"john johnson" wrote in message . au...
"Charles A. Sherwood" wrote in message
...
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
do have drive pins. Is this a problem that I need to fix??
I seem to remember this question before and it might be ok??

thanks
chuck


Hi Chuck,
When I got my used Bridgeport clone, I couldn't afford the
tooling, so I made some R8 blanks up at the local tech colledge as part of a
cnc course I was taking. The instructor asked me how I was going to mill the
slot for the drive pin. I told him my machine didn't come with one. He told
me I'd better get it back in there, as he had seen an accident where the R8
arbour had slipped, and tightened the draw bar to the point where it had
broken, shooting it out of the top of the machine.

One of the blanks became a 6'' dia fly cutter, and I've always wondered if I
should have taken his advice, or if he was pulling my leg. Seems to me that
as the arbor slips it will tighen the draw bolt, and I imagine this will
stop the slip well before the UTS of the drawbolt has been reached. Also, if
that much torque was present, I couldn't see how the pin would hold it
either, so I didn't replace it. So far no problems in 15 years.

regards,

John

He was obviously bull****ting you, because if the drawbar was that
tight, it would have stopped the collet from slipping.
M.K.