Online Custom CNC Milling Services
3ERP provides CNC milling services with competitive pricing. Equipped with advanced 3-, 4-, and 5-axis CNC milling machines, we deliver consistent quality, tight tolerances, and fast turnaround for projects large or small.
- Custom CNC Machined Prototypes (One-Off & Small Batch)
- High-Volume Production: 100K+ Units
- Precision Tolerances up to ±0.01 mm
- All uploads are secure and confidential.
High Quality Rapid CNC Milling Service
Xometry integrates seamlessly with thousands of qualified manufacturing partners, including US-based ITAR-registered, AS9100D, ISO 9001, and ISO 13485 certified CNC milling facilities. Our massive network enables us to accommodate almost any milling requirement. We support 3-axis, 4-axis, 5-axis, and right-angle milling capabilities to help you rapidly create designs from simple straight lines to complex geometric shapes.
Xometry offers instant pricing, on-demand lead times, and design-for-manufacturability feedback on custom CNC-milled parts, regardless of industry. Get your instant quote today. The price of milled prototypes includes tariffs and shipping for standard parcels.
Our CNC Milling Capabilities
From simple prototypes to highly complex components, our advanced milling capabilities — including 3-axis, 4-axis, and 5-axis CNC machining — bring your designs to life with unmatched precision. By utilizing both vertical and horizontal milling setups, we efficiently handle a wide range of geometries and part sizes while maintaining high dimensional accuracy and fast turnaround times.
3-Axis CNC Milling Service
3-Axis CNC milling is the most cost-effective way to get simple CNC prototypes and production parts done with accuracy demands.
4-Axis CNC Milling Service
Besides less set-up compared with 3-axis milling, 4-axis milling is an exclusive option for the long parts with features on the side wall.
5-Axis CNC Milling Service
5-Axis CNC milling is the best solution for complex precision parts. The workpieces can be milled from multiple directions.
Flexible CNC Milling Solutions
Our advanced online CNC machining services offer the flexibility to meet your design needs and development timelines. We produce prototypes, test parts, and low-volume production runs with the speed and accuracy needed for modern product development.
Rapid Prototyping
With custom milling, 3ERP can quickly produce high-precision CNC prototypes, functional prototype parts, and intricate machined components for various applications before full-scale production.
Low and High-Volume Production
Our low-volume milling services deliver precision parts quickly and cost-effectively. With flexible production, rapid turnaround, and no tooling costs, we help you validate designs, bridge to full production, or fulfill small-batch orders with consistent quality.
CNC Milling Materials
At 3ERP, we provide a full range of CNC milling surface finishes that enhance both functionality and appearance, improving durability, resistance to corrosion, and aesthetics as part of our comprehensive CNC machining process.
Aluminum is a highly versatile CNC machining material known for its excellent strength-to-weight ratio, corrosion resistance, and overall durability. It machines exceptionally well, allowing for high speeds, tight tolerances, and cost-efficient production. Its balance of performance, finish quality, and reliability makes it a go-to choice for a wide range of CNC-machined components.
The following aluminum materials can be found on Xometry’s quoting menu:
- 2024
- 2A12
- 5052
- 5083
- 6061
- 6063
- 7075
- MIC-6
Plastics offer exceptional versatility in CNC machining, providing lightweight strength, chemical resistance, and excellent electrical and thermal insulation. We offer options ranging from general-purpose to high-performance engineering plastics, which enable cost-effective solutions across a wide range of design and performance requirements.
Our machinable plastics include:
- ABS
- Acetal (POM)
- Delrin
- Acrylic
- HDPE
- Nylon 6/6
- PC
- PEEK / PEEK GF30
- UHMW PE
- ULTEM 1000
- PP
Brass, bronze, and copper are known for their excellent machinability, wear resistance, and conductivity. These materials produce smooth finishes, retain fine details, and perform well in applications requiring durability or electrical and thermal efficiency.
Xometry auto-quotes the following brass, bronze, and copper materials:
- 260 (Brass)
- C110
- C932 (Bronze)
- C360 (Brass)
- 110
Stainless steels are valued for their exceptional strength, corrosion resistance, and long-term durability. They deliver reliable performance in demanding environments while maintaining precision, making them well-suited for high-strength, wear-resistant components.
