I finally got to use the vector controlled VFD for something practical.
Was turning using the second highest speed on the Hercus and needed to drill a 40 mm long x 25 mm diam hole.
I ran a 6 mm pilot at that speed and then dropped the rpm to 15Hz (190 RPM) and not a problem with the 25mm hole - not even a hint of bogging down.
It's only a 1HP motor.