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9A Quick Change Gearbox problem

1BadDart

Plastic
Joined
Nov 5, 2019
I've been working on and sprucing a 9A that my Uncle years ago. I don't know the history as my Uncle worked for the state and bought the lathe at a government auction. He piddled with it off and on for a few years then bought a larger more modern lathe and gave me the 9A.

I built a stand for it a few years ago and used it for small projects. There were problems with the motor, the chuck was wore out and the bearing was out of the live center. After replacing al three items and fixing some other stuff I took all the gears off and cleaned them and the lathe. After cleaning it up I ran the lathe, everything was fine until I put the quick changes levers in their highest settings.

The lathe didn't want to start and when it did it was obviously loaded very heavy. I looked in the qcgb and it was gunked up badly so I removed it and soaked it in the parts washer over night. The next day I scrubbed it up good and let it dry for a couple days then lubed it up good and reinstalled it. Same deal.

If I take the RH lever on the gear box and disengage it the lathe runs smooth and easy to turn by hand. Engage the lever and again it acts as if it's bound up. So again I removed the gear box, this time I took it apart and cleaned all the gears checked the shafts lubed and reassembled. Same deal, everything turned smooth after I assembled the gear box before installing.

You can hear a cyclical noise as it runs that gets louder, it will eventually stall the motor. Nothing is hot to the tough when it does this. In the lower speed settings it has enough power to run.


Both times I've had it apart I left about .020" of end play on the lead screw. I removed, cleaned and lubed the apron and saddle before doing any of the above. Everything seems to be good there.
Tomorrow I'm going to remove the qcgb again and take the main screw out and install it without it and see what happens. I'll check the main screw for straightness while it's out.

Any ideas? I'm not a machinist so I hope this makes sense.

Thanks, Justin
 
I have to say I've never tried to run the leadscrew on any of my lathes at the maximum possible speed. I'm not quite sure why you'd want to do that. However a questions I have to ask is what spindle speed were you using when you tried to do this? If the spindle speed was high, the the leadscrew speed would be very high--maybe approaching 2x the spindle speed depending on the particular QCGB you happen to have on that lathe. I'm not surprised you had trouble if this is what you tried to do.

South Bends are all about "slow and easy."
 
The problem was in the apron. I removed the gear box, then removed the lead screw from the gear box. Then ran the lead screw through the apron with the clutch disengaged and it was very hard to turn. After completely disassembling the apron I found that the port that you fill the oil well through was plugged and the worm was dry in the housing. Everything looked good so I cleaned, lubed and reassembled. Now the lathe runs like it should.

Thanks, Justin
 
Justin,

If you have not already done so, I suggest you buy Steve Brooks' book A Guide to Renovating the South Bend Lathe (appropriate version) and his felt replacement kit.

You will probably find many problems with oil passages and felts, like you found in the apron.
 
If you have not already done so, I suggest you buy Steve Brooks' book A Guide to Renovating the South Bend Lathe (appropriate version) and his felt replacement kit.

+1 on this. You can get it on ebay for about $90 (the book and the felt/gasket kit). The seller's ebay name is stevewb. His company, ILION Industrial Services, LLC produces the book.
 
Ditto to all the above- including the spindle wicks. The good thing about SB's- esp. the 9's- is that they were prolific and well made. Still plenty around getting worn/parted out and most parts can be replaced or made without a great deal of difficulty ('cept for the plain spindle bearings).
 








 
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