Made in the USA

Terms and Calculations

Chip Load

The amount of material removed by each flute of the cutter.

Chip Load = Inches Per Revolution / Number of Flutes

Chip Load = Inches Per Minute / (R.P.M. X Number of Flutes)

Feed Rate or
Feed Per Tooth

The inches per minute of work piece movement toward the cutter between each tooth

Inches Per Minute (IPM)

The number of linear inches the cutter passes through the work piece in one minute

Inches Per Minute (IPM) = R.P.M. X Inches Per Revolution

Inches Per Revolution (IPR)

Feed rate of the cutter for each revolution of the cutter. In the inch system, the feed rate of the cutter can be calculated for each revolution of the cutter.

Inches Per Revolution (IPR) = Chip Load X Number of Flutes

Depth of Cut
(DOC)

The depth of cut of the end mill into the part surface axially. With CNC milling, it is measured in the Z axis direction.

Millimeters Per Revolution (MMPR)

Feed rate of the cutter each revolution of the cutter. In the metric system, the feed rate of the cutter can be calculated for each revolution of the cutter.

Millimeters Per Revolution (MMPR) = Chip load x Number of flutes.

Revolutions Per Minute (RPM)

The spindle speed rate of the cutter. This value will be calculated from a selected S.F.P.M. or MPM.

Revolutions Per Minute (RPM) = (3.82 X SFM) / Cutter Diameter.

Meters Per Minute (MPM)

The cutting speed of the end mill. This system is used in all countries that use the Metric system. MPM represents the rate of the surface of the cutter passes over the surface of the part. Cutting speed is measured in Meters per minute.

Surface Feet Per Minute (SFPM)

This the cutting speed of the end mill in the United States. It is the number of feet per minute that a given point on the circumference of a cutter travels per minute.

Surface Feet Per Minute (SFPM) = 0.262 X Cutter Diameter X R.P.M.

Selecting Speed and Feed Rates and the Depth of Cut

The following items must be selected by the machinist when using endmills.

  • SFPM - cutting surface speed
  • Chip Load - material removal rate
  • Depth of Cut - depends on specific part applications requirements
  • Considerations - cutting depth never to exceed flute length

Excessive depth of cut will result in tool deflection.
As the depth of cut increases, use the largest diameter cutter available to maintain a depth to diameter ratio of 1:1.
Width of Cut - (maximum amount should not exceed 2/3 x Cutter diameter)