Re: [CAD_CAM_EDM_DRO] turning loooonnnnng skinny tapers.

Hi Chris:
Sounds like you are trying to imitate the action of a Swiss automatic,
in which the stock is fed forward through a bushing and the tool is right up
against the front face of the bushing.
2 things I know about this kind of setup:
1) the stock is almost always centerless ground to tight tolerances and is
fed through a carbide bushing with pressurized heavy oil as a lubricant for
the bushing. (to prevent seizing just as you fear may happen with your
setup). Clearances are typically less than 0.0005".
2) the quality of the job can almost always be improved by mounting the tool
upside down on the back of the slide so the turning forces tend to lift the
cross slide up against its dovetail and stabilize it. An overload condition
will tend to disengage the tool as well.

In the absence of this kind of setup, I would do the following:
Definitely go with pressure lube through the bushing.
This shouldn't be too difficult to arrange with some heavy cutting oil and a
pressurized canister.
All you want is a steady trickle through the bushing, not a hundred gallons
a minute or anything like that.
Gonna be a helluva mess to clean up afterwards though!!!
Make the bushing adjustable as you describe to get around the bushing
clearance issue.
Consider also, as an alternative, a 3 bearing travelling roller steady that
you can adjust to zero clearance on the stock. A heavy spring on one of the
legs will accomodate for variations in the stock diameter along its length.
The side load will be murder on the bearings though.
Consider 303 stainless as a possible material choice: You can get it
precision finished, and it turns nicely without much effort. It's a bit more
ding resistant than 12L14 and, of course, doesn't rust.
Hope this gives you some ideas.
Please let us know how you make out; this is interesting stuff even though
it isn't directly connected to CAD CAM EDM DRO topics.

Cheers

Marcus