Chip Load Calculator

What is Chip Load?

The term Chip load (also called Maximum Chip Thickness), can be confusing since it has two different meanings that are commonly used!

Chip Load milling sketch
Figure – 1

Meaning #1 – As used in milling catalogs, and by most machinists.

The maximum load that the cutting edge of a specific milling cutter (or indexable insert) can withstand without yielding or having a very short tool-life.

The chip load is specified in mm/tooth or Inch per tool (IPT) units. What makes this property very useful, is the fact that it depends only on the geometry of the cutting edge and the type of workpiece material, and does not depend at all on application conditions such as speed or depth of cut. It is convenient for both the tool suppliers and the users. For the suppliers it enables them to list the recommended feed rates in one number, independent of the application conditions. The programmer or cam software can calculate the correct table feed according to the chip load and the other application parameters. It is convenient for the users because once they figure out a chip load that works well for them for a combination of a specific cutter and raw material, they can use this data with confidence in many other applications by calculating each time the table feed based on the known chip load.

Meaning #2 – The physical meaning of the property.

The maximum width of the chip that the tooth (or indexable inerts) of a milling cutter cuts out of the material in one spindle rotation.

Please look at figure-1 above and note the following important remarks:

  • The chip load equals exactly the feed per tooth (Fz) when the radial depth of cut (Ae) is greater or equal to the cutter radius. As Ae becomes smaller the chip load also becomes smaller. Some people refer to the Fz as if it is the chip load. This is a mistake since it is not true in all conditions!
  • The width of the chip is largest at the point of entry and gradually gets smaller until it is zero at the point of exit. The chip load is the maximum value. A related term is Average Chip thickness which is used for force and power calculations.

Chip Load Chart – Inch

Chip Load in IPT per Milling Cutter Diameter and workpiece material

Tap the icons to view the chip load of more raw materials

Chip Load Chart – mm

Chip Load in mm/tooth per Milling Cutter Diameter and workpiece material

Tap the icons to view the chip load of more raw materials

Getting Cutting Data from Chip Load

The chip load value by itself cannot be used to program the milling machine. The parameter used by the controllers is the Table Feed. However, the Chip Load is the basic parameter needed to calculate the Table Feed.

From Chip Load to Table Feed 1

To calculate the Milling Feed Rate you will need first to prepare the following basic data:

  1. Chip Load [CL] – What you obtained from this calculator.
  2. Cutter Shape [90°, Ballnose, Chamfering, Round, etc]
  3. Cutter Diameter [D] – If you are using a shaped cutter (Non 90°), you should use the Effective Cutter Diameter.
  4. Number of Teeth [Z]

The user always knows the above three.

  1. Milling width of cut Radial Depth of Cut [Ae] – Depends on how you plan to perform your application.
  2. Cutting Speed [Vc] – Get wit with our Speeds and Feeds Calculator or from the tool supplier’s catalog/website.

With the above parameters, you can proceed to calculate the Milling Feed (Table Feed)

  1. Calculate the Chip Thinning factors in order to get the Feed per Tooth.
    The Chip Thinning factors make sure that the actual Feed per Tooth [Fz} will maintain the desired Chip Load according to the tool geometry and application settings.
  2. Radial Chip Thinning Factor [RCTF] –
    The radial chip thinning factor should be implemented with the Radial Depth of Cut [Ae] is smaller than the cutter’s radius. (When Ae is bigger the factor is 1). At very small Ae the factor can be up to 3 times!
Radial Chip Thinning factor calculation:
Radial Chip Thinning Sketch
\( \large RCTF = \)

\( \huge \frac{1}{\sqrt{1-\left ( 1 – 2 \times \frac{Ae}{D} \right )^{2}}} \)

  1. Approach Angle Chip Thinning Factor [ACTF] –
    The Approach Angle Chip Thinning factor should be implemented when the cutter is not a standard 90° shape (For example a Ballnose or Chamfaring cutter).
Chip Thinning factor for Chamfer/feed milling cutters:
Radial Chip Thinning Sketch
\( \large ACTF = \)

\( \huge \frac{1}{\sin({K_{apr})}} \)

For other shaped (like Ballnose, Round inserts, etc.) visit our Chip Thinning Calculator.
  1. Calculate the Feed per Tooth, based on the Chip load and Chip thinning factors:

\( \large F_z = CL \times RCTF \times \ ACTF\)
  1. Calculate the RPM from the Cutting Speed and Cutter Diameter:
\( \large n = \frac{ \huge \unicode{86}_c \times 12}{\huge \pi \times D} \)

* If your Vc is in m/min units use 1000 instaed of 12 in the above formula.

  1. Final Stage: Calculate the Table Feed:
\( \large \unicode{86}_f = F_z \times n \times Z \)
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