Seneca falls lathe threading gearbox question

I have a Seneca falls star lathe, it's getting very close to its 100th birthday but I am here to figure out on the threading plate it has an adjustment called a stud and it says 48in, 48out, and 24out. I don't know what or where this stud is I just finished mounting a new motor, the previous one was gravity tensioned and caused major waves in the surface finish. But yea I need to machine an internal thread for a dividing head so I can mount a chuck

and what I'm asking is what the difference is between 48in and 48 out. I know that it is in 48 out because of the threads it cuts.

End gears - on the way down to the QC gear box - sounds like there is a 48 tooth that can be pushed in or pulled out for making differing ratios

Usually the "stud" was the first gear below the reversing tumbler gears

Lodge & Shipley had a similar arrangement and referred to it as a "SLIP" gear

The difference is double or 2 to 1 - as can be seen by 5 3/4 and 11 1/2 TPI on your photo

The only SF I was around was a LO SWING that weighed about 25,000 lbs

Thanks, next time I'm in the shop ill take a look and see what I see

My 1907 Flather (with the Norton Style change gears) had a similar layout.

The "stud gear" (so named) was an intermediate gear between the gear driven by the lathe spindle (as John says above for you the gear-shaft driven by the forward-reverse tumbler gear set) and the lead screw spindle.

In most "loose change gear" lathes the gear train plate would indicate a TPI (threads per inch) and gear entries for "spindle" and "screw" - meaning the gear to be placed on the spindle and lead screw. NO gear specified for the stud position because the stud was an extension of the "banjo" which was an adjustable bracket made to take ANY size stud gear and bring it to engagement between the two other gears.

It was generally understood among lathe operators of that era that ANY gear not otherwise used in the gear train could be used as stud gear - as long as it made up the difference between spindle and screw. It was common to use the largest diameter available loose gear as that afforded the greatest adjustment - and widest range of TPI.

Hence also the modern business expression "He was the stud gear (i.e. boss) - everything turns around HIM."

A further refinement was made on certain lathes by making the stud gear such that TWO gears could be used in the stud position such that the two gears were arranged to turn together and afford a way to get compound gearing - thus doubling the possible TPIs from a given gearset.

A further refinement on this was made for the Flather. On this a single stud gear was arranged with TWO positions and TWO matching gears on BOTH spindle and screw - by this one needed to simply slide the stud gear "in" or "out" to thereby double the gearset possibilities for TPI. (There may be some adjustment of the banjo in this.) Many lathes manufacturers did this after common adoption of quick change.

Hope this helps. Examine your gear train carefully for gears with broken teeth. Given the many adjustments and in the expediency of time, lathe operators would often make quick-change gear set changes "on the fly" - including the stud gear position - and thereby risk clashing the gears and breaking a gear tooth. A situation which may or may not translate into irregular action of the gear train. A single broken tooth is frequently not fatal - but may result in some clicking in operation or irregular feed which shows in your cut threads.

Joe in NH

Thanks, that makes sense. I should get home at a reasonable time today so I can have a look at the gears. Is that really where the phrase of being a stud comes from? Hahaha