# My new 90 year old south bend



## Riguy14 (Aug 21, 2021)

Picked up this beauty today! It works ok, needs a good cleaning


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## markba633csi (Aug 22, 2021)

Looks pretty clean already! Congrats, they are good machines
-Mark


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## MrWhoopee (Aug 22, 2021)

Nice patina!


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## Riguy14 (Aug 22, 2021)

Thanks, it was bone dry but little to no rust on it! Now I just need to figure out an alternative to the leather belt it came with because it slips constantly, I can barely drill a 3/16 hole in aluminum with it as is.


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## MrWhoopee (Aug 22, 2021)

Riguy14 said:


> Now I just need to figure out an alternative to the leather belt it came with because it slips constantly, I can barely drill a 3/16 hole in aluminum with it as is.


Serpentine belt. Just won't slip.


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## Zack (Aug 23, 2021)

Good old South Bend iron!  Just doesn't look right with a QCTP on it though.  Gotta have a rocker tool post.


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## brino (Aug 23, 2021)

Nice lathe!

Did you get a bunch of gears for feed change and thread cutting?

-brino


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## Riguy14 (Aug 24, 2021)

Zack said:


> Good old South Bend iron!  Just doesn't look right with a QCTP on it though.  Gotta have a rocker tool post.


I do have a few of those that came with it along with a very interesting boring bar mounted in one.


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## Riguy14 (Aug 24, 2021)

brino said:


> Nice lathe!
> 
> Did you get a bunch of gears for feed change and thread cutting?
> 
> -brino


Yes I did, a full set from what I can tell! it looks like a previous owner messed around with the idler gear because its marked "boston gear" or something and doesn't look like anything like what I saw in pictures online for these lathes. I was able to find an original idler gear (i think its 18 teeth mounted to an 81 tooth gear) on ebay. It was also missing the carriage lock, but luckily I was able to find that as well.


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## Riguy14 (Aug 24, 2021)

In my quest to fix the slipping belt I decided to have a look in the head stock. The bearings look pretty good to my untrained eye, but I thought I read somewhere that there were supposed to be shims in the bearings (there weren't any). For the spindle to spin freely, I have to loosen the four bolts locking the top part of the bearing a lot, to the point where it vibrates a ton when I make a test cut. Does anyone know what thickness I should use for the shims? Or are there pre made shims available? I am pretty new to machining and at this point I've spent more time trying to get my benchmaster and this lathe up and running than actually using them! Any advice would be much appreciated!


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## Riguy14 (Aug 24, 2021)

Here are some photos of the bearings. Also anyone have any idea what the part in the last photo is?


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## brino (Aug 24, 2021)

Zack said:


> Just doesn't look right with a QCTP on it though. Gotta have a rocker tool post.



I definitely prefer the QCTP for getting things done; change tools without resetting centre height every single time.



Riguy14 said:


> Does anyone know what thickness I should use for the shims? Or are there pre made shims available? I am pretty new to machining and at this point I've spent more time trying to get my benchmaster and this lathe up and running than actually using them! Any advice would be much appreciated!



It is not a fixed number, but trial and error to adjust to the wear on your lathe.
You can buy a pack of assorted shim stock like this:
https://www.leevalley.com/en-ca/sho...materials/40946-brass-shim-stock?item=27K0750

You could try to figure out a starting point with a feeler gauge or two.
Then cut a shim add it between the bearing halves and test it.
Tighten the bolts to a reasonable torque.
With a dial indicator on the top of a chuck try lifting, or even lightly prying the chuck up and look for movement.
It it's too loose you'll see it on the dial indicator.
If it's too tight then it does not spin easily by hand and you can feel it get warm after a few minutes of running.
Different shims can be stacked-up.

You can likely find some suggested values for dial indicator readings and maybe bolt torque on here somewhere.

-brino


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## Riguy14 (Aug 25, 2021)

Thanks, I did some digging and found some premade ones on eBay, pricey but they are the laminated ones and after a weekend of unjamming parts and cleaning I decided to treat myself. Do you think having the bearings to loose would cause the spindle to stall? I tried drilling a 3/16 hole in aluminum and it stalled the spindle (but not the motor or countershaft). I fed it very slow with lubricant and the bit was sharp. I’m going to try and get a serpentine belt on it soon to see if that helps. 

I’ve also tried some really light depth of cut, about 10 thou, and on top of an atrocious surface finish it bogs the spindle down very very easily.


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## graham-xrf (Aug 30, 2021)

Riguy14 said:


> Thanks, I did some digging and found some premade ones on eBay, pricey but they are the laminated ones and after a weekend of unjamming parts and cleaning I decided to treat myself. Do you think having the bearings to loose would cause the spindle to stall? I tried drilling a 3/16 hole in aluminum and it stalled the spindle (but not the motor or countershaft). I fed it very slow with lubricant and the bit was sharp. I’m going to try and get a serpentine belt on it soon to see if that helps.
> 
> I’ve also tried some really light depth of cut, about 10 thou, and on top of an atrocious surface finish it bogs the spindle down very very easily.


