What are Machined Machined Parts & Components?

A guide to CNC machined parts and components that play a vital role in various industries because of their high precision and cost effectiveness. It also discusses the compatible methods of machining, the benefits associated with them and design factors to put into consideration. Find out about the types of materials used for such purposes, the common uses as well as the choice you have in terms of getting these products made through today’s advanced CNC technology.

Table of Contents

What are machined parts?

Machined parts are components whose shapes are derived from materials like metal or plastic through machines, including mills, lathes, and routers. The tools remove additional stuff to shape as desired.

Manual machinists can do the machining, or it can be done digitally using CNC (Computer Numerically Controlled) machines. Rapid tasks requiring human precision are best suited for manual machining, while CNC machining is suitable for complex and repeatable shapes.

Consequently, with techniques like milling and turning, CNC machining has improved precision n manufacturing machined components and increased efficiency. Consequently, machined parts have become indispensable in sectors such as aerospace and automotive, where exactness of component dependability is paramount.

Furthermore, some engineered components are first cast or molded and then machined to complete them. These parts are sometimes referred to as partially machined or post-machined parts, indicating the versatility and significance of machining in modern manufacturing processes.

The applications of machined parts

cnc machined aluminum parts
cnc machined aluminum parts

Aerospace Industry:

  • Applications: Aircraft engine components, airframe structural elements, landing gear, etc.
  • Industry Characteristics: Requires extremely high precision and reliability.
  • Requirements for Parts: Must withstand extreme temperatures and pressures and have high corrosion resistance and strength.
  • Advantages: Precision machining ensures that components meet stringent safety standards, enhancing flight safety and efficiency.

Automotive Industry:

  • Applications: Engine components, transmission systems, suspension system parts.
  • Industry Characteristics: Mass production with high costs and efficiency demands.
  • Requirements for Parts: High durability, good mechanical strength and wear resistance.
  • Advantages: Machined parts improve vehicle performance, reduce failure rates, and extend service life.

Medical Industry:

  • Applications: Surgical tools, implantable devices, joint replacements, and dental implants.
  • Industry Characteristics: Extremely high requirements for product biocompatibility and precision.
  • Requirements for Parts: Non-toxic, biocompatible materials must be highly precise to fit complex human anatomies.
  • Advantages: Precision machining ensures the safety and functionality of medical devices, improving treatment outcomes.

Electronics Industry:

  • Applications: Components for computer hardware, mobile devices, and communication equipment.
  • Industry Characteristics: Pursuit of miniaturization and high integration of technology.
  • Requirements for Parts: Extremely high precision and complex miniaturization designs.
  • Advantages: Precision machining makes electronic devices more compact, efficient, and functional.

Energy Industry (such as oil and gas):

  • Applications: Drilling equipment, components of transmission systems.
  • Industry Characteristics: Harsh environments with high demands on equipment reliability and durability.
  • Requirements for Parts: Must withstand high pressure, high temperatures, and corrosive environments.
  • Advantages: Machined parts enhance equipment performance and safety, reducing maintenance costs and downtime.

How to design custom machined parts

Design Principles For Machined Parts

To ensure that custom machined parts are functional and long-lasting, it is important to follow some design principles. If the right specifications are used, mechanical mishaps can be avoided, and the components can seamlessly fit into their assemblies, reducing the need for costly adjustments and repairs. This also improves the final product’s quality per the standards’ guidelines, leading to trust and general satisfaction among users.

Thickness of the wall

While working on machined parts, it is necessary to mention that metals should have a minimum wall thickness of 0.8 mm and plastics – 1.5 mm. This will allow for engineering during fabrication and usage of the component without breakage or deformation in the future. For example, aluminum parts with thicknesses below this advice can vibrate and bend.


Without special tools, undercuts are not supposed to go beyond approximately 0.5mm deep. Alternatively, standard equipment allows undercutting by a depth of three millimeters. However, when designing such designs as require more profound undercuts, it is necessary to bear in mind an extra cost and likely compromises regarding structural integrity.

