In article ,
Roy wrote:
On 30 Jun 2004 17:51:28 GMT, (Charles A.
Sherwood) wrote:

===I recently bought a used rockwell mill. There is no drive pin in the
===spindle that is suppose to engage with the R8 collet. My other mills

[ ... ]

All the indexing pins, thats what it actually is and serves onbly that
purpose and thats to index the tooling........were removed from all
the machines in the USArmy machinist tech school, for no other reason
other than to eliminate a screwed up spindle or collet if a student
crashed the mill. An R-8 collet / spindle setup is self locking by
design, and the pin serves no part in driving it or keeping the collet
from rotating.

Well ... where it helps, really, is when loosening or tightening
the drawbar. It keeps the collet and drawbar from rotating as a unit,
without you having to stretch one hand up high to wrench the drawbar
while the other is down at the collet, holding it and the took in the
spindle firmly enough to keep it from rotating under the influence of
the drawbar.

But -- aside from that, it is not really necessary.

I've seen in the MSC flyers from time to time a tool which has
three flanges on a handle, to allow you to hold the collet from rotating
more easily (without a tool in it), or to allow you to unscrew the
collet from the spindle (without an index pin being there). The flanges
fit into the three radial slots on the collet's end, to allow you to
either rotate it or to stabilize it.

I think that this tool is intended to be used on CNC machines
where the collet is tightened by power assist.

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.

The larger lahte (12x24" Clausing) does have such a pin in the
(5C) collet adaptor, which is helpful while I'm at the other end of the
headstock, screwing the drawbar down to the right point where the lever
will lock it. For *that*, I am glad to have the indexing pin.

Enjoy,
DoN.

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