For turning, it is common to use Constant Surface Speed (CSS) such that the spindle speed depends on the diameter of the stock (for milling tools, the surface speed only depends on the RPM and tool diameter).
When using Constant Surface Speed, Inventor HSM presents the feedrates for the given stock diameter.
Example diameter used for calculating spindle speed and feedrates when using CSS (Constant Surface Speed)
The surface speed and the feedrate parameters are automatically updated when the stock diameter is changed.