What Materials Can Be CNC Machined?

The Short Answer

CNC machining handles most metals and rigid engineering plastics. We group materials into three machinability tiers: free-cutting metals such as aluminium 6061 and brass; moderate-difficulty alloys including stainless steel 304 and carbon steel; and challenging materials like titanium Grade 5, PEEK, and tool steels. Higher hardness or thermal sensitivity increases cycle time and tool wear.

Metal Families

Aluminium (6061 / 7075)

Aluminium offers excellent machinability, high strength-to-weight ratio, and predictable chip formation. Alloy 6061 is the default for general brackets and enclosures, while 7075 suits high-stress aerospace components. Standard tolerance for aluminium is ±0.01 mm.

Carbon Steel

Carbon steel provides high structural rigidity at a lower raw material cost than alloy steels. It machines well but requires flood coolant to manage heat and prevent built-up edge. Typical applications include shafts, gears, and heavy-duty automation frames.

Stainless Steel (303 / 304 / 316L)

Grade 303 contains sulfur for improved chip breaking, making it ideal for high-volume CNC turned parts. Grades 304 and 316L work-harden quickly and demand rigid setups with sharp tooling. They are standard for medical devices and food-contact hardware.

Copper & Brass

Brass is exceptionally stable during cutting, yielding fine surface finishes without extensive deburring. Pure copper is gummy and requires specific rake angles to avoid tearing. Both hold a standard tolerance of ±0.05 mm due to their softness.

Titanium (Grade 5 / Ti-6Al-4V)

Titanium Grade 5 combines low thermal conductivity with high strength, requiring slow feed rates and abundant coolant. It is specified for aerospace fasteners and surgical implants where biocompatibility is mandatory. Tight tolerances require careful thermal management during the cut.

Tool Steels

Tool steels are typically machined in an annealed state before final heat treatment. Hard-milling after quenching demands specialized tooling and is reserved for mold inserts and die components. Lead times increase due to secondary processing steps.

Engineering Plastics

POM / Delrin

POM cuts cleanly with sharp edges and minimal burrs, behaving similarly to free-cutting metals. It has low moisture absorption, ensuring dimensional stability after machining. We hold ±0.05 mm for POM components.

PEEK

PEEK requires controlled cutting speeds to prevent localized melting and thermal deformation. Clamping forces must be minimized to avoid distorting the semi-finished blank. It is used for sterilizable medical and semiconductor parts.

Nylon

Nylon absorbs ambient moisture, which can cause slight swelling if not conditioned properly before final inspection. Machining generates stringy chips that require frequent clearing. Tolerances are held to ±0.05 mm.

PTFE

PTFE is extremely soft and deforms easily under standard vise pressure. Dedicated soft jaws or vacuum fixtures are necessary to maintain geometry. Deburring must be done manually with sharp blades rather than abrasive tumbling.

How to Choose the Right Material

For deeper insights into achievable limits, review our guide on CNC machining tolerances.

How to Specify Material on a Drawing

• Grade and temper: Always state the exact designation, such as "Aluminium 6061-T6" or "Stainless Steel 316L". Avoid generic terms like "aluminium" or "steel".
• Certification requirements: If traceability is critical, explicitly request a material certificate per EN 10204 3.1 on the drawing title block.
• Substitutions: State whether equivalent grades are acceptable. If no substitution is allowed, write "No material substitution permitted".
• Stock form: Indicate if the part must be machined from plate, bar, forging, or casting, as this affects grain flow and mechanical properties.
• Heat treatment: Specify the required condition after machining, such as "annealed", "T6", or "hardened to 45 HRC".

What Changes the Price

Material removal volume directly dictates machine time; starting with oversized stock increases both raw material waste and spindle hours. Harder materials like titanium and tool steels consume cutting tools faster and require slower parameters. Thin walls introduce vibration risks, often necessitating custom fixtures or multiple roughing passes.

Tighter tolerances—such as ±0.005 mm evaluated per project, or ±0.002 mm achieved via grinding—increase inspection time and scrap risk. Batch size matters significantly; setup costs amortize over larger runs, though we accept orders starting from 1 piece. Finally, raw material market volatility means quotes are valid for a limited window.

Material and Finish Compatibility

Surface treatments depend entirely on the substrate. Aluminium accepts Type II and Type III anodising, while steel requires zinc plating, nickel plating, black oxide, or powder coating. Stainless steel is typically passivated or polished, and copper alloys respond well to nickel plating. Sandblasting serves as a universal pre-treatment across most metals. Review our full manufacturing capabilities to see how our 50+ CNC machines process these combinations.

Pre-Submission Checklist

Before sending your files for quotation, verify the following points to ensure our engineers can respond within 24 hours:

• Material grade and temper are clearly stated on the drawing.
• Critical tolerances are highlighted; non-critical dimensions follow standard machining practices.
• Required surface finishes (e.g., Ra 0.4 µm) are specified on relevant faces.
• Quantity is defined, keeping in mind our 1-piece minimum order.
• Documentation needs, such as First Article Inspection (FAI) reports or EN 10204 3.1 certificates, are noted.
• 3D CAD models match the 2D PDF drawings exactly. Check our guide on what files you need for a CNC quote for format details.

Our quality control process utilizes Mitutoyo height gauges, VMS, and CMM (±0.003 mm) to verify every batch against these specifications. Whether you need complex CNC milled parts or precision turned components, clear documentation accelerates production. Our equipment list includes 3+2 five-axis centres, turn-mill machines, wire EDM, and surface grinders ready for your project.

FAQ

Can you machine both metals and plastics?

Yes, our facility processes aluminium, steel, stainless steel, copper, brass, titanium, and engineering plastics like POM and PEEK. Each material requires specific tooling and fixturing strategies to maintain dimensional accuracy.

What is the tightest tolerance you can hold?

We routinely hold ±0.01 mm for metals and achieve ±0.002 mm through surface grinding operations. Tolerances tighter than ±0.005 mm are evaluated on a project-by-project basis depending on geometry and material.

Do I need to supply my own raw material?

No, we source all raw materials directly from certified suppliers to ensure consistent quality. If you require specific mill certificates, simply request an EN 10204 3.1 document on your purchase order.

What is the minimum order quantity?

We accept orders starting from a single prototype piece up to full production batches. Small quantities are ideal for design validation before committing to larger manufacturing runs.

How long does it take to get a quote?

Our engineering team reviews submitted drawings and 3D models to provide a detailed quotation within 24 hours. Complex assemblies requiring custom fixtures may occasionally need slightly more evaluation time.

Which surface finishes do you offer in-house?

We provide eight surface treatments including Type II and Type III anodising, powder coating, zinc and nickel plating, passivation, polishing, black oxide, and sandblasting. The available finishes depend strictly on the base material selected for your part.