Overdrive sub-spindle for manual lathe?
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  1. #1
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    Default Overdrive sub-spindle for manual lathe?

    Every now and then when reading literature for some of these old heavy iron manual lathes, I've seen sub-spindle attachments that gear down the spindle speeds. These would apparently thread onto your spindle nose and bolt onto the bed ways for alignment. This is one Hendey used to make:
    img65.jpg
    I was thinking the other night, why couldn't you do the same in reverse, increasing your spindle speed? Have any lathe manufacturers ever offered such?

    I can already see some issues in that for either one to be accurate, you would need some way to dial the sub-headstock casting in, or have it fitted to exactly match the height and alignment of your primary headstock. Any wear up close to your headstock would throw it off. You would also sacrifice a bit of bed room, so it might only be practical on machines with longer beds, but it would be handy to have the option of increasing your spindle range by 1:2 RPM when doing small diameter work, but still have the low n slow range for medium to big stuff.

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    I think these creatures are available for mills, maybe called speeders. For a lathe you might have to buy an under drive unit and change the gearing if the bearings can take it?

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    Yes, like a milling speeder, only more ridged and fixed to the bed of the lathe but not a permanent part of the machine. Something that you could change out between jobs.

    Most of the low speed lathe spindles I've seen, bearings particularly, would have no chance of surviving having their top speed doubled. But with an attachment that goes on the spindle nose, the motor and headstock speed's don't change at all. If anything you would have an increased load on the motor accounting for the extra gearing.

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    No ideas? I've half a mind to attempt to make one someday. My Hendey has enough bed length if I can sort out the wear up close to the headstock.

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    Would think that the underlying issue would be rigidity and stiffness....
    Unit would need gearing that takes room, then bearings for the over sped spindle.
    All gets to be a long package if you maintain some distance between the output spindles bearings
    For small work guessing perhaps not so important...but then you would be dealing (guessing here) with a larger machine that would
    be heavy on the carriage and controls. Not what you would want for small light detail work.....

    Would think the better solution if you want a high speed spindle would be to run a spindle inside the original lathes spindle, having an end bearing that fitted up the the original spindle nose.
    and at the rear a bearing at the rear end of the original spindle.....Fits up like a collet closer.....
    The drive provided via serpentine style belt at the end and driven via a variable frequency electric motor. (speed control) with no gearing.

    Most shops i think would rather have a smaller high speed machine for such, and leave the brutes to the big stuff.....


    Cheers Ross

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    Quote Originally Posted by AlfaGTA View Post

    Most shops i think would rather have a smaller high speed machine for such, and leave the brutes to the big stuff.....


    Cheers Ross
    I would compare the cost of a smaller lathe as an addition if you have the room.
    I have made the comment before when posters have asked which lathe to get: Get them both, you can not have too many lathes!

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    Quote Originally Posted by FredC View Post
    I would compare the cost of a smaller lathe as an addition if you have the room.
    I have made the comment before when posters have asked which lathe to get: Get them both, you can not have too many lathes!
    Agree'd that there is no one-size-fits-all machine. The rule of thumb I've always gone by is that 99% of shops be it a hobby or production operation, will have a large and a small machine. You're manufacturing needs would determine if your "small" spindle is a 10" swing or 20" swing.

    In our shop, our manual lathes range from a 9" South Bend, up to the 16" Hendey. The Hendey maxes out at 600 RPM though which is a little slow for some stuff. So I'm thinking a sub spindle would not replace the smaller lathes, but just improve the bigger lathes range.

    Upgrading to a more modern, faster 16" lathe is of course the most practical solution. I'm just musing the sub spindle concept here...

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    Quote Originally Posted by M.B. Naegle View Post
    No ideas? I've half a mind to attempt to make one someday. My Hendey has enough bed length if I can sort out the wear up close to the headstock.
    Been done. One of the few I'd call worth duplicating:

    Globe Milling and Dividing Attachments

    You would not need ALL of it.

    My "starter culture" - cast housing, bearings, pulley, is a 50-taper supplementary spindle seems to have come off a medium/large T&C grinder.

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    It’s not fun doing small work on a large lathe. Everything is so “big” it’s hard to see what you’re doing. Also as mentioned there’s no feel.


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by adh2000 View Post
    It’s not fun doing small work on a large lathe. Everything is so “big” it’s hard to see what you’re doing. Also as mentioned there’s no feel.


    Sent from my iPhone using Tapatalk
    Agree'd. It looks like Hendey used their low speed head stock as part of the set-up for low lead threads. It was less about the speed range and more about changing the spindle-to-lead-screw ratio.

    But like I said, My interest in the concept wouldn't replace a smaller lathe, just give a higher speed range to the big lathe, for IT'S smaller work. I'm thinking around 2 to 3" diameter or long shafts (You don't often see small lathes with very long beds anyway). If you're turning big plates, pipes, etc. 600 RPM is fine, but our 15" Colchester Clausing gets up to 1200 RPM, which I often use on pieces up to 4 diameter (lots of coolant and an enclosure). This class of lathe is still small enough (IMO) to be comfortable to operate, but they have the mass to take some heavy cuts and hold their numbers.

    I'm just curious if such a thing was ever done. "High Speed" lathes were a thing long before head stocks with a wide range of speeds became the norm, so perhaps someone offered an attachment like the vertical high speed milling heads that were sold for mills?

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    Remember the speeder ratio has to be taken into account when single pointing threading. A belt drive may not work for threading at all as any slippage would wreck your threads unless the belt was a timing type.

    I see your dilemma even your small lathe being a South Bend does not have "high speed".


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