Feed rate, denoted as Fₙ is the speed at which the cutting tool moves through the material during machining. It is a fundamental parameter that directly impacts material removal rates, surface finish, tool wear, and overall machining efficiency. Feed rate is typically measured in units of distance per unit time or distance per spindle revolution, depending on the machining process and the type of machine being used.

In milling operations, Fₙ commonly refers to the feed per tooth, measured in millimeters per tooth (mm/tooth) or inches per tooth (in/tooth), while in turning and drilling applications, it represents the feed per revolution (mm/rev or in/rev). The overall feed rate F (mm/min or in/min) can be calculated using:

where:
- FFF = total feed rate (mm/min or in/min)
- FnFₙFn = feed per tooth or per revolution
- ZZZ = number of cutting edges (flutes) on the tool
- NNN = spindle speed (RPM)
Feed rate is influenced by multiple factors, including tool geometry, material properties, spindle speed, depth of cut, and the desired surface finish. A higher feed rate increases material removal efficiency but can lead to poor surface quality, excessive tool wear, or even tool failure if pushed too far. Conversely, a lower feed rate may improve surface finish but can lead to excessive heat buildup or inefficient cycle times.
Choosing the correct feed rate requires considering the material being machined, the tool material and coating, and the rigidity of the machine setup. Manufacturers often provide recommended Fₙ values for different tool and material combinations, which serve as a starting point before adjustments are made based on actual machining conditions.