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cnc machining

The Ultimate Guide to Machining Parts & Components

CNC machining parts is pivotal to all industries due to their high accuracy, repeatability, and precision. These machined parts are prevalent across industries because they are cost-effective for demanding applications. CNC machinists and product engineers manufacture parts with cutting-edge CNC technology, which involves automated machining operations.

This guide discusses machined parts and components, their compatible machining techniques, advantages, and design principles. You’ll also learn about the materials used for machined parts, their applications, and helpful tips on choosing the proper machined parts manufacturer.

What Are Machined Parts and Components?

cnc machined part
CNC Machined Part

If you look around, you’ll notice different machined parts and components everywhere. Manufacturers create these parts with machining processes where specialized cutting machines (including routers, mills, and lathes) gradually remove excess materials from workpiece bar stock using sharp cutting tools to create the desired shape.

These digital manufacturing processes include CNC drilling, milling, turning, and grinding, used to cut a block of material into preferred shapes or parts. Generally, machined parts can be created with manual or automatic (Computer Numerically Controlled) machining. However, machinists now produce custom-machined parts using computer-aided design. Besides, you can make your CNC parts with any metal alloy, plastic, or any other material that can be cut without drastic degradation.

Machining Techniques and Processes

machining techniques and processes
Machining Techniques and Processes

Manufacturers and machinists employ varying CNC machining processes to produce parts for different purposes. Here are the standard manufacturing techniques and methods used to achieve varying results:

  • Milling: This subtractive manufacturing process involves using a CNC mill to remove material from a workpiece, forming CNC parts with contoured or flat surfaces. The common types of milling operations include CNC milling, face milling, and end milling. These machining processes involve utilizing various milling machines and cutting tools.
  • Turning: This metal cutting process involves rotating the workpiece bar stock while feeding a cutting tool to cut material and machine cylindrical shapes. CNC turning is a reliable method for machining threads, shafts, and intricate features on the external surfaces of machined parts.
  • Drilling: The drilling process uses rotating drill bits to create holes in a workpiece. It is an essential process commonly used in industries to make holes of varying sizes and depths in machined parts and components.
  • Broaching: It is a process that uses a specialized tool called the broach to cut material in a controlled way. Machinists use the broach to create splines, keyways, and other intricate internal shapes.
  • Grinding: Grinding involves using abrasive wheels to cut material from machined parts’ surfaces to create a high-precision and smoother finish.
  • Electrical Discharge Machining (EDM): This machining technique utilizes electrical discharges to cut material from a workpiece to create a specified shape. This process offers the high precision required in machining intricate shapes or hard materials.
  • Laser Cutting: Laser cutting involves using a high-powered laser beam to blow, vaporize, or melt material to make precise cuts on a workpiece. It is a suitable technique for cutting plastic, metal, and other materials.
  • Ultrasonic Machining: This technique removes material from the workpiece’s surface with ultrasonic vibrations and abrasive slurry. It is well suited for machining delicate and brittle materials.

What Are the Advantages of Machined Parts?

cnc machined parts
CNC Machined Parts

CNC parts and components are more beneficial than 3D printed and injection molded parts. This section discusses the typical advantages of machined parts:

Excellent Prototypes

CNC machining techniques offer machined parts and prototypes with complex designs and intricate features. These machined prototypes are ideal and affordable since they can be machined as one-offs.

Moreover, making quick replicas of sheet metal parts easier since CNC machining is digital and much faster. Hence, you can conduct the necessary tests and assessments with your prototypes before making the final products.

Furthermore, the material versatility of machining allows you can order machined prototypes and parts in varying metal alloys or composite plastics to examine the one that performs best considering all factors involved.


One of the significant advantages of machined parts is that you don’t need a minimum order quantity to purchase them. You can easily machine parts from a workpiece bar stock, making low-volumes or one-off parts cost-effective. As a result, you can easily place an order for the exact amount of machined parts needed.

CNC machining is practically unique in producing superior-quality parts without minimum order quantity requirements or excess inventory risks. Therefore, it is perfect for prototyping, low-volume production runs, and smaller companies.


