Choosing the Right CNC Material
CNC machining supports an exceptionally wide range of materials, from lightweight aluminium alloys and free-cutting brass to high-performance engineering plastics such as PEEK and PTFE. Choosing the right material is the single most important decision in any machining project, because it directly determines mechanical performance, machinability, surface treatment options, weight, and cost.
We divide materials for CNC machining into two main families: metals and plastics. Metals, including aluminium, steel, stainless steel, brass, copper, and titanium are chosen when high strength, hardness, or thermal performance is required. Engineering plastics, including PEEK, POM (Delrin), Nylon, Polycarbonate, PTFE, and ABS offer lower weight, chemical resistance, electrical insulation, or self-lubricating properties that metals cannot provide.
The sections below explain the key properties, available grades, machinability characteristics, and typical applications for each material family. If you need help selecting a material for a specific part, contact us for a quote. Our engineers will advise on the best choice for your application, tolerances, and budget.
Metal CNC Machining
CNC Machining Metals
Metals are the most common material family for CNC machining. They offer high strength, good thermal conductivity, and in most cases, the ability to accept protective surface treatments such as anodizing, powder coating, or plating. Below are the five main metal families Davantech machines.
ALUMINUM
The most widely used CNC machining metal. Aluminium combines excellent machinability with low density, good corrosion resistance, and compatibility with anodizing and powder coating. It is the default choice for lightweight structural parts, housings, heat sinks, and complex milled components across aerospace, automotive, and electronics industries.
- Excellent machinability
- Anodizable
- Lightweight
Common grades: 6061-T6, 7075-T6, 2024-T3, 5052-H32, 6063
BRASS
Brass is the easiest metal to CNC machine. Its free-cutting grades produce excellent surface finishes, sharp threads, and tight tolerances with minimal tool wear. High electrical and thermal conductivity make it ideal for connectors, fittings, valve bodies, and precision turned components. Brass is routinely used in electronics, plumbing, and precision instrumentation.
- Easiest to machine
- Excellent finish
- High conductivity
Common grades: CW614N, C360, C510 (Phosphor Bronze), C630
STAINLESS STEEL
Stainless steel offers outstanding corrosion resistance, high strength, and excellent hygiene properties. Grade 303 machines more freely than 304 or 316L and is preferred for general turning. Grade 316L adds molybdenum for superior corrosion resistance in marine and chemical environments. Widely used in medical, food processing, marine, and industrial applications.
- Corrosion resistant
- High strength
- Medical grade available
Common grades: 303, 304, 304L, 316, 316L, 17-4 PH
STEEL
Carbon and alloy steels are the backbone of load-bearing and structural applications. Steel 1018 and 1045 are general-purpose grades suited to shafts, gears, and structural brackets. Alloy steels 4140 and 4340 provide higher tensile strength and hardenability for demanding mechanical parts. Steel components can be case-hardened, nitrided, zinc-plated, or powder-coated for protection.
- High strength
- Heat treatable
- Wide availability
Common grades: 1018, 1045, 4140, 4340, A2 tool steel
COPPER
Copper offers the highest electrical and thermal conductivity of all common CNC machining metals, making it indispensable for electrical busbars, heat exchangers, RF components, and electrode contacts. Oxygen-free copper (C101) is used where purity is critical. Copper requires careful workholding and sharp tooling to prevent smearing and maintain dimensional accuracy.
- Highest conductivity
- Thermal management
- Soft — needs care
Common grades: C110, C101 (OFC), C145 (tellurium copper)
TITANIUM
Titanium has the best strength-to-weight ratio of any CNC machining metal, with exceptional corrosion resistance in seawater and body fluids. Grade 2 (commercially pure) suits corrosion-critical applications; Ti-6Al-4V (Grade 5) is the aerospace & medical standard, combining high fatigue strength with biocompatibility. Both require specialist tooling, low cutting speeds, and high coolant flow.
