South Bend 9 A spindle stopped turning after attempting to disengage the back gear

I have a new to me SB 9A (1947 model year) and never operated a lathe till I got this machine from a friend.

I needed to cut some soft steel. I found that high gear was too fast for the task and engaged the back gear. I pulled the bull gear lock engagement pin out, moved the back gear lever on the the left side of the back gear shaft to engage it, pushed the bull gear pin back into place, and went on to cut some metal.

I then tried to reverse the back gear engagement process without success. The back gear is still engaged and I cannot move the left side lever to disengage the back gear shaft. Moreover, the motor does not turn the spindle when the bull gear pin is pushed in. With the pin in the spindle will **only turn** via lots of muscle power and a breaker bar in the jaws of the chuck. The motor turns the spindle in high gear **without issue** when the bull gear pin is pulled out, but that is not how the lathe was working when I first got it.

I removed the left Quill Gear Guard and right Bull Gear Guard covers. This revealed that the back gear shaft is eccentric to the mounts on either side. Also the gears on the left side and right side of the back shaft are engaged with the opposite gears of the spindle.

Suggestions on how to proceed would be appreciated.

Please note that while other high schoolers were in shop class, I was busing tables in a restaurant between classes to pay my high school tuition. My experience since then has been everything but mechanical in nature. In fact, I still mouth "righty tighty and lefty loosy" when turning bolts. Hence, please keep my mechanical impairment in mind if you wish to provide any badly needed guidance.

Thank you.

Mark B.

Late note. A request for pictures was made. Here you go.


Later Note:

Special thanks to John Evans and his thoughts regarding the back gear bushings. It focused my search and I found South Bend Maintenance Form # 2000 dated 10-1-65 titled "Back Gear and Eccentric Shaft". The one page document has four sections titled I. To Disassemble, II. To Reassemble, III. Adjusting Back Gears and IV. Oiling.

I am going to cross my fingers and try to adjust the back gears using Section III directions. Should that prove unsuccessful, I will dissemble, reassemble and try adjusting again. if that fails, I guess I'll get a bigger hammer and longer breaker bar.

The work will not take place till late Saturday or early Sunday so anyone with thoughts, suggestions, or warnings should feel free to jump in. Something like this may be old hat to most of the folks here, but it is rocket science to me.

Thanks to all who have responded so far. I've learned something from each response.

Saturday afternoon progress

I removed the left side hex nut and set screw and right side C screw, spring and shoe. The eccentric bushing taper pin called for within the South Bend Form 2000 back gear and eccentric shaft illustration was missing.

Quill gear and eccentric shaft fell away from the spindle at this point. In other words, nothing is jammed up now.

I'll reassemble and adjust the back gears once I find a replacement taper pin from McMaster Carr, Enco, or preferably some place local.

Not looking forward to the adjustment as the instructions are terse.

Best wishes to all.

I think you have a few different issues here. First your understanding of the back gear engagement. The lathe is made to operate in one of two configurations. First, with the back gear disengaged(the back gear shaft in the rear position with the gears not meshing), and the bull gear pin engaged into the pulley. This is your "open belt" range and the spindle will turn the same speed as the pulley(the two are pinned together) The second range of speeds(back gear) is obtained whit the pull pin OUT and the back gear shaft engaged(gears meshing). In this arrangement, the spindle turns slower than the pulley because the motion is transferred through the gears to get a speed reduction. The spindle WILL NOT turn if both the pin and the gears are engaged, and forcing it to is going to break something.
As to why the back gear is stuck in the engaged position, I don't know, some pics might help. It may be as simple as lubing thigs up a bit.
Before you go any further, and possibly damage something or yourself in a big way, you should really get some basic info on running the machine. South Bend published a book called "How to run a lathe" and it will answer 99% of your questions plus give you a ton of info you didn't even know you needed. You should have little trouble getting a copy.

Derek,

Thank you for responding. Your explanation of back gear engagement and bull gear pin position/relationship is clear to me now.

I have the "How to Run a Lathe" book and read it, but reading and comprehending all are two different things.

I've just applied some Kroil to either end of the back gear shaft. I'll let it soak a bit.

Let me read up on how to add pictures to a post and I'll include some.

Are you in the phoenix area? The spindle pulley has a bushing inside that must be lubed,did that seize up. In back gear the pulley runs faster than the spindle is turning.

