In article ,
Interious wrote:

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?
Dave

The 5616, the 2.25 HP VS bigger brother of the 5615 (I own both) is
barely adequate for thr 3/4" r bit... depending on material.
The variac does nothing for 'speed' as such, it just makes it weak,
which is fine for a light bulb.
You will seriously affect the 5615's ability to cool itself as well.