- Best strength/weight
- Biocompatible
- Specialist machining
Common grades: Grade 2 (pure), Grade 5 (Ti-6Al-4V)
Plastic CNC Machining
CNC Machining Engineering Plastics
Engineering plastics are chosen when low weight, electrical insulation, chemical resistance, or self-lubricating properties are required that metals cannot provide. CNC machined plastic parts are found in medical devices, electronics, chemical processing equipment, food contact applications, and many industrial settings. Below are the most commonly machined engineering plastics.
PEEK
PEEK (Polyether Ether Ketone) is the highest-performance machinable thermoplastic. It retains its mechanical properties up to 250°C, resists chemicals, hydrolysis and radiation, and is inherently flame retardant. Biocompatible in its unfilled form. Used in aerospace, medical, semiconductor and chemical processing applications.
- High temp: 250°C
- Biocompatible
- Premium grade
Grades: Unfilled, 30% Glass-filled, 30% Carbon-filled
POM
POM (Polyoxymethylene), also sold as Delrin or Acetal, is the easiest engineering plastic to CNC machine. It offers exceptional stiffness, dimensional stability, low friction, and excellent wear resistance. Resistant to moisture, solvents, and many chemicals. Used for gears, bearings, bushings, valve components, and precision structural parts.
- Easiest to machine
- Low friction
- Self-lubricating
Grades: POM-H (Homopolymer/Delrin), POM-C (Copolymer/Acetal)
NYLON (PA6/PA66)
Nylon (Polyamide) offers high tensile strength, good impact resistance, low friction, and excellent wear resistance. PA66 has a higher melting point (265°C) and greater stiffness than PA6. Both grades absorb moisture. This must be accounted for in tolerancing. Used for gears, bearings, bushings, structural brackets, and cable management components. Read our full Nylon machining guide.
- High strength
- Wear resistant
- Note: moisture absorption
Grades: PA6, PA66, PA12, Glass-filled PA66
PTFE (TEFLON)
PTFE (Polytetrafluoroethylene) has the lowest coefficient of friction of any solid material, exceptional chemical resistance to virtually all acids, bases and solvents, and excellent electrical insulation properties. It is soft and requires careful workholding. Used for seals, gaskets, bearings, electrical insulation, non-stick liners, and chemical handling components. FDA compliant for food contact.
- Lowest friction
- Chemical resistant
- FDA compliant
Grades: Virgin PTFE, Filled PTFE (glass, carbon, bronze)
PC (POLYCARBONATE)
Polycarbonate is a strong, optically transparent thermoplastic with very high impact resistance and good dimensional stability up to ~120°C. It is self-extinguishing and offers good electrical insulation. Used for optical lenses, windows, safety shields, electronic housings, and any application requiring both transparency and toughness. Can be machined to achieve optical-quality surface finishes.
- Optically clear
- High impact strength
- Flame retardant
Grades: Clear PC, UV-stabilised, Glass-filled
ABS
ABS (Acrylonitrile Butadiene Styrene) is a versatile, cost-effective thermoplastic with good impact resistance and ease of machining. It exhibits good dimensional stability, chemical resistance, and can be bonded and painted easily. Used in automotive trim, electronic enclosures, housings, jigs, and prototype functional parts. ABS machines well but generates heat. Adequate coolant and sharp tooling prevent surface melt.
- Cost-effective
- Easy to machine
- Good for prototypes
Grades: Natural ABS, Black ABS, ABS-PC blend
PMMA
PMMA (Polymethyl Methacrylate), commonly known as acrylic or Plexiglas, is a transparent thermoplastic with excellent optical clarity, UV resistance, and weatherability. It is lighter than glass and can be polished to optical-grade surfaces. Used for windows, display panels, light guides, signage, lenses, and cover plates. PMMA machines well but is brittle — cutting parameters must be conservative to prevent cracking.
- Optical clarity
- UV resistant
- Note: brittle
Grades: Clear PMMA, UV-filter PMMA, Impact-modified
PVC
PVC (Polyvinyl Chloride) is a widely used thermoplastic known for its chemical resistance, flame retardancy, and cost-effectiveness. Rigid PVC (uPVC) machines well and is used for pipes, fittings, fluid handling components, and chemical tanks. It offers good electrical insulation and is compatible with most common chemicals. PVC generates chlorine fumes during machining. Good ventilation is essential.
