Lathe question

Pete Wass

Well-known member
I have a South Bend 10" toolroom lathe. It has a 110 Sears motor on it. While using it today I noticed that when I first fire it up, there is a vibration which goes away after a time. I also think I noticed that the spindle speed isn't very fast. Could it be that the motor has or is giving up the ghost? I don't have any way to measure the RPM's of the spindle but there seems to be very little difference from one pulley position to another. Pete
 
You have one of my favorite lathes, I spent many hours as a teenager working at one of those in my grandfather's shop...

My guess is the motor is shot or possibly the belt is slipping if you don't see much difference in speeds. Does it have a hard time getting up to any respectable speed with the belt in the fastest position (on the smallest diameter step to the left) on the spindle cone pully? If so, I'd recommend changing the motor as I think it would be pretty obvious if the belt were slipping... The other possibility is that it doesn't have a large enough motor to begin with and struggles at any speed. Again, change the motor should fix the problem. According to my 10" Southbend Lathe manual, if run on single phase power, it should be a one hp motor at the very least.

Happy Shooting,
Mitch & Shadow...
 
Pete,

Maybe the belt (s) are taking a "set" while they set and it takes a time to loosen up? Just a thought.
 
Pete,

Maybe the belt (s) are taking a "set" while they set and it takes a time to loosen up? Just a thought.
Waynes response is probably the answer. When you are not using the lathe, move the belt tension lever from the left to the top or to the right. This will take the tension off the flat belt. The Vee belt will not be a problem.

With a 110V single phase motor you will give some 60-cycle feedback and it may show up as a minor chatter especially on thread cutting.
 
I have a South Bend 10" toolroom lathe. It has a 110 Sears motor on it. While using it today I noticed that when I first fire it up, there is a vibration which goes away after a time. I also think I noticed that the spindle speed isn't very fast. Could it be that the motor has or is giving up the ghost? I don't have any way to measure the RPM's of the spindle but there seems to be very little difference from one pulley position to another. Pete

Pete,

Get a pic of the nameplate data.

It might be stuck on the starter winding, and not shifting to the running windings.

If it were slipping (slow) out of phase, it would likely trip the breaker and get very warm.

Is there a capacitor bolted to the side of the motor?

Again, a pic and I might be able to help you troubleshoot it.

Ben
 
And one other thing...

which may sound unlikely and too simple, but which I've actually encountered on the same model lathe: check the spindle bearings to see that they are getting enough oil and are not galling/seizing. One of the South Bend 10" lathes in our shop, (which had been use for years), developed a similar problem, which I traced to the misplacement of the oil wick for the chuck-side bearing, causing the spindle to run dry.
mhb - Mike
 
I will look at this

which may sound unlikely and too simple, but which I've actually encountered on the same model lathe: check the spindle bearings to see that they are getting enough oil and are not galling/seizing. One of the South Bend 10" lathes in our shop, (which had been use for years), developed a similar problem, which I traced to the misplacement of the oil wick for the chuck-side bearing, causing the spindle to run dry.
mhb - Mike



Tha oil cups show oil in them but I guess this could be deceptive.
 
Pete:

It was deceptive: we oiled the spindle cups regularly, but because the wick didn't extend into the bearing gallery, the bearing wasn't getting the oil.
mhb/Mike
 
Belt

Pete,

Maybe the belt (s) are taking a "set" while they set and it takes a time to loosen up? Just a thought.



I had a belt made for it several years ago. It is a braided fabric belt which appears to be tight. The belt does slip off the bottom pulley almost every time the switch is turned on, what is the meaning of that?

I have turned the spindle by hand and it does not seem to be rough. the thrust collar at the back of the spindle has lube showing and I lube it frequently where all the cups are.

The motor does humm or sort of growl when it is first turned on. After a minute or less the growl goes away and it isn't noisy.
 
The spindle being free and getting oil should be easy to confirm, with the belt tensioner in the relaxed position, you should be able to spin the spindle freely by hand. If so, put power to it and let it run for a while and feel the tops of the spindle bearing caps, at best, they should be only warm, never hot.

I trust your speed problem you wrote about in the initial post is in direct drive, not with the back gear engaged?

Mitch...
 
Correct on the back gear

The spindle being free and getting oil should be easy to confirm, with the belt tensioner in the relaxed position, you should be able to spin the spindle freely by hand. If so, put power to it and let it run for a while and feel the tops of the spindle bearing caps, at best, they should be only warm, never hot.

