What is CNC milling, and when should I choose it over CNC turning?

Choose CNC milling for flat, prismatic, multi-sided, or complex surface features. CNC turning is usually more efficient for cylindrical parts, while mill-turn is useful when rotational parts also require flats, slots, or cross-holes.

What is the difference between 3-axis, 4-axis, and 5-axis CNC milling?

The main difference is tool access and setup strategy, not simply accuracy. 3-axis suits accessible prismatic features, 4-axis adds rotary access, and 5-axis is useful for compound angles, deep cavities, multi-face parts, and complex surfaces.

What materials can be CNC milled?

Most engineering metals and plastics can be milled, including aluminum, stainless steel, steel, titanium, brass, bronze, copper, ABS, POM, nylon, PC, PMMA, PTFE, PEEK, PEI, and G10/G11. Material choice should consider load, environment, dimensional stability, finish, and cost.

What tolerances can CNC milling achieve?

Critical features can reach ±0.005 mm on suitable parts. Actual capability depends on material, size, geometry, tool reach, workholding, thermal behavior, and inspection method.

Can you support both prototype and production CNC milling?

Yes. We support one-off functional prototypes and low-volume or repeat production. Prototypes focus on fit, material, function, and finish; production adds stable fixtures, machining sequences, inspection, and repeatability controls.

How much does custom CNC milling cost?

Cost depends mainly on material, machining time, setups, axis requirements, deep features, tolerances, inspection, and finishing. Larger internal radii and tighter tolerances only where needed can reduce machining time and cost.

What files should I send for a CNC milling quote?

A STEP file is enough to start. Add a 2D drawing when the part has GD&T, critical fits, threads, specific surface roughness, coating requirements, or inspection requirements. Material and quantity also improve quote accuracy.

How quickly can CNC milled parts be delivered?

Simple prototype parts can be delivered in a few business days. Complex multi-axis geometry, difficult materials, tight inspection, heat treatment, or secondary finishing will extend lead time.

Can CNC milling produce threaded holes?

Yes. Standard metric, UNC, and UNF threads can be tapped or thread milled. Thread milling is particularly useful for larger diameters, difficult materials, deeper features, and some non-standard threads.

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Our CNC Milling Capabilities

3-Axis CNC Milling

For plates, brackets, housings, pockets, and slots with straightforward tool access. Usually the most cost-effective choice for simple prismatic parts.

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4-Axis CNC Milling

Adds rotary access for side holes and multi-sided features, reducing re-clamping and helping maintain feature relationships.

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5-Axis CNC Milling

For compound angles, deep cavities, complex surfaces, and multi-face parts. Ultra-precision machining is available down to ±0.0025 mm on suitable critical features.

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Mill-Turn Machining

For rotational parts with flats, slots, cross-holes, or other milled features. Combining turning and milling reduces transfers between machines.

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Choosing the Right CNC Milling Process

More axes do not automatically mean higher accuracy. Choose the simplest process that reaches the required features while controlling setups, tool access, cycle time, and cost.

Process	Best For	Main Engineering Benefit	Key Limitation / Cost Driver
3-Axis Milling	Plates, brackets, flat housings, fixtures, pockets	Simple setup and lower machining cost	Side and angled features may require additional setups
4-Axis Milling	Multi-sided parts, side holes, indexed cylindrical features	Rotary access reduces re-clamping	Complex freeform surfaces may still require 5-axis machining
5-Axis Milling	Complex housings, angled holes, deep cavities, curved surfaces	Multi-direction access with fewer setups and shorter tool reach	More complex programming and machine time; unnecessary for simple parts
Mill-Turn	Shafts, bushings, connectors and rotational parts with milled features	Keeps turned and milled features within a coordinated process	Most economical when the main geometry is rotational

From CNC Prototypes to Repeat Production

CNC prototypes validate fit, function, material, and finish. Repeat production adds stable workholding, inspection, and process control.

CNC Milling Prototyping

Machine functional prototypes in intended materials to verify fit, assembly, performance, and finishing before design release.

Start from 1 piece
Test intended metals or plastics
Critical features down to ±0.005 mm
Validate fit, threads & interfaces

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CNC Milling Production

Move approved designs into repeat production with controlled setups, workholding, inspection, and finishing.