- Chemical resistant
- Flame retardant
- Ventilation required
Grades: uPVC (rigid), CPVC (high-temp), Grey PVC
PE (POLYETHYLENE)
Polyethylene is a low-cost, versatile thermoplastic with high chemical resistance, good electrical insulation, and low friction. HDPE (High-Density PE) is the most common machined grade, rigid, impact-resistant, and FDA-compliant for food contact. UHMW-PE (Ultra-High Molecular Weight) offers outstanding abrasion resistance and is used for wear pads, guide rails, and chute liners. PE is soft and requires sharp tooling to avoid smearing.
- Chemical resistant
- FDA food-safe
- Low cost
Grades: HDPE, LDPE, UHMW-PE
Material Comparison Table
Side-by-side comparison of the most commonly used CNC machining materials. Machinability ratings are relative (5 = excellent/easiest, 1 = very difficult). Use this table as a starting point. Specific alloy selection should always consider the full application requirements.
| Material | Machinability | Density | Strength | Corrosion | Typical use |
|---|---|---|---|---|---|
| Metals | |||||
| Aluminium 6061-T6 | ●●●●● | 2.7 g/cm³ | 276 MPa | Good | Housings, brackets, heat sinks |
| Aluminium 7075-T6 | ●●●●○ | 2.81 g/cm³ | 572 MPa | Good | Aerospace, high-load structural |
| Brass CW614N | ●●●●● | 8.5 g/cm³ | 400 MPa | Good | Connectors, fittings, valve bodies |
| Stainless 303 | ●●●○○ | 7.9 g/cm³ | 620 MPa | Excellent | Shafts, fasteners, medical parts |
| Stainless 316L | ●●○○○ | 7.98 g/cm³ | 485 MPa | Excellent+ | Marine, food, medical, chemical |
| Steel 4140 | ●●●○○ | 7.85 g/cm³ | 655–1000 MPa | Low | Gears, shafts, dies, tools |
| Copper C110 | ●●●●○ | 8.9 g/cm³ | 220 MPa | Good | Busbars, heat exchangers, contacts |
| Titanium Ti-6Al-4V | ●●○○○ | 4.43 g/cm³ | 1000 MPa | Excellent | Aerospace, medical implants |
| Engineering Plastics | |||||
| PEEK | ●●●●○ | 1.32 g/cm³ | 100 MPa | Excellent | Aerospace, medical, semiconductor |
| POM (Delrin) | ●●●●● | 1.41 g/cm³ | 68 MPa | Good | Gears, bearings, precision parts |
| Nylon PA66 | ●●●●○ | 1.14 g/cm³ | 82 MPa | Good | Gears, bushings, structural parts |
| PTFE | ●●●○○ | 2.2 g/cm³ | 25 MPa | Excellent | Seals, gaskets, chemical handling |
| Polycarbonate | ●●●●○ | 1.2 g/cm³ | 62 MPa | Good | Lenses, windows, enclosures |
Material Selection
How to Choose the Right Material?
Material selection depends on five main factors: mechanical requirements, operating environment, weight constraints, surface treatment compatibility, and budget. Use the cards below as a starting framework, then discuss your specific application with our engineers for a definitive recommendation.
NEED LOW WEIGHT?
Weight is a constraint, aerospace, portable equipment, or moving parts
→ Aluminium 6061 or 7075. If even lighter: PEEK or Nylon. Titanium where strength/weight ratio is paramount.
NEED HIGH STRENGTH?
Load-bearing, structural, or high-cycle fatigue applications
→ Steel 4140 or 4340 (heat treatable). Ti-6Al-4V for high strength + low weight. Stainless 17-4 PH for corrosion resistance + strength.
NEED CORROSION RESISTANCE?
Marine, food, medical, or chemical processing environments
→ Stainless 316L for general corrosion. PTFE or PEEK for aggressive chemicals. Titanium Grade 2 for seawater or body fluid exposure.
