Rethinking the leadscrew nut repair

Googling didn't find encouragement for retapping a bronze nut built up with Babbitt. The lathe could be set up to hold the tap and nut thread in alignment before pouring the metal in and draining most out. Babbitt is effectively 95/5 solder with 5% copper chips or scouring pad dissolved in it.

If you can thread a new bronze bushing could you make a thicker walled steel nut shell and a two part bronze bushing threaded on the outside so the halves can be tightened together to minimize free play.

The nut shell, bushings and locknuts could be a lathe job except for the non-precision hex on the locknuts. The bushing outer ends could be notched for a pin spanner to allow wrench clearance to tighten the thin locknuts. This would let you omit a hex on the end and be able to trial cut the thread to a close fit in the nut.

Here's another way:

I have decided to go with the sleeve option . I just ordered a 13" piece of cored (1.25 od/.75 id) ampco 18 to fabricate the sleeve - I have bronze on hand but don't know which alloy . Better to know for sure . Next decision will be how to secure it in the shell . I'll do some testing when the stock gets here to see if I can use maybe silphos or a lower temp brazing rod . Maybe silver solder or if those require too high a temp I might try regular lead/tin solder . Last resort would be something like sleeve retaining Loctite with some brass/bronze pins for additional security . I'd really prefer a solder/brazed joint because I think it will be stronger ...

"Snag" wrote in message news:1135j7q$2qjd6$ snipped-for-privacy@dont-email.me...

I have decided to go with the sleeve option . I just ordered a 13" piece of cored (1.25 od/.75 id) ampco 18 to fabricate the sleeve - I have bronze on hand but don't know which alloy . Better to know for sure . Next decision will be how to secure it in the shell . I'll do some testing when the stock gets here to see if I can use maybe silphos or a lower temp brazing rod . Maybe silver solder or if those require too high a temp I might try regular lead/tin solder . Last resort would be something like sleeve retaining Loctite with some brass/bronze pins for additional security . I'd really prefer a solder/brazed joint because I think it will be stronger ... Snag

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If you can afford the extra length the sleeve could have a shoulder on one end and a thin nut on the other. You might be able to shorten the bored nut to keep OAL the same. A step on the nut and the shoulder would hold the sleeve while you tighten the nut.

GM U joints spiders are very firmly retained with injected plastic in matching grooves, heat to soften/melt and remove.

On 7/13/2026 4:15 PM, Snag wrote: > I don't think I have enough room under the table to do the delrin nut I was thinking about . Right now I see 3 options other than the delrin approach. I can ream the existing nut out and sleeve it with a bronze threaded bushing but I'm concerned about the strength of the shell remaining

Legitimate concern:

Easy... one of the Loctite sleeve and bearing lockers.

Are you going to split the sleeve so you can use the three screw method in the existing nut for reducing backlash?

I converted a little CNC mill from a split sleeve nut (don't make me describe it, cuz I get dumber just thinking about it) to DumpsterCNC antibacklash nuts once. Instead of making the nut line up with anything I made the motor mount and the bearing mount adjustable. Crank it up against. Tighten them down. Done.

I like the shoulder/nut idea . I plan to utilize the original split nut - only 1 screw - and make the threaded portions longer . The combination of the shoulder/nut/sleeve retaining loctite should be more than adequate .

It might cost you some X axis travel.

My Clausing's accurate work envelope is relatively small. I've machined assemblies longer than the mill table to adequate relative though not absolute accuracy by drilling scribed and center punched hole locations to a convenient dowel pin size in the first part and using dowel pins etc to match it to the blanks and align with the spindle for the rest. For the tractor bucket loader the holes and pins were 1/2" which accepts the 0.500" end of an edge finder. A spacer block the same height as the milling vise table helped keep long parts level and holes parallel.

Match drilling allowed me to build a multi part assembly 16 feet long with nominally zero clearance, 3/8" bolts in 3/8" holes. The shanks average

Looking at the wear pattern on the leadscrew adding a quarter inch at each end wont affect travel .

Looking at the wear pattern on the leadscrew adding a quarter inch at each end wont affect travel .

It occurred to me if you're going to use a flex to reduce backlash you might need to do a little more research and how you're going to fasten the sleeve to the old nut. Loctite is pretty strong but I'm not sure it can handle the flex

Good point , glad you mentioned it . I've got a few days waiting for the materials to arrive . You mentioned a 3 screw setup , and on the left side I've got more room than on the right where my power feed lives . I'm going to let things ferment in my subconscious . May even end up fabbing a new holder for the nut that will accommodate a backlash adjustment device . There's no mad rush , after all with me it's just a hobby ... but the new setup will damn sure have more length/bearing surface since the original only lasted around 20 years .