Need a reliable source for a SB9 cross feed nut

[6061billet]

I'm doing a light rebuild of a South Bend 9C. Just cleaning it up and putting new oil wicks in, I'm not repainting anything. The cross feed has about 20 thou of backlash and it's not coming from the dial. I tested it after adjusting the dial clearance. The nut is sloppy and loose at all points on the leadscrew and the leadscrew doesn't look worn. I'd be happy if I can get down to 5 to 10 thou backlash with a new nut.

I've found two ebay sellers that make replacements: Derewa2/BMPartsTech and LargeVise

Anyone familiar with either of these vendors or someone else who makes a quality replacement cross feed nut?

[nickel-city-fab]

I'm not familiar with them, but there's always a few. One thing to watch for is to make sure they are genuine bronze like the originals. You can get brass ones pretty cheap, but they don't last like the bronze does.

[mc_n_g]

I have used LargeVise (Jayhawk Machinery/Jayhawk Man) in the past from another site. Never had any problems with his items. I had a large nut and acme screw built by him for a Sheldon/Vernon 0 horizontal milling table. No problems. We communicated via email several times for that specific order. For 'regular' items he has it is just a simple purchase.

I also am not sure I understand why you need to get a new nut for the lathe. I, as well as others, have worked on lathes making tolerance parts with far more wear and play in the machine. The lathe is quite capable of making good to excellent parts as is. Ultimately it is your machine and money.

[J Tiers]

.................

I also am not sure I understand why you need to get a new nut for the lathe. I, as well as others, have worked on lathes making tolerance parts with far more wear and play in the machine. The lathe is quite capable of making good to excellent parts as is. Ultimately it is your machine and money.

"Need" vs "want", or "prefer"......... You "need" food, you do not "need" a lathe at all.

He is working on the machine, and it's a logical time to deal with issues. While you CAN deal with that sort of thing, there are reasons to fix it on lightweight lathes like SB when it is not an issue on heavier machines.

For instance, on interrupted cuts, that amount of slop can lead to a "jackhammer" action as the slide slams back and forth through the backlash. That is due to the very light crosslide, and is not a factor on a machine where the slide alone may weigh more than the entire carriage of an SB machine.

Unless you have a crosslide lock, and are willing to lock and unlock for every single movement, or put up with a very stiff slide movement, you can get that "jackhammer" effect. Adjusting the slide for stiff movement will increase the wear rapidly.

[old mart]

A test for the wear of the leadscrew is to record the exact ammount of backlash every 1/2" of the travel. Commonly there tends to be more wear in the central part, but knowing the total wear could be useful. As NSF advises, bronze is the preferred material.

[tom_d]

My 10L has about 20 thou backlash too. It's the newer large dial machine, so that's 20 thou linear, or 40 on the diameter. I've never experienced any problems with it. Do as is suggested in post #5, and map out the screw. If you still feel you need to replace the nut then by all means do so. And yes, bronze is the material of choice. Never done business with either of those 'bay sellers, so can't help there other than say trust your instincts and common sense. As to cross slide rigidity, I've had more problems with the gibs being way too loose than nut backlash.

[nickel-city-fab]

I do know that jahawk/large vise has been on ebay a long time, and has good mentions on PM. I think he's in Milwaukee, a commercial shop that makes batches of these parts on the side.

[Moxiedad2001]

Can't tell you about those dealers, but I bought a new nut for my 10L from Tom Ross in Omaha 11 years ago. It removed 0.025 backlash along the whole length of the screw, but the play in the middle remained 0.002 to 0.005 greater than either end, as it was before (and as expected). The lesson: Yes, there will be some wear in the screw. But because all of the nut is continually in use, but only part of the screw at any moment, the wear in the nut is going to be far the greater contributor to excessive backlash.

[reggie_obe]

Recommendations for other suppliers can be found on the SB io group and the SB sub-forum on PM.

[mc_n_g]

"Need" vs "want", or "prefer"......... You "need" food, you do not "need" a lathe at all.

He is working on the machine, and it's a logical time to deal with issues. While you CAN deal with that sort of thing, there are reasons to fix it on lightweight lathes like SB when it is not an issue on heavier machines.

For instance, on interrupted cuts, that amount of slop can lead to a "jackhammer" action as the slide slams back and forth through the backlash. That is due to the very light crosslide, and is not a factor on a machine where the slide alone may weigh more than the entire carriage of an SB machine.....

Yes I am aware of this. I myself cannot speak to what the OP is aware of based upon what was written.
I commonly see people talk about budgets but they still repair machinery. I have no idea what the OP has intents for or budgeted before going down some level of rabbit hole with money.
As I referenced it is his decision, just providing options as you have.