SBL 10K - Making chips at low speeds, bogs down at higher speeds

I recently acquired a SBL 10K manufactured in 1971. Overall it is in good condition; very little wear, no broken gear teeth, no unearthly noises, and no vibrations. Most everything was stiff from old oil and everything is now oiled with the correct A,B,C,W oils. From the picture you can see it can cut chips.

Before I start making parts I wanted to check all the capabilities of the lathe. When I increased the speed of the lathe (no part, no cutting) with the Variable Speed Drive (VSD) , it increased speed nicely to 1100 rpm, but then it started to bog down (audibly) so i cranked the speed back down to 400rpm.

I then hooked up a clip ammeter and ran the speed up while measuring (IR) casting temperatures on the lathe. The only temperature that went up notably was the headstock bearing casting (near the chuck).


Time Rpm Amps HdStck Casting (degF)
6:26 450 7.6 76
incrspd 550
6:28 550 7.7 77
incrspd 650
6:30 650 7.9 80
incrspd 750
6:32 750 8.1 87
6:34 725 8.6 99
6:36 730 8.4 104
6:38 730 8.4 107
6:40 710 9.0
6:41 500 10.4 122

What is causing the temperature rise? I suspected the flat belt load was too high. I adjusted the turnbuckle
to it’s shortest length ( least belt load) and repeated the test.

Time Rpm Amps HdStck Casting (degF)
7:16 450 7.7 76
incrspd 550
7:18 550 7.8 77
incrspd 650
7:20 650 8.1 79
incrspd 750
7:22 750 8.3 83
7:24 720 9.4 90
7:26 750 8.1 91
7:28 750 8.0 91
7:30 753 8.0 90
incrspd 850
7:32 850 8.2 90
7:34 850 8.2 91
7:36 856 8.2 92
incrspd 950
7:38 950 9.3 108
decrspd 550 heard motor load increase
7:40 550 8.3 116

It seems that by backing off the flat belt tension I was able to keep the headstock temperature from spiking until 950 rpm (first test it spiked at 750 rpm). This leads me to suspect that the belt tension is not adjusted properly.

Question 1: Does anyone have the 10K flat belt adjustment procedure? (I checked in ILIONs “A guide to Renovating……” and I could not find it there.)

Speaking of belts, there are 2 V-belts for the variable speed drive. It seems the previous owner replaced the top belt and the lower belt is OEM (PT2817KK1).

Question 2: Does anyone know if the original VSD had both belts (top and bottom) the same?

The V-belts seem loose to me. When I compared the distance between the belts as they sit versus if I took up the slack with my forefinger and thumb, the belts get closer together by about 2-2.5 inches. The motor is at it’s most extended so I can’t take up the slack by sliding the motor in its slots. I suspect the previous owner replaced the top belt with the wrong size belt and when he couldn’t move the motor anymore, they adjusted the turnbuckle.

Question 3: What is the original v-belt tensioning procedure? (I checked with Hi-Lo Mfg (provider of the VSD) and they had no more information to offer.)

Thanks in Advance. I’ve perused the forum and seems there is a wealth of experience in all things South Bend Lathe. I’m looking forward to learning from you and sharing my experiences with this 10K.

BobsYourUncl


View attachment 304747
View attachment 304748

BobsYourUncl said:

Most everything was stiff from old oil and everything is now oiled with the correct A,B,C,W oils.

Click to expand...

Did you change the spindle wicks? My guess is that your spindle is being oil starved because the wicks are clogged with the old, hardened oil. If you didn't change them, then STOP everything you are doing with the lathe and REPLACE them. To continue to operate the lathe without adequate spindle lubrication is causing irreversible damage.

As for the flat belt alignment, the pulleys are crowned, so the belt should climb to the peak of the crown. The upper and lower pulley sets just have to be in the same plane. With a factory bench, I don't see how they can become "un-aligned".

thats not at all hot..

whats the motor and vfd specifics?? belt positions?

suspect a parameter or an over running of the motor causing power loss.

BobsYourUncl said:

Most everything was stiff from old oil and everything is now oiled with the correct A,B,C,W oils.

Click to expand...

Did you tear down and replace felts, or just oil the machine?
If you didn't change out the headstock bearing wicks, I'd suspect the heat is lack of lubrication of the bearings.
Felt wicks harden over time and will not wick by capillary action as they're designed.

If that's the case, I'd pull the spindle and replace the wicks, lest you burn up the bearings (if they haven't been damaged already).

At the risk of starting another spindle oil range war, try switching over to one of the light Mobil 1 synthetic oils....maybe something like 0W-20 or something similar. I've found the synthetic oils to offer better lubrication in cases where bearing temperatures seem to be a problem. There will be all sorts of rebuttals to this suggestion but try it anyway. I think you'll like the results.

First of all, thanks for everyone who read this post and especially to the ones who replied. Your ideas and facts have helped me with my plan and actions.

Since last time:
Cleaned and lubricated the VSD and linkage.
Replaced the v-belts. Adjusted v-belt to correct tension.
Adjusted under cabinet plate to reduce spindle belt tension.

Reran test - Went up to 1100 rpm before temperature spiked.

Removed spindle and inspected bearings. Found bearing discoloration and carbon traces. Spindle has very light discoloration. Fingernail did not catch anywhere on spindle in the bearing areas. On the bearings, one spot felt rough(6 oclock, closest to chuck). Took 0000 steel wool and removed carbon and smoothed out the discolorations on the bearing. Waiting for "prussian blue" to determine bearing high spots (couple of days).

My plan of attack is to blue the shaft and see what transfers to the bearing. Depending on the contact pattern, I'll either put it back together and re-test OR figure out how to knock down high spots, reblue, and re-test.

