Rebuilding Half Nuts

[Hank's Garage General Repair]

Ive got a 9" South Bend Lathe with worn out half nuts that id like to fix before I sell. Has anybody done that themselves before? Any pointers for fixturing?

Note: I've got a really nice south bend 9 lathe and a south bend shaper at my disposal for fixing them.

 

[great white]

Holy moly! If they look like these:





then thats no easy task. Looks like a set of castings that are machined after the fact. Out of my wheelhouse for sure.

Full disclosure: I don’t have. SB9, I just grabbed those pics off an ebay auction. They’re not exactly going that cheap on ebay either (nothing new, all “preowned”). I looked them ip to get an idea on whether or not I could offer some advise, but thats above my pay grade.


I’ll never complain about buying half nuts for my Atlas TH42 again….

 

[MyLilMule]

I recall a YT video on someone that repaired half nuts. Just have to think outside the box.

 

[Hank's Garage General Repair]

Holy moly! If they look like these:

View attachment 453127

View attachment 453128

then thats no easy task. Looks like a set of castings that are machined after the fact. Out of my wheelhouse for sure.

Full disclosure: I don’t have. SB9, I just grabbed those pics off an ebay auction. They’re not exactly going that cheap on ebay either (nothing new, all “preowned”). I looked them ip to get an idea on whether or not I could offer some advise, but thats above my pay grade.


I’ll never complain about buying half nuts for my Atlas TH42 again….

Yep! Thats them! The actual machining isn't really that big of a deal but how do you hold something like that!

 

[Hank's Garage General Repair]

I recall a YT video on someone that repaired half nuts. Just have to think outside the box.

I watched that one, and id like to basically do the same, but mine are like those pictured above, difficult to hold and keep held.

 

[RJSakowski]

Not all that difficult. The half nuts look like they do to make it easier to cast. The fully machined part doesn't have to look like that. First, you have to identify all the mating features and their relationship to each other. I see three features; the half nut threads, the pivot points, and the cam followers. Aside from those the only other concern is possible interference.

I would start out with a single rectangular block and cut the thread first, then bore the two pivot holes. and holes for dowel pins for the cam followers then I would split the block into two halves and remove any of the extraneous material as required for proper operation. The last step isn't a precision op[eration and can be done with a die grinder.

 

[benmychree]

To my eye, they do not look bad at all, don't fix if not broke ---

 

[MyLilMule]

To my eye, they do not look bad at all, don't fix if not broke ---

I don't believe that is the OP's photo.

 

[Hank's Garage General Repair]

I don't believe that is the OP's photo.

Correct, my half nuts are more like half pipes

 

[benmychree]

Correct, my half nuts are more like half pipes

Yes, correct.