I think yes - and yes.
That is, if the bearings are too tight, the spindle can bind up.
If the bearings are too loose, it won't usually bind up, but if so loose they can't retain lubrication, guess what happens.
There is a correctly specified amount of clearance for the oil film to exist in. This should be in the literature somewhere.
I am now motivated to nail this down exactly - because soon, I will also have to do this!

The test is as @brino described, and if you look, there are YouTube videos showing how.
Set up an indicator on the top of the spindle. Clamp a piece of pipe in the chuck to use as a lifting lever. Pull up, and push down, looking for the dial indication for the difference. I think this is done without oil in there.
Same trick at the rear bearing. Put a bar or pipe some way up the spindle. Lift up, and then press down.

*The required free play*
I can't recall right now the correct gap, but 0.0007" to 0.001" comes to mind, and I am not sure if that is supposed to be the clearance all around, or if it was the DTI shift in total when you load the spindle.

When you say "stall". Does that mean the belt is slipping, or did you actually stall the motor (a condition to quickly reach burnout)?
With the spindle "free to rotate", you can turn the chuck by hand. Even though you may be able turn it without obvious binding, it can be that there is still not enough room for the film of oil lubrication. The reason these fine things can get to be 90 years old without becoming utterly trashed is that in normal running, the spindle metal is generally not in contact with the bearings metal. It's all about the (quite high) pressure in the oil film.

You can fine-adjust shims even with various weights aluminum foil. Usual cooking foil is 35 microns (0.0014") Many have resorted to the extremely well controlled thickness found in soft drink cans. Use a micrometer. There is no need to to hit the wallet with pre-made shims. You can cut your own. Just be sure that there are no burrs on them before putting them together.

*Re: The red belt.*
I see those, but I don't know them, nor how noisy they might be. I went for the "serpentine" style as widely used for spinning automotive alternators - the type with that are normally driven from a multi-grooved pulley, except I let it run direct on its little ribs on the spindle cone. This arrangement will_ not_ readily slip. I rely on separate electrical overload trip to stop things. One virtue of the old leather belt with the "clack-clack" joints is that it does slip if you overload the drive chain, either from spindle binding, or a overly ambitious depth of cut on too large a diameter part. A leather belt slipping has saved many lathes from serious damage when the unfortunate collision with the toolpost happens.

Easy to find - I meant this one..
Nasedo375 refers to the South Bend book H-4 with the specifications in it.
In case you don't already have it, I have attached a PDF.


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## brino (Aug 30, 2021)

Riguy14 said:


> Do you think having the bearings to loose would cause the spindle to stall?



I have not heard of spindle lock-up/stall from being too loose.
However, bearings that are too tight can run hot and then expand and get tighter.

Loose spindle bearing can cause a horrible surface finish. It is called chatter.
When you try to take a cut any slack (spindle bearings, cross slide, top slide, tool post) causes the tool to be pushed away from the work piece.
It can spring back, may take a little cut, then spring away again.
This can set up a real resonance with loud noises, and very rough stepped surface finishes.

Do you have the turnbuckle that allows you to tension the flat belt set correctly?
I like to leave it just tight enough that it will slip if I do something stupid.



Riguy14 said:


> I’m going to try and get a serpentine belt on it soon to see if that helps.


I use old automotive serpentine belts. Here's a post with pictures:
https://www.hobby-machinist.com/threads/help-on-replacing-the-belt.93684/post-866303

-brino


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## Riguy14 (Aug 30, 2021)

Thanks for the info! The spindle is what’s slipping, the belt on it, the motor doesn’t seem to be struggling at all. I do get some pretty bad chatter and awful surface finish even with minimal depth of cut.
There was no way to tension the belt, the counter shaft and motor were held on steel tube u-bolted to the frame, and was tensioned via “gravity”. I had to chop the whole assembly apart to get the pulley out as it looks like the bearings were pressed on the shaft then the housings were welding in place. I’m 99% it was a belt tensioning issue, as well as the angle of the belt from the spindle to counter shaft. I got new bearings and a new shaft for the counter shaft and am going to mount the motor to the wall with the whole I also have a serpentine belt ready to go as well.


The Mount is coming in the mail today so hopefully I’ll have it up and running tonight! Then waiting another week for the bearing shims to arrive.


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## martik777 (Aug 30, 2021)

You need to measure your spindle bearing clearance first, then reduce shim thickness if it is too loose.


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## Grendel (Aug 31, 2021)

I have a 102 year old south bend and mine is also gravity tensioned, it does cut fine, but the spindle can be stalled with too heavy a cut as I found out yesterday when flattening off a faceplate, generally though mine is fine, though I do have a 1 1/4" flat cloth reinforced belt driving mine


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## Riguy14 (Sep 1, 2021)

martik777 said:


> You need to measure your spindle bearing clearance first, then reduce shim thickness if it is too loose.


Thanks for that video! As soon as my shims get here I’ll get it all adjusted!


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