On Tue, 29 Mar 2011 23:02:59 -0400, "Wild_Bill"
wrote:

The add-on fixturing plate gives you lots of options that a bare faceplate
doesn't offer (without more drilling of the faceplate, anyway).
A thicker fixturing plate would provide more workholding alternatives
without extending the workpiece as far from the spindle bearing that a
full-sized chuck would likely cause.
I think the faceplate solution saved you a lot of grief as far as minimizing
the potential for chatter, by keeping the workpieces close to the headstock
bearing (especially since the lathe doesn't have variable speed).

Today I did the crucial second piece and learned more about the
process. As far as chatter goes there is a trade-off: Not getting
close enough to the work-piece makes the *tool* chatter. I could not
understand why I did not have chatter problems doing the ID on the
previous piece and could not get rid of it this time. Then I shortened
the (identical)_ boring bar as much as I could, running the plate
really close to the carriage, and voila! All was well.

Complexity and expense nearly always enter into the equation for
convenience, it seems.. but hey, it's for the enjoyment of metalworking.

Road with many curves leads to sheep losses (don't ask! :-)

I haven't used double-sided tape for workholding, although I've seen that
it's a fairly common method.. but I think I'd feel more confident with
mechanical fasteners retaining the workpiece.

Second piece held fine even as I got bolder with the depth of cut. I
did not even clamp this piece like the first one (the strength of the
adhesion of a double-sided sticky tape is given by the pressure
applied to the bond). I still had to heat it up with a heat gun to get
it off.

For the ultimate in precision (typically not my goal), having the workpiece
securely seated on a (clean) metal surface would insure that the workpiece
is precisely flat against the fixture plate/reference surface.

The tape is about 0.003" thick. Well beyond my requirements for
accuracy.

I did notice your excellent safety bar approach.. inexpensive and practical.
A soft tip on the end would ensure that the bar doesn't affect the spindle's
internal taper, in the unlikely event of an Oh **** incident.

The end goes nowhere near the spindle - just inside the opening. Like
yourself I did not want to risk spindle damage.

With other workholding methods, centering shouldn't be an issue with the
shoulder of the fixture plate recess to accurately center the rings,
otherwise, adding a disk/ring in the ring I.D. area for other fixture plates
may work well.

I don't recall at which stage of the process you're finishing the I.D. of
the rings.

AT this point it goes like this:

1) Turn OD to precisely 5.400"
2) If one side of the ring is reasonably flat, fix in the recessed
plate
3) Turn ID
4) Face off

2a) If neither ring side is reasonably flat (and there is a reason to
believe that it would not hold with the double-sided sticky tape) face
off in 3-jaw as far as possible
3a) Manually remove any excess metal near the ID which would prevent
it from seating in the recess (this may not be necessary in future as
I am turning a sort of "recess within recess" while I am boring the
ID)
4a) Proceed with (2)

Michael Koblic,
Campbell River, BC