South bend 9 cross slide

Oildrips

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Hi there. Have a new to me South Bend 9 that seems to have some play in the cross slide. I can turn the handle a fair bit before the screw bites into it. I have seen on eBay that a new brass feed nut is available (trying to order one), but in looking at the parts diagram led me to a few questions:

1. what does the pin in the neck do?
2. are replacement pins available
3. What does the set/lock screw in the top of the nut actually lock?
4. Is it normal for there to be a bit of play in the cross feed?
 

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i'm not sure what the pin does :dunno:

unless you have a brand new machine, there will be play in the leadscrew.

the brass nut will be the first thing to wear, then the screw is next.

you may be able to change the nut, but the screw may also have wear- just be aware.

i made nuts from delrin and eartalyte . i was able to make the clearances tight, even on a worn screw.
the delrin nut worked especially good
 
Mike, do you think the delrin would make a better, more durable nut?
 
You most likely will have to replace the cross slide screw also.

Not sure what the pins are for (maybe has something to do with a taper attachment).

The top thread is where the nut is screwed into the cross slide.

Sometimes the play on an older machine is just too great to be able to do good work. My cross slide had 0.060" of slop in it when I got it, which made it near impossible to thread.
 
Could the pin be a lock pin? Tighten down the screw on top and it pushes the pin against the bore of the slide? I’d assume there would be a bit of rotation of the nut as you turned down the lock screw that could take up slack
 
@Oildrips do you have a photo of the pin?
I have the SB 9 rebuild manual which may have some info.


Sent from my iPhone using Tapatalk
 
The rebuild manual indicates the pin is used to vertically center the nut. (There is a procedure involved so that the nut doesn’t bind in operation.). The top thread is for the cross-slide bolt (that bolt comes out to disengage the cross-slide leadscrew when you are using the taper attachement to move the cross-slide). I would guess that without the pin, the bronze nut would shift around more when the cross-slide nut is removed.

Rick
 
Mike, do you think the delrin would make a better, more durable nut?
for longevity, yes. delrin will wear the shaft less than brass or bronze will
a bronze or brass nut will transmit force better and deform less during heavy cutting forces.
but in a small lathe the forces are not as great, so the playing field may be equal
 
It will be a bit down the fix-it-up road for me, but I am also thinking to do this (use plastic for something better than bags). So..

Is Delrin maybe another trade name for what I know as nylon?

I have come across a few more materials.
Turcite, Rulon, Moglice, and I dare say there may be many more.
The game seems to be to mix various harder wearing particles into polymer plastics e.g bronze powder into PTFE.
Some of these in sheet form are used to stick to machine ways. (Burn your bridges and grind them down first)!

Some plastics are tough in hanging on to their own substance, but are maybe too "flexible", Try to file some nylon and see.

Then we have the cross-linked hard stuff. All kinds of epoxy. What happens if one machines a nut out of carbon fibre composite? Maybe experiment, and mix some bronze powder, or any other stuff that one thinks might have a better future than wear-out-able brass, with some JB-Weld Marine, and make a nut?
Hmm - maybe the JB-Weld by itself might do.

Seriously though, Delrin sounds like it might be the easiest, most logical "upgrade". Very easy to get, and you can go for something else if it gives you problems.
 
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