Machinists create machined parts from solid pieces of materials called blanks. These are usually extruded or cast materials. Hence, the machined parts are stronger than other parts like 3D printed parts. Likewise, molded parts are not as strong as their machined equivalents because molded parts often possess thin walls which exhibit limited mechanical performance.

Design Freedom

design freedom

Machined parts allow unhindered design freedom, enabling different design features like shapes and sizes. These parts usually have fine and detailed features, even though they can be thick and robust.

CNC machining remains one of the most geometrically versatile manufacturing methods because it can handle design requirements such as fine details, intricate features, or complex geometries. As such, machined parts offer intricate design features that meet the demands of various applications.

Faster Lead Times

CNC machining techniques create metal components and plastic parts faster than other manufacturing processes, such as molding. Although CNC machining parts don’t use labor-intensive tooling, the production process is highly efficient.

Some CNC machines have faster machining centers equipped with linear guide rails at rapid rates. Besides, the speed of CNC machining centers and the one-step attribute of the machining process quicker lead times for machined parts.

Surface Finish

precision cnc aluminum parts with hard anodized coating
Precision CNC Aluminum Parts with Hard Anodized Coating

CNC parts allow higher surface finishing standards with moderate post-processing operations. Additionally, machining offers a superior finish because it doesn’t leave visible layer lines. CNC machined parts and components are compatible with extensive surface finishes, allowing your parts to meet design specifications and perform well.


Generally, machined parts are fabricated to a very high standard due to the precise control of CNC machines. These precision-machined parts usually offer fine finishes and tighter tolerances that meet the requirements of your design. However, clients can indicate the required tolerance that machinists need to achieve. Consequently, the machine operator may take longer on tight tolerance machining parts and respective features.

Easy Alterations

You can make digital design alterations easily at any production stage since CNC machined parts are created from a digital CAD file. This characteristic benefits R&D and prototyping when product developers and engineers must make fractional modifications to the machined part to make various versions. It helps mitigate material wastage since the machined parts are not usually defective.

Design Principles for Machined Parts

design principles for machined parts

Generally, it is advisable to follow design for manufacturing (DFM) principles when machining parts. That is, design parts according to the intended manufacturing process. However, you can easily design machined parts by following the design principles below:

Wall Thickness

Thin walls are not ideal for machined parts because it affects performance. Therefore, ensure your machined parts design doesn’t have thin wall thicknesses. However, it would be best to use injection molding for your parts if thin walls are pivotal to your design.


Undercuts are complex cuts that require the use of standard cutting tools due to a section of the part that’s blocking it. They require special machining design considerations and special cutting tools like the T-shaped machining tool.

However, undercut dimensions must be in whole millimeters to correspond with the cutting tool since these tools are available in standard sizes. The undercut can vary from 3 to 40 mm, with undercut depth precisely twice the width depending on the machining tool. Nevertheless, you can make your machined parts faster and reduce efforts if undercuts can be avoided.

Cavities, Holes, and Threads

It is crucial to recall that cavities and holes depend on the cutting tools when drawing the design for your machined parts. You can machine cavities and pockets into a part to a depth about four times the cavity width. It would help to know that deeper cavities will necessarily require fillets, rounded instead of sharp edges, due to the cutting tool diameter needed.

Besides, holes made using drill bits must bear a depth not more than four times the width of the drill bit. Likewise, hole diameters must match standard drill bit sizes where possible. On the other hand, the threads used to integrate fasteners such as screws should not be deeper than thrice the diameter.


CNC machined parts practically have limited size since you must create them within the machine’s build envelope. CNC-milled parts have to measure precisely 400 x 350 x 150 mm, while turned parts should maintain maximum dimensions of Ø 500 mm x 1000 mm.

However, it would be best to note that larger dimensions are achievable with larger machines but must be first discussed with the machinists before production begins.


It is usually challenging to make tall protruding sections as with thin walls because the cutting tool’s vibration can degrade the section or cause lower accuracy. Hence, you must maintain a protruding feature with a height not beyond four times its width.

