The main parts and angles of a plain milling cutter as shown in Figure are described below:
Body of cutter: It is the part of the cutter left after exclusion of the teeth.
Face: The portion of the teeth next to the cutting edge is known as face.
Land: The relieved back portion of the tooth adjacent to the cutting edge. It is relieved to avoid interference between the surface being machined and the cutter.
Outside diameter: The diameter of the circle passing through the peripheral cutting edges.
Central hole: It refers to the hole present at the centre of the cutter. A keyway is cut inside the hole.
Relief angle: It is angle the between the land of the tooth and the tangent to the outside diameter of the cutter at the cutting edge of the particular tooth. (approx 7.5 °)
Primary clearance angle: It is the angle between the back of the tooth and the tangent drawn to the outside diameter of the cutter at the cutting edge. (approx 15 °)
Secondary clearance angle: It is the angle formed by the secondary clearance surface and the tangent to the periphery of the cutter at the cutting edge.
Rake angle: The angle measured in the diametral plane between the face of the tooth and a radial line passing through the cutting edge of the tooth. The rake angles may be positive, negative or zero. If the face and the tooth body are on the same side of the radial line, the rake angle between the radial line and the tooth face is positive.The tooth face and tooth body may be on opposite sides of the radial line. Then the rake angle is negative. If the radial line and the tooth face coincide in the diameter plane the rake angle is zero.
Milling Cutter Materials: The milling cutters are generally made of the following materials.
- Tool steel
– High speed steel (HSS)
– High carbon steel (HCS)
- Cemented carbide
In general shop work, the high speed steel cutters are most widely used.