View Full Version : SB9 carriage clutch

08-31-2014, 12:43 PM
Lately, I've been hearing this gawd awful scraping noise when I hand crank the carriage back and forth on my SB9. I figured a piece of swarf was caught behind the apron somewhere. Had some time today, so decided to pull it apart. When I took the cover off the clutch, I found a thin spring had broken and was rubbing against the cover (red arrow).

http://i1305.photobucket.com/albums/s551/browne92/DSC01130_zps80c6a144.jpg (http://s1305.photobucket.com/user/browne92/media/DSC01130_zps80c6a144.jpg.html)

I also noticed that the worm gear (green arrow) seemed very dry compared to everything else.

I removed the broken spring, put it back together, and it seemed to work without it, on the bench at least. Has anyone else run theirs with this spring missing? Any side effects? Even if I had a replacement, it would take some head scratching to figure out how it goes in there.

Since I had it out, I decided to pull the clutch back apart and clean out the 'oil sump'. I found a good bit of dirt, enough to clog the oil feed hole from the front of the apron to the back (blue arrow):

http://i1305.photobucket.com/albums/s551/browne92/DSC01131_zpsee3c7390.jpg (http://s1305.photobucket.com/user/browne92/media/DSC01131_zpsee3c7390.jpg.html)

I think the reason the worm gear was so dry is the oil wasn't getting from the front of the apron to the rear for the clutch gear to carry up to the worm.

I really need to get today's project going, so I'm going to make a new gasket and get it back together after lunch, give it a try, and hope it works. I would advise any SB9 owners to check this the next time they have their machine apart.


08-31-2014, 02:25 PM
Bill, I have owned 5 of these 9A southbends, some of them have that spring and some of them didn't. Alls the spring does is holds the 2 butterflies in place. They are not a necessity so you don't have to worry about getting another, which they don't make anymore anyways, I know of one guy that made one but its not necessary as long as you bench test and make sure that the butterflies/leaves engage the clutch and don't pop out you are ok...
Also, you should take a pipe cleaner and run through the oilers that don't have wicks in them and see if they are clogged. maby even some light pressure with a air gun. hope this helps! remember, bench test!

08-31-2014, 03:47 PM
This is what it should look like


Photo taken from this (http://www.practicalmachinist.com/vb/south-bend-lathes/9a-apron-clutch-question-157919/) thread on PM


Photo taken from this (http://www.practicalmachinist.com/vb/south-bend-lathes/clutch-engagement-south-bend-9a-234240/#post1673501) thread again on PM

My 1942 SB 9" is missing the spring with no ill effects, I also have a Boxford which is based on the SB with a near identical apron design in that they discontinued the spring completely.

Made the gasket for mine from a thin brown paper envelope and a smear of Hylomar to finish.



09-01-2014, 11:17 AM
Thanks guys. I cut out a new gasket from a roll of automotive gasket material, probably too thick, but it seemed to work well. Put it back together, bench tested again, put it back on the machine, and off we went. Used it all afternoon and evening with no problems. Guess I'm not going to worry about finding a new spring for it.

Thanks again.