Getting Started with Milling and Its Tools

In this chapter, we will start moving from the turning world (which we should now be a bit familiar with) to the milling world, which has lots of potential and wide horizons for us to explore. Of course, this will lead us to new challenges and additional complexities that we will try to overcome during this chapter and the ones that follow.

We will discover the difference between a three-axis milling machine and a five-axis one, review the most common milling operations, and take a glimpse at the weirdly shaped tools that are involved in the cutting processes.

As always, we will learn useful formulas for parameter evaluation and a couple of golden rules that may save your day in the future.

In this chapter, we will cover the following topics:

• Understanding what milling is and how it works
• Understanding the main cutting parameters
• Introducing the most common milling operations

Technical requirements

We won’t dig too much into milling theory and best practices since this book targets beginners, so there aren’t any mandatory requirements for this chapter. However, reading the chapters on turning theory, particularly Chapter 1, will enhance your understanding of the subject since most of the formulas and concepts involved are very similar.

Understanding what milling is and how it works

Milling is probably the most flexible and capable machining method, able to create the most complex geometries with good productivity at appealing (cheap and flexible) costs.

Contrary to turning, in milling, the spindle holds the cutting tool (and not the part) and it moves in multiple directions relative to the part being machined.

We will try to keep things plain and simple during this introduction, but there are so many things we must skip or oversimplify that purists may get a bit skeptical! Don’t worry, though – the core concept we are about to discuss is based on a solid ground founded on theory (just consider that you may find several exceptions in the real world that we don’t have time to discuss).

Let’s introduce milling processes by splitting machining into two main categories according to the number of degrees of movement of the spindle relative to the stock:

• Cartesian machines (up...

Understanding the main cutting parameters

Milling is a complex process that requires us to understand many different parameters and working operations. However, we shouldn’t be too scared of it since we should already be familiar with many turning operations.

In the following pages, we will discover how cutting parameters are conjugated for milling.

Spindle speed and cutting speed

Spindle speed and cutting speed are our old friends from turning operations; these concepts are the same for milling as well, so we will recap them a bit faster.

Spindle speed () is how fast our spindle (and our tool) rotates and is measured in revolutions per minute (RPM).

Cutting speed () is the tangent velocity on the cutting edge measured in meters per minute (m/min) and can be calculated via the following formula:

Here, is the outer diameter of the cutting tool measured in millimeters.

The following figure shows a graphic visualization of the cutting...

Introducing the most common milling operations

Milling flexibility translates to a wide range of different machining operations that can realize almost any shape conceivable.

We can divide milling operations into five main categories according to the tool used and the machined shape:

• Face milling
• Shoulder milling
• Slot milling
• Profile milling
• Other

Let’s introduce them one by one in the simplest way possible.

Face milling

Face milling is one of the most common and most simple milling operations. Its goal is to machine a flat surface perpendicular to the tool’s rotation axis. It can be considered both a roughing operation and a finishing operation according to the tool used and its cutting parameters. The following figure shows a typical facing operation:

Figure 6.10: Face milling

As we can see, face milling tools can have complex geometries; they often have several replaceable inserts with the strangest...

Summary

With that, we have introduced milling operations. It was not as detailed as it could have been, but a more complete overview would have required a dedicated book on the subject. I hope that the information provided has encouraged you to explore this amazing technology further.

Now, let’s recap what we have learned. First, we understood how a milling tool can move relative to the stock, and the differences in degrees of movement between a traditional three-axis machine and a multi-axis machine.

Then, we plunged into the theory behind milling operations and looked at the main cutting parameters present in formulas for cutting power and cutting torque. After presenting those formulas, we learned how to use them to calculate a missing parameter when we know all of the others.

Moving on, we presented the main milling operations, and we provided a couple of useful suggestions on how to avoid hidden troubles when implementing our CAM operations.

Understanding all...