# Auxiliary Lead Screw Drive



## Jeff May (Jul 3, 2016)

I know this has been done before. 
The one set up I have seen used a right angle gear drive motor, pulleys and a belt to drive the lead screw from the tail stock end.
It would certainly give you an infinitely number of feed rates. Of course you wouldn't be able to thread with this set up.
I have several thoughts on this,
I have a DC motor out of a tread mill. Would this work with a variable speed control unit?
Would it go slow enough and still have the torque needed to run the lead screw?
I also have thought about a wiper motor, also with a variable speed control.
Has anyone on here ever done something like this?
Any thoughts or ideas would be welcomed...
Thanks....


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## David VanNorman (Jul 3, 2016)

A wiper motor would be in the speed range.


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## Silverbullet (Jul 3, 2016)

I'd bet a wiper motor would be perfect. Wire in a potentiometer and you've got variable feed to control it more . I'm sure you can make a simple slip feed nut or a belt tension control. That way no problem cutting threads. Simply disengage the drive.


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## Dave Smith (Jul 4, 2016)

Jeff----here is my Logan with what you are talking about--works great ---I explained it in the Logan lathe section I think in 2013--one lever is a variable speed with a second lever for quick reverse---I was going to use an air motor, which would also have variable speed and reverse, and very simple with plenty of power----Dave


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## wa5cab (Jul 4, 2016)

Different strokes for different folks.  But frankly, I have never understood why anyone would go to the trouble to do this.


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## Jeff May (Jul 4, 2016)

wa5cab said:


> Different strokes for different folks.  But frankly, I have never understood why anyone would go to the trouble to do this.


WHY?? 
I've gotten along many years with the gear drive. I don't have the quick change gear box on my Atlas. I thought this would be a good way to vary the feed rates. Instead of changing the gear sets every time I want to speed up or slow down the feed.
Besides, I need another project to add to my list of projects to be done in the shop anyway...


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## Dave Smith (Jul 4, 2016)

wa5cab said:


> Different strokes for different folks.  But frankly, I have never understood why anyone would go to the trouble to do this.



if your lathe has the quick change gear box then you wouldn't understand ---it takes a lot of time to manually change gears often just for feed rates--this process makes it easier--- even much faster than a quick change--- it just takes a little space on the end of lathe and can be removed quickly to use gear drive again for threading-----Dave


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## David VanNorman (Jul 4, 2016)

When I was in the sewing business we used those little  vari drives for running pullers that would work great. Those drives was not cheap at the time.


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## bill stupak (Jul 5, 2016)

Bill


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## bill stupak (Jul 5, 2016)

http://www.hobby-machinist.com/threads/craftsman-12-36-mods.44951/


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## Jeff May (Jul 8, 2016)

Thank you to all for the great ideas.... 
I do have a wiper motor that was slated for a power quill feed for my mill. As I use the lathe more I think I'll change my plans and use it for the lathe.


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## dlane (Jul 8, 2016)

I would think the belt tension would ware out the leed screw support bearing prematurely , unless roller bearings were used.


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## uncle harry (Jul 8, 2016)

dlane said:


> I would think the belt tension would ware out the leed screw support bearing prematurely , unless roller bearings were used.



A timing belt and "gear" pulleys would provide positive driving without excessive tension.


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## wa5cab (Jul 9, 2016)

With the sprocket belt or for that matter with gears, there is still a side load that will wear the bearing and lead screw on either the inside or the outside.  The only way around that is to drive the lead screw with some sort of a right angle gear box.


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## Jeff May (Jul 9, 2016)

I suppose one could make an adapter of sorts to fit the wiper motor right to the lead screw. I looked the lead screw area over quickly last night, I'm not sure there is enough room to put a bearing of sorts in there. Naturally a new lead screw support would need made up, but I'm not sure you would find bearings small enough to make it work.
I tend to agree with "uncle harry" above. A timing belt and toothed pulleys shouldn't put that much more tension on it.
My mill uses a timing type belt to run the head with toothed gears, its been running that way for over 30 years, never a problem.
Thanks to all for some excellent suggestions and advice.


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## David VanNorman (Jul 9, 2016)

I had a small gear drive motor run a lead screw  on a SB 9 C for years and I used a  small roller chain todo it .  The nice thing  about that was feed direction  was just a switch away and speed was guickly set.


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## John Hasler (Jul 9, 2016)

Jeff May said:


> I have a DC motor out of a tread mill. Would this work with a variable speed control unit?
> Would it go slow enough and still have the torque needed to run the lead screw?


You'd want about a 10: 1 speed reduction.


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## John Hasler (Jul 9, 2016)

wa5cab said:


> With the sprocket belt or for that matter with gears, there is still a side load that will wear the bearing and lead screw on either the inside or the outside.  The only way around that is to drive the lead screw with some sort of a right angle gear box.


You could couple the end of the lead screw to a short shaft with its own bearings and put the sprocket on that shaft.


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