Machined Part Materials

machined part materials

CNC machined parts are usually made from an extensive list of materials, such as metal alloys and plastics. However, some materials are more straightforward to machine, while others are complicated. Rigid materials are challenging to cut and may lead to tool chatter and vibration, compromising workpiece quality.

On the other hand, very soft materials and those with extremely low melting points are susceptible to deformation when they interact with the cutting tool. Below are the typical machined parts materials:

  • Metal: Titanium, Bronze, Brass, Copper, Aluminum, Stainless Steel (17-4, Inconel 625 & 718), Zinc, Magnesium.
  • Plastic: ABS, PC, POM, ABS+PC, PP, PMMA (Acrylic), PS, PEEK, HDPE, DHPE, PPS, Teflon, PAGF30, PCGF30.

Machined Part Surface Finishes

metal surface finishing
Metal Surface Finishing

Various compatible post-processing operations help to enhance the surface texture and functionality of machined parts. Below are some of the standard machined parts’ surface finishes:

  • As-Machined: The machined finish option doesn’t involve applying surface treatment to the machined parts. It is the exact surface condition of the machined part as it exits the CNC machine. It is often perfect for many internal, non-cosmetic functional parts.
  • Powder Coated: Powder coating finish involves spraying powdered paint in any preferred color onto the machined part, after which it is oven-baked. It forms a solid coating on the machined part, improving its wear resistance. The coating is more durable than regular paint coatings.
  • Anodized: This electrochemical process improves aluminum machined parts’ corrosion resistance. It forms a scratch and corrosion-resistant layer on metal parts. The Type II anodization process provides a corrosion-resistant finish on aluminum machined parts. Conversely, the Type III anodization creates a thicker coating on machined parts for better wear and chemical resistance.
  • Bead Blasted: It involves firing abrasive media (tiny beads) at the surface of machined parts at high velocity. This process helps to remove sharp edges, burrs, and residual materials. However, you can modify this process to achieve a certain level of roughness. However, bead blasting may be incompatible with fine features since the procedure removes material and can affect the machined part’s geometry.

Machined Part Tolerances

Manufacturers create machined parts made to tighter tolerances with modern CNC machines. Although looser tolerances may be utilized for non-mechanical parts and prototypes, tight tolerances may be crucial for mechanical parts that must interact with other components. Below is a table for CNC machining tolerances:

Tolerance Lever Overall Dimension Range
Specifications <<3 & >0.5 <<6 & >3 <<30 & >6 <<120 & >30 <<400 & >120 <<1000 & >400 <<2000 & >1000
F ±0.05 ±0.05 ±0.1 ±0.15 ±0.2 ±0.3 ±0.5
M ±0.1 ±0.1 ±0.2 ±0.3 ±0.5 ±0.8 ±1.2
C ±0.2 ±0.3 ±0.5 ±0.8 ±1.2 ±2 ±3
V ±0.5 ±1 ±1.5 ±2.5 ±4 ±6

What Are the Applications of Machined Parts?

what are the applications of machined parts

CNC machined parts and components are compatible with various applications in every industry since they have become indispensable. Typical machined components used in different applications include valve bodies, ball joints, rollers, housings, gears, fasteners, brackets, etc. Below are common industries that use machined parts:


Engineers in the aerospace sector depend on machined parts such as engine components, engine mounts, fuel panels, landing gear components, and prototypes due to the industry’s demand for high precision. In aerospace machining, is no room for the slightest discrepancies because it can result in catastrophic failure. Therefore, precision machined parts in this sector are paramount.


The medical industry has diverse applications for machined parts and components. Precision machining is suitable for creating machined stainless steel and titanium parts, including implants, surgical instruments, medical devices, and other complex diagnostic equipment.

More so, machining techniques such as Swiss screw machining is ideal for machining medical parts. Machined medical parts often require tighter tolerances, given the requirements for safety and accuracy in various medical procedures.

