This cutting speed and RPM calculator for machining relates spindle speed (N), cutting speed (V) and diameter (D) using V = πDN/1000. Enter the diameter plus either the speed or the RPM to find the other.
Cutting Speed & RPM Calculator
Formula
V = π D N / 1000 • N = (V × 1000) / (π D)
How to Use This Calculator
- Enter the work/tool diameter in mm.
- Enter the cutting speed (to find RPM) OR the RPM (to find cutting speed).
- Click Calculate.
Worked Example
For D = 50 mm at a cutting speed of 30 m/min: N = (30 × 1000) / (π × 50) = 191 RPM.
Frequently Asked Questions
What is cutting speed in machining?
Cutting speed is the speed at which the cutting edge moves relative to the workpiece surface, measured in metres per minute (m/min).
What is the formula for spindle RPM?
N = (V x 1000) / (pi x D), where V is cutting speed in m/min and D is diameter in mm.
Why is cutting speed important?
Correct cutting speed gives good surface finish and tool life; too high causes rapid tool wear, too low reduces productivity.