Fastest1,
1. The most reliable Kernel speed is 25000HZ. Hood posted a nice write up by Art on the matter some time ago. Kernel speed can limit your vlecoity
and you can easily see the effect just by changing the kernel Speed to something higher and noting how how much more you can increase the velocity in motor tuning. That dosen't mean nothing if the system can't take advantage of the higher kernel speed.
2. Machining metal - There are general recomended speeds and feeds based on historical testing and also studies that have been done over time.
What is recomended is based on chip load, spindle rpm, coolant type, cutter type , cutter material, etc and then basicaly you can derive the hosrepower required to accomplish the machining, Of course surface finish and other things come into play.
So what i am saying is that even if you can use a high kernal speed to up the IPM it may not mean nothing if the increased speed is not applied
appropriately to what you want to machine.
3.Given some set of conditions ,such as torque to speed as defined by a motor curve, the electrical conditions such as how motors are wired and available voltage, etc can have a big affect on velocity / feedrate of the axis.
In summary, 1,2, 3 above are all interelated and one needs to keep each in perspective.
FWIW,
RICH