South Bend 9" Upgrade Question(s)

[graham-xrf]

I have a South Bend 9c with some nice extras (4-jaw chucks etc.) that I acquired for a bargain.
Yes - I am the guy on the end of "The £147.71 Green South Bend (something)" thread.
The lathe seems in quite good condition with respect to wear, even though it has a less than tasteful green paint job.

I sometimes see on auction sites, things like South Bend 9a gearbox, or a lathe carriage apron described as "for 9a or 10K". I have no idea how much 9a dimensions are shared with 10K.

Is the basic South Bend 9" series "upgradeable", in a ways where a 9c might accept parts to turn it into a 9b or a 9a?
Thanks if you know..

 

[Mark_f]

Converting a "c" to a "b" is easy . Change the apron and maybe the lead screw ( it has to have the key way in it). And the cross feed screw.

Converting to an "a" can be done the same way but you have to drill an extra hole in the bed for the gear box mounting and it can be a little tricky. That is the basic plan for it. I have considered changing my b to an a, but it is expensive.

 

[pineyfolks]

If you're not looking for power cross feed or planning on doing a lot of threading you can add a windshield wiper motor to the tailstock end of your leadscrew and a rheostat for indefinite feed range. A much cheaper option than changing a model C to an A or B

 

[graham-xrf]

Converting a "c" to a "b" is easy . Change the apron and maybe the lead screw ( it has to have the key way in it). And the cross feed screw.
Converting to an "a" can be done the same way but you have to drill an extra hole in the bed for the gear box mounting and it can be a little tricky. That is the basic plan for it. I have considered changing my b to an a, but it is expensive.

Thanks for the reply Mark. I think the power cross feed of the "B" would be a nice feature to have.
The lead screw does have the keyway, for the longitudinal power feed, and when threading using the independent change gears.
The description of features for Model C 9-inch lathe says "plain apron providing a series of 45 screw threads and 14 power longitudinal feeds".

The apron on the Model B 9-inch lathe somehow increases 14 longitudinal feeds up to 26. Surely not using a different lead screw?? I don't know.
The description for the Model B 9-inch lathe says "providing a series of 45 screw threads, 23 power cross feeds, and 26 power longitudinal feeds".
45 threads for both makes sense if they both use the same set of change-out gears, but I have yet to figure out the rest.

For me, it is what it is - a nice little lathe, strong, simple, clean(ish). I would happily upgrade if it fits on reasonably easy.

 

[graham-xrf]

If you're not looking for power cross feed or planning on doing a lot of threading you can add a windshield wiper motor to the tailstock end of your leadscrew and a rheostat for indefinite feed range. A much cheaper option than changing a model C to an A or B

Ahh yes. The "electronic gearbox". Actually a very good solution concept, though it has been a long time since I used a rheostat. (I still have one in the garage). The AC servo motor control kit is now so good, and much more affordable. While most kit can sense RPM speed from the motor currents, the best would is to use encoder feedback. You even set the mind thinking about "motorizing" the cross feed instead. Not for me - not yet!
You have to appreciate that there is a whole lot of fun stuff to be tried, even as it is. That said, I do like the idea of a re-purposed windscreen wiper motor!

 

[Mark_f]

The c and b have the same lead screw. The b has the star wheel to engage the feed clutch and a lever to switch from feed to cross feed an threading. Sometimes you can find a b saddle and apron reasonable on eBay. That would change it. I am not sure if there is a difference in the number of change gears or not. I would have to look at the catalog.

 

[martik777]

If you cut many threads a gearbox is very worthwhile. Here's a video of a B-A conversion:

Trouble with a wiper motor is that they need so much amperage to run. Mine needed a 12v car battery or cordless drill battery to run properly.

Adding a handwheel to the end of your leadscrew on the tailstock end will enable you to vary the fine feed with finishes very close to power feeding. You may need to mill off some of the leadscrew bearing support to fit the handwheel.

Have you actually used this lathe yet?

 

[graham-xrf]

If you cut many threads a gearbox is very worthwhile.
Trouble with a wiper motor is that they need so much amperage to run. Mine needed a 12v car battery or cordless drill battery to run properly.
Adding a handwheel to the end of your leadscrew on the tailstock end will enable you to vary the fine feed with finishes very close to power feeding. You may need to mill off some of the leadscrew bearing support to fit the handwheel.

Have you actually used this lathe yet?

Hi
Many thanks for the video link. This is so good!
I used the lathe only for the short while it took to verify that all was running smoothly. I did all the obvious things one does when trying out some new acquisition. It was all I needed to then decide on some changes. The previous user had reversed the pulleys on the drive counter-shaft, and made an arrangement to mount it from a block on the floor. Also, the bench was way too low for me. I plan to put it back to original, and on a better bench height.

I picked up the lathe with two extra 4-jaw checks in good condition, and a whole bunch of extra tooling for the quick-change post (Sandvik carbides) for the equivalent of $147.71 (at the time), after an unexpected eBay bid withdrawal mayhem.
I began a clean-up, and resolved to put the (very green) paint job back to something like the lathe in the video link, while checking out and fixing anything that needed it. I will probably do things in careful stages.

The current state is non functioning, simply because I have the motor assembly taken off for refurbish and a new drive belt. All else is still together, after a wipe-down, and covered in light chainsaw oil.

Regarding my reference to "electronic gearbox", you are right about amperage if one is using 12V DC wiper motors.
The current is of course much lower for the same torque if a higher voltage AC servo motor is used. Servo drives I have used in my work always make a rectified DC bus from the available AC mains supply, and then use higher frequency switching electronics to deliver synthetic AC to multi-pole AC motors. With encoder feedback, these can deliver high torque, smoothly, even at very low speeds. With another encoder on the spindle, it is possible to electronically contrive any desired ratio relationship within the capabilities of the servo. The price of these has been coming down for years.

For the lathe, I would still go for having the lead screw turned by gearing, whether that be change gears, or a nice convenient gearbox. The old South Bend need not aspire to be servo-controlled. In good condition, it is capable of excellent work and a joy to own. A servo leadscrew is a real good solution if a gearbox is too expensive or hard to come by, and probably the sort of project that makes one feel pretty good when it gets to work.