I love to see operators use long pry bars and big hammers when fixing machines. Also cleaning the ways of chips with air... Makes my day. Hit it harder.Hit it harder is my favorite chant. (just++ kidding) Rich

John,

Yes to Phoenix area. Specifically, the east valley east of Gilbert and south of Mesa.

The spindle cone pulley does turn when the bull gear pin is disengaged. I've been adding oil to both the spindle and back gear prior to running the lathe for the day. The person I got the lathe from said he did like wise, and he got the lathe from someone who had rebuilt it.

Everything seemed to turn fine until I tried to disengage the back gear. The back gear lever won't move and the gears from the back gear are staying engaged to the gears on the spindle.

Thank you.

After much forum reading, I came to the conclusion that a compressor blow gun was not the way to go. Thus, I've been using a brush and shop vac to move chips and such. I'm not sure how long the vacuum will last, but it makes clean up really fast.

My hammer is only moderately large. Do I need a bigger one?

Thanks.

Other end of town for me or I would offer to come by and take a look. Moore Tool here in Phoenix has a 9 A and I would look at it to see if I could figgure out the prob but he is closed till Tuesday. The back gear system is simple cam engagement ,the only thing off the top of my head is some how running the backgear went over center in relation to the spindle gears and is now binding up past center. Never owned a SB but have repaired/worked on a few but can't remember just how the backgear excentric bits are set up. If it is like I'm thinking the excentric bushings may have come loose and rotated further while running and now the backgear assy is over center. Look over that area and see if something in that line might have happened.
Good luck,John

JohnEvans said:

Other end of town for me or I would offer to come by and take a look. Moore Tool here in Phoenix has a 9 A and I would look at it to see if I could figgure out the prob but he is closed till Tuesday. The back gear system is simple cam engagement ,the only thing off the top of my head is some how running the backgear went over center in relation to the spindle gears and is now binding up past center. Never owned a SB but have repaired/worked on a few but can't remember just how the backgear excentric bits are set up. If it is like I'm thinking the excentric bushings may have come loose and rotated further while running and now the backgear assy is over center. Look over that area and see if something in that line might have happened.
Good luck,John

Click to expand...

John,

Thanks. I added some pictures to my original post. One shows the eccentric position of the back gear shaft. Not sure if a picture however, shows whether bushings are are over center.

Let me look at the parts diagram I have and see if I can ID the bushings you are talking about. Knowing how they fit in relation to everything else may give me some insight.

I haven't fooled with mine in so long, my memory isn't clear(I don't have the machine in front of me right now either), but I believe there are set screws on the back side of the headstock which tension the back gear bushings to keep it is somewhat stiff to move. Try to find these and loosen them. If it's not set screws, there's some adjustment to put some drag on the back gear engagement, I'm sure of that!

There are two setscrews, one on each side of the headstock, underneath where the backgear shaft passes through the headstock casting. Remove them both, see if that frees up anything. One works in conjunction with a spring and brass shoe to tension the backgear, so as to keep the gears meshed when in use. The other works as a stop to set the gear mesh. I'm not near my lathe now, but I believe it's a slotted head setscrew with integral pin.

Do yourself a favor - put away the breaker bar.

Paul

I'm not seeing items D or E. I don;t have a 9, but it looks like this would allow the eccentric shaft to go over center, esp. if lots of force was applied.
Edit, I don't see item C and associated spring and shoe either.

To my untrained eye, if all of the above are missing, one should be able to remove the shaft - I'd first thought drive it aft, but on second look it looks more promising to remove the handle and drive it forward enough to disengage the gears.

paulsomlo said:

There are two setscrews, one on each side of the headstock, underneath where the backgear shaft passes through the headstock casting. Remove them both, see if that frees up anything. One works in conjunction with a spring and brass shoe to tension the backgear, so as to keep the gears meshed when in use. The other works as a stop to set the gear mesh. I'm not near my lathe now, but I believe it's a slotted head setscrew with integral pin.

Do yourself a favor - put away the breaker bar.

Paul

Click to expand...

Paul et al,

I removed the set screw and hex nut from the left side of the head stock casting where the back gear shaft passes (left being head stock side and right being tail stock side). Hex nut was loose but set screw was more than finger tight.