Thoughts?

I don't think you need to prussian blue bearings or shaft.

The bearings dont look terrible, though I'd clean those spots and spindle as you suggest.

The main issue with heat and those discolorations, is how tight you have the clearance set. The spec according to original manuals is like .00075" to .001". I really think many people go too tight. Even at .00075, that is really tight for an oil clearance. And that is no oil pressure, that is oil wipe. Many, many types of machine parts with bushing type bearings call for like .001", with oil pressure. Using spindle oils. . .yea maybe you can tighten it up, but the South Bend section is filled with threads of guys smoking those spindle bearings.

I'd set your bearing clearance to .001" to .00125". Set spindle end thrust to .0005". Guarantee you won't smoke.

Other thoughts, speed is a factor. If you are running top speed, or high speed most often, then you will have some temperature rise.

Another, I haven't kept up with the a,b, c oil list. But whatever the spindle oil is make sure its atleast spindle oil #10, not #6. I personally think #10 is too thin anyway, but #6 is thinner. Spindle oils are a mineral oil from the same stuff as DTE oils, just a lighter weight. The next step up from #10 spindle oil in weight is DTE Light, which is SAE 10w. I might consider experimenting with DTE Light or ATF to see how nice your spindle spins.

1) I am unfamiliar with 10Ks with bearing expanders. Your lathe has these. Be *sure* you know the correct procedure for using these.

2) be *sure* you know the correct way to check the bearing clearances. Ask if you don't know how.

3) have them adjusted to the high end of clearance range for now.

4) I've never been able to run any southbend plain bearing spindle, adjusted to the midrange clearance, using the factory spec oil. The spindle always heats and bogs down. My personal solution is to drain the reservoirs and flush, and re-fill, with mobil one synthetic engine oil. 0W20 is a good choice. This is nothing more than a quart from your local auto store. Be sure the clearances are measured and adjusted if need be.

As I read this post I made the assumption that this lathe has the stock Variable Speed Drive not a manual speed change cone head. Not sure what the first two attachments, photos maybe, are as they won’t open. Is your lathe like this one on Tony’s site
South Bend "10-K" Light Ten Lathe. If so just trying to clarify for your questions.
Regards Z

Hey man congrats on your SB lathe!

Your first post is glitched, please edit the attachments so they show up!

You seem to be pretty intelligent and good at gathering info.

I own a SB16 with the bearing expanders.

BE VERY AWARE on how the expanders work!!
If you LOOSEN your expanders that will cause the bearing to TIGHTEN on the spindle!!.

You did a finger nail test on your bearings and spindle journals? That tells you NOTHING.

If you can feel ridges with your finger nail on bearing journals and the bearings are already TOAST.

Your spindle wicks look pretty bad.

These nice gentlemen (looking at you slk001 ) told me much of what they are telling you!

When I got my SB I was super excited to try it out too, they all warned me!

I was having a bad day and say EF IT I need a “pick me up” so I’ll run it for a short spell.

The front bearing got hot to the touch 110+F easy fast.

Turns out my wicks were clogged up.

PLEASE REPLACE YOUR WICKS OR YOU WILL END UP WITH A PAPERWEIGHT

Here’s the bearing procedure














My bearing caps had rust forming between the cap and bearings and bad dry wicks.
All added up to some seriously hot bearings.

I run mobil velocite 10 in the headstock with new replaced wicks and have my CHUCK side bearing clearance set RIGHT AT .0007 +/-.00005 and The rear bearing at .0010 +/-.0001

I run at top speed often For around 1-3 hours MAX and at MOST the front bearing gets a lil warm (80-90F)

My 10k is usually run near top rpm, 1500’ish..
Front bearing is set at .00075 - .001 clearance range.
Mobile light spindle oil.
Oil wells cleaned & wicks replaced early on.

It only over heats and bogs down when the outboard ball thrust bearing adjuster works tight & removes the axial clearance at the front bearing thrust face. Not sure why it tightens itself up from time to time but it does.

That said, photos of your bearings do look like they have been tight at some point.

smt

1) I tried to edit the first post to update the pictures But I was not able to figure out how to edit the post. Can anyone point me in the direction of how to edit a post?
https://www.practicalmachinist.com/vb/attachment.php?attachmentid=308323&d=1608688344
https://www.practicalmachinist.com/vb/attachment.php?attachmentid=308324&d=1608688361

2) It seems I have a high spot by the bearing wedge. I was going to file it down but that got me thinking about the correct installation procedure for the bearing with the wedge. I have the rebuilding guide and all it says is to tighten the two screws down but it doesn’t specify a torque. So I assume the bearing wedge is used for positioning of the bearing and some preload. Any advice on how to correctly install the bearing and wedge on the single bolt bearing cap 10k?
https://www.practicalmachinist.com/vb/attachment.php?attachmentid=308325&d=1608688421
https://www.practicalmachinist.com/vb/attachment.php?attachmentid=308327&d=1608688754

3) I purposely did not disturb the shim pack. I loosened the bolt only. My next step is to reinstall the spindle and see if the temp spikes. If it does I’ll remove spindle, steel wool any spots, reinstall, use 0w20 and retest.
Https://www.practicalmachinist.com/vb/attachment.php?attachmentid=308326&d=1608688519

On any post, you have 24 hours to make edits, then no more edits.

When you install the spindle, put a dial indicator pointer at 12 oclock chuck side. Get a prybar between cone pulley and headstock and try to raise spindle, about 50 pounds of effort. Get your oil clearance reading from dial indicator.

Do the same to the other side of spindle.

You can use the dial indicator to check thrust too. Put pointer on face side of chuck. Use screw drivers or pry bars to thrust spindle back and forth.