Lead Angle (KAPR) and Cutting Characteristics

Function of Tool Features for Face Milling

Lead Angle 90°

Back force is in the minus direction. Lifts the workpiece when workpiece clamp rigidity is low.

•Lead Angle 75°

Lead angle 75° is recommended for face milling of workpieces with low rigidity such as thin workpieces.

•Lead Angle 45°

The largest back force.
Bends thin workpieces and lowers cutting accuracy.

* Prevents workpiece edge chipping when cast iron cutting.

* Principal force : Force is in the opposite direction of face milling rotation.
* Back force : Force that pushes in the axial direction.
* Feed force : Force is in the feed direction and is caused by table feed.

APPROACH ANGLE AND THE TOOL LIFE

Approach Angle and Chip Thickness

When the depth of cut and feed per tooth, fz, are fixed, the smaller the lead angle (KAPR) is, then the thinner the chip thickness (h) becomes (for a 45° KAPR, it is approx. 75% that of a 90° KAPR). This can be seen in below. Therefore as the KAPR increases, the cutting resistance decreases resulting in longer tool life. Note however, if the chip thickness is too large then the cutting resistance can increase leading to vibrations and shortened tool life.

Approach Angle and Face Wear

Below shows wear patterns for different lead angles. When comparing crater wear for 90° and 45° lead angles, it can be clearly seen that the ctater wear for 90° lead angle is larger.