Xometry offers stainless steel alloys such as:
- Stainless Steel 17-4
- 300 Series Stainless Steel (e.g., 303, 304, 316)
- 400 Series Stainless Steel (e.g., 410, 416, 420, 440C)
Carbon and tool steels are trusted for their strength, toughness, and versatility. They can be machined to precise tolerances and can be heat-treated for enhanced hardness and wear resistance, making them ideal for durable, high-performance components.
Xometry’s steel options include:
- 1018
- 1215
- 4130
- 4140
- 4340
- A36
- Tool Steel A2
- Tool Steel O1
CNC Milling Surface Finishes
At 3ERP, we provide a full range of CNC milling surface finishes that enhance both functionality and appearance, improving durability, resistance to corrosion, and aesthetics as part of our comprehensive CNC machining process.
As Machined Finish
Milled parts come directly from the machine with visible tool marks and a slightly rough surface. Ideal for functional prototypes or internal components where precision is critical, offering fast turnaround and cost savings.
Anodized (Type II or Type III)
Type II creates a corrosion-resistant finish. Parts can be anodized in different colors—clear, black, red, and gold are most common—and are usually associated with aluminum. Type III, also known as hardcoat anodizing, is thicker and creates a wear-resistant layer in addition to the corrosion resistance seen with Type II.
Sandblasting & Bead Blasting
The part is cleaned, deburred, and placed in an abrasive blaster where surface deposits are removed by applying fine glass beads at high pressure, without damaging the surface. Bead blasted parts will have a matte or satin-like appearance.
Sanding & Polishing
Removes tool marks and rough areas, delivering smooth, glossy surfaces while maintaining dimensional accuracy. Perfect for customer-facing parts and high-end prototypes.
Powder Coat & Paint
Powder coat and wet paints provide a durable, protective layer that resists corrosion, wear, and UV damage. They offer a uniform, attractive appearance while preserving the underlying part’s precision and performance.
Chemical Finishes
These are treatments that enhance the surface properties of machined parts without significantly altering dimensions. Processes such as chromate conversion, passivation, black oxide, and electropolishing improve corrosion resistance, surface cleanliness, appearance, and in some cases, lubricity or electrical performance.
Advantages of CNC Milling
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Rapid Turnaround
Using the latest CNC machining capabilities, Xometry produces highly accurate, quick turn parts in as fast as 1 day. Our instant quoting platform can cut days off your RFQ process.
High Precision Tolerances
Our CNC milling capabilities offer high-precision tolerances, including sub ±.001″ tolerances.
Scalability
CNC machining processes are perfect for prototype and production parts. Xometry can help you scale from initial prototype and testing phases to production runs of 100,000 parts or more.
Material Selection
Choose from over 50 metal and plastic materials. CNC Machines offer a wide variety of certified materials.
Tolerances for CNC Milling
CNC milling tolerances define how precisely part dimensions are controlled during machining.
Our precision CNC milling services follow ISO 2768-m for metals and ISO 2768-c for plastics, delivering stable, repeatable dimensional accuracy across 3-axis, 4-axis, and 5-axis CNC milling.
| 3-Axis | 4-Axis | 5-Axis | |
| Maximum Part Size | 3000 x 1500 x 500 mm | 1000 x 500 x 500 mm | 1000×800×600 mm |
| Minimum Part Size | 5 x 5 x 5 mm | 5 x 5 x 5 mm | 5 x 5 x 5 mm |
| General Tolerances | ±0.1 mm | ±0.1 mm | ±0.05 mm |
| Lead Time | Delivery of simple parts can be as fast as 1 day. | 5 bussiness days for most projects. | 5 bussiness days for most projects. |
Design Guidelines
Good CNC milling design improves machinability, lowers costs, and ensures quality. When milling, avoid deep pockets, thin walls, and sharp inside corners; use generous radii to reduce stress and tool wear. Chamfers enhance appearance and safety. Limit complex multi-axis curves to simplify fixturing. Explore our full CNC design guide for more tips.
Feature alignment
For 3-axis machining, it costs more to add features to multiple faces. It can therefore help to design parts with holes and other features aligned on a single face.
Fillets
Internal fillets should be as large as possible to allow a large-diameter tool to be used. The radius of the internal fillet should be greater than 1/3 the cavity depth to prevent tool damage.
Wall thickness
Metal parts typically require a minimum wall thickness of 0.8 mm, while plastic parts require 1.5 mm. Thinner walls are vulnerable to vibration and deformation.
Cavity depth
To minimize chatter, tool deflection, and other issues, the depth of machined cavities should be no more than 4x the width.
