In article ,
Harold & Susan Vordos wrote:

"DoN. Nichols" wrote in message
...
In article ,
snip-.

Of course, none of my milling machines have such an index pin,
because one uses 30 taper, one uses 40 taper, and one uses ER
double-angle collets, none of which have such key slots.

It's been years since I last ran a mill with a 50 taper, but I recall that
even they have keys, only in this case they are drive keys.

Yes -- *drive* keys -- not index pins to keep the collet from
spinning while you tighten the drawbar. :-)

Large mills
are capable of turning large cutters, so they can easily overcome the taper
drive. The #50's with which I was familiar were used in spindles on
Cincinnati, Van Norman and K&T mills. The shoulder at the large end of the
taper had opposing slots that accepted hardened drive keys that were a part
of the spindle. Do your holders have such slots?

The Bridgeport BOSS-3 (Series I) has the 30-taper Erickson
spindle. The holders have the slotted flange, and this is used (in
place of a drawbar) to both index (with 180 degree out possible) and to
draw the taper up firmly. (A set of rotating ears fit through the slots
as well as the keys. When you rotate the locking collar, the rotating
ears swing over the flange and tighten against it to draw it in.

There are times (like with a boring/facing head) when I would
feel more comfortable with a drawbar. :-)

The Nichols mill (40-taper) is a bit different. What it has is
a pair of threaded holes for large Allen head cap screws to act as
drivers, and the official 1" arbors (and presumably other sizes) are
cross-drilled with about a 0.300" drill rod inserted through it, with a
set screw at right angles to keep the two ends equidistant from the
surface of the arbor. However, the Allen head cap screws will serve as
driving lugs for the slotted flanges as well -- and even for CAT-40 end
mill holders -- once you heat them to soften the Loctite, unscrew the
draw stud, and machine up a replacement neck with internal thread to
accept the standard drawbar. (I have done this with a couple of them
from eBay auctions in sizes which I could not find with the standard
flange.

Of course -- these *are* drive flanges, while the index pin for
an R8 has nowhere near the strength if you manage to overcome the
taper's friction drive. It will probably shear off in a hurry.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---