View Full Version : Need pics of SB leadscrew tumbler.

10-19-2004, 01:07 AM
My Rockwell doesn't have any type of detent for the tumbler. You have to loosten a bolt and lock it down. Seems kinda screwy to me so I am thinking of making a detent similar to a SB. I'd appreciate any pics that show the mechanism.

10-19-2004, 11:19 AM
Might this help.

www.lathes.co.uk/soutbend9-inch/page7.html (http://www.lathes.co.uk/soutbend9-inch/page7.html)

I have a 9" South Bend floor model, though no digital camera for actual pictures. I do have the factory drawings for the gearbox if they might help.

10-19-2004, 11:48 AM
The SB model A 9" has a bolt which must be loosened, at least on a 1948 one.

Here's a closeup of the Emco Maximat tumbler reverse. The plunger is pulled toward you and positioned into the upper or lower detent hole. Den

10-19-2004, 11:59 AM
Nheng's photo is not what I was thinking of. Are you looking for the gearbox tumbler or the reverse tumbler? On my SB the feed reversing lever (reverse tumbler) is a kept in place by a spring loaded pin. The same idea, though in a different configuration as the photo shows. Again, I have the drawings for that also.

10-19-2004, 12:11 PM
Yeah, I wasn't sure about that either. Now, when you say gearbox tumbler, are you referring to the QC select levers?

Here's a link I had to a variety of SB drawings and part lists but it is only partially complete:


[This message has been edited by nheng (edited 10-19-2004).]

10-19-2004, 12:43 PM
I was talking about the lever that reverses the leadscrew. I just wanted some pics to get Ideas. I know what a SB lever "feels" like but I never cared about looking to see how it worked. This is what I have so far:


It's sort of a proof of concept deal. I have a pin that goes through the lever and will locate in a piece of angle iron bolted to the headstock. If it works I'll build a new one when the lathe is running and when I get my mill. Don't worry, that piece of angle iron will be pared down so it's not so obtrusive. It's tough just working with a welder, drill press and files...

[This message has been edited by hoffman (edited 10-19-2004).]

10-19-2004, 03:27 PM
Have a look at this, might be of help


look at what he has done under HF9x20 improvements


[This message has been edited by zl1byz (edited 10-19-2004).]

[This message has been edited by zl1byz (edited 10-19-2004).]

10-19-2004, 07:34 PM
These are pictures of my SB 10K lead screw tumbler.
The pictures make things look dirty but I use a product called gear shield. it makes a mess but it works really good it comes in a aerosol can. The stuff comes out black and if you get it on your hands you will wear it off.

[This message has been edited by gundog (edited 10-19-2004).]

10-19-2004, 08:56 PM
Thanks guys. I may just scrap what I have and go with a pull knob arrangement. I was thinking about the SB's that have the "spoon and lever" arrangement and based my design on what I remember.

10-19-2004, 10:07 PM
It looks like the design you have going will work. It looks like your detent will work off the spoon handle with holes drilled in the angle iron.

What do you do now to move the lever? Do you loosen up the bolt and then retighten when it is in the right position?

[This message has been edited by gundog (edited 10-19-2004).]

10-19-2004, 10:19 PM
I used a stiff wave washer on mine....it saves me from having to tighten and loosen the screw. I just snug it up enough to still let me move it without using a wrench

10-19-2004, 10:34 PM
Mine is locked in position with a bolt. I would much rather have a simple lever operated tumbler so that I wouldn't have to keep moving my wrench to it. These gears are naturally kind of noisy. One of the tips that I've read about was to use some sawdust with the grease on the gears. This gets pressed into the teeth and sort of smooths out the ride. I don't know if some kind of rubberized coating might not achieve the same thing pretty well.

I like the lever and pin idea pretty well but maybe something spring-loaded that goes over-center in one direction and the other direction might work. This would keep the tumbler gear fully enmeshed, and might reduce some slack in the drive and maybe even make them run smoother with less gear noise.