Holes and threads
Hole and thread diameters should correspond to standard drill bits and threading tools. Hole depth should generally be no more than 10x the diameter.
Undercuts
T-slot undercuts can be around 3–40 mm wide. Dovetail undercuts work best at a standard angle of 45 or 60 degrees.
FAQ
What kinds of CNC milling machines does RapidDirect have?
At RapidDirect, we have a variety of CNC milling machines to meet diverse manufacturing needs. Our inventory includes 3-axis, 4-axis, and 5-axis CNC milling machines.
The 3-axis machines are perfect for simple operations, handling basic cutting tasks along the X, Y, and Z axes.
Our 4-axis machines add an extra rotational axis, allowing for more complex geometries and more efficient production of parts with features that require continuous machining around a fourth axis.
Finally, our advanced 5-axis CNC milling machines offer the highest level of precision and versatility, enabling the creation of intricate parts with complex shapes and angles.
These machines are capable of machining in five different axes simultaneously, reducing the need for multiple setups and ensuring exceptional accuracy and quality in every component we produce.
What tolerances can you achieve with CNC milling?
Our CNC milling tolerances depend on machine type, material, and part geometry.
Standard tolerances follow ISO 2768-m (metals) and ISO 2768-c (plastics)
Typical general tolerances: ±0.1 mm
High-precision 5-axis milling can achieve tolerances as tight as ±0.01 mm for critical features
For tighter tolerances, we recommend specifying requirements directly on the drawing so our engineers can optimize tooling, inspection, and cost.
When should I choose 3-axis, 4-axis, or 5-axis CNC milling?
3-axis milling is ideal for simple geometries and flat features
4-axis milling enables machining around multiple sides with fewer setups
5-axis milling is best for complex geometries, tight tolerances, and parts requiring multi-angle machining
Choosing the right axis configuration can significantly reduce lead time and improve accuracy.
How fast can you deliver CNC milled parts?
Lead times depend on part complexity and machining axis:
Simple 3-axis parts can be delivered in as fast as 1 day
Most CNC milling projects are completed within 5 business days
Expedited options are available for urgent production needs.
CNC milling vs CNC turning: how do I choose?
CNC milling is ideal for complex geometries, slots, pockets, and contours, while CNC turning is best suited for cylindrical parts such as shafts and bushings.
If your part includes both rotational and prismatic features, combining milling and turning may be the most efficient solution.
What are the Differences Between Vertical and Horizontal CNC Milling?
Vertical CNC milling machines, with their vertically oriented spindles, are ideal for precision work on smaller components, offering excellent visibility and versatility for tasks like drilling and boring. Horizontal CNC milling machines, featuring horizontally oriented spindles, excel in handling larger, heavier workpieces and provide enhanced stability and efficient chip removal. For projects requiring extensive material removal and high durability, horizontal milling is preferred. In contrast, vertical milling is best for intricate, detailed work. Choosing between these types depends on your specific CNC milling services needs, whether for precision or bulk machining.
What is tool offset in CNC milling?
In CNC milling, tool offset refers to the adjustment made to account for the tool’s dimensions—specifically its length and diameter—during the machining process. These offsets ensure that the cutting tool operates with precision relative to the workpiece. By accurately setting tool offsets, a machinist can determine the correct starting point for machining, ensuring that the part is cut to the exact specifications required. Proper tool offsets are crucial for achieving accurate and consistent results in CNC milling operations.
What is CNC milling?
CNC milling is a subtractive manufacturing process where material is removed from a solid block using rotating cutting tools controlled by computer programs.
CNC milling is widely used to produce precision parts with complex geometries, tight tolerances, and consistent quality. It supports multi-axis machining (3-axis, 4-axis, and 5-axis), allowing features such as pockets, slots, holes, and complex contours to be machined efficiently.
At RapidDirect, CNC milling is commonly used for functional prototypes, low-volume production, and end-use parts across industries such as automotive, aerospace, and industrial equipment.
What types of materials do CNC mills use?
CNC mills can work with a diverse range of materials. Metals frequently used include aluminum, brass, and steel, each offering different properties for various applications. Additionally, CNC milling is effective on various plastics such as ABS, acrylic, polycarbonate, and polypropylene, which are valued for their versatility and ease of machining. This variety of materials allows CNC mills to be employed in numerous industries, from aerospace to consumer products, making them a highly adaptable tool for manufacturing.