The corner angle affects the tool life.
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Corner angle and cutting resistance
Cutting resistance of face milling cutters changes according to the corner angle of the cutting edge.
The image shows the cutting resistance values of the face milling cutters with various corner angles (0°, 15°, 45°).
Corner angle and cutting resistance
Back force pushes the face milling cutters towards the spindle. The back force of a face milling cutter with 45° corner angle is the largest. This is because with a large corner angle, the force generated by the table feed also works in the back force direction. Meanwhile, for the shoulder milling type with 0° corner angle, the back force works in a minus direction. With 0° corner angle, the force generated by the table feed is not dispersed into back force. If the tool has a high axial rake angle this can lead to the workpiece being drawn towards the spindle.
When machining workpieces that lack rigidity with face milling cutters that have a large corner angle (45°), the workpiece can bend due to the back force. This can lead to poor machining accuracy. In such cases cutters with a 15° corner angle are more suitable.
- Click and see the effects
on the back force!
Corner angle and chip thickness
When the depth of cut and feed per tooth, fz, are fixed, the larger the corner angle (CH) is, then the thinner the chip thickness (h) becomes (for a 45° CH, it is approx. 75％ that of a 0° CH). This can be seen in the images to the right. Therefore as the CH 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.
- Click on the different degrees in the image and see the effects on chip thickness due to the variation of the corner angles.
Corner angle and crater ware
The table below shows wear patterns for different corner angles. When comparing crater wear for 0° and 45° corner angles, it can be clearly seen that the crater wear for 0° corner 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 wear develops then cutting edge strength will reduce and lead to fracturing.
Workpiece: JIS SNCM439 287HB
Tool: D1=125mm
Insert: M20 cemented carbide
Cutting conditions: ap=3.0mm, ae=110mm, fz=0.2mm/tooth
Coolant: Dry
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