Basic machining operations and associated machines

In the aerospace, automotive, medical and precision turning industries, every mechanical part undergoes one or more material removal operations. SAMO helps you to understand these operations and to choose the machine tool best suited to the needs of your workshop. This article explains the main machining operations and the associated machine tools.
Machining refers to all processes aimed at obtaining a compliant part through the controlled removal of material. Modern industry relies heavily on machining operations.

With the rise of digital technology, machining centres and CNC machines have profoundly transformed these operations. Our guide explains how machining centres work.

Understanding machining operations

Machining is based on a simple principle: removing material from a rough shape to produce precise parts. Historically carried out on mechanical machines, these operations are now mostly carried out on CNC equipment offering repeatability, precision and productivity. Machining centres, which combine several functions, have become an integral part of modern workshops and continue to push back the technical limits.

The choice of process depends on a number of essential parameters. The material is the first criterion, as some alloys are better worked by turning than by milling, while others require grinding or electro-erosion. Dimensional tolerances and the desired surface finish also influence the choice: a part requiring micrometric precision can only be obtained by finishing on a grinding machine. Geometry plays an equally important role: cylindrical, prismatic or complex parts require different machines. Lastly, the volume of production determines whether multi-purpose machines or a dedicated mass-production facility are preferable.

The 4 basic machining operations

1 Turning

Turning is the benchmark operation for cylindrical parts. The part turns on itself, while a fixed tool removes the material. This process applies in particular to shafts, axles, bushes or parts of revolution. Conventional lathes are still common in some workshops, but CNC lathes now dominate the market thanks to their production capacity and increased precision.

2 Milling

Milling is characterised by the rotation of the tool, which machines the material to produce flat surfaces, grooves, shoulders or complex 3D shapes. This highly versatile process is mainly used for prismatic parts or parts requiring several machined faces. Dedicated equipment includes milling machines, as well as multi-axis machining centres, which are increasingly used to reduce rework times and increase productivity.

3 Drilling

Drilling is an essential part of most production lines. Whether it involves through or blind drilling, tapping or countersinking, it is carried out on pillar drills or directly on machining centres. Precision and repeatability are highly dependent on the rigidity of the machine and the quality of the guidance.

4 Grinding

When precision or surface finish requirements are high, grinding becomes unavoidable. This process uses an abrasive wheel to remove minute layers of material. It enables micrometric tolerances and very fine roughness to be achieved. Flat or cylindrical grinding machines are widely used in the automotive, aerospace, precision engineering and tooling industries.

Other complementary machining processes

1 Broaching

Broaching consists of machining internal grooves or profiles using a tool with progressive teeth. Widely used for keys or specific shapes, it guarantees high precision and excellent repeatability, particularly in series production.

2 Reaming

Reaming allows an existing hole to be enlarged or ground to a perfectly cylindrical geometry. It is an essential finishing process for demanding mechanical assemblies.

3 Electrical discharge machining (EDM)

Used when materials are very hard or shapes are impossible to achieve by mechanical removal, EDM relies on controlled electrical discharges. EDM wire or die sinking machines are preferred for tool or mould applications.

4 Industrial sawing

Before any machining, the blanks must be prepared. Industrial sawing, carried out on band or circular saws, guarantees clean, optimised cuts to reduce material losses.

How do you choose the right machine tool?

Workpiece geometry

Cylindrical parts naturally gravitate towards turning, while prismatic or multi-sided parts require milling equipment or machining centres. Complex parts may require multiple axes or electro-erosion.

Precision and surface finish

Finish is a decisive factor in the choice of machine. Parts requiring extreme precision will be ground or reamed to ensure compliance with the strictest tolerances.

Level of automation

Conventional machines remain relevant for single parts or repairs, while CNC machines or machining centres offer full automation and high productivity. The advantages are detailed on our page dedicated to machining centres.

Production volume

Mass production favours equipment optimised for repeatability. Small production runs rely on versatility and rapid set-up.

FAQ - Frequently asked questions about machining operations

What is the most common machining operation?
Turning and milling account for the majority of operations in industrial environments.

What is the difference between a CNC lathe and a conventional lathe?
The CNC offers automation, repeatability and precision, whereas the conventional lathe relies more on the experience of the operator.

Can a machining centre replace several machines?
Yes. Versatile and high-performance, it combines drilling, milling, reaming and sometimes tapping.

When is grinding used?
The grinding machine is used when the surface or precision must meet micrometric tolerances.

Which process should I choose for very hard materials?
EDM is ideal for hardened steels or materials that are difficult to machine by removal.