Cavities, Holes, and Threads

To facilitate efficient tooling and provide material strength, design standards for cavities suggest that these features should be no less than 4mm deep and no deeper than 10mm. Threaded holes must also be designed with this in mind; therefore, the thread should have a depth equal to the M6 recommended diameter—9mm—in case any load-bearing situation occurs.


The scale of machining components determines dimensional tolerance levels tolerated by such components’ designers until they are unacceptable limits. Tolerance of small-scale components (under 50 mm) is usually ±0.05 mm, while larger ones (over 100 mm) could be relaxed up to ±0.1 mm due to the material’s behavior during machining processes.


Machined part protrusions like tabs or bosses are not meant to extend more than three times their base thicknesses upwards from surfaces they originally intended to be attached or located on top of. Oppositely, one must ensure that a protuberance with a base thickness measuring 2mm does not exceed 6mm high if it does not want its structure to weaken, causing buckling or snapping.

Inside Corner Radii

The internal radii corners are crucial for reducing machined parts’ stress concentration. For most materials, the recommended radius is a minimum of 1 mm, but for tougher ones, such as stainless steel, it could be from 2 mm up to prevent cracking due to utilizing them.


In most cases, pockets in machined parts have a maximum depth of three times the diameter of the tool. A pocket should not exceed this figure if it is made with a 4mm diameter tool to ensure efficient chip removal and stability of the tool.

Pre-Drill Tapping Depth

To ensure proper thread formation, pre-drill tapping depth must be at least one and a half times bigger than the tap’s diameter. If we take the M8 standard tap with 6.8mm in diameter, then pre-drilling would be approximately 10.2mm to allow complete engagement without affecting its strength.

Tapped Holes

Tapped holes on machined surfaces need to have some minimum internal diameter to perform their functions properly. In other words, an M4 tapped hole should be drilled at least 3.3 mm before being threaded into, and any screw loaded on with at least a length size equal to 8mm.

Text and Lettering

For legibility after painting or other finishing processes, there must be text and lettering on machined parts at least five millimeters high; however, their depths should not drop below the millimeter mark. Machine control panels usually feature engraved labels that need to remain easily discernible even in harsh industrial conditions where they are used5.

Surface Finish

Machined part surface finishes differ depending on the application’s demand. While most industrial applications may only require a roughness (Ra) value of1.6 µm, finer finishes such as those of hydraulic valves may fall within the range specified by ASME B46.1, which is 0.4 µm.

Machined parts material

machined plastic parts
machined plastic parts

The choice of materials in mechanical design and production is very important for the products’ functioning, reliability, and economy. The right materials are necessary for maintaining the strength of the structure, improving productivity, reducing environmental impact, and cost-cutting, which are vital to success in the marketplace.

  • Metals: They include mainly processed materials like steel (e.g., carbon or alloy steel), aluminum, copper, and stainless steel. These materials have good mechanical properties and can be easily processed.
  • Plastics: At the same time, non-load components can be developed from certain specific engineering plastics like nylon, polycarbonate, and PTFE (Teflon) where high strength is not needed.
  • Ceramics: On the other hand, ceramics such as silicon carbide and alumina are expensive to machine but can withstand challenging conditions such as high temperatures or highly abrasive situations.
  • Composites: Carbon fiber composites and glass fiber-reinforced plastic composites are used in specialized applications because of their excellent strength-to-weight ratio.

Advantages of machined parts


One of the significant advantages of machined parts in manufacturing and design is that they have no minimum order quantity. This attribute brings flexibility to organizations, allowing them to manage their costs and inventory effectively.

Good Prototypes

Machined parts also offer prototyping capabilities, which are significant factors in machining. Engineers can build and test prototypes quickly, enabling rapid iteration and development. This process, therefore, reduces the time taken for a new product to reach the market.

Design Freedom

Machined parts have excellent design freedom. That’s because manufacturers can generate complex shapes and intricate details, which are not possible with other manufacturing methods. Ultimately, this characteristic improves both the functionality and aesthetics of final products.


In terms of quality, machined parts are ahead of their alternatives. They are produced with precision; hence, tighter tolerances can be achieved than those cast or forged counterparts would attain. These aspects make higher-quality components that result in better performance and longer-lasting end-user products.