NEED ELECTRICAL INSULATION?
Electrical enclosures, connectors, PCB spacers, or HV components
→ PEEK for high-temperature insulation. Polycarbonate for transparent enclosures. Nylon or POM for general insulation and structural plastic parts.
NEED HIGHEST MACHINABILITY?
High volumes, tight tolerances, fast cycle times, or complex threads
→ Brass CW614N (best metal). Aluminium 6061 (metals in general). POM/Delrin (best plastic). These materials are cost-effective in volume and produce excellent surface finishes.
NEED FOOD/MEDICAL CONTACT
FDA compliance, biocompatibility, or cleanroom requirements
→ Stainless 316L (passivated). Titanium Grade 2. PEEK (unfilled). PTFE (virgin). UHMW-PE. All are FDA/USP-compatible depending on grade and application.
Frequently Asked Questions
Common questions about material selection for CNC machining — answered by Davantech's engineering team.
What materials can be used for CNC machining?
CNC machining supports a broad range of metals and engineering plastics. Common metals include aluminium alloys (6061, 7075, 2024), brass (CW614N, C360), copper (C110), stainless steel (303, 304, 316L), carbon and alloy steels (1018, 1045, 4140), and titanium (Grade 2, Ti-6Al-4V). Common engineering plastics include PEEK, POM (Delrin/Acetal), Nylon (PA6, PA66), Polycarbonate (PC), PTFE (Teflon), ABS, PMMA (Acrylic), PVC, PE, and PPS.
Which metal is best for CNC machining?
Aluminium (especially 6061-T6 and 7075-T6) is the most commonly used metal for CNC machining due to its excellent machinability, low weight, and corrosion resistance. Brass (CW614N, C360) is technically the easiest metal to machine — free-cutting grades produce excellent surface finishes with minimal tool wear and are ideal for high-volume precision turning. For applications requiring high strength at elevated temperatures, stainless steel 303 or 316L is preferred. Titanium Ti-6Al-4V offers the best strength-to-weight ratio but requires specialised tooling and slower cutting speeds.
What is the easiest plastic to CNC machine?
POM (Polyoxymethylene/Delrin/Acetal) is generally the easiest engineering plastic to CNC machine. It machines cleanly, holds tight tolerances, has excellent dimensional stability, and produces excellent surface finishes without burring. Nylon (PA6/PA66) and PTFE are also straightforward to machine but require attention to workholding — Nylon can distort under clamping pressure, and PTFE's low stiffness requires solid support.
What is the difference between PA6 and PA66 Nylon for CNC machining?
PA6 and PA66 are both Nylon (Polyamide) grades used in CNC machining. PA66 has a higher melting point (265°C vs 220°C for PA6), greater stiffness, and better resistance to heat and abrasion. PA6 has slightly better impact resistance and toughness, and is more widely available as machining bar stock. Both grades absorb moisture, which can cause dimensional changes of 0.5–2% — parts with tight tolerances should be conditioned in their service environment before final inspection.
Can PEEK be CNC machined?
Yes. PEEK (Polyether Ether Ketone) machines well and is one of the most capable engineering plastics available for CNC work. It maintains its mechanical properties up to 250°C, offers excellent chemical resistance, is inherently flame retardant, and is biocompatible in its unfilled form. PEEK is more expensive than other engineering plastics and requires sharp carbide tooling, correct speeds and feeds, and controlled chip evacuation to avoid thermal degradation of the cut surface.
How do I choose the right material for CNC machining?
Material selection should consider five main factors: (1) Mechanical requirements — strength, hardness, fatigue life, wear resistance; (2) Operating environment — temperature range, chemical exposure, corrosion risk, sterilisation requirements; (3) Weight constraints — aluminium and engineering plastics save significant weight over steel; (4) Surface treatment compatibility — not all materials accept all coatings; (5) Budget and volume — aluminium and brass are the most cost-effective options, titanium and PEEK are premium. Davantech provides free DFM and material advice with every quotation — submit your drawings and we will recommend the most suitable material for your application.