Cutting Data & Formulas


When Does an End Mill Need Resharpening?

When wear land reaches a certain level as a function of diameter and type of end mill (for values see table to right).

When the chips change to a blue color.

When dimensional accuracy is not acheived.

When large burs appear on the edge of the workpiece.

When smoke and an unusual noise appear.

When motor amperemeter levels increase.


Maximum Permited Land Wear before Resharpening
Diameter Finisher
< 3/8 ~0.004
< 3/4 ~0.006
< 1 ~0.008
< 1-1/4 ~0.010
The above values indicate the upper limits, after which there may be a break.

Formulas

Feed per Tooth:
IPT= IPM ÷ Z ÷ RPM
Spindle Speed:
RPM = SFM x 3.82 ÷ D
Table Feed:
IPM= IPT x Z x RPM
Cutting Speed:
SFM= D x 0.26 x RPM
Inch (Feed) per Revolution:
IPR (FR) = IPM ÷ RPM
Metal Removal Cubic Inches per Minute:
MR= IPM x RDC x ADC

Legend

D = Tool Diameter
Z = No. of Flutes
FR = Feed per Revolution
IPM = Table Feed
IPR = Inch per Revolution
IPT = Feed per Tooth
SFM = Cutting SpeedRPM = Spindle Speed
ADC = Axial Depth of Cut (Length)
HP = Actual Horsepower Available at running RPM
PC = Power Constants for HP (HP/Cl-MR)
RDC = Radial Depth of Cut (Width)
MR = Metal Removal Rate (Cubic Inches per Minute)