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Gears needed to change SB 9 C to A

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Dan1900

Aluminum
Joined
Jul 29, 2017
Hello,

I am planning on adding a gear box to convert my 9c to a. In doing some research, it seems I will need to purchase 20 and 40 tooth stud gears (1 each) and a 56 tooth gear box gear. I can also use my existing 80 tooth idler gear. What other gears will I need for the conversion? In looking at some photos, it seems as if there are more gears than just these.

Also, my lathe did not come with reverse tumbler gears. How often do you find yourself using these?

Thanks
 
Are you sure you're done with your research? You know that the carriage apron is different between the 9C and the 9 A & B? And you know that you need a different lead screw, right? And I'm not quite sure what you mean about the missing the reversing tumblers. Is something there to replace the tumbler? Without the reversing tumbler, how are you going to reverse the direction of the carriage or the cross feed? Those are fairly common functions that you'll be giving up. I'd say you need to go find the reversing tumbler set before you get too far along.
 
I am aware of the change in apron and lead screw. The only thing I am still confused on is the gear change. I know of the ones I do need, but looking at photos it seems as if there are more than what I mentioned above. Can you advise if I need anything more than those?

I dont run the lathe in reverse all that option, but having the ability to is not a bad idea.
 
By the time you get all the parts, you might as well buy the 9A and sell off your 9C. I know there is the thought you are going to do this yourself and save a buck (I tried that route for 10 years too before I wised up), but the best course of action is to get the machine that is close to your needs and move on from there. Better to speed your time and funds on the better machine.

John
 
You have all the gears covered you need in your post. You need to post a picture of where the reverse tumblers are supposed to be. We/I are a little confused as how the machine ran without them although possible if it was only hand cranked. I believe doberman above hit the nail on the head. You will not be reversing your spindle that often but you may have to cut from left to right using power feed. That is the reason for the tumblers. Without the tumblers you have no place to put that 20 or 40 tooth gears you need to make the gearbox work.
 
I agree with Doberman. There are more parts than meet the eye needed for your proposed change over. I believe the cross feed screw is different on the C as opposed to the A & B as well. With no reverse tumbler, I would think that the lead screw would be perpetually in neutral. The tumbler is needed to transfer power/motion from the headstock spindle to the gear train and lead screw. Might be simpler (and cheaper) to buy a good used model A and sell the C. The difference between the pricing might be less than you would spend in time and money chasing the parts, depending on how cheap or how readily you could find good parts, It would be a different story if you already had the parts.
 
"Also, my lathe did not come with reverse tumbler gears. How often do you find yourself using these?"

Are you sure you don't have a top oiler model 5? It has a slightly different apron from the later 9C, I'm not sure you can do this swap easily...

allan
 
tommy1010 said:
You have all the gears covered you need in your post. You need to post a picture of where the reverse tumblers are supposed to be. We/I are a little confused as how the machine ran without them although possible if it was only hand cranked. I believe doberman above hit the nail on the head. You will not be reversing your spindle that often but you may have to cut from left to right using power feed. That is the reason for the tumblers. Without the tumblers you have no place to put that 20 or 40 tooth gears you need to make the gearbox work.
Click to expand...

Hi Tommy, see album for gear setup: Imgur: The most awesome images on the Internet
 
Note: If your machine was made in 1942 or earlier, You will more than likely have to replace the following items.

1: Saddle.

2: Banjo.

This is over and above the price of the Gearbox, Lead screw, Apron and gears.

Also, there's a good chance that you will have to do some machining on the bed so that the apron clutch will clear the bed. This involves taking about 9/16" off the lower front rail between the To feet.

If the reversing tumbler is just missing, it is doable, If you know what you're doing. But if your lathe did not come with a reversing tumbler lever on it, you're wasting your time.

Show us a picture of your lathe, specifically the gear section of the headstock, also give us the serial number.

As others have mentioned, You will probably be better off replacing it with a model A.

stay safe and have fun.

Joe.
 
Dan1900 said:
Also, my lathe did not come with reverse tumbler gears. How often do you find yourself using these?

Thanks
Click to expand...

If you want to use the power feed, you will use this a lot. For regular right to left power feed you run it in forward. To face outside to in you have to use the reversing lever. I also use neutral on mine a lot just so I don't have to listen to the geartrain when hand feeding stuff.

I think I have to agree with other suggestions about shopping for a complete 9A or something a little bigger that already has the gearbox and power feed apron. A heavy 10 would be a nice way to get all that, plus a little more swing and stiffness without moving to a vastly larger machine. I got my 10L for a fair bit less than 9A's regularly go for.
 
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