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Solid carbide cutter parameters sketch
  • The Axia depth of cut is also called Stepdown and Cut depth.
  • It is designated by ap or ADOC.
  • The maximum possible depth depends mainly on the cutter’s diameter.
  • It ranges from 4D (4 times the diameter) for large diameter cutters (Above 3/4″, 20 mm) and up to 10D for small diameter cutters (Below 1/8″, 3 mm).

Optimal Cut Depth Calculators

The typical (and wrong!) opinion is that the larger the depth, the more vibrations will be in the cut. There are optimized cut depths that give minimum vibration.

Optimal Depth of Cut Calculator

The calculator below shows the cut depths (ap), which yield the least vibrations. (Read below why)

Optimal Milling Cutter for a given Depth

The calculator below shows the diameters and helix angle combinations, which yield the least vibrations for a given depth. (Read below why)

Reducing vibrations by optimizing the depth of cut

The cutting force during a milling operation depends on the depth of cut, chip load, raw material, cutting angles, and the total length of engagement between the cutting edges of the endmill and the material being cut. All the parameters stay constant throughout the operation except for cutting-edge engagement. The length of the helix, which is in contact with the material, varies as the cutter rotates.

Milling cutting force as a function of time graph

Therefore, a typical graph for the cutting forces acting on a solid carbide endmill as a function of time (or rotation angle) is like shown here.


However, specific combinations of diameters, number of flutes, helix angles, and depth of cut yield a constant contact length independent of the rotation angle, therefore, a constant force.

Since the diameter, helix angle, and flute count of the milling cutter can be changed. We can find an optimal cut depth that will yield a constant cutting force:

You can use our above calculator to find out this depth of cut. All the multiples of this depth will also yield constant force.
When you machine with a constant force, you will get less vibrations, a better surface finish, and a longer too-life.

You can also use this theory in another effective way. Suppose you have a mass-production job and must constantly machine at a certain depth. If you reverse the formulas, you can find specific combinations of diameter, flute count, and helix angles to yield constant force and smooth machining. The result will be non-standard figures. But it may be well worth designing and purchasing a special cutter according to these parameters for a mass-production job.
You can use our above calculator to find out the optimal milling cutter geometry for your required depth of cut.

The Axial Depth of Cut is closely related to the radial depth of cut. In most cases, you need to consider both when making decisions. Learn More in our In-Depth Milling Depth of Cut guide.

Stepdown, Cut Depth
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