I trust your speed problem you wrote about in the initial post is in direct drive, not with the back gear engaged?

Mitch...

both the spindle and drive unit run free. I am thinking the motor might be the problem. In the past, the lathe has functioned properly.
 
both the spindle and drive unit run free. I am thinking the motor might be the problem. In the past, the lathe has functioned properly.

That definitely sounds like the motor is the problem... One other possibility is amount of power getting to the lathe. Lathes ar notoriously power hungry when starting up before they reach operating speed due to the mass and momentum of the cone pullies, spindle, chuck and weight of the object being turned. When you say this is a 110 Sears motor, I assume its wired with a standard plug and plugged into an outlet? This may be a weak point in the system, you should measure the voltage at the motor when it is under starting load and be sure its over 110 VAC. If not, this may be part of the problem...

My recommendation would be to use a 220 VAC single phase motor and direct wire it to a master switch/with its own fuses or circuit breakers in a circuit similar to what an electric drier or range would use...

An even nicer solution, if you have to replace the motor, get a 1 hp, 3ph, 220 VAC and use a VFD device to run it off the single phase power if that is all you have available. This will allow you variable speeds at each belt setting...

As to the belt slipping off the pully, that can be for two reasons, one, usually the belt is too loose and slipping. Adjust the belt tension and when not running the lathe, the belt tension lever should always be in the relaxed position to allow the belt to recover from the heat and tension stretching that occurs when in operation.

The second cause is that the belt is the wrong material...

Southbend recommends a two layer belt, outer layer being a plastic polymer bonded to an inner layer of leather. The polymer, probably nylon from the looks and feel of it, is the strength of the belt and the leather is what grips the pully...

Before Southbend was bought up by Le Blond, you used to be able to purchase an endless loop belt kit direct from Southbend for these lathes. The belt, as described above, comes with the ends skived and a small can of some type of what I assume is a flexible epoxy resin used to glue the belt into one continuous loop in place around the pulleys.

When I overhauled and rebuilt my 16" Southbend toolrom lathe, I bought one of these belt kits from Southbend and installed it when I put the lathe back together. Once adjusted initially and again after a week or so of use, I've never had to adjust the belt again in over 20 years of intermittent use... Its a fantastic drive belt, smooth and quiet and no slip... When I bought my 1978 Southbend 13" toolroom lathe, it came with this type belt and again. results are the same, no need for adjusting, no slipping and plenty of power, and smooth and quiet...

Seems to me I read recently that Southbend Lathe Co. has been either bought again, or has become independent and is no longer part of Le Blond.

Parts are still available however Grizzly is now the parts distributor:
http://www.grizzly.com/products/brands/southbend/parts.aspx

Happy Shooting,
Mitch & Shadow...
 
Thanks So Much

I will look into this. A friend showed me his endless belt he had made from an automotive serpentine belt. It looked good. I guess it must have been a project from a How To site.

I can easily do 220 but there is no 3 phase power near where this lathe is located. The power cord is rather big for this machine and it is plugged into a socket that has nothing else plugged in. I'll see about a motor.

Thanks,

Pete
 
I will look into this. A friend showed me his endless belt he had made from an automotive serpentine belt. It looked good. I guess it must have been a project from a How To site.

I can easily do 220 but there is no 3 phase power near where this lathe is located. The power cord is rather big for this machine and it is plugged into a socket that has nothing else plugged in. I'll see about a motor.

Thanks,

Pete

Pete,

You don't need three phase power to run a 3 phase motor. The VFD (variable frequency drive) can split the phase for you. Although.......wiring one isn't for the hobbyist. A variable speed lathe is a wonderful thing, but not practical for an occasional user.

I'd call Gilman electric in Bangor and they can help you, or lead you to someone that can.

Your motor can likely be repaired for short money.

Ben
 
Last edited:
Thanks Ben

Pete,

You don't need three phase power to run a 3 phase motor. The VFD (variable frequency drive) can split the phase for you. Although.......wiring one isn't for the hobbyist. A variable speed lathe is a wonderful thing, but not practical for an occasional user.

I'd call Gilman electric in Bangor and they can help you, or lead you to someone that can.

Your motor can likely be repaired for short money.

Ben

I noticed on Ebay one can buy what appear to be very good 1 hp motors for not a lot of money. I think I would go to 220v instead of the 110 it has been. A concern is wiring the thing up. As I recall, I struggled getting the motor to work with the switch on the lathe but did finally get it to work.
 
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