# Thread reduction drive unit



## road (Dec 7, 2014)

Hey all, 

I'm not sure if this is the correct thread for this . so If it needs to be moved go for it. 


When I purchased my used lathe ( Craftex B1979C ) This drive reduction unit was mounted to the tail stock end of the bed. 

I have not delved into lathe threading as of yet, I am interested in re-installing it. 


Here are pics of the drive. 

It was an expensive part from my knowledge. 


Can any one shed some light on the subject ?


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## Terrywerm (Dec 7, 2014)

In most cases, setups like this are used to provide power feed on the lathe's leadscrew. It is variable speed, allowing you to have better control of the finish on your parts. They do not work for threading however, as there is no way to synchronize the lead screw to the spindle, which is a necessity for threading on the lathe.

With this setup, the gear motor mounts on the tailstock end of the bed or bench, and a pulley is installed on the right hand end of the leadscrew.  A cog belt is then used to connect the gearmotor to the leadscrew.

If you have change gears for your lathe, or a quick change gear box (QCGB) you remove the cog belt when using the spindle and gears to drive your leadscrew. such as when threading. Some of the small lathes have no threading ability due to the lack of change gears or QCGB, but as far as I know, your lathe comes with change gears. Using the motor power feed is faster and easier than setting the change gears for a specific feed rate, plus it gives you fully variable feed rates.


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## JimDawson (Dec 7, 2014)

+1 what Terry said.


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## road (Dec 7, 2014)

OK , thanks Terry. 

 A better finish is a good thing. 
I will figure out how to re-install this unit with a little more eye appeal and set it up with a linear pot. for speed control


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## Terrywerm (Dec 7, 2014)

It sounds like you are spot on!  

My old Logan 200 has change gears instead of a QCGB, and I have been contemplating the installation of a lead screw drive like the one that you have, as it would be so much easier than changing the change gears for every operation. The only hard part is figuring out how to adapt the end of the leadscrew so that I can attach a drive pulley, but I think I have that problem solved.


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## John Hasler (Dec 7, 2014)

terrywerm said:


> It sounds like you are spot on!
> 
> My old Logan 200 has change gears instead of a QCGB, and I have been contemplating the installation of a lead screw drive like the one that you have, as it would be so much easier than changing the change gears for every operation. The only hard part is figuring out how to adapt the end of the leadscrew so that I can attach a drive pulley, but I think I have that problem solved.



How do you plan to do it?  I'm thinking about something similar for my Logan 400.  I'm considering drilling and tapping the end of the leadscrew and then screwing on a shaft extension (secured with epoxy in the threads).


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## Terrywerm (Dec 7, 2014)

Hi, John.  Actually I was thinking about modifying the end of the lead screw that rides in the bushing in the end support. Modification would include milling two flats on the last 1/2" or so of the lead screw. A new part made to match would be made so it would effectively lengthen the lead screw so that a pulley could be mounted on the end, and the whole thing could be driven by a gear motor and cog belt. There might be a better mod to make to the end of the lead screw that would work just as well or even better.

Another idea (and I personally like this one better) would require modifying the change gear cover so that a gear motor could be mounted below the change gears. A pulley would be placed on the far left end of the lead screw, which in turn would be driven by a cog belt from the gear motor.

A third idea also involves modifying the change gear cover, putting a small (about 1") hole in it directly in line with the leadscrew. The gear motor drive would then stick in through that hole and would use a six point socket to engage the nut on the left end of the lead screw.

So far I have not drawn anything up, I've only been tossing ideas around in my head. I am open to ideas, so spill 'em if ya got 'em!


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## BRIAN (Dec 8, 2014)

Hi .. you may find some inspiration here <!-- title / author block -->    [h=3]Power lead screw for 7x12.[/h]

You can simply drop the gear out of mesh when you want to screw cut, and the variable speed is just wonderful can't praise it enough.


Brian


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## Ebel440 (Dec 8, 2014)

I have a logan 200 I am thinking about modifying in a similar manner but making a timing belt and gear that will fit on the leadscrew instead of the change wheel.  Also thinking of fitting a quick change gearbox the same way. But I've got a lot to do before that happens so I have not really worked out the details yet.


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