Interious writes:

I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?

While a variac is great for fan motors, especially if you go three
phase, it's not a good idea on cutting tools. Go for the variable
speed unit, it will anyway be cheaper then the variac.

--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
Phone: +49 228 73 2447 FAX ... 7869
Physikalisches Institut der Uni Bonn Nussallee 12, D-53115 Bonn, Germany
CERN: Phone: +412276 76461 Fax: ..77930 Bat. 892-R-A13 CH-1211 Geneve 23