On 3 Dec 2004 00:37:40 -0500, (DoN. Nichols) wrote:
snip
For onesy-twosy work, you would single-point it on a lahte,
which means (if you get a Taig) that you need to investigate Nick
Carter's mod which gives it threading capability.

Normal taps and dies are difficult to start square without some
kind of machine support helping you. You *could* have any special tap
and die made for you by the companies which make them, but it would cost
you quite a bit, and you still have the problem of getting them started
straight. And if you don't get them started straight, you have lens
elements tilted relative to the axis of the equipment, thus offering
optical abberations.

I think that if you are going to be doing much of this sort of
thing, you want to look for a dual-system lathe, with threading setups
for both Imperial and metric threads. (To do this properly means two
leadscrews with matching threading dials, and two quick-change gearboxes
to provide the proper ratios for the different systems.)

It is possible (with a set of transposing gears) to cut metric
threads on an Imperial machine or vise versa, but it will be a serious
pain, as you can't disengage the half-nuts until the thread is complete,
with however many passes it requires.

So -- while I have the Metric transposing gears for my Clausing,
as long as the size can be handled by my little Compact-5/CNC, I will
use it for metric threads, as all I need is to flip a switch to change
systems. (And even then, the 0.800" x 0.5mm thread would require
setting it up for metric threading, and converting the 0.800" to mm
before programming the machine.)

If I recall correctly, there was something called a Frog which could
control a Taig, and would do threads under program control. Yeah,
here it is http://www.avatartools.com/Merchant2/merchant.mvc

I considered trying that, but wound up getting another lathe with
threading capabilities before I ever pulled the trigger on purchasing
a Frog.

I kept the Taig, and still use it for a lot of little fiddly projects. It is
excellent for small work. But threading jobs go on one of the other
lathes, or get handled by taps and dies.

Adding a Frog still looks like an attractive way to upgrade a Taig to
1 axis CNC. With 2 Frogs, you could do 2 axis CNC (the Frogs can
talk to each other, so interpolated taper and radius turning would
be possible in addition to fully automatic multipass threading).
At $199 each, that's starting to cost real money, but it is still a lot
cheaper than most CNC retrofits.

Gary