CNC Machining Design Guide
Review inside corners, tool reach and tolerances before sending a milled part for quoting.
Read the CNC Design GuideCustom CNC Milling for Precision Parts
BoValley provides custom CNC milling services for metal and plastic components, from functional prototypes to low-volume and production parts. We machine precision features such as pockets, slots, holes, contours, and mounting surfaces to meet your design and functional requirements.
Project Review
- Drawing Review
- Material Grade Review
- Datum and Tolerance Planning
- Inspection Requirements
- Part Geometry
- Pockets, slots & contours
- Setup Planning
- Tool access review
- Stock Type
- Metals & engineering plastics
Overview
What is CNC Milling?
CNC milling uses rotating cutting tools to remove material from a workpiece, creating flat surfaces, pockets, slots, holes, contours, and other engineered features.
It is well suited to components that require defined geometry, accurate mounting interfaces, and consistent dimensional relationships. Depending on the part design, milling can be combined with drilling, tapping, boring, and other machining operations.
CNC Milling Capabilities
Review cutter access, pocket depth, corner radii and workholding against the drawing. Identify mating surfaces and other features that need dimensional or finish control.
3-Axis CNC Milling
- Use 3-axis setups for features a cutter can reach from one direction. Additional faces may require refixturing.
4-Axis CNC Milling
- A rotary axis can index a part to machine features around its perimeter. Check the rotating clearance and workholding before choosing this route.
5-Axis CNC Milling
- Five-axis positioning can improve access to angled or contoured features. Review tool-holder clearance and how the finished part will be held.
Production CNC Milling
- For repeat orders, plan workholding, tool-change intervals and inspection points after the first sample is approved.
Materials & Part Geometry
- Pair the stock and alloy with the geometry. Review pocket depth, inside corner radii and thin walls for tool deflection or part movement.
Tolerances & Finishes
- Call out critical datums, dimensions and finishes on the drawing. Separate cosmetic requirements from functional surface roughness.
MaterialsMaterials
CNC Milling Materials
Select a metal or engineering plastic based on part function, cutter access, and the required surface finish. Confirm the grade and stock form during review.
- Aluminum
- Stainless Steel
- Carbon Steel
- Brass
- Copper
- Aluminum 6061
- Aluminum 7075
- Stainless Steel 304
- Stainless Steel 316
- POM (Acetal)
- Pocket depth and tool access
- Internal corner radii
- Flatness after material removal
- Clamping allowance
- Alloy and temper
- Strength in service
- Wear at mating surfaces
- Corrosion resistance
- Electrical isolation
- Heat exposure
- Dimensional stability
- Stock availability
- Grain or fiber direction
- Machinability
CNC Milling Design Parameters
Choose suitable surface finishes to meet your part’s appearance, durability, corrosion resistance, and functional requirements.
| Parameter | Project Considerations |
|---|---|
| Part geometry | Pockets, slots, holes, contours, and complex features |
| Material | Aluminum, steel, brass, copper, and engineering plastics |
| Tolerances | Based on engineering drawings and part requirements |
| Surface finish | As-machined or specified finishing |
| Quantity | Prototypes, low-volume orders, and production parts |
| Inspection | Critical dimensions and agreed inspection documentation |
The Process
How Does CNC Milling Work?
From CAD review and DFM planning to CNC machining, inspection, surface finishing, and delivery, each step supports efficient, precision part manufacturing.
The advantages
- Complex Features:• Machine pockets, slots, holes and detailed contours from engineering drawings.
- Functional Interfaces:• Focus on mounting surfaces, hole patterns and mating features that affect assembly.
- Material Flexibility:• Select metals and engineering plastics based on functional and environmental needs.
The challenges
- Tool access:• Deep pockets and small inside radii can require long, slender cutters that deflect under load.
- Part movement:• Thin walls and flexible stock can move during cutting or after release from the fixture.
QualityApplications for CNC Milling
Milling is useful for housings, fixtures and brackets with flat datums, pockets or mounting features. Review tool access and critical mating dimensions.
Automotive Components
Brackets, housings, and mechanical components.
Robotics
Mounting plates, supports, and structural components.
Aerospace Prototypes
Custom components subject to project specifications.
Optical Equipment
Instrument housings and precision mounting parts.
Electronics & Telecommunications
Precision CNC machined housings, heat sinks, and electronic components.
Industrial Machinery
Custom machined parts for automation systems and industrial equipment.
| Types of Parts | Function |
|---|---|
| Mounting plates | Locate holes and datums for repeatable installation. |
| Housings and pockets | Provide space for components and controlled mating features. |
| Machining fixtures | Create locating faces, slots, and threaded mounting features. |
Ready to Start Your Next Manufacturing Project?
Share your CAD files and project requirements. An engineer will review the details and follow up with pricing and any manufacturability questions.