Glort, you are talking rubbish. and again becoming hysterical and dramatic.
Smallish Induction motors are designed to run at 50 and 60 cycles for a worldwide market, and a safe percentage above and below. If they are not overloaded, they will happily run on higher or lower frequencies, exactly as happens with variable speed drives.
A generator should NOT vary its voltage significantly when running above or below its stated RPM, this is the job of the AVR. Even if it did, all motors are rated within plus/minus 20 percent constant. voltage , with substantial safety margins.
What issues with the AVR? Are you saying it will burn out attempting to saturate the stator? Another myth.
The sander in question will be powered by a capacitor start motor,as it is not required to have high starting torque, therefore any centrifugal switch is not present. Increased wear on bearings??? Rubbish.
The rotor in an induction motor has shorting bars, not windings, so how can the rotor be "stressed" above and beyond?
Your suggestion of a VFD is ridiculous for such an application, its likely to cost more than the sander.
The gentlemans query was to slow run a cheap sander easily and presumeably cheaply I believe.
This also implies intermittent use of the appliance anyway..
You are very quick to have an opinion on stuff you know very little about.... google does your thinking i suspect.
Yes, I can demonstrate this, I do this frequently with my drill press, but I wont....... your incessant need to be right, you will poo poo any demonstration and start a slanging match, as you have so done before, and attempting to do now.