Manufacturing process

CNC Machining

CNC machining removes material from bar, plate, castings or forgings under programmed control to produce precise metal and plastic parts — from single prototypes to recurring batches.

Process overview

CNC machining supports the production of precision components from metals and engineering plastics using controlled milling, turning and multi-axis operations. It is suited to prototypes, complex geometries, tight-tolerance parts and repeat production where dimensional consistency is important. Manufacturing requirements can include material grade, tolerances, surface finish, inspection criteria and production volume.

Most machined parts are made by milling, turning or a combination of both. Milling moves a rotating cutter across a fixed workpiece and suits prismatic parts such as housings, plates and manifolds; turning rotates the workpiece against a stationary tool and suits shafts, bushings and other round parts. Mill-turn centres and multi-axis machines combine the two, which can reduce set-ups and improve feature-to-feature accuracy on complex parts.

The cost of a machined part is driven mainly by set-ups, cycle time and inspection effort rather than by tooling. That is why machining is commonly used for prototypes and low-to-medium volumes, and for finishing near-net-shape castings and forgings. Tight tolerances, deep pockets, thin walls and hard materials all tend to increase cycle time; relaxing non-critical tolerances is often the most effective way to reduce cost.

Achievable accuracy depends on the machine, fixturing, material, part size and temperature control. Many shops work routinely to a general tolerance class such as ISO 2768-m and hold tighter values on the specific features where the drawing calls for them.

Typical capabilities & what manufacturers can produce

What manufacturers can produce

  • Milled housings, brackets, plates and manifolds
  • Turned shafts, pins, bushings, fittings and threaded parts
  • Multi-axis parts with compound angles and freeform surfaces
  • Finish machining of castings, forgings and weldments
  • Precision components with bores, threads and sealing faces
  • Machined plastic insulators, guides and wear pads

Capabilities under this process

Suitable materials

Materials commonly used with this process — an editorial reference, not a statement about facilities in the Metraxio network. Suitability always depends on the part and its application.

Relevant industries

Industries whose Metraxio industry guides list CNC Machining as a common process, with the typical use in each.

What buyers should specify

The details that make CNC Machining quotes comparable and let facilities be assessed on the right criteria.

Drawing and CAD model
2D drawing (PDF) with tolerances and notes, plus a 3D model (STEP) for programming. State which one governs if they differ.
Material and grade
For example aluminium 6082 or stainless 316L, with temper or condition where it matters (6061-T6, quenched and tempered).
Critical tolerances
Mark the features that really need tight tolerances or GD&T and leave the rest to a general tolerance class.
Surface finish
Roughness values (for example Ra) for functional surfaces and any cosmetic requirements on visible faces.
Quantity
Batch size, expected annual volume and whether prototypes are needed before series parts.
Treatments after machining
Anodising, plating, heat treatment or passivation — and whether the machinist should arrange them.
Inspection and documents
First article or dimensional report, CMM measurement and material certificates (EN 10204 3.1) if required.

On Metraxio these details become a structured manufacturing requirement. Processes, capabilities, materials, certifications and part size are checked against facility profiles; tolerances, finishes and inspection details travel with your drawings and are reviewed during quoting rather than used as automatic filters.

Frequently asked questions

What tolerances can CNC machining hold?

It depends on the machine, material, feature size and set-up. General machining commonly works to ISO 2768-m; tighter tolerances are possible on specific features but usually increase cycle time and inspection cost, so they are best specified only where function requires them.

Is CNC machining suitable for series production?

For many parts, yes. Because there is no part-specific tooling, machining is economical from one-offs to medium volumes. At higher volumes, casting, forging or extrusion followed by finish machining may be cheaper, depending on geometry.

Should I send a STEP file or a drawing?

Ideally both. The 3D model is used for programming, while the drawing carries tolerances, surface finish, material and notes that a model alone does not.

Do I need 5-axis machining?

Not always. 5-axis machines reach several faces in one set-up and machine compound angles, which helps on complex parts; many parts are made efficiently on 3-axis machines with more set-ups. The right choice depends on geometry and quantity.

CNC Machining by country

Start a Manufacturing Project

Upload a drawing or describe what you need. Process context from this page can be reviewed before it becomes a structured requirement.

Suggested process is prefilled for review — you can change it.