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Lathe motor slows down or stops when taking a cut.

Kevin T

Stainless
Joined
Jan 26, 2019
I got that backing plate in the mail today and screwed it on to the spindle to get busy. I found couple cutters in the box of stuff that came with my lathe so I figured what harm can a couple rough passes do? I set up for the lightest cut, hand fed it and was surprised that the motor came to a stop with a light cut. I hate to ask if this means my motor is toast....but does it?

I tried to look online but didnt see any answers. Thanks for any help or ideas. :scratchchin:

P1050348.jpg

P1050349.jpg
 
Does the motor stop happen if you press a scrap piece of wood to the plate?

Check all the electrical controls and connections to the motor. You want to have a situation here where an external component is causing the stop.
Otherwise it is bad.

More details leads to more suggestions.

I'm not a South Bend guy but to me all lathes are brothers. Even the imports.
As you may have noticed on this forum the older brothers always pound away on their younger (import) brothers.
 
not what you were asking about but those carbide tipped bits dont work so great in a armstrong style holder unless they are reshaped.
 
not what you were asking about but those carbide tipped bits dont work so great in a armstrong style holder unless they are reshaped.

Hey! That is exactly what I chucked up in there! How did you know? I was going to ask about all the sparks next!
 
Hey! That is exactly what I chucked up in there! How did you know? I was going to ask about all the sparks next!


Laff! Cause you posted a photo of it! If you are getting sparks, there is another issue to deal with. You might read up on feeds and speeds, relief angles on cutters, oh heck, if only someone wrote a book about operating a Southbend lathe, hey, that'd be great! Oh, look! South Bend Lathe Works - Publication Reprints - How To Run A Lathe 55th Edition | VintageMachinery.org

And, you are going to need this one also. I had "an old leather belt" on mine when I got it. I didn't bother and cut it off and replaced it with a synthetic belt I bought from SBL (pre-Grizzly). Search around, belt discussions abound.
South Bend Lathe Works - Publication Reprints - How To Run A Lathe 55th Edition | VintageMachinery.org

Welcome aboard.
 
i can see the bit in your pic.
in an armstrong style holder they dont have enough front clearance..may not have any clearances at all...a good piece of HSS is the way to go in those holders IMO.

sparks generally mean too fast.
 
Couple other suggestions:
I think you have a lathe from right around WWII. If you look at the spindle bearing caps, there will not be two small screws in the center of the cap right in line with the spindle. If this is true, you have the integral cast iron bearings and "superfinished" spindle. It's a good system, some think it better than the bronze bearing system that was used before and after this period.
I'd want to check the oiling felts. Mine were worn down beyond oiling when I got my lathe. IF there are *not* two screws in the center of the bearing caps, you can pull the caps and lift the spindle. IF those screws exist, it is another procedure you have to do first or you'll mess up the bronze bearings.
You might want to just replace the felts while you are in there.
Anyway, How to: South Bend Lathe Works - Publication Reprints - Keep Your Lathe in Trim -- SB Bulletin H-4 | VintageMachinery.org

Second: Speeds and feeds. I have been doing this a while, but I still use this handy little tool:
Speeds & Feeds - LittleMachineShop.com

Third: Cast iron is incredibly abrasive. If it gets on the ways, it then gets under the saddle, and wears the lathe everytime you move the saddle. Unless you spend LOTS of time cleaning it off. before you cut that plate, get some newspaper/butcher paper etc and some tape and dress that lathe up like you were about to do surgery on it. Compound rest sticking up out of the paper, the other controls are "reach below the paper".
Using a shop vac to catch chips is a good idea too. I must have already pulled part of the paper off when I took this. Cover your TA ways as well.
DSC01252.jpg
 
i can see the bit in your pic.
in an armstrong style holder they dont have enough front clearance..may not have any clearances at all...a good piece of HSS is the way to go in those holders IMO.

sparks generally mean too fast.

I forgot I put the pictures up! I am not sure I have any HSS around I need to go through the pile. I have a ton of cobalt blanks so I thought I would give it a try. Like I mentioned I didnt really do my homework on this first run. I was too excited to make chips! But alas as Rudd pointed out I made a bunch of messy dust! I'm going to back up a bit and slow things down. It's a hard place to get to also that close to the headstock. I found that my cross slide is moving around so I need to look in there first and bone up a bit on making cutters that work too!
 
IME cast is a pleasure to cut with a good tool.
for an armstrong holder look in the HTRAL book and check out a round nose tool run at the proper speed.

dont be afraid to go deep..experiment..you have plenty of meat to cut down to fit your chuck.
 
Couple other suggestions:
I think you have a lathe from right around WWII. If you look at the spindle bearing caps, there will not be two small screws in the center of the cap right in line with the spindle. If this is true, you have the integral cast iron bearings and "superfinished" spindle. It's a good system, some think it better than the bronze bearing system that was used before and after this period.
I'd want to check the oiling felts. Mine were worn down beyond oiling when I got my lathe. IF there are *not* two screws in the center of the bearing caps, you can pull the caps and lift the spindle. IF those screws exist, it is another procedure you have to do first or you'll mess up the bronze bearings.
You might want to just replace the felts while you are in there.
Anyway, How to: South Bend Lathe Works - Publication Reprints - Keep Your Lathe in Trim -- SB Bulletin H-4 | VintageMachinery.org

Second: Speeds and feeds. I have been doing this a while, but I still use this handy little tool:
Speeds & Feeds - LittleMachineShop.com

Third: Cast iron is incredibly abrasive. If it gets on the ways, it then gets under the saddle, and wears the lathe everytime you move the saddle. Unless you spend LOTS of time cleaning it off. before you cut that plate, get some newspaper/butcher paper etc and some tape and dress that lathe up like you were about to do surgery on it. Compound rest sticking up out of the paper, the other controls are "reach below the paper".
Using a shop vac to catch chips is a good idea too. I must have already pulled part of the paper off when I took this. Cover your TA ways as well.
View attachment 283918

Thanks for looking over my shoulder Rudd. I just spent that last 13 months going through this entire machine so she is ready...it's me that needs a bit of polish!