Precision is critical for implants because they must fit perfectly with the patient’s body. As a result, CNC machining is the standard method used in making these implants because it offers the required precision and helps to achieve complex machined part geometries.


The automotive industry depends on CNC machining to make machined parts such as one-off custom parts, lighting components, engine blocks, pistons, gears, and steering systems.

Manufacturers in this sector depend on cutting-edge machining methods, including 5-axis CNC machining, to create complex automotive machining parts with high precision and efficiency.

Consumer Products

Most household appliances and goods comprise machined parts. Also, sporting equipment may be CNC machined, and consumer electronics use different machined metal and plastic components due to remarkable electrical conductivity properties.

Typical examples of machined parts in this application include sockets, laptop casings, electrical insulation, connectors, etc.

Other applications of CNC machined parts include:

  • Military
  • Robotics
  • Electronics
  • Renewable energy

How to Choose A Machining Partner for Your Custom Parts

your one stop machine shop for quality cnc machining services
Your One Stop Machine Shop for Quality CNC Machining Services

You need a reliable machining partner to outsource your CNC machining needs for low- or large-volume machined parts or prototypes. It is usually beneficial to partner with a third-party CNC machining services provider over an in-house solution because of the factory space and the required expertise to operate the machine tools and equipment.

Although it can be pretty challenging to choose a reliable machining partner for your machined parts, here are some helpful factors and practices to consider:

  • Certifications: Although certifications will not tell you the machining company’s scope of abilities, ISO certifications are helpful because they are a remarkable guideline for identifying capable machining companies.
  • Word of Mouth: It would help to speak with other hardware companies partnered with machined parts manufacturers in the region to discover their outsourcing experiences.
  • Demand Information: Ensure you ask questions about everything until you are convinced that a manufacturer can handle your project once you establish contact with the company. However, if they fail to respond convincingly to your questions, they may not be suitable manufacturing partners.
  • RfQs: Requesting a quote from different shortlisted machining companies to compare the prices and determine the best one for your project is advisable. Consequently, your CNC machining cost remains effective.
  • Visit Factories: It is essential to visit a potential manufacturing partner’s factories to see how they operate and the machining tools and equipment they possess. In certain situations, getting a manufacturing agent to organize visits to several sites in a given area may be possible.

Nevertheless, below are other helpful tips to observe when dealing with the outsourced machined parts manufacturer:

  • Adhere to DfM Guidelines: Ensure the strict adherence of digital part design to the machining guidelines, including holes of limited depth, no thin walls, etc.
  • Use Universal Standards: Deliver a complete technical drawing with the digital files to avoid ambiguity, and employ universal standards to prevent any form of miscommunication.
  • NDA: Signing a non-disclosure agreement when outsourcing your machined parts would be best. It legally stops the manufacturer from sharing or using your design for any other party.
  • Factor in Shipping Times: If you are working towards tight deadlines, it is advisable to consider the shipping times of your outsourced parts. This is because outsourced parts take longer time to arrive than in-house parts.
  • Prepare for Payment: Manufacturers often request up-front payments when handling first-time orders. However, they may allow you to order on credit for subsequent projects.


Machined parts have varying designs and versatile uses; hence, it is essential to understand the intricacies of achieving successful parts’ technical drawings and production. However, you can easily create superior-quality machined parts that meet your requirements by following DfM guidelines, considering material properties, and partnering with an experienced machining partner.

AT-Machining is a reliable partner for all CNC machining services for your rapid prototyping and machined parts needs. We offer high-quality parts and prototypes at competitive prices with shorter lead times. Our efficient quality control system helps to launch your products into the market faster. We have good years of experience producing machined parts for different industries.

Our machine shop houses cutting-edge machinery with a quality management system capable of producing high-quality CNC parts with high precision and accuracy. Contact us today, and let’s assist you with your machined parts!

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Hey there, I’m Sam!

From AT-Machining, I’m a CNC Machining Expert in this field for more than 20 years.  We offer cost-effective machining services from China. Ask for a quote for your ongoing or upcoming projects now!

Best Regards, Sam, Co-Founder

AT Machining

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