1–2,000 pcs low-volume production
Stable fixtures & machining sequences
FAI/CMM for critical dimensions & GD&T
Finishing, marking & assembly coordination

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Custom & Specialty CNC Milling

Micro features, thread milling, thin walls, and deep cavities require careful control of tool access, deflection, workholding, and inspection. Share the CAD before freezing these features.

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CNC Machining Materials

Material choice affects machinability, dimensional stability, tool wear, burr formation, and finishing. The same geometry can behave very differently across metals and engineering plastics.

Aluminum

Stainless Steel

Steel

Brass

Copper

Titanium

Zinc

ABS

Delrin® (Acetal / POM)

Polycarbonate (PC)

Nylon

Acrylic (PMMA)

PTFE (Teflon®)

PEEK

ULTEM®

Garolite

Aluminum

Aluminum combines low weight, good machinability, and a broad range of strength levels. Alloy selection should consider load, corrosion environment, dimensional stability, and the required surface finish.

Key Characteristics

Lightweight with high strength-to-weight ratio

Excellent machinability

Good corrosion resistance

Cost-effective for most applications

Suitable for cosmetic surface treatments

Common Grades: 6061, 6063, 2024, 7075, 7050, MIC-6

Typical Applications: Consumer Electronics, Robotics, Industrial Equipment, Automotive Components, Aerospace Structures

Available Finishes: As-Machined, Anodizing, Bead Blasting, Powder Coating, Painting, Polishing

Stainless Steel

Stainless steel combines corrosion resistance, strength, and durability, but grades such as 304 and 316 require more control of heat, tool wear, and work hardening than free-machining alloys.

Key Characteristics

Excellent corrosion resistance

High mechanical strength

Good wear resistance

Suitable for demanding environments

Long service life

Common Grades: 303, 304, 316, 316L, 17-4 PH, 420

Typical Applications: Medical Devices, Food Processing Equipment, Industrial Machinery, Marine Components, Energy Systems

Available Finishes: As-Machined, Passivation, Electropolishing, Brushed Finish, Polishing

Steel

Steel provides high strength, stiffness, and wear resistance for structural, tooling, and load-bearing parts, with machining behavior strongly affected by alloy and hardness.

Key Characteristics

High strength and toughness

Excellent wear resistance

Good machinability

Heat treatable

Cost-effective for industrial applications

Common Grades: 1018, 1215, 4130, 4140, 4140PH, 4340, A2 Tool Steel, O1 Tool Steel

Typical Applications: Machine Components, Tooling, Industrial Equipment, Structural Assemblies

Available Finishes: As-Machined, Black Oxide, Plating, Powder Coating, Painting

Brass

Brass offers excellent machinability, dimensional stability, corrosion resistance, and good electrical conductivity for precision fittings, connectors, and instrument parts.

Key Characteristics

Outstanding machinability

Good corrosion resistance

Excellent dimensional stability

Attractive appearance

Good electrical conductivity

Common Grades: C260, C360

Typical Applications: Connectors, Valves, Fittings, Instrument Components, Decorative Hardware

Available Finishes: As-Machined, Polishing, Nickel Plating, Chrome Plating

Copper

Copper is selected for electrical and thermal performance, but its ductility can increase burr formation and built-up edge during machining.

Key Characteristics

Excellent electrical conductivity

Outstanding thermal conductivity

Good corrosion resistance

Suitable for precision milling

High ductility

Common Grades: C101, C110

Typical Applications: Busbars, Heat Sinks, Electrical Contacts, Power Distribution Components

Available Finishes: As-Machined, Polishing, Plating

Titanium

Titanium combines high strength-to-weight ratio, corrosion resistance, and biocompatibility, but low thermal conductivity increases cutting heat and tool wear.

Key Characteristics

High strength-to-weight ratio

Excellent corrosion resistance

Heat resistant

Biocompatible

Suitable for harsh environments

Common Grades: Grade 2, Grade 5 (Ti-6Al-4V)

Typical Applications: Aerospace Components, Medical Devices, Robotics, Performance Equipment

Available Finishes: As-Machined, Bead Blasting, Polishing

Zinc

Zinc alloys offer good dimensional stability and cost efficiency for functional and decorative components. They are commonly used where moderate strength and corrosion resistance are required.