I would never have been able to get this far without the people in here.

South Bend 16 Toolroom Lathe - The Adventure Begins...


I really appreciate the tips on cutting that material too! I can see that it is a messy deal and I will do as you say when I get ready to cut it down again. I have a few things to work out first with my compound slide and making a decent cutter too! There is a lot of material to remove on that piece! Cheers and Aloha
 
Still a little embarassed about this thread but I have been spending so much time on the machine that I missed the "concept" that there are two cone pulleys so the one I can see is moving and slowing down but the lower one slipping never crossed my mind! LOL
I found that my compound was sloppy too but I had not tightened the nut under that holds it together! Whew! i was scratching my head there until I felt under and the screw was loose that holds the bronze nut! Cheers.
 
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just one note of caution from personal experience, some inexpensive pre-threaded backplates are nasty junk and hard as glass. try turning some known material such as genuine Durabar cast iron for comparison. it is important to try cutting a known material first so you have some reference.

good luck and stay safe, :cheers: from NYC
 
Its just on par with learning new stuff, it happens. You tore down and built the machine, which is a feat. You're not a machinist by trade, but just being active on forums and reading helps a lot, which you do. Also, finding things to adjust, fix, or improve on a lathe will probably keep happening till they start throwing dirt on you, haha.

Kinda funny story from my younger days. More mechanic related, but I think it helps with machine work too. I spent a large part of my career, and early learning part, haha, with an outfit from the north east coast. The owner and the shop foreman were two really smart guys. Knew not only the business, but we're hands on types. They knew every inch of what we did, that they could troubleshoot blind all the time. That's the good, lol.

The bad is, they we're both harsh SOB's. Screaming and hollering all day. It was like working for 2 Sgt Gunny's from Full Metal Jacket. Harsh, but funny if it wasn't you, lol.

A line from the owner: "USE THESE THINGS !" Pointing at your eyeball, damn near touching it. "MAYBE YOU'LL SEE WHAT THE F#%* IS WRONG !"

Shop foreman on phone to road mechanic: "LOOK, TOUCH, FEEL. YOU'RE THERE, I'M NOT. YOU TELL ME WHAT IT'S DOING, WTF !"

Yea, it was a good time, lol. But taking those beatings, kinda drove people to think more. Run the process of what ever it is we we're looking at through our head. Not just thinking of the problem, but running the machines working process through our head.

Troubleshooting is a high percentage of what I do. I like to run a game of prove/dis-prove in my head. I want to be right. So I need to prove my self correct. But you can get short sighted, if only looking to be right, and overlook other things.

So whatever my working theory on a given problem, I try to prove it wrong. By working to both prove my theory right, and wrong, I start a chain of process of elimination. And as a side to that, I'm running the given machine's working process through my head. How it works, and why it works.
 
just one note of caution from personal experience, some inexpensive pre-threaded backplates are nasty junk and hard as glass. try turning some known material such as genuine Durabar cast iron for comparison. it is important to try cutting a known material first so you have some reference.

good luck and stay safe, :cheers: from NYC

Thats a good suggestion thanks. I have a lot of non-cast material to cut and play with but the only thing I have that is cast is that backplate. I am going to take a hunch that you're right about it's quality.
 
Its just on par with learning new stuff, it happens. You tore down and built the machine, which is a feat. You're not a machinist by trade, but just being active on forums and reading helps a lot, which you do. Also, finding things to adjust, fix, or improve on a lathe will probably keep happening till they start throwing dirt on you, haha.

Kinda funny story from my younger days. More mechanic related, but I think it helps with machine work too. I spent a large part of my career, and early learning part, haha, with an outfit from the north east coast. The owner and the shop foreman were two really smart guys. Knew not only the business, but we're hands on types. They knew every inch of what we did, that they could troubleshoot blind all the time. That's the good, lol.

The bad is, they we're both harsh SOB's. Screaming and hollering all day. It was like working for 2 Sgt Gunny's from Full Metal Jacket. Harsh, but funny if it wasn't you, lol.

A line from the owner: "USE THESE THINGS !" Pointing at your eyeball, damn near touching it. "MAYBE YOU'LL SEE WHAT THE F#%* IS WRONG !"

Shop foreman on phone to road mechanic: "LOOK, TOUCH, FEEL. YOU'RE THERE, I'M NOT. YOU TELL ME WHAT IT'S DOING, WTF !"

Yea, it was a good time, lol. But taking those beatings, kinda drove people to think more. Run the process of what ever it is we we're looking at through our head. Not just thinking of the problem, but running the machines working process through our head.

Troubleshooting is a high percentage of what I do. I like to run a game of prove/dis-prove in my head. I want to be right. So I need to prove my self correct. But you can get short sighted, if only looking to be right, and overlook other things.

So whatever my working theory on a given problem, I try to prove it wrong. By working to both prove my theory right, and wrong, I start a chain of process of elimination. And as a side to that, I'm running the given machine's working process through my head. How it works, and why it works.

Great story. I have been saying for a few years that the presence of "Bullys" in society is actually good for a lot of things.
 
At what speed? If you've been turning small stock at higher speeds and didn't change the speed that large diameter piece is "at the wrong end of the lever".

Oh yeah I have a plan now.

cast iron speed.jpg

It looks like it will be a backgear process too. My backgear popped out on the few times io was messing around with it but I will look into tightening up some nuts and try again.
 








 
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