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South Bend 9 compound lead screw replacement

Rickoo

Plastic
Joined
Jan 19, 2021
I'm considering trying my hand at replacing the acme lead screw on my compound. I see there are acme threaded rods available in 1/2-10. I know the south bend screw is 7/16-10 which doesn't seem available. Using 1/2-10 would require a new custom brass nut which I'll likely try my hand at as well.

I got the idea from a seller on Ebay that offers this repair.

Has anyone here done this? Bad idea?
 

Rickoo

Plastic
Joined
Jan 19, 2021
McMaster carries Acme threaded rod in 1/2" - 10, right and left hand thread. Not seeing 7/16" - 10, but there is always the roll your own option.

You know, that was my first thought, but after seeing these available and not at all experienced in threading, I'm thinking buying pre-made rod might be best.

Acme rod is also available on Ebay. I see there is stainless steel and carbon steel.

Anyone have an opinion on one over the other?
 

dalmatiangirl61

Diamond
Joined
Jan 31, 2011
Location
BFE Nevada/San Marcos Tx
Looking at the McMaster selection, I would use the 4140 black oxide, it is harder than the 1018 or SS. Practice, lots and lots of practice will give you experience, and turning a 7/16" acme thread will give you that practice:D.
 

4GSR

Diamond
Joined
Jan 25, 2005
Location
Victoria, Texas, USA
With help from a follower rest, I made a new screw for my 9" SBL many years ago. Made it from drill rod already ground to 7/16 size. I spliced it into the existing screw. Worked like a charm. I even single pointed a new bronze nut, too. Still have the boring bar that I did it with. I don't think my eyesight would let me do it again today! Ken
 

Rickoo

Plastic
Joined
Jan 19, 2021
Did you heat treat the drill rod after cutting the screw?


With help from a follower rest, I made a new screw for my 9" SBL many years ago. Made it from drill rod already ground to 7/16 size. I spliced it into the existing screw. Worked like a charm. I even single pointed a new bronze nut, too. Still have the boring bar that I did it with. I don't think my eyesight would let me do it again today! Ken
 

paulsomlo

Stainless
Joined
Oct 15, 2009
Location
Colorado
I'm thinking that Dennis Turk may have done something like this, way back when, you'd need to search through his posts. If you're buying off the shelf acme screw, check the accuracy.
 

Gard

Aluminum
Joined
Mar 18, 2016
I did a similar repair on the cross slide, using the precision threaded rod from mcmaster and purchased the new nut to fit on line, very happy with how it turned out. Have enough rod left over to do another.
 

4GSR

Diamond
Joined
Jan 25, 2005
Location
Victoria, Texas, USA
Did you heat treat the drill rod after cutting the screw?

What for? The new screw will last for at least the next three generations if lubricated properly. At least three time longer than the original one that is made from 1215/12L14 material. I made a replacement one for my old 13" Sheldon Sebastian lathe back when I bought it in 1979. To this day, it only has about .005" slop in the nut and screw. I also made a new bronze nut for the new screw back then, too. Working on rebuilding my third Sheldon lathe, a 15" and it will have a new nut and screw when I get finished with it, too. Ken
 








 
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