I've been trying to follow up on details of some suggestions.

Regarding the threads in lens holders in eyepieces, the use of collapsing
taps seems to be prohibitively expensive, although in searching for them
the collapsing taps I've found don't seem to be for that range of sizes.
On the other hand, one doesn't have to make them exactly the way they are
made in commercial products. One reason given for the odd sizes was so that
other things don't get screwed in by mistake. For making my own, I probably
don't need to worry about that. There might still be a reason one wants
very fine threads. One thing that occurred to me was that maybe by making
multiple threads, one could achieve the same fineness. Alternatively, by
using CNC one might just be able to tell the lathe exactly how to cut the
threads.

Hence, regarding CNC: it was mentioned that Nick Carter has some device called
a Frog for upgrading a Taig lathe to CNC for about $200. I'm not sure what
assumptions are made regarding the configuration about the Taig nor what
assumptions are made regarding the computer to which the Frog is supposed
to be able to be connected, if one wants to connect the Frog to a computer.
To take an extreme example, suppose I find a vacuum cleaner discarded on
the street and perform a motorectomy on it and order the K1019 deal at
http://www.taigtools.com for $144.50 and one Taig Frog for $199 from Nick
Carter. Then for a total of $344, more or less, I have a lathe and a Frog,
but it's not clear to me whether there is enough Taig there to use the
Frog with it. Obviously, one can't have the Frog tell the Taig to do stuff
that requires a tailstock, but there are things one can do without a tailstock.
(More on this below.) As regards the computer, will the Frog work with the
computer if it is a PC running some version of RedHat Linux (as mine is)?

I haven't taken any courses on lathes. I happened to read Joe Martin's book,
Tabletop Machining, and I read Gingery's book, The Metal Lathe, and I have
version 55 of the South Bend Lathe Book, from around 1958. In particular,
Gingery shows you the lathe in various stages of completion and how to
use it to bootstrap the rest of the lathe. So, I compared the parts list
at http://www.taigtools.com/mlathe.html with what I found in Gingery's book,
not too meticulously, but enough to give me some idea. The part list of the
Taig Micro Lathe II kit mentions a bed but doesn't mention anything about
ways. I think I'm supposed to realize that the bed includes the ways.
In the Gingery lathe, there is a lead screw. I'm not sure but I think the
analogous part for the Taig is 100-09, which is the carriage rack (there is
also a pinion gear, so I think I am still within bounds of the subject
"rack and pinion"). On p.100, Gingery writes: "At this point, you have
built a lathe that is as complete as some that are sold commercially.
If you have been in the market for a lathe very long, you are not surprised
to learn that some lathes are sold without a tail stock. I could hardly call
a tail stock an accessory, as some do, but the partially finished lathe can
do many jobs now." Gingery declines to say what the jobs are that the
partially finished lathe can do, but How to Run a Lathe says: "Work that
cannot readily be mounted between the lathe centers is usually held in a
chuck, as shown above, for machining." I assume that is meant to include
the case where there is no tailstock. It goes on to mention, specifically:
(1) taper turning with a chuck and compound rest and (2) cutting screw
threads with a chuck and compopund rest, using gears that connect the
headstock spindle to the lead screw." Maybe there are other things and
maybe more can be done using the Frog with it, but I don't see it clearly.
For example, I'm not sure what, in the case of the Taig, would take the
place of the gears that engage the screw thread to achieve (2).

Regarding the motorectomy, I'm reading the book, "Fractional horsepower
motors: use, selection, operation, repair and maintenance", by Rex Miller
and Mark Richard Miller. I'm about 100 pages into the book and a lot of
just goes past me, but it has already discussed removing and repairing
a vacuum cleaner motor. The book lists a lot of tools and parts one needs
to get involved with motors, probably adding up to a significant investment,
but I think the authors are assuming that anyone who reads the book is
probably giving at least some thought to opening up a repair shop. What
one actually needs just to scavenge one motor from a discarded vacuum
cleaner for use with a lathe is probably not much.

Incidentally, the micro lathe parts diagram and parts list at the Taig
site seems to have a small typographical error: there is a part in the
parts diagram labeled 100-28 but there is no such part in the parts list.
--
Ignorantly,
Allan Adler
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.