* 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.
• Tool Cutting Edge Angle 90°
Back force is in the minus direction. Lifts the workpiece when workpiece clamp rigidity is low.
• Tool Cutting Edge Angle 75°
Tool cutting edge angle 75° is recommended for face milling of workpieces with low rigidity such as thin workpieces.
• Tool Cutting Edge Angle 45°
The largest back force.
Bends thin workpieces and lowers cutting accuracy.
* Prevents workpiece edge chipping when cast iron cutting.
When the depth of cut and feed per tooth, fz, are fixed, the smaller the tool cutting edge angle (KAPR) is, then the thinner the chip thickness (h) becomes (for a 45° KAPR, it is approx. 75% that of a 90 ° KAPR) . Therefore as the KAPR increases, the cutting resistance decreases resulting in longer tool life.
The table below shows wear patterns for different tool cutting edge angles. When comparing crater wear for 90° and 45° tool cutting edge angles, it can be clearly seen that the crater wear for 90° tool cutting edge angle is larger. This is because if the chip thickness is relatively large, the cutting resistance increases and so promotes crater wear. As the crater develops then cutting edge strength will reduce and lead to fracturing.