Have I over chucked my south bend 9C?

haus · Oct 6, 2018

Hi...

I've lurked and gathered very helpful tips here for about a month since picking up a 1939 South Bend 9C. I'm brand new to machining and this is my first lathe. She spun up nicely at purchase but I have yet to set up in my studio as I'm building a sturdy butcher block style bench and acquiring some bits like a few change gears and a replacement chuck.

The jaws on the 5" Union scroll chuck that came with the machine are quite worn but I thought no matter as I want a larger 4 jaw anyway. Having read elsewhere on this forum that 6" about right for these SB workshop lathes I picked up a very nice 6 1/2" on ebay. The point I neglected to consider is whether I should look for a light or a heavy duty chuck. The one I picked up turned out to be a heavy duty Burnerd that tops the scale at 25 lbs (about 4 times the 5" I want to replace)! With chuck mounted & spindle spun by hand everything feels buttery smooth and I would expect some extra weight could be useful to prevent problems like chatter but see my pictures... the chuck certainly looks large for the machine. I plan to face the backing plate before using any chuck I purchase (I learned that here) but my question is, would a chuck this heavy be at all useful or even safe for use on a South Bend 9?

Original

"New" chuck

5" to 6.5"

4" deep

Opened to 7", ~1/2" clearance to bed

Thanks - Mike

StrayAlien · Oct 9, 2018

FWIW, I run an 8" 4 jaw on my 10L. It looks pretty darn big but does the job fine. I don't spin it too fast.

I have a 6" 4 jaw as well, but the extra holding capacity on the 8" and the bore size means it is the one I normally reach for.

Greg.

thermite · Oct 9, 2018

haus said:
Hi...

I've lurked and gathered very helpful tips here for about a month since picking up a 1939 South Bend 9C. I'm brand new to machining and this is my first lathe. She spun up nicely at purchase but I have yet to set up in my studio as I'm building a sturdy butcher block style bench and acquiring some bits like a few change gears and a replacement chuck.

The jaws on the 5" Union scroll chuck that came with the machine are quite worn but I thought no matter as I want a larger 4 jaw anyway. Having read elsewhere on this forum that 6" about right for these SB workshop lathes I picked up a very nice 6 1/2" on ebay. The point I neglected to consider is whether I should look for a light or a heavy duty chuck. The one I picked up turned out to be a heavy duty Burnerd that tops the scale at 25 lbs (about 4 times the 5" I want to replace)! With chuck mounted & spindle spun by hand everything feels buttery smooth and I would expect some extra weight could be useful to prevent problems like chatter but see my pictures... the chuck certainly looks large for the machine. I plan to face the backing plate before using any chuck I purchase (I learned that here) but my question is, would a chuck this heavy be at all useful or even safe for use on a South Bend 9?
View attachment 239576
Original
View attachment 239575
"New" chuck
View attachment 239577
5" to 6.5"
View attachment 239578
4" deep
View attachment 239579
Opened to 7", ~1/2" clearance to bed

Thanks - Mike

Fifty, sixty years or so ago, a "premium" optioned SB shipped with a Cushman about half-way in between the two you show. Cushman about the same heft as the Pratt-Burnerd you have, but arguably stronger and better - they did fight over that - went onto spindles of Monarch 10EE and the like with a tad more heft under them and far greater power back of them.

This one has eaten a chunk of scarce longitudinal daylight. That's about all.

You won't run it long enough nor hard enough to much affect the bearings. Not unless you start making parts ten hours a day, every day. Which would be well short of "sane" on an SB 9 manual, anyway.

"Safe", then, is up to you.

That said, if the chuck is well-made?

I'd be tempted to find a nicer lathe to put under it.... and have done.

steve-l · Oct 9, 2018

No problem at all. I have run a 6" SB 4 Jaw and a 6" 3 Jaw SB chuck on my 10K since new (1980. The original SB 5" 3 jaw was no where near as good as the SB 6"......huge difference in everyway.

Cole2534 · Oct 9, 2018

The bearings shouldn't care, I'd be more concerned with the extra bed length and horsepower it's eating. On the other hand, it could be pushing you toward a better spot on the ways?

Blob · Oct 9, 2018

steve-l said:
No problem at all. I have run a 6" SB 4 Jaw and a 6" 3 Jaw SB chuck on my 10K since new (1980. The original SB 5" 3 jaw was no where near as good as the SB 6"......huge difference in everyway.

Agree. I run both 6-1/4" and 5" 3 jaw Bison chucks on my 10k - the 6 is a heavy sucker but no problems. The 6" Bison 4 jaw I have is WAY lighter than the 3 jaw.

Tony Quiring · Oct 9, 2018

Mass and newton...

Flywheel effect.

The larger rotating mass will consume a bit more power to startup so motor may complain when starting in higher speeds.

Also note this larger rotating mass will mean less margin for error if you get something where it does not belong.

Careful management of jaw placement is critical as you have not to much overall movement so reversing them may get old.

ALWAYS rotate by hand to insure a jaw does not tag the ways or carriage.

Sent from my SAMSUNG-SM-G930A using Tapatalk

k3vyl · Oct 9, 2018

My 9" workshop lathe came with a 7 1/2" 3jaw chuck fastened to its face plate. Im not sure what the previous owner was doing with that setup.I never used it because I got a 4" 3jaw that is very handy on that lathe. Some day I will make a plate to use that thing on my 13" Regal,it opens really wide.Point is someone had a use for that chuck on that little lathe.

promacjoe · Oct 12, 2018

As others have said you should not have any problems using that chuck. just pay attention to what you are doing. On the other hand putting it on and removing It, Might be a challenge. You may smash a few fingers in the process. I suggest putting a good 3/4 wooden dowel well into the spindle. Leave enough on either side to use as handles. Also put a piece of wood across the bed to protect it. That thing is too heavy to take chances with.

Stay safe and have fun.

Joe.

fciron · Nov 6, 2018

I occasionally use some heavy 8" chucks on my 10L, primarily for the larger through hole. It takes noticeably longer to spin up, but no other issues to date.

With the chuck mounted on the spindle, I traced its outside diameter onto a 2x4 laid across the ways, then cut that out to create a rest that can be used to slide the chuck onto the spindle and to prevent the chuck falling on the ways or my hand during removal.

I got the idea from someone on this forum, but it was years ago and I've forgotten who to credit.

Vladymere gr · Nov 11, 2018

Nice looking chuck. A good brand with a reputation of well made. Just don't over extend the jaws and clip the bed or carriage and you will be golden.

Vlad

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