Machining is a group of manufacturing processes in which a tool progressively removes material from a workpiece in the form of chips until the part achieves the required shape and dimensions. Unlike forming, where material is merely reshaped, or additive manufacturing, where material is added layer by layer, in machining material is always removed — the principle is simple, but the combination of the machine, tool and cutting parameters determines the precision, surface quality and cost of the part.
Machining comprises three main technologies, which differ primarily in terms of what moves during cutting — the workpiece, the tool, or both.
The three main machining technologies
CNC milling
In milling, the cutting tool (milling cutter) rotates whilst the workpiece remains stationary or moves along several axes simultaneously. Milling is a versatile technology suitable for parts with complex shapes — grooves, recesses, holes and flat surfaces. Modern 5-axis CNC milling machines can machine a part from multiple sides without changing the clamping, which reduces production time and increases precision.
CNC turning
With turning, the process is the reverse — the workpiece rotates whilst a firmly clamped tool removes material from it. Turning is the natural choice for rotary components: shafts, sleeves, flanges and threaded parts. The combination of turning and milling on turning-milling centres makes it possible to produce even more complex rotary parts in a single clamping operation.
Grinding
Grinding is a finishing operation — the grinding wheel removes a thin layer of material so that the part achieves precise final dimensions and a low surface roughness. It is used where milling or turning alone is not sufficient to achieve the required tolerance or surface quality, for example in the case of hardened components or functional surfaces with high precision requirements.
When is machining worthwhile?
Machining is particularly worthwhile where precision, repeatability and surface quality are crucial — in other words, precisely where casting or 3D printing reach their limits. Typically, this includes:
functional engineering components with tight tolerances,
prototypes and small batches, where it is not cost-effective to invest in a mould,
spare parts manufactured directly from drawings without the need for tooling,
parts made from materials that are difficult to cast or print, such as stainless steel or titanium.
Conversely, for very high production runs of simple shapes, casting or stamping may be more advantageous — in such cases, machining is often used only to finish the functional surfaces.
Machining at Metal One
At Metal One, we cover all three technologies — CNC milling, CNC turning and grinding — with tolerances of ±0.01 mm, and up to ±0.005 mm for specialised applications. We work with aluminium, stainless steel, structural steel, brass, titanium and engineering plastics, from one-off prototypes to batch production of up to 10,000 pieces. The standard lead time is 3 to 14 working days, and we will prepare a quotation within 24 hours of receiving your drawing.
If you are unsure which technology is best suited to your part, please send us the drawing — we can advise you on the choice of process as well as on the manufacturing itself.