Have a look at the motor curve....if one is available for your particular motor. It will provide a torque to motor pulse /rpm curve based on some voltage and also for different wiring of the stepper.
From that you pick where you will have the most power or where you will be on the curve. That tells what can be expected in terms of torque to motor rpm. You need to relate that to your intended use of the machine. You have what you have and cannot compare to someone elses machine and can only do so much. Speed is useless if there is no reliability.
Now if you were starting from scatch, you define the intended use of the machine and design accordingly.
IE; - define the desired axis feedrate / IPM
- define the desired resolution
- define the cutting that will be done
- find a motor which can provide for the above ( a stepper may not work and you need to go to a servo )
- based on the above, check that the other parts of the system ie; computer, power supply and drive are correct for the application
All the above may not work so it becomes a compromise of them all.
Have a look at this for a flavor of the above:
http://www.machsupport.com/forum/index.php/topic,12484.msg80824.html#msg80824There is nothing wrong with duplicating someone's machine that is very similar to yours but one needs to understand any differences between the machines and how it
may affect your outcome.
RICH