Feed Rate Calculator Formula
Understand the math behind the feed rate calculator. Each variable explained with a worked example.
Formulas Used
Table Feed Rate (Vf)
feed_rate = feed_per_tooth * num_teeth * spindle_rpmFeed per Revolution
feed_per_rev = feed_per_tooth * num_teethVariables
| Variable | Description | Default |
|---|---|---|
feed_per_tooth | Feed per Tooth (fz)(mm/tooth) | 0.1 |
num_teeth | Number of Cutter Teeth (z) | 4 |
spindle_rpm | Spindle Speed (N)(RPM) | 1000 |
How It Works
Milling Feed Rate Calculation
The table feed rate determines how fast the workpiece moves past the cutter.
Formula
Vf = fz x z x N
where fz is the feed per tooth (chip load), z is the number of cutting teeth on the milling cutter, and N is the spindle speed in RPM. The result is the linear table feed rate in mm/min.
Worked Example
A 4-flute end mill at 1000 RPM with 0.1 mm/tooth feed.
- 01Feed per revolution = 0.1 x 4 = 0.4 mm/rev
- 02Table feed = 0.1 x 4 x 1000 = 400 mm/min
Frequently Asked Questions
What determines the optimal feed per tooth?
Feed per tooth depends on tool material, workpiece material, cutter diameter, and depth of cut. Typical values: aluminium with carbide 0.05-0.20 mm/tooth, steel with carbide 0.05-0.15 mm/tooth, cast iron 0.10-0.25 mm/tooth.
What happens if feed rate is too high?
Excessive feed causes poor surface finish, tool breakage, machine overload, and potentially inaccurate dimensions. Tool chipping is common with excessive chip loads.
What happens if feed rate is too low?
Too-low feed creates rubbing instead of cutting, generating excess heat and causing work hardening of the surface. It also wastes productive time. Each tool-material combination has a minimum practical feed.
Ready to run the numbers?
Open Feed Rate Calculator