I removed the C screw, spring and shoe from the right side of the casting. I discovered that the order of the three from outside to inside were C screw, shoe and spring rather than C screw, spring and shoe as called for in the South Bend form 2000. I also discovered that the taper pin called for the right side eccentric bushing was absent.

I was careful and it did not fall out on its own. It was not in place.

At this point the Quill gear assembly fell away from the spindle and everything freely turns now. Hence, I believe it is time to reassemble everything and follow the "Adjusting Back Gears" procedure set out in the Form 2000.

Two issues before proceeding.

1. Taper pin
Should I source and install an eccentric gushing taper pin or should I leave it out since it was not installed in the first place. I assume it should be installed but thought I ought to check with you folks first.

2. Taper pin size
Unless advised to the contrary by someone here, I'm going to measure both holes in the eccentric bushing and hit the hardware store and then McMaster Carr or maybe Enco to find one that fits. I found online how to cut my own but I only have one lathe and it is not turning things right now.

My apologies over the hand holding needed to get this far. I truly appreciate everyone's attention to the challenge in front of me.

Mark B.

Rudd said:

View attachment 148599

I'm not seeing items D or E. I don;t have a 9, but it looks like this would allow the eccentric shaft to go over center, esp. if lots of force was applied.
Edit, I don't see item C and associated spring and shoe either.

To my untrained eye, if all of the above are missing, one should be able to remove the shaft - I'd first thought drive it aft, but on second look it looks more promising to remove the handle and drive it forward enough to disengage the gears.

Click to expand...

Nut and set screw as well as C screw, spring and shoe called for in the illustration were in place. There is a hole for a taper pin in the right side "G-Eccentric Bushing" but no taper pin was present. I guess I need to find one and install it.

In any event, thank you!!!

Mark,
"My apologies over the hand holding needed to get this far. I truly appreciate everyone's attention to the challenge in front of me."
We have all been in the exact same place as you at one point or another. This is why the forum exists.
I'd be sure and put the taper pin in. If SB thought everything would work fine without it, they would have saved the cost of putting it in. If you can't find a decent source for the pins, I have a mess of different sized ones. Give me the big and small end diameters and I'll mail ya one. Measure with drill bits, what's the biggest one that just fits in the hole.

My local Ace Hardware has a taper pin assortment.

Without the taper pin, the two eccentric bushings can rotate relative to each other and get out of "phase". So, yes, you need the pin.

I'm not sure about 1947, but in later years, that taper pin shows as a #2, 1.25" long. You might find one at the local hardware or Fastenal.

Paul

I'm on my way out the door, so don't have time to read all the replies. However, for what it's worth, I accidentally left the pin in after engaging the back gears, and broke the pin. But mine spun freely--only worked in back gear. Perhaps you broke yours as well, but the broken part became wedged in between the pulley & bull gear. I don't know if that's possible, but it's a thought.

Rudd said:

Mark,
"My apologies over the hand holding needed to get this far. I truly appreciate everyone's attention to the challenge in front of me."
We have all been in the exact same place as you at one point or another. This is why the forum exists.
I'd be sure and put the taper pin in. If SB thought everything would work fine without it, they would have saved the cost of putting it in. If you can't find a decent source for the pins, I have a mess of different sized ones. Give me the big and small end diameters and I'll mail ya one. Measure with drill bits, what's the biggest one that just fits in the hole.

Click to expand...

Thank you for the offer!!

I measured the shanks of drills that fit in the two holes. The large hole diameter comes out to .187 and the small hole size is .171.

I tried the local True Value and they looked at me funny when I asked about taper pins. Ace may have them according to another forum member and that is my next stop.

My taper pin research may have revealed a more comprehensive solution. I found that there are two standard tapers. I also found the size of the pin is determined by diameter of the larger end. If I then jump to a conclusion I assume I can slide a 4.5 inch #4 taper pin (.25 large diameter by .156 small end) available from Amazon into place, tap ever so lightly, smoothly cut off each end and then pin punch the larger end to hold the pin in place.

Amazon has packs of ten for $4.13 per pack. It seems this would solve the immediate problem plus give me spare taper pins when I break, er, ah, ahem, I mean when I find others missing in the future.

Did I jump to the wrong conclusion about sourcing a taper pin?

Thanks again to everyone.

Sounds like a #2: American Standard Taper Pins | smithy.com