On 2008-02-11, Joseph Gwinn wrote:
In article ,
"DoN. Nichols" wrote:

[ ... ]

Nope! You don't rotate the holder -- you set it up with one
side parallel to the face of the chuck, and the second parallel to the
axis. The third is towards the tailstock end of the lathe, and is used
when you need to work closely to a live center in the tailstock, or to
produce a step facing towards the headstock. I don't have that one, but
I would like to have it as part of the collection.

Is this approach universal? A toolpost maker will be trying to
accommdate all customers, even the misguided.

It is the way the CNC pretty much must be, since you can't be
changing the toolpost angle in mid program without losing your zero
points. Of course, bevels and chamfers are cut under CNC control, not
by off-setting a (non-existent) compound. Actually, there is a plate
which takes position off the spindle face or some workpiece chucked in
the chuck to guide the orientation of the toolpost.

And when I use the tool turret on the Compact-5/CNC, the QC
toolpost and its plate are removed from the cross-slide, and the
motorized turret bolts in place of the combination.

It is also the way that I use my Phase-II Aloris BXA clone.
Whenever I shift the compound, I re-zero the toolpost to be parallel
with the spindle axis and the chuck face.

However, there is another interesting toolpost which has a
cylindrical OD which has a ground surface which looks like a bunch of
dowel pins merged together, and the tool holder has a mating set of
female cylindrical shapes. A pair of hooks grab the two sides and pull
the holder into firm contact with the post. IIRC, the virtual dowel
pins are such that you get 15 degree increments on position. So
obviously, this lets you set the angle of the tool without disturbing
the setting of the actual toolpost, so you can retain a zero set to be
parallel to the axis and/or the chuck faceplate.

But with the Aloris style toolpost, I like having a collection
of tools to cut the various angles while leaving the toolpost set
parallel.

It obviously cannot be *universal*, as you were preparing to
shift the toolpost to get angles, so many others probably do so as well.

But I like the reliability of getting an indexable insert tool
back to the same position each time, so I don't have to constantly
re-zero the dial on the cross-slide crank.

[ ... ]

The only time you should have to unclamp the toolpost and change
its angle is when you loosen the compound and set it to a new angle, at
which point you should reset the toolpost so its faces are parallel to
the references surfaces again.

This is entirely unlike the usual operation with a lantern style
toolpost where you are constantly adjusting the tool angle.

[ ... ]

What I would suggest is that once you have your pin in service,
set the compound to the various common angles (29-1/2 degrees left and
right for normal threading, 60 degrees left and right for chamfering,
and perhaps 14 degrees left and right for acme threading) and drill
holes for the pin matching each of these, so you can more quickly set
the toolpost to the proper angle when changing the compound setting.

Sounds like a good idea, although the angles cannot be too close
together or the pin holes will overlap. The pin center is 1.000" from
the pivot axis, and the pin hole is 0.272" in diameter, which subtends
an angle of 15.22 degrees. So, 29.5 degrees ought to work.

O.K. 0, +/- 29.5, +/- 60, and if the plate can be lifted a bit
and rotated 180 degrees to provide a new working area, a separate set for
the +/- 14 degrees for Acme threads should work.

No easy place to put such a pin through the Phase-II BXA sized
toolpost -- the coarse threaded drum which moves the wedges up and down
doesn't leave the clearance. But perhaps you could drill the corner
opposite the two dovetails on a piston style post -- I'm not sure how
large the cam cylinder is.

Of course, there could be a shallow hole for the pin in the
bottom of the post, but then the post would have to be lifted enough to
clear the pin when rotating it.

BTW I took a look at the underside of my EMCO (Dickson style) toolpost
today and find the taper was a lot smaller than I had
remembered. It looks something like this (set font selection to
a fixed-pitch font like Courier to avoid distortion of the
image):

+------------+ +-----------+
| | | |
| | | |
| | | -------- | ------ bore for hold-down rod
| | | |
| | | |
| __| |__ |
| / _ \ |
+--------+ |\ +-------+
\
----- ground and polished tapered hole.

and the washer at the top has a step to drop into the bore size and keep
the screw (a big metric Allen screw) fairly centered.

Obviously, I've left out the details like the V-ways and the T-studs
operated by internal cams, as they are not necessary for what I was
showing.

I've got to bring that toolpost and the bevel protractor up here
where it is warm to try measuring the angle of the taper so i can
duplicate it.

I'm not visualizing this above. Is the recess all taper, or is there a
cylindrical part?

O.K. The view is from the middle of the operator's chest. The
tapered hole is at the bottom, and the straight cylinder is going
through most of the rest of it. The V-ways are to the left and away
from your view on the other side.

There is no cylindrical part of the taper itself. There is a
slight bevel at the bottom. Then there is the much reduced bore for the
hold-down rod or screw.

On my toolpost, there is a similar recess on the bottom, centered on the
hole that accepts the 5/8-18 clamp rod. This recess is tapered, and
then cylindrical, and the cylindrical part accepts a 1.5" diameter
collar. The recess is not ground to precise shape. In any event, the
collar I just made will go between this recess and a similar one to be
machined into the ridged plate.

O.K.

BTW -- while I had the toolpost up here and warm enough to
handle, I took apart the cams and T-studs and cleaned and re-lubed them.
In the process, I looked it over thoroughly, and found no signs of any
hole for a pin.

I guess that I could put the thing to my Rockwell hardness
tester to see just how hardened it is, but I expect it to be pretty
hard. I also don't know whether it is a case hardening or full through.
It all depends on the metal, I guess.

FWIW -- the toolpost (for size comparison) is 40 mm (39.97mm)
high, and 57.21mm front to back and side to side. (Note that mine has
only left and boring ways, not the right hand set which you apparently
have.

The main bore is 17mm (16.95mm) diameter. The taper at the
bottom is 9.18mm deep to the step, 19.93mm wide at the full depth, and
20.12mm just a bit below the surface of the bottom (the bevel makes it
hard to get the true diameter at the bottom.

Enjoy,
DoN.

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