16" South bend, losing speed/power

Liv · Feb 23, 2022

I’ve been digging for information on our lathe in order to repair it. I am not an expert in lathe repair, but do need to get this one running.

The issue started when we were doing a run of drilling and tapping for some leg slugs to accept leveling feet. At the end of the run, the lathe started to loose power, even when just centering. So, I stopped the production of the slug. Upon closer look/feel, when I tried turning the chuck manually it felt like it was sticking. I flushed the spindle bearings with kerosene, and filled back up with spindle oil. Initially it sounded as those it was running better than ever. Really humming. Then, the next morning I came in to get it running before my guys arrived, and again, it was the same issue. I’m using a very light spindle oil as recommended in the literature from south bend that I have found online. I did note when draining and flushing the bearings that there seems to be no wicks where I was expecting them.

What else might you recommend for getting it running again. It soon will become a problem if I can’t find a solution.

Thank you so much for any assistance you can offer.

magneticanomaly · Feb 23, 2022

When you observed the slowing-down, were the spindle bearings warm or hot to the touch?

Might help if you specified what age or model SB, or posted a picture of it.

Sounds like you have plain bearings. Have you checked clearance? Is there any possibility that cap screws have been tightened, or a shim has been lost or shifted? How about the axial play adjustment (nut at end of spindle opposite chuck)?

Kevin T · Feb 23, 2022

There is a South Bend specific forum in here. It may help to post there to get some more eyeballs on your issue. Pictures are useful too so that things like which era your machine was made can be useful.

crossthread · Feb 23, 2022

When you say there are no felt wicks, do you mean there is no provision for them ? Are the springs that push the wicks against the spindle bearings still there and the wicks are just gone? I pulled my spindle not to long ago to install a serpentine belt and was told the best way to adjust the bearings is to take out all the play with the removal/addition of shims and then run it at high speed and check for any heat buildup. I think with plain bearings this is probably the best way to do it.

jim rozen · Feb 23, 2022

Check the spindle bearing clearances according to the published information here. Report back with the two numbers.

Liv · Feb 23, 2022

It appears that the wicks are just gone.

Liv · Feb 23, 2022

magneticanomaly, it is a 1957 South Bend lathe, 16 X 6 Turret, Model KKX?, Serial no. 8937HKX11.
I did not feel anything hot when it was slowing down, but I will run it again and see what happens.
There is every possibility that the cap screws have been tightened and the shims shifted. How much play should I have at the take up nut?

jim rozen · Feb 23, 2022

1) DO NOT remove the bearing caps unless you understand what's under them and how to remove them correctly.

2) learn how to measure the bearing clearances correctly.

Paolo_MD · Feb 23, 2022

I would suggest opening the cover over the spindle and check if the belt is slipping (just make a few marks with a Sharpie on the pulley and the belt and see if it more or less track or slips), if the bull-gear locking pin is engaged or disengaged (i.e. the cone pulley spinning more or less freely on the spindle), or if the electric motor is dying.

If you don't notice any warming of the spindle bearings, don't mess with them. At most, after slacking the belt, you can check how freely the spindle spins. If you hear noises from the headstock, it might well be that the cone pulley is disengaged and spinning on the spindle without adequate lubrication.

Paolo

wood2steel · Feb 23, 2022

Liv, There's also a chance you may be experiencing a thrust bearing adjustment issue as well. The lock collar on the left end of spindle may have loosened and is tightening the spindle under load. A Co-worker just experienced that exact problem a couple months ago on his personal 16 SB. As stated above; if you're not getting heat on the bearing covers then your lubrication is probably not the cause. As Jim highlighted;; do not remove those bearing covers unless you're fully clear on proper removal; they look simple but they're not-- Good Luck.
Johnny

wood2steel · Feb 23, 2022

Magneticanomaly had already hit on that axial/thrust issue above, but it is definitely an overlooked concern on Southbend lathes when heavy drilling as well as forward and reverse operations come into play. That lock adjustment collar is a somewhat weak link in those solid bearing spindle systems

texasgeartrain · Feb 24, 2022

You wont see the spindle wicks unless you remove spindle. They are the spring loaded type at 6 oclock, bottom side of spindle.

