SB9B Vibration/Wobble

macleeodd3 · Oct 26, 2020

Recently picked up this south bend 9 model B for 450 bucks. Came with milling attachment all that good stuff. Cleaned it up. Oiled everything down nice. I made a very solid bench for it off the wall of my garage, tons of braces underneath, metal top, etc.

Table feels solid. No wiggling when I just move it.
Headstock seems to turn nice and free and smooth. Motor running by itself seems to run pretty smooth, slight tick in one of the bearings but runs smooth.
When I go to engage the counter shaft and actually turn the head stock the countershaft rocks pretty good causing a vibration/wobble onto the lathe.

I did do a serpentine belt, seems like good smooth transitions at the joint, but cannot figure out what else to check or try.
I tried smoothing the joint out on the belt even more because I thought maybe that was it but doesn’t seem to help

macleeodd3 · Oct 26, 2020

dalmatiangirl61 · Oct 26, 2020

I watched your video, could not see a problem, maybe a different angle and more than a few seconds of vid would help to see it.

macleeodd3 · Oct 26, 2020

It might hard to see the the countershaft is "rocking" which seems to be transferring into the headstock causing the whole thing to rock.

SLK001 · Oct 26, 2020

The sound is in sync with your belt, so you might want to look harder at it. Agreed that we need more video.

macleeodd3 · Oct 26, 2020

macleeodd3 · Oct 26, 2020

Hope this helps. i do agree it does sound in sync with belt now that you say that.
What are my options as i thought i had a pretty smooth transition where i glued the belt together but maybe not. i thought possibly misaligned pulleys but they are decently aligned

dalmatiangirl61 · Oct 26, 2020

Much better angle, did you replace both belts?

SLK001 · Oct 26, 2020

We ask for more video and we get an extra second (WHOO HOO!!).

Try giving us 30 seconds of your potato in one place, then disengage the drive and video just the CS and the motor running for 30 seconds. Then give us 30 seconds of viewing the headstock pulley with your potato held still.

dalmatiangirl61 · Oct 26, 2020

macleeodd3 said:
i thought i had a pretty smooth transition where i glued the belt together but maybe not.

Bingo! I'm going to say the glued joint is the issue.

macleeodd3 · Oct 26, 2020

macleeodd3 · Oct 26, 2020

haha sorry the one more second was crucial! My bad SLK. motor seems smooth by itself.
Tips on smoother belt glue joint?

dalmatiangirl61 · Oct 26, 2020

macleeodd3 said:
haha sorry the one more second was crucial! My bad SLK. motor seems smooth by itself.
Tips on smoother belt glue joint?

Pull the spindle, replace with a continuous belt.

SLK001 · Oct 27, 2020

dalmatiangirl61 said:
Pull the spindle, replace with a continuous belt.

This is not a bad idea, but it also isn't for the faint of heart. You not only have to pull the headstock spindle, but also the countershaft spindle. The CS spindle will be the more difficult, as SB used tapered pins to lock some things together.

Also, if you do opt for a continuous belt, you'll be able to visually inspect all the drive bearings for wear, in case they were the issue all along.

But before you jump into that pool, I suggest that you work on your splice of your current belt. What does it look like? Is there an obvious bump? You might try smoothing any bump with a belt sander.

One other option is to just ignore the problem and just make things. Unless you have contracts with NASA for parts, the effects of the vibration will be minimal.

dalmatiangirl61 · Nov 2, 2020

SLK001 said:
This is not a bad idea, but it also isn't for the faint of heart. You not only have to pull the headstock spindle, but also the countershaft spindle. The CS spindle will be the more difficult, as SB used tapered pins to lock some things together.

I'm not seeing your point, I've replaced belts on similar lathes, tapered pins are not that big of a deal imho. If he was using a leather belt I could see doing a glue joint, did not realize that was common practice with rubber belts.

SLK001 · Nov 2, 2020

dalmatiangirl61 said:
I'm not seeing your point...

There are many posts from people trying to disassemble a SB product with no visible means to hold them together. Sometimes, buried under layers of paint, a faint circular image on a shaft may appear. But tapping it with a punch doesn't move it. And banging on the punch with a hammer doesn't move it. Before they know it, they have peened the end of "something" so bad that it now has to be drilled out. And they're still not sure that the "circular thing" is holding things together. I said "not for the faint of heart" because of unknowns like this.

Also, where can one get a continuous flat belt (not saying they don't exist, just would like to know)?

tommy1010 · Nov 2, 2020

Use an automotive serpentine belt of the proper length. Taking apart the countershaft is easy peasy. As long as someone has not driven the set screws into the shaft. No tapered pins to remove. It is a little more fiddling with the spindle than the CS. Well worth the time and effort!!

SLK001 · Nov 2, 2020

tommy1010 said:
Use an automotive serpentine belt of the proper length.

That makes sense. I wish that the 10L could have a continuous belt (without having to glue).

dalmatiangirl61 · Nov 2, 2020

SLK001 said:
There are many posts from people trying to disassemble a SB product with no visible means to hold them together. Sometimes, buried under layers of paint, a faint circular image on a shaft may appear. But tapping it with a punch doesn't move it. And banging on the punch with a hammer doesn't move it. Before they know it, they have peened the end of "something" so bad that it now has to be drilled out. And they're still not sure that the "circular thing" is holding things together. I said "not for the faint of heart" because of unknowns like this.

Also, where can one get a continuous flat belt (not saying they don't exist, just would like to know)?

Sounds like dilettante problems to me, like I said, never did an SB because I dislike flat belts (bad first experience with them), many other mfrs, with similar headstock layout used V-belts, I've never had a problem taking those apart. For taper pins you need a good punch, no half ass tapping, 1 determined swing should drive it out. You can get belts in varying lengths from auto parts stores, Grainger, and McMaster, and probably other sources.

tobnpr · Nov 7, 2020

I love my V-belt drive...

SB9B Vibration/Wobble

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