Machining involves using cutting tools to remove material from a metal or plastic workpiece in order to give it the desired shape and dimensions. Unlike casting or forging, no material is added; excess material is removed in a controlled manner. For this reason, the method is also referred to as \u201csubtractive manufacturing.\u201d.<\/p>\n\n\n\n
Whether it\u2019s machining a block of aluminum to produce a precision fitting or adjusting the diameter of a steel shaft to within a micron, it\u2019s all part of machining. From automotive to defense, and from aerospace to medical, virtually every industry that requires precision relies on this method.<\/p>\n\n\n\n
In this article, we explain how machining works, its main methods, the benefits it offers, and when it should be used.<\/p>\n\n\n\n
The principle is simple: there is a rotating tool or a rotating workpiece; controlled contact is established between the two, and the cutting edge removes thin layers (chips) from the material. The tool\u2019s rotational speed, feed rate, and depth of cut are predetermined.<\/p>\n\n\n\n
In modern workshops, these movements are controlled by a computer. A 3D model of the part is converted into toolpaths in CAM software, and from there, it is translated into commands (G-code) that the machine can understand. The operator secures the raw material to the machine, starts the program, and the machine processes the part with micron-level precision. This automation is known as \u201cCNC machining.\u201d.<\/p>\n\n\n\n
There is no single machining method; different processes are used depending on the part\u2019s geometry. The most common ones are as follows.<\/p>\n\n\n\n
In turning, the workpiece rotates at high speed while the cutting tool moves along a fixed axis to cut the material. It is the ideal method for cylindrical and conical parts: shafts, bushings, pins, couplings, and flanges. In addition to machining the outer diameter, drilling, grooving, and threading are also performed on the lathe. We have covered this topic in detail in a separate article: What Is a CNC Lathe?<\/em>.<\/p>\n\n\n\n The logic of milling is reversed: this time, the tool rotates while the workpiece is clamped to the table and moves. Flat surfaces, pockets, slots, gear profiles, and complex three-dimensional shapes are produced by milling. Milling is indispensable for prismatic and free-form parts.<\/p>\n\n\n\n Drilling the hole is the first step; however, if a precise bore or clean thread is required, the process doesn\u2019t end there. The hole is reamed to achieve the desired precision, and the thread is cut using a tap. These operations are often completed in a single setup on a lathe or milling machine.<\/p>\n\n\n\n Grinding comes into play where the highest surface quality and tightest tolerances are required. An abrasive wheel removes very thin layers from the workpiece to polish the surface and fine-tune the dimensions. Grinding is essential for hardened steels and parts requiring a surface finish below Ra 0.2.<\/p>\n\n\n\n On conventional machines, the operator performs every movement by hand; achieving the correct dimensions depends on the operator\u2019s experience. They are still used for single-piece or simple jobs.<\/p>\n\n\n\n On CNC machines, however, the movements are controlled by a computer. In practical terms, this means:<\/p>\n\n\n\n In mass production and precision machining, CNC is almost always the preferred choice.<\/p>\n\n\n\n There are several key advantages that make machining so widespread:<\/p>\n\n\n\n There\u2019s another side to the coin: the resulting chips represent material loss, and at very high production volumes, this can lead to a higher unit cost for the casting. The right method depends on the part\u2019s geometry and the production volume.<\/p>\n\n\n\n Machining offers flexibility in terms of materials. The most commonly used materials are:<\/p>\n\n\n\n Each material has its own specific cutting speed, tool selection, and cooling requirements. We cover material selection in a separate guide: Which Metals Can Be Machined Using CNC?<\/em>.<\/p>\n\n\n\n Precision parts are needed almost everywhere, but some industries are particularly reliant on machining:<\/p>\n\n\n\n A rule of thumb: If a part requires tight tolerances, good surface quality, or complex geometry, and the production volume ranges from a single piece to a medium-sized batch, machining is often the most appropriate method. It\u2019s also ideal for avoiding tooling costs during the prototyping phase; plus, you can seamlessly transition to mass production using the same program you used for the prototype.<\/p>\n\n\n\n For parts with very high production volumes, simple geometries, and loose tolerances, methods such as casting or stamping may offer a cost advantage.<\/p>\n\n\n\n What is the difference between machining and casting?<\/strong> Casting shapes molten metal by pouring it into a mold and works by adding material. Machining, on the other hand, shapes material by removing chips from a block. Casting is economical for high-volume production; machining, however, excels in precision and flexibility. In most parts, both processes are used together: casting provides the rough shape, while machining delivers the final dimensions.<\/p>\n\n\n\nMilling<\/h3>\n\n\n\n
Drilling, reaming, and tapping<\/h3>\n\n\n\n
Grinding<\/h3>\n\n\n\n
The difference between CNC and conventional machining<\/h2>\n\n\n\n
\n
The advantages of machining<\/h2>\n\n\n\n
\n
What materials are processed?<\/h2>\n\n\n\n
\n
In which industries is machining used?<\/h2>\n\n\n\n
\n
When should you opt for machining?<\/h2>\n\n\n\n
Frequently Asked Questions<\/h2>\n\n\n\n