CNC Milling Service

Get custom milled parts for rapid prototyping and production.

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Certifications ISO 9001:2015

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Our CNC milling process produces custom prototypes and production parts in as fast as 1 day using advanced 3-axis and 5-axis indexed milling technologies. We machine more than 30 engineering-grade metals and plastics, delivering precision parts for industries ranging from aerospace to consumer products.

In addition to rapid manufacturing, we offer FAI reports, material certifications, anodizing, chromate conversion coating, powder coating, and other finishing options to meet your project requirements.

For larger production volumes, our manufacturing network provides cost-effective pricing without compromising quality, traceability, or performance.

Our CNC milling service is commonly used for:

functional prototypes
jigs and fixtures
production components in lower volumes

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CNC Milling Design Guidelines and Capabilities

Our CNC milling design guidelines provide essential Design for Manufacturability (DFM) recommendations to improve part manufacturability, enhance surface quality, reduce machining complexity, and optimize overall production efficiency.

Maximum Dimensions
Minimum Dimensions
Threading
Tolerances
Radii

Maximum Dimensions

Maximum depth that can be milled is 2 in. (50.8mm) from either side of part. For specific milling dimensions by material, see maximum part extents for machining.

	Material	US	Metric
3-axis**	ABS Acetal	10 in. x 14 in. x 1.75 in.	254mm x 356mm x 44.5mm
3-axis**	ABS Acetal Nylon	22 in. x 14 in. x 0.75 in.	559mm x 356mm x 19.1mm
3-axis**	Aluminum	22 in. x 14 in. x 3.75 in.	559mm x 356mm x 95.3mm
5-axis	Hard metals* Brass Copper	10 in. x 7 in. x 1.75 in.	254mm x 178mm x 44.45mm
5-axis	Aluminum	10 in. x 7 in. x 3.75 in.	254mm x 178mm x 95.3mm
5-axis	Stainless Steel 304	4.25 in. x 3.25 in. x 3.75 in.	107.95mm x 82.55mm x 95.25mm

*Hard metals: Titanium (6Al-4V), Stainless Steels (303, 316, 17-4PH), Steel Alloy (4140)

**Denotes two-sided machining only

Minimum Dimensions

	US	Metric
Size	0.25 in. x 0.25 in	6.35mm x 6.35mm
Nominal Thickness	0.040 in.	1.02mm

Threading

In the Protolabs automated factory, we currently support UNC and UNF threads from #2 up to 0.5 in., and metric threads from M2 to M12. Avoid modeling internal threads on your part design.

We also offer the following for milled parts:

Coil inserts
Key inserts

Tolerances

Standard Tolerances
For parts that don’t require a technical drawing we typically can hold a machining tolerance of +/- 0.005 in. (0.13mm). Part features are recommended to be thicker than 0.020 in. (0.51mm) in all regions and a nominal part thickness above 0.040 in.

High-Requirement Tolerances
For additional tolerance requirements, we require a technical drawing at time of upload. Linear tolerance quoted to ISO 2768-1-1989-f, standard hole tolerance of +/- 0.005 in. (0.13mm) and hole and bore-style tolerance on specified features may be +/- 0.0005 in. (0.01mm).

Radii

Sharp inside corners on a part will be radiused (rounded) as a natural result of the CNC machining process. Resulting radii will be the minimum allowable tool radius.

Maximum Dimensions

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Minimum Dimensions

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Threading

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Tolerances

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CNC Machining Services for End-Use Parts

Get high‑quality machined parts faster with our expanded automated CNC milling—parts ready in as fast as 4 days

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CNC Milling Werkstoffe

We stock more than 30 production-grade plastic and metal materials to support a wide range of applications across diverse industries, ensuring the ideal material solution for both prototypes and end-use production parts.

Plastics

ABS
Acetal
CPVC
HDPE
Nylon
PEEK
PEI
PET

PMMA
Polycarbonate
Polypropylene
POM (Delrin)
PPSU
PTFE
PVC

Metals

Aluminum
Brass
Copper
Stainless Steel
Steel Alloy
Steel Mild Low Carbon
Titanium

Evaluate standard surface finishes for CNC machined parts as well as advanced capabilities to improve durability, surface finish, and add color.

Explore Options

Surface Finish on Milled Parts

By default, all CNC machined parts are deburred to remove sharp edges and improve handling safety. Plastic parts are supplied in an as-machined condition, which may retain visible machining marks. For metal components, a variety of surface finishing options are available to enhance appearance, surface quality, and performance. If sharp edges are specifically requested, parts should be handled with appropriate care.

Material: ABS Black
Finish: Broken edge

Material: ABS Natural
Finish: Broken edge

Material: Aluminum
Finish: Broken edge

cnc milled aluminum part with bead blast finish

Material: Aluminum
Finish: Bead Blast

Material: Aluminum
Finish: Sharp edge

What is CNC Milling and How Does it Work?

CNC milling is a subtractive manufacturing process. It starts by fixturing a block of metal or plastic material inside the CNC mill. Using G-code, the CNC machine is programmed to rapidly mill out parts from the block of raw material. Our 3- and 5-axis CNC machines are equipped with various toolsets to maximize efficiency and production speed.

Machined plastic parts are left as-milled, which typically means they show visible tool marks. Some metal parts allow more finishing choices like anodizing and chromate plating. When the run is complete and your required surface finish is applied, parts are boxed and shipped shortly thereafter.