In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

Joseph Gwinn fired this volley in news:joegwinn-
:


And, it does a bad job on the sheet metal. Solution is a Unibit.


Even a BFB of a drill bit will do a fine job if the spindle is rigid and
the work is rigidly mounted. It can't make anything but a round hole if
nothing moves.

Those epicyclic triangular holes you get are from relative motion between
the drill bit and the work.

True enough, but the edges still tear. Unibits are still easier. I use
them to drill thick stainless steel sheet, with lots of pressure and
lots of black sulfur oil, and it works a treat.

Joe Gwinn