Key Characteristics

Cost-effective

Good corrosion resistance

Easy to machine

Suitable for decorative applications

Common Grades: Zinc Alloy

Typical Applications: Consumer Products, Decorative Hardware, Mechanical Components

Available Finishes: As-Machined, Plating, Powder Coating, Painting

ABS

ABS CNC milling is a cost-effective solution for functional prototypes and production parts requiring toughness, impact resistance, and ease of fabrication.

Key Characteristics

Good impact resistance

Cost-effective

Easy to machine

Lightweight

Common Grades: ABS Standard

Typical Applications: Functional Prototypes, Housings, Consumer Products, Industrial Components

Available Finishes: As-Machined, Vapor Polishing, Painting

Delrin® (Acetal / POM)

Delrin milling is commonly used for precision plastic parts requiring low friction, dimensional stability, and wear resistance. It performs exceptionally well in moving mechanical assemblies.

Key Characteristics

Low friction coefficient

Excellent dimensional stability

Good wear resistance

Moisture resistant

Common Grades: Delrin 100, Delrin 150

Typical Applications: Gears, Bearings, Bushings, Mechanical Assemblies

Available Finishes: As-Machined, Fine Surface Finishing

Polycarbonate (PC)

Polycarbonate milling provides excellent impact resistance and optical clarity. It is widely used for transparent and protective components requiring superior toughness.

Key Characteristics

High impact resistance

Transparent

Tough and durable

Good dimensional stability

Common Grades: PC Standard

Typical Applications: Protective Covers, Machine Guards, Optical Components, Enclosures

Available Finishes: As-Machined, Polishing

Nylon

Nylon milling is ideal for durable engineering components that require wear resistance, low friction, and mechanical strength in demanding industrial environments.

Key Characteristics

High wear resistance

Good toughness

Low friction

Lightweight

Common Grades: Nylon 6, Nylon 6/6

Typical Applications: Gears, Rollers, Bearings, Wear Components

Available Finishes: As-Machined

Acrylic (PMMA)

Acrylic milling is commonly used for transparent components requiring optical clarity, excellent appearance, and weather resistance.

Key Characteristics

Excellent transparency

Good weather resistance

Lightweight

Easy to machine

Common Grades: PMMA Standard

Typical Applications: Display Components, Lighting Covers, Signage, Optical Applications

Available Finishes: As-Machined, Polishing

PTFE (Teflon®)

PTFE milling is preferred for components requiring exceptional chemical resistance, low friction, and reliable performance in aggressive operating conditions.

Key Characteristics

Excellent chemical resistance

Very low friction

Non-stick surface

High temperature resistance

Common Grades: Virgin PTFE, Filled PTFE

Typical Applications: Seals, Bearings, Chemical Processing Equipment, Insulation Components

Available Finishes: As-Machined

PEEK

PEEK milling is widely used for high-performance components in aerospace, medical, semiconductor, and industrial applications. It offers outstanding mechanical strength, thermal stability, and chemical resistance.

Key Characteristics

High temperature resistance

Excellent chemical resistance

Outstanding dimensional stability

High mechanical strength

Common Grades: PEEK Natural, PEEK GF30, Medical-Grade PEEK

Typical Applications: Medical Devices, Aerospace Components, Semiconductor Equipment, Electrical Components

Available Finishes: As-Machined, Fine Surface Finishing, Polishing

ULTEM®

ULTEM milling is suitable for demanding applications requiring high strength, heat resistance, dimensional stability, and flame-retardant performance.

Key Characteristics

High temperature resistance

Excellent dimensional stability

Flame resistant

High strength

Common Grades: ULTEM 1000, ULTEM 2300

Typical Applications: Aerospace Interiors, Medical Equipment, Electrical Insulation, Industrial Components

Available Finishes: As-Machined

Garolite

Garolite milling is commonly used for structural and electrical applications requiring high strength, dimensional stability, and excellent insulation properties.

Key Characteristics

Excellent electrical insulation

High mechanical strength

Lightweight

Moisture resistant

Common Grades: Garolite G10, Garolite G11

Typical Applications: Electrical Insulators, Industrial Fixtures, Structural Components

Available Finishes: As-Machined

Surface Finishing Options for CNC Milled Parts

Plan finishing before machining when tight bores, threads, mating faces, or cosmetic surfaces are involved. Coating build or material removal can change final dimensions and fit.

