End milling

Length of cut

Flute length and overhang

Usually, the flute length of an end mill has to be a little longer than the length to be machined. However, too much flute length is not desirable. This is because with a longer length of cut, the overhang also has to be increased and will decrease rigidity.


Overhang affects the rigidity of end mills.

End mill deflection is proportional to the length of overhang, L (cubed) and is found by using formula shown in the previous chapter.

This means that even with a slightly longer overhang, the amount of deflection will become much larger. For example, if the overhang doubles with the same diameter, the deflection will be 8 fold as shown in figure to the right. For example, the deflection of a machined surface when using high-speed steel end mill is approx. 0.2mm, if the tool overhang is doubled, the deflection will be increased to 0.2mm × 8 = 1.6mm under the same cutting loads. This shows that a very large deflection will be produced on the machined surface.

- Click below to read more about the effects of overhang!

Y2 = 8Y1

Y1, Y2: Deflection

W      : Load