Milling Formulas

General Milling Formulas for Working with Carbide Tools, Engravers, End-Mills and Cutters

To Find

Using
Formula

SFM
Surface Feet per Minute

RPM – Revolutions per Minute
Dia – Diameter of End Mill

RPM ÷ 3.82 x Dia = SFM

RPM
Revolutions per Minute

SFM – Surface Feet per Minute
Dia – Diameter of End Mill

SFM x 3.82 ÷Dia = RPM

IPM
Inches per Minute

RPM – Revolutions per Minute
IPT – Inch per Tooth, Chipload
# FL – # of Flutes

RPM x IPT x #FL = IPM

IPT
Inch per Tooth, Chipload

IPM – Inches per Minute
RPM – Revolutions per Minute
# FL – # of Flutes

IPM ÷RPM ÷#FL = IPT

IPR/FR
Inch (Feed) per Revolution

IPM – Inches per Minute
RPM – Revolutions per Minute

IPM ÷RPM = IPR (FR)

MR
Metal Removal
Cubic Inches per Minute

ADC – Axil Depth of Cut
RDC – Radial Depth of Cut
IPM – Inches per Minute

ADC x RDC x IPM = MR

HP
Horsepower Required

IPM – Inches per Minute
RDC – Radial Depth of Cut
ADC – Axil Depth of Cut
PC – Power Constants

IPM x RDC x ADC x PC = HP