Finish	Typical Result	Engineering Consideration
As Machined	Visible machining pattern; typically Ra 1.6–3.2 μm	Lowest-cost option; specify a tighter Ra only where function requires it
Bead Blasting	Uniform matte texture	Can soften very sharp edges and change cosmetic appearance between lots
Type II Anodizing	Corrosion protection and decorative color on aluminum	Coating growth can influence tight fits; threads and mating surfaces may need masking
Type III Hard Anodizing	Harder, more wear-resistant aluminum surface	Greater dimensional build than decorative anodizing; allow for coating on precision bores and interfaces
Passivation	Improved corrosion resistance on stainless steel	Minimal dimensional change; does not create a thick coating
Electroless Nickel / Zinc Plating	Corrosion, wear or functional surface protection	Adds coating thickness; account for final fit on holes, threads and mating surfaces
Chem Film / Chromate Conversion	Thin corrosion-protection layer on aluminum	Lower dimensional build than anodizing and useful where electrical conductivity matters
Powder Coating / Painting	Protective or cosmetic colored coating	Coating thickness makes masking important around precision interfaces
Polishing / Brushing	Cosmetic or lower-roughness surface	Removes material and may round edges, so avoid uncontrolled polishing on critical datums
Laser Marking	Permanent text, serial numbers or identification	Minimal dimensional influence on the machined geometry
Deburring / Edge Break	Removes burrs and sharp machining edges	Define edges that must remain sharp or dimensionally controlled

CNC Milling Tolerances & Design Guidelines

Critical features can reach ±0.005 mm, with ultra-precision 5-axis machining down to ±0.0025 mm on suitable parts.

Item	Capability / Guideline	Engineering Consideration
Ultra-Precision 5-Axis Features	Down to ±0.0025 mm	For suitable critical features; depends on geometry, material and inspection method
Critical Feature Tolerance	Down to ±0.005 mm	Practical tight-tolerance capability for defined functional and mating features
General Machined Dimensions	Typically ±0.05–0.10 mm	Depends on material, size and geometry
Minimum Part Size	5 × 5 × 5 mm	Very small parts require stable workholding
As-Machined Roughness	Typically Ra 1.6–3.2 μm	Lower Ra may require dedicated finishing passes
Minimum Hole Diameter	Ø1 mm	Small or deep holes depend on tool length and material
Hole Depth	Prefer ≤4× diameter	Deeper holes may require special tooling
Minimum Wall Thickness	Metal 0.8 mm / Plastic 1.5 mm	Thin walls are sensitive to cutting force, heat, and clamping
Internal Corner Radius	≥ ~1/3 pocket depth preferred	Larger radii allow stronger, shorter tools
Threads	ISO Metric, UNC, UNF	Deep or non-standard threads require review
Flatness / Perpendicularity	Part-specific	Depends on size, material condition, and workholding

CNC Milling Equipment & Manufacturing Capabilities

Processing Equipment

CNC Milling Project Showcase

Why Choose Mastars for CNC Milling?

Quality Systems

ISO 9001, ISO 13485, and IATF 16949 systems support controlled inspection and documentation. CMM, FAI, and in-process checks verify critical dimensions, hole positions, and GD&T requirements.

Engineering & Project Support

100+ engineers support design review, machining strategy, tooling, quality, and production coordination from prototype development to manufacturing release.

Manufacturing Experience

Backed by 20+ years of manufacturing experience, Mastars supports CNC milling projects from prototype validation to repeat production with stable process control.

Flexible Capacity

5+ production bases support one-piece prototypes, low-volume builds, pilot quantities, and repeat CNC production from 1 to 100,000+ units.

CNC Milling DFM Review

Manufacturing risks including tool access, deep pockets, thin walls, workholding, and tolerance requirements are reviewed before machining.

Integrated Manufacturing

CNC milling, 3D printing, sheet metal, metal casting, injection molding, tooling, finishing, assembly, and inspection are coordinated within one manufacturing program.

Certifications

ISO9001:2015 Certificate

IATF16949:2016 Certificate

ISO13485:2016 Certificate

Medical A-Class Supplier

Partners

How CNC Milling Works

Upload Your Design

Share your CAD files, drawings, quantity, material, and any critical requirements.

Get an Engineer-Reviewed Quote

Receive pricing, lead time, and manufacturability feedback based on your part requirements.

Production Begins

Once you approve your quote, manufacturing starts — from prototype tooling to full-scale runs.

Parts Shipped

Finished parts are inspected, packaged, and shipped with the required quality documentation.

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