Milling – An overview
Milling machines are perhaps the most widely used in manufacturing after lathes.
However, milling machines use multi point cutting tool but lathe machines use single point cutting tool.
What is milling?
A milling machine uses a cutter with a multiple teeth, these teeth (one by one) engage with the work piece for a very small amount of time. This results in a small chip size and variation in chip thickness. The surface finish obtained by the milling process is generally of very good quality.
Characteristics of milling
- Interrupted cutting
- Small size of chips
- Variation in chip thickness
Types of milling machines
Knee and column type
- Turret type
Production (bed) type
- Rotary table
- Drum type
- Copy milling (die-sinking machines)
- Keyway milling machines
- Spline shaft milling machines
Types of milling cutters
Based on construction
- Inserted tooth type
Based on mounting
- Arbour mounted
- Shank mounted
- Nose mounted
Based on rotation
- Right hand rotation (counter clockwise)
- Left hand rotation (clockwise)
Based on helix
- Right hand helix
- Left hand helix
Types of milling
Up milling (conventional milling)
This is a type of milling in which direction of rotation of wheel and movement of workpiece is opposite. You can refer below image to understand the concept and the difference between up milling and down milling.
Down milling (climb milling)
In this type of milling the direction of rotation of wheel and movement of workpiece is same.
With this diagram showing up and down milling you can understand the process in a better way.
Advantages of down milling
- Suitable for thin and hard to hold machine parts
- Work need not to be clamped tightly
- Consistency maintained specially for thin parts
- Requires 20% less power than up milling
- Used in milling deep and thin slots
Disadvantages of down milling
- It cannot be used unless the machine has backlash eliminator
- It cannot be used for milling hard materials, since it can damage cutter