Joseph Gwinn fired this volley in news:joegwinn-
:

They don't have to be pretty to work, but
should approximate a the slope-sided flat one sees on endmill bits.

Iggy, the "slope-sided" ones are variously called "safety flats". If a
flat is ground - well - _flat_, then when the setscrew loosens a bit, the
bit can creep free of the collet, unless the flat has a "stop" near the
butt of the bit.

When a taper is ground into a flat with the taper moving toward a larger
diameter closer to the butt of the bit, then any creep tends to snug up
against the setscrew again, lessening the chance that it will remove
itself. It also will make the bit loose in the Z-axis if the setscrew
creeps out. But that's better (for safety) than having the bit fly out
under power.

Such has long been used on woodworking equipment, although I seldom see
it on metalworking machinery.

If you have the tools, and are willing to carefully mark out your work,
you can cut a vee-groove "flat" to engage the setscrew. This will
essentially lock the bit in place, while minimizing the Z-axis looseness
if the setscrew backs up some.

LLoyd


LLoyd