rossetta stone?

[10] Like what you see?
Click here to donate to this forum and upgrade your account!
This is on my 1916 Southbend Lathe

any idea of what it is decoding?

I am really hoping it somehow is telling me what gears to use and their position to let me cut threads.

now that I have all of these



"am really hoping it somehow is telling me what gears to use and their position to let me cut threads. "

You got it!
Do what it says, one change gear on the stud, the other on the lead screw. Shows the resulting thread pitch. Intermediate gears do not change the gear ratio, as long as they are not compound gears. Intermediate gears do change the direction of rotation.
Tells you how many teeth each gear needs to cut a given thread.

Screw gear is the gear mounted on the end of the lead screw.
Stud gear is gear closer to the spindle.

Note that cutting 8 TPI requires the same number of teeth on each gear. IE it has an 8 tpi lead screw.
to cut 16 TPI the screw gear has twice as many teeth as the stud gear and so on.
This should help the decode.

This pic shows a double gear in the change gear position, make sure both the other gears are using the same gear, as said already, the number of teeth do not matter on that gear. Both gears are used in compounding, namely for doing metric gears. Do not worry about that for now.

Google the "How to run a lathe", there is PDF copies all over the internet. Or watch E-bay for the actual books.

Another good site.

Yours is old enough, it will be more like my South Bend (1930, definitely not a 9a/c). In this thread :


Someone on that thread also linked to Vintage Machinery, where you may be able to find the manual. Using the chart above, and gear placement according to that other ahead (or your manual if you have it), you should have the information you need. As always, I'd suggest making "sure" by chucking up some waste stock or scrap, and trying to turn a thread.
It looks like you may have all the needed change gears if at least one of them is on the lathe. For inch threads, anyway. You will also need transposing gears to do metric threads, probably 127 and 100 teeth. You will need to find, read, and understand a manual to learn some of this.
[5] [7]