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View Full Version : Adding a gearbox to a SB 9" lathe......



emj
03-20-2005, 09:07 PM
I have a Southbend 9" lathe with a 54" bed that did not come with a gearbox. I have since bought two gearboxes and one came with the leadscrew, gearbox, sector bracket/gears but it is for a shorter bed than what I have. Is it feasible to cut the two leadscrews and make one? How much stress is placed on the leadscrew when the gearbox is operating? Thanks, emj.

J. R. Williams
03-20-2005, 09:20 PM
Add an extension to the short lead screw. I doubt very little work is ever done with the average user on the far right end of the bed.

JRW

JCHannum
03-20-2005, 09:22 PM
Is it possible to modify the non-QC leadscrew? That would be my first choice.

If not, I have seen writeups on splicing leadscrews by turning a reduced diameter spigot on one piece to fit a bored hole in the other and silver soldering them together. Care should be taken to maintain concentricity and matching the threads of course.

I would make the joint about 1" long.

precisionworks
03-20-2005, 10:16 PM
I've used the method JC mentions. Works well on shafting as long as spigot OD and bore ID are close -- size-on-size preferably. Never tried this with an Acme thread like the SB leadscrew but it should work well.

hammerhead74000
03-20-2005, 11:34 PM
I would just order a length of new precision acme rod (MSC carries it), and turn it to fit the gearbox and end bearing.

rick peer
03-21-2005, 08:31 PM
if your model c came with a leadscrew, your better off using it. you will have to cut the left end off to fit to the gearbox and cut a keyway the length of the acme thread, this cost me $35.00 at a local machine shop. good luck

[This message has been edited by rick peer (edited 03-21-2005).]

emj
03-22-2005, 12:07 AM
[This message has been edited by emj (edited 03-21-2005).]

emj
03-22-2005, 12:10 AM
<font face="Verdana, Arial" size="2">Originally posted by J. R. Williams:
Add an extension to the short lead screw. I doubt very little work is ever done with the average user on the far right end of the bed.

JRW</font>


I never thought of that. Thanks,emj.

emj
03-22-2005, 12:14 AM
<font face="Verdana, Arial" size="2">Originally posted by rick peer:
if your model c came with a leadscrew, your better off using it. you will have to cut the left end off to fit to the gearbox and cut a keyway the length of the acme thread, this cost me $35.00 at a local machine shop. good luck

[This message has been edited by rick peer (edited 03-21-2005).]</font>


I was kind of thinking of doing this also. I may try adding an extension on the leadscrew that came with one of the gearboxes as mentioned by JRW and see how well it works. Thanks,emj.

emj
03-22-2005, 12:16 AM
<font face="Verdana, Arial" size="2">Originally posted by JCHannum:
Is it possible to modify the non-QC leadscrew? That would be my first choice.

If not, I have seen writeups on splicing leadscrews by turning a reduced diameter spigot on one piece to fit a bored hole in the other and silver soldering them together. Care should be taken to maintain concentricity and matching the threads of course.

I would make the joint about 1" long. </font>

Another option to consider. Thanks, emj.

Paul Alciatore
03-22-2005, 01:23 AM
I would be concerned about accuracy in splicing the leadscrew together. It is going to be hard to synchronize the two threads. What you will have is a jump in threads at that point, likely worse than any wear that might be found on a well used screw.

I would either construct another one from precision acme rod or look for the correct one on E-Bay or other used sources. Sadly, many SBs are parted out.

Paul A.

emj
03-22-2005, 12:46 PM
<font face="Verdana, Arial" size="2">Originally posted by Paul Alciatore:
I would be concerned about accuracy in splicing the leadscrew together. It is going to be hard to synchronize the two threads. What you will have is a jump in threads at that point, likely worse than any wear that might be found on a well used screw.

I would either construct another one from precision acme rod or look for the correct one on E-Bay or other used sources. Sadly, many SBs are parted out.

Paul A. </font>


The added extension will be at the rear of the leadscrew where there are no threads. If I cut/splice the front of the leadscrews together, it would be just after the front leadscrew support. There is a large diameter journal located just past the support. Or machine the leadscrew off my 54" bed SB to match the shorter leadscrew that came with one of the gearboxes. I have a few more options then I originally thought I had. Thanks, emj.

sandman2234
03-23-2005, 09:57 PM
What I want to know is what are you going to do with the extra gearbox?
David from jax

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