Hi technicrdd,
the maximum speed the motors can run are set up under config, motor tuning,at least that's the way I set mine up in mach3.
So if you set up your x motor to go 30 inches per minute, then even if your g code is f50, the motor will max out at 30ipm's.and mach will keep track of the correct distance it travels, even if the program wants to run faster.
If the unit/min set to 1 , the feed rate will be 1 inch per minute, (very slow.) When trying out new motors, start at 5 or 10 unit/min and keep increasing it until it starts faulting (missing steps) , then back that speed back 10%, to give you a reasonable speed that doesn't keep faulting every time you rapid across the mill.
Hope this helps,
Glenn
Ah, Chaoticone beat me to it, while I was typing but here's mine for what it's worth