I've cut a few 4" conduit holes in industrial control boxes with a
Starrett hole saw in a large Milwaukee D-handle drill. The holes were
in side walls so chip clearance was no problem. I had to wedge myself
against the opposite wall of the enclosure to get enough force on the
hole saw to make it cut well, and whenever the saw grabbed the handles
were guaranteed to make a quarter revolution while the motor coasted to
a stop, regardless of which part of me was in the way.

jw