The helix angle is the angle that an end mill's helical cutting edge makes with the plane of its centreline. On the periphery, the helix angle is the axial rake angle of the peripheral cutting edges. A higher helix angle means a larger rake angle, thereby increasing sharpness to the tool.
- Click below to read more!
Helix angle and cutting resistance:
Helix angle and cutting resistance: Change of cutting resistance
For helical flutes, the cutting resistance gradually builds on a workpiece from the end cutting edge and thereby changes slightly. Meanwhile, with a straight flute, the cutting resistance is simultaneously placed on the whole cutting edge length and therefore changes significantly throughout the cutting cycle. The image below shows an example.
Helix angle and cutting resistance: Change of cutting resistance with different angles
The back force of cutting resistance is applied in an end mill's axial direction. As the helix angle increases, cutting resistance from the component in an axial direction increases the back force. The image below shows a measured example. When machining thin parts and workpieces that lack rigidity with an end mill with a high helix angle, care should be taken because bending of the workpiece and vibration can occur.
Helix angle and deflection
The figure below shows the effects on deflection when using various helix angled end mills to machine a slot. It can be seen that the largest amount of deflection occurs with a certain helix angle. As the helix angle increases the amount of force acting towards the up cut side of the slot increases.
Helix angle and tool life
Surface roughness improves with a higher helix angle. This is because increased sharpness reduces cutting resistance.
The helix angle also affects tool life. As the helix angle increases, the contact length of the cutting edge also increases, the result of which leads to a decrease in tool wear. However, as shown in the graph below, when a helix angle increases over a certain limit, the cutting edge strength decreases and tool life shortens.