Calculate Feed Rate for Turning in CNC Programming Easily

To calculate the feed rate for turning in CNC programming, multiply the feed per revolution (f) by the spindle speed (N). The formula is Feed Rate (F) = f × N, where F is in mm/min or inches/min depending on units.

Syntax

The feed rate for turning is calculated using the formula:

F = f × N

• F: Feed rate (mm/min or inches/min)
• f: Feed per revolution (mm/rev or inches/rev)
• N: Spindle speed (revolutions per minute, RPM)

This formula gives the linear speed at which the cutting tool moves along the workpiece.

plaintext

F = f * N

Example

This example calculates the feed rate for a turning operation where the feed per revolution is 0.2 mm/rev and the spindle speed is 1500 RPM.

python

feed_per_revolution = 0.2  # mm/rev
spindle_speed = 1500       # RPM
feed_rate = feed_per_revolution * spindle_speed
print(f"Feed Rate = {feed_rate} mm/min")

Output

Feed Rate = 300.0 mm/min

Common Pitfalls

Common mistakes when calculating feed rate include:

• Mixing units: Ensure feed per revolution and feed rate use consistent units (mm or inches).
• Using spindle speed in the wrong units or forgetting it is in RPM.
• Confusing feed per revolution with feed per tooth (used in milling, not turning).

Always double-check units and the type of feed value used.

python

feed_per_revolution = 0.2  # mm/rev
spindle_speed = 1500       # RPM
# Wrong: Using feed per tooth instead of feed per revolution
feed_per_tooth = 0.05      # mm/tooth (incorrect for turning)
feed_rate_wrong = feed_per_tooth * spindle_speed
print(f"Incorrect Feed Rate = {feed_rate_wrong} mm/min")

# Correct calculation
feed_rate_correct = feed_per_revolution * spindle_speed
print(f"Correct Feed Rate = {feed_rate_correct} mm/min")

Output

Incorrect Feed Rate = 75.0 mm/min
Correct Feed Rate = 300.0 mm/min

Quick Reference

Parameter	Description	Units
F	Feed rate	mm/min or inches/min
f	Feed per revolution	mm/rev or inches/rev
N	Spindle speed	RPM (revolutions per minute)

Key Takeaways

Feed rate for turning is calculated by multiplying feed per revolution by spindle speed.

Always use consistent units for feed per revolution and feed rate.

Spindle speed must be in revolutions per minute (RPM).

Do not confuse feed per revolution with feed per tooth in turning operations.

Double-check calculations to avoid tool damage or poor surface finish.