What Is Chip Removal in Machining and How to Manage It

When you work with mechanical machining, such as drilling but also turning and CNC milling, there is an aspect that must be managed with extreme care. We are talking about chip removal. What are we talking about?

It is the removal of a section of base material that allows you to achieve the final result. In other words, the chip is nothing but the scrap material produced during mechanical machining of materials - such as wood and iron - through removal processes such as turning, milling, or drilling. Now, you might think that after all it's not worth paying attention to this process because after all we're talking about waste material. No, you need to pay attention to chip removal.

What Does Chip Removal Mean?

By this term we mean the result of various cutting operations that fall within precision machining: at the moment when we drill, thus make a hole on a surface, we obtain an empty shape. The chip is the material that is produced. The same goes for drilling and turning, which use machines for chip removal that are particularly high-performance.

So, we can say that this operation allows those dealing with the process in question to achieve the desired result. And that the quality of the chip obtained from the path allows us to obtain valuable information about the machining.

To read: what are the differences between turning and milling?

How Is a Chip Formed During Machining?

The concept: the tool does not cut the material cleanly but causes plastic deformation of the material in front of the cutting edge. The blade advances and compresses the machining object until it reaches a breaking point: there is an inclined plane where the material separates from the workpiece. And is pushed upward by the tool. In this phase, the chip is created which is, precisely, removed.

What Are the Main Machining Operations for Removal?

There are various technical operations that allow you to work on chip removal, a step that - it's right to remember - determines the desired result. Which operations exploit material removal and chip formation to achieve the goal? Let's start with the most common: drilling, that is, making a blind or through hole in the material. There are also variants such as reaming to finish holes, countersinking to enlarge the entrance, tapping (threading).

Then we have turning with related roughing, finishing, and threading activity and milling used to create flat zones, grooves, cavities, complex profiles, gears. Not to forget grinding for millimeter-wise machining and broaching. That is, a particular process where a multi-tooth tool is pulled or pushed through the workpiece to create very articulate internal profiles.

Why Is the Chip Formed in Different Ways?

The parameters that contribute to chip formation are different. First, we have the material being machined: ductile ones, like aluminum or mild steel, tend to form continuous chips while brittle ones like cast iron generate discontinuous forms.

A larger rake angle of the tool simplifies sliding and reduces deformation but a leading role in chip formation is played by cutting speed. This parameter, in fact, influences the temperature in the cutting zone and the behavior of the material. The same can be said of lubrication which reduces friction influencing the shape of the chip.

Is It So Important to Evaluate This Aspect?

First of all because from the shape of the chip we determine the quality of the machining. For example, from this detail we can determine whether the cutting parameters such as speed, feed, depth are going in the planned direction.

But this element can also help us understand whether the tool is now worn and needs to be changed, just as they can determine the successful completion of the machining. Not by chance, various cutting tools, like those brazed for turning from Krino, have shapes that allow them to eject the chips effectively: if they are reintroduced into the machining process, they can scratch the machined surface or overheat the tool. Chip removal management also affects downtime and costs.

How to Evaluate a Chip by Shape

Let's assume that we cannot evaluate the chip and its shape in absolute terms because everything can change based on the material. But some parameters can be a warning signal or a synonym for work efficiency. For example, a continuous and uniform chip indicates stable machining, while an irregular chip can signal vibrations or problems.

In the first case, when the chip takes on the shape of a long ribbon or spiral, we are still talking about a ductile material but the synthesis is that the cutting parameters are correct and the cutting edge is in good condition. This condition can be dangerous because the long spiral chip wraps around the workpiece or tool. For this reason there are chip breakers on the inserts, like the NR you see on this Krino face mill, which create obstacles to break it into shorter pieces.

When the chip breaker works well, you have spirals that break every 5-10 cm, and that's good. If the chip, instead, is discontinuous or fragmented, the cutting speed may be too low or the cutting edge has inadequate geometry, or there is an excess of vibrations or irregularities in feed. It's not always a negative signal, with brittle materials it's normal.

But if the chip first has a long and homogeneous spiral and then changes, changes becoming fragmented, there's something wrong. The extreme situation is that of torn or irregular chip, frayed and with variable thickness.

Stop everything and check because it means the parameters are off. The options are different but there's an old mechanic's trick we want to share with you: keep in the workshop samples of chips that describe different situations - optimal cutting, worn cutting edge, inadequate parameters - so you can quickly compare and understand if something is wrong or if everything is proceeding at best. Because chip analysis allows you to understand if you're working well or if you need to better manage your process.