Hey Carl and Lynn, hey JDog, hey all,
By the way only an induction motor on a VFD (“spindle”) will hold the set speed nearly perfectly independently of mechanical load, up to its power limit, and if you exceed its power limit, the VFD will simply trip and with a correct emergency stop wiring, this will also stop the CNC program (to avoid breaking the bit). On a hand trim router (a carbon-brushed universal motor), you can set a speed according to the table in the manual, but (besides the fact that its rated wattage/hp does not correspond to the effective power on the shaft (with a spindle it should), and this motor type’s much poorer efficiency so is comparable only to a spindle with far less watts/hp than written on its package/homepage), as the mechanical load will slow it down and the more you reach its power limits, the hotter it will get and if you exceed its power limit, you have the danger of damaging it because of excessive heat (up to burning up).
So I think you’re right with assuming that with a spindle that produces 2.2 kW mechanical power at its shaft you can do a lot of depth of cut and width of cut more, thus more material removal rate, than with the router. I think with such a spindle, the bottleneck is then the machine rigidity and not the motor (unlike with the Makita hand trim router, which is the bottleneck then)