Rebuilding South Bend but need help

[thecheapskate]

Hi, first post here, I looked at some of the past posts from many years ago that confirm my thoughts but still thought I would explain my situation and see what ideas come up. I have a really clean 1930s South Bend 9 inch lathe. Its a dandy other than the first couple feet or so of threads on the keyed lead screw that runs parallel to the bed is worn out. I was originally just going to turn it a half round and mill a new slot on the other side to get rid of the worn slot but the thread themselves are pretty much pointed and sharp next to the head. I just spent all afternoon searching the net for replacements without much luck, for $22 a foot I can buy the threaded shaft so then I would have to mill a slot in it and probably cut the ends off the original and weld on the new all threaded shaft. My other option would be to put the new slot in the worn out threaded section and cut off the two ends and reverse it. Of course instead of having 7 ft of threaded lead screw I would only have 4 or so of usable so that seems like a lot of work to build a shorter lathe. I have picked up several old lathes and they all got the same problem. I already replaced the half nuts and that did take out part of the slop but I would really like one nice lathe to work with. Thanks for any ideas or suggestions, maybe I am not thinking of something obvious? If there is any place that specializes in South Bend Lathe long lead screws please advise, I find cross feed ones all over the net but not any long ones specific for this need.

Thanks, Aaron

 

[benmychree]

Cutting a key slot in a new piece would likely cause it to bend by relieving stresses, I assume that the threaded stock is formed by cold rolling, not by machining and is thus highly stressed. I have seen it done to reverse the lead screw end for end, however you lose some threading capacity at the tailstock end.

 

[Weldingrod1]

Hang up the shaft and give it a good cooking with a weed burner.
Then cut your keyway.

Sent from my SM-S911U using Tapatalk

 

[piper184]

Do they cold roll acme threads? I have no idea, but annealing the shaft should relieve any stresses. It it was heat treated in any way, that would have to be done again but that introduces the aspect of warping, especially with a slot cut lengthwise, it won't quench evenly.

The supplier of the threaded rod should be able to tell you if it was made from stress proof or if it is heat treated in any way. As well as what the alloy of the steel is.

Could the old screw be repaired where the threads are damaged? Some people have good luck on broken gears by building them up with brazing and then filing back to shape. If you only have a few teeth to worry about, perhaps that would be easier than replacing the whole screw.

 

[G-ManBart]

There are quite a few different SB 9" lathe lead screws on eBay right now....did you look at those?

You could also send a note to Ted Pflunger who has had a LOT of SB parts over the years. He's very helpful: latheman2@aol.com

 

[MikeInOr]

A picture of the problem area of the lead screw would help others visualize the problem and make better recommendations.

 

[Darkside]

your lead screw is worn but your ways are not? post some pics

 

[Danzo187]

Hi, first post here, I looked at some of the past posts from many years ago that confirm my thoughts but still thought I would explain my situation and see what ideas come up. I have a really clean 1930s South Bend 9 inch lathe. Its a dandy other than the first couple feet or so of threads on the keyed lead screw that runs parallel to the bed is worn out. I was originally just going to turn it a half round and mill a new slot on the other side to get rid of the worn slot but the thread themselves are pretty much pointed and sharp next to the head. I just spent all afternoon searching the net for replacements without much luck, for $22 a foot I can buy the threaded shaft so then I would have to mill a slot in it and probably cut the ends off the original and weld on the new all threaded shaft. My other option would be to put the new slot in the worn out threaded section and cut off the two ends and reverse it. Of course instead of having 7 ft of threaded lead screw I would only have 4 or so of usable so that seems like a lot of work to build a shorter lathe. I have picked up several old lathes and they all got the same problem. I already replaced the half nuts and that did take out part of the slop but I would really like one nice lathe to work with. Thanks for any ideas or suggestions, maybe I am not thinking of something obvious? If there is any place that specializes in South Bend Lathe long lead screws please advise, I find cross feed ones all over the net but not any long ones specific for this need.

Thanks, Aaron

Aaron,
I was just at ebay and saw bunches of south bend lead screws for under 100 bucks, even ones that are same thread but long ..easy to modify

 

[thecheapskate]

I just wanted to thank everyone, I have had some problems with broadband so I have not been online much since I posted. I will try to get some pictures up soon. I looked on Ebay but none of them were as long as mine. Thanks again.

 

[thecheapskate]

This shows the place in question, .175 slot to .276. The outside of the threads go from 1.107 to 1.124 with some threads pretty sloppy in new half nuts. I can mill a new slot in the opposite side but worry about the threads. The threaded part is about 79 inches long and have not seen anything that long on Ebay. Thanks for any thoughts