Id comfirm no belt slipage first, as well as spindle spinning free.

Raise handle on motor base and spin spindle with reverse lever in neutral. Does it spin nice ?

If so, run lathe and watch flat belt and both pulleys while it works. Most likely flat belt is slipping. Maybe vee belts to motor, but usually its the flat belt.

And as stated above, if the spindle caps are not warm or hot, you are not siezing up. The belt is either not adjusted tight enough, or its not gripy enough, and a new belt would help with that.

Liv · Feb 24, 2022

Thanks Jim (and everyone). Yes, I've done quite a bit of reading and YouTube watching regarding the disassembly and reassembly of the headstock spindle. I've got quite a few things to try out today. I'll report back with progress. Thanks again.

jim rozen said:
1) DO NOT remove the bearing caps unless you understand what's under them and how to remove them correctly.

2) learn how to measure the bearing clearances correctly.

Liv · Feb 24, 2022

Paola_MD,
Indeed I think the belt on the cone pulley is quite loose. However when I turn the nut to tighten it, it doesn't seem that anything is happening.
My colleague recently changed the belt, so maybe this is our issue. How do I determine what the length of the belt should be? Thank you so much.

Paolo_MD said:
I would suggest opening the cover over the spindle and check if the belt is slipping (just make a few marks with a Sharpie on the pulley and the belt and see if it more or less track or slips), if the bull-gear locking pin is engaged or disengaged (i.e. the cone pulley spinning more or less freely on the spindle), or if the electric motor is dying.

If you don't notice any warming of the spindle bearings, don't mess with them. At most, after slacking the belt, you can check how freely the spindle spins. If you hear noises from the headstock, it might well be that the cone pulley is disengaged and spinning on the spindle without adequate lubrication.

Paolo

texasgeartrain · Feb 24, 2022

Liv said:
Paola_MD,
Indeed I think the belt on the cone pulley is quite loose. However when I turn the nut to tighten it, it doesn't seem that anything is happening.
My colleague recently changed the belt, so maybe this is our issue. How do I determine what the length of the belt should be? Thank you so much.

On the motor base, maybe in more than one location, but I'm pretty sure the rear side. There are adjusting screws with jam nuts. Those adjusting screws can limit the amount of travel that the lower assembly moves for adjusting flat belt. If in doubt, just crack the jam nuts loose, and start loosening the adjusting screws. You may see that the whole lower assembly begins to lower, there by tightening belt.

If new belt is needed, remove current belt and measure total length.

Tony Quiring · Feb 24, 2022

If under drive the lever that you rotate is an over-center lock meaning it gets full tight then goes past the high spot and goes towards loose just a bit.

It should be stiff as it goes over the too.

If it turns tooo easy the link arm may be adjusted to cause motor to move more.

If belt is old it may be stretched out and no adjustment left.

Look for what looks like all thread and see if it can be adjusted.

If new belt is needed make it a bit shorter than what you have.

Sent from my SM-G781V using Tapatalk

Kevin T · Feb 24, 2022

There is a lock nut/bolt on the back of your lathe that controls how far the engine mount plate can pivot (which is related to how much tension you can get on the flat belt. I would look into that. There is a South Bend publication called "How To Keep Your Lathe In Trim" that goes over this in detail. It's free to download from the vintage machinery website.

Liv · Feb 25, 2022

Trying to upload a photo of the motor....

Liv · Feb 25, 2022

Can anyone tell me how to test the voltage on the motor? Photo above...

Just a Sparky · Feb 27, 2022

Those are old friction tape splices.

Peel off the tape and you'll find either a cluster of crimp lugs bolted together or a soldered pigtail underneath.

When you're done, re-insulate with Super 33+ and then protect with an outer layer of friction tape. Home Depot sells both.

Careful when testing. Modern grounding and bonding practices didn't exist when most of these lathes were produced. The lathe might be incidentally bonded by the conduit supplying it if you're lucky, or maybe the neutral might have been bonded to the machine if it was wired 110V. Many times these old machines were left floating in their entirety, especially if they were cord-and-plug connected. One live wire touches steel and the whole machine becomes hot, just waiting for someone to touch it and find out. I'd be surprised if there are even provisions for landing a ground wire anywhere on the machine unless it's a later example.

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