alloy after another, then not necessarily even come good before you give it up!

:)
 
Not a new need, nor even close to one.

CNC goods can do it with ease.

Legacy approach used a (universal) mill with powered and synchronized rotab or Dividing Head.

If you have access to neither?

Might be wisest to farm it out ....before it sucks all the spare time out of your life trying to implement alternatives that do not simply ruin one chunk of alloy after another, then not necessarily even come good before you give it up!

:)

Not.

The universal mill approach works fine for the screw, but what about the nut? That of course is the hard part. The CNC guys I spoke to did not want to do it. Whether their machine could do it or not we didn't get to. I farmed some out to a Cri-Dan guy and they came out nice. But he bitched and complained and charged me enough to discourage a return trip.

Thanks to John Oder for coming up with exactly what I want, at least on paper. Knowing one exists is comforting, now to find one.
 
P+W thread mill would be the item of choice.

Most of the big name lathe builders offered a "sub-headstock". I have only seen one (1) in the wild. Company in Greensboro had a toolroom that must have been 1500sq/ft. After 100+ years in business Packed full of goodies from junk fixtures, to special cutters, to unobtainable accessories. One of those was the sub headstock.

Scrapper bought the lot for not much. Loaded a roll off dumpster with a bobcat.
 
Not.

The universal mill approach works fine for the screw, but what about the nut? That of course is the hard part. The CNC guys I spoke to did not want to do it. Whether their machine could do it or not we didn't get to. I farmed some out to a Cri-Dan guy and they came out nice. But he bitched and complained and charged me enough to discourage a return trip.
Hear yah. Once wasted $6,000 on a similar CAD/CAM "CNC" exercise. Need of / market for the item we designed had gone obsolete before we even tested the second unit, so it never entered service.

This, of course, is also where a pragmatic designer with limited resources steps back and ponders over a way to find some other route to the end result that doesn't need a particularly troublesome device AT ALL.

Nearly always, such a solution IS found. Not uncommonly, it is also a BETTER one, designers as motivated as they can be by fear of starvation, if nothing else!

Good luck with it!

:)
 
What is the actual lead requirement? And what thread/groove form? And how big of a hole does the nut have?

I've heard that the proper way to do this is to put a motor drive on the feed box input shaft. Then the spindle is backdriven through the end gears, reducing the torque that would otherwise be required to overdrive the feed box via input from the spindle.

That being said, cutting a very coarse thread manually is a royal PITA for the guy operating the lathe. I've done it for the odd worm thread, which isn't really all that coarse, and it is soooo sloowww. Keeps you busy humping the levers, though.

I'm not sure what the practical limits are on a cnc lathe. I think my old Mits will handle a 10" lead, but that's probably maxed out at about 40 rpm. Still, the cnc is so much quicker on retract because it doesn't have to be run backwards, which a manual lathe almost surely would, if you didn't want to stand there for a couple of minutes waiting for the thread dial to come around at 5 rpm or something.
 
Monarch made something appropriate for the model 60 - called it a subheadstock:

monarch_sub_headstock.jpg


Not sure how it was a "popular accessory" since I've never seen one in the wild.
 
Monarch made something appropriate for the model 60 - called it a subheadstock:

monarch_sub_headstock.jpg


Not sure how it was a "popular accessory" since I've never seen one in the wild.

I've got a heavy Hungarian lathe here (28" swing) that will cut down to 7/8 DP (that's about 3.59" lead) without doing anything but shifting some levers. Will also do multistarts up to 6 with an indexer thingy built into the top of the headstock. It's one thing to see it on the chart, and another to actually do it :D
 
Since I started this thread almost a year ago I have been looking for one of these spindle speed reducers for long lead threading. Finally someone in another thread, which I cannot find right now, posted about one on craigslist in the UP. I made contact and on Friday drove up picked it up:
74823b3e4f7b2eef3a7bd18a4b215abc.jpg

This is Pratt & Whitney, D1-6 mount, reduces spindle speed by 6. Came with the lathe:
2143557f706032a5101f7597c87650c9.jpg

Serial number 502 if I'm remembering correctly which I think puts it at 1947. Spindle is very quiet even at top speed of 1000 rpm. Some noise coming from what I think must be the clutch area. Very useable though the way it is so won't have to be searching for the unobtainable spindle bearings. I hated to buy such an old lathe but this P&W has some cool features. It can already cut 1 tpi without the reducer:
e9b21c5722351e196db90c84e2eabb3a.jpg

Almost no 12" lathe can do that. Lowest spindle speed is 14:
a2f60a4e72310fa3c0e8af0b4ab283ca.jpg

So thanks to the PM community for getting me into yet another project that I don't need!



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P&W 12 X 30 Model C. I'll bet yours is D1-5" - my 1950 was

Manuals can be emailed if you want to PM that address

Owned and enjoyed a 12 X 30 for over 20 years

Maybe you already know it has lead screw reverse on the apron - handy!
 
It came with this manual:
1a948dea83eb6e2cf6c15c891db3d335.jpg

If you have something else I'd be interested. Or if anyone would like a copy of this one that I have that would be no problem.

If I understand the threading instructions correctly the threading dial is not needed except for multistart threads. For single start threads you go back and forth with the leadscrew reverse. Just like the Hardinge HLVH.


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