"Upscale" wrote

Not familar with spiral milling cutters. Are they some type of upcutting
bit? What advantage would one be over a standard 3/4" router bit?

A router bit does not cut at the center of the bit, and as mentioned, they
do not lift the chips out of the hole.

I would use a forsner style drill bit, shortened, if need be, and turned
down by a machine shop to fit your _variable-speed_ router. It could be
a good idea (depending on the design of the bit) to modify the cutting angle
of the face to only be a few degrees so it will not try to feed too fast and
over-load your router.

I think this setup would make a more precisely dimensioned and smooth set
of holes than an end mill cutter, and be less likely to clog up with chips.
--
Jim in NC