Bingo. As in, with the 32 tooth gear on, and everything else set for
20 TPI, putting the 16 tooth on would reduce the feed rate to 40 TPI.
Sounds like maybe an attempt to come up with a "sorta" quick change
box without ****ing someone elses patent lawyers off. I'd have to
look at the chart again, but it's possible that it's set so for any
given range of threading, one gear would give the three most common
multiples used in that range.

One thing that makes the old machines so interesting, for any given
function, there must have been at least 100 different ways to do it,
and all of them have been patented and marketed, the designers
convinced that their way was "unique and genius". They all boiled
down to the same thing, keeping a given ratio between turns of the
spindle to turns of the lead screw. Beyond that, it's all just
avoiding stepping on someone elses toes.

The amazing thing is the amount of tooling you got with it. Not usual
to see something this complete. Especially as a freebie. (Well, what
you didn't pay in money, you'll pay in labor.)

It's getting less amazing the more I look at it. Of the massive quantity of
gears that came with the lathe, only two fit. The rest, including a full
matched set on a rod, are the wrong pitch and/or the wrong bore and/or width. I
think whoever gave this machine to the guy I got it from cleaned out all the
orphan tooling and parts and said they went with it.

Looks like I'll have to see what these gears _do_ fit and start dealing.

GTO(John)