What is spindle speed?
The fetched Omni spindle speed page defines spindle speed as the rotational speed of the spindle in rpm. It directly affects surface finish, tool life, and how aggressively the cut proceeds.
Spindle speed and feed rate formulas
Ns = 1000 x V / (pi x D)
Fr = Ns x Ft x Z
Here V is cutting speed in m/min, D is diameter in mm, Ft is feed per tooth in mm, and Z is the number of teeth.
Source example
Omni's example uses a 20 mm workpiece, 5 m/min cutting speed, one tooth, and 10 mm feed per tooth, resulting in 79.58 rpm and 0.7958 m/min feed rate. Those values are loaded by default.