Lead Times

Generally, lead times for machined parts tend to be shorter than those for other production processes. The direct nature of machining ensures faster turn-around times since there is no need for molds or setups. Such quick response abilities help companies respond promptly to meet market demands.


During production, machining allows easy alterations to be made to the components. In case changes on a part become necessary, they can be executed promptly without causing longer downtime or being too expensive at all. Therefore, such flexibility highly contributes to refining product designs.


The strength within machined parts is another advantage that cannot go unnoticed by these items. The choice of materials, including metals and high-strength plastics, ensures durability while resistance against harsh conditions plus high stress levels, making them ideal for critical applications.

Surface Finish

Finally, machined parts often provide superior surface finishes as compared with any other manufacturing processes involved in making them for good reasons. Since the tools used in machining are precise, the resulting surfaces are either ready for use or require minimal post-processing. This attribute is important to parts having high aesthetic standards or specific performance requirements.

The techniques and processes for machining parts

precision cnc machined parts
precision cnc machined parts

The variety of manufacturing processes and methods allows developers and producers to select the most appropriate technique for specific features of the products and properties of the materials. Consequently, such adaptability ensures that machining can effectively change in shape ranging from simple forms to complex, as well as materials from soft plastics to hard metals. Therefore, there is a need for machine tools with flexible capacities and high precision for mass production or individual orders because they are ready to meet stringent requirements and variable demands.

  • Milling: In milling, the CNC mill produces milled parts from the stock material. It makes parts with flat or contoured surfaces using different machines and cutting tools such as face milling, end milling, CNC milling among others.
  • Turning: In turning, turned parts are produced as a workpiece rotates while a cutter removes material in order to produce cylindrical shapes. CNC turning facilitates making threads on machined objects like shafts as well as external features.
  • Drilling: Drills turn round while boring holes into their targets during this process. By doing so, they create holes of varied sizes and depths on machined parts across industries.
  • Broaching: This is where broaches come into play when it comes to the special cutting tools that are used in precisely producing keyways splines internal intricate shapes having an improved finish quality when compared to other processes such as grinding or milling operations.
  • Grinding: Grinding is done by means of abrasive wheels, which remove material, resulting in high precision smooth finishing on machined parts.
  • Electrical Discharge Machining (EDM): This technique uses electrical discharges to remove material from complex or hard-to-machine shapes.
  • Laser Cutting: A high-power laser beam is employed in this technique for accurately melting, vaporizing, or blowing away target materials, including plastic or metal pieces being cut.
  • Ultrasonic Machining: For fragile, brittle materials requiring machining intricate features, microscopically, ingredients that should be used must be slurry-based ones involving abrasive slurry so that ultrasonic waves can vibrate them.

Surface finishes of machined parts

cnc machined parts surface finishing
cnc machined parts surface finishing

Surface finishes are used to improve both the outlook and working performance of machined components. They prevent corrosion through their covering, enhance wear resistance, and increase surface hardness. To that extent, varnishes serve not only a function of protecting the parts but also of improving their looks for visible uses.

  • As-machined: the surface finish of a workpiece after machining is impregnated with tool marks. Therefore, this type of finish is inexpensive for applications where purely visual aspect is not considered. It provides a sliding ability for some mechanical parts.
  • Bead blasted: these finishes use glass beads to blast evenly at high speed and produce a matte or satin surface. It’s to say that marking down the surface reflectivity cancels out the appearance of machining marks, which is done for both visual and safety reasons.
  • Anodized: anodizing utilizes a process of applying a thin ceramic layer, which is hard and nonconductive, on top of aluminum parts. This method will minimize pitting, wear, and corrosion, and then the piece can be dyed in any color for design.
  • Powder coated: A free-moving, dry powder is applied in powder coating processes. This powder is generally cured in heat to form a skin. This finish gives a much better thickness and abrasion. That way, it’s a perfect surface for outdoor use or high-traffic areas.
  • Plating: the process of plating consists of the formation of a fine layer of another metal on the surface. The alloying process can increase the corrosion resistance, rock hardness, visual appeal, or any other desired properties according to the metal used.
  • Polishing: this process involves either removing the very top layer physically or chemically from the material. This finish is ideal for decorative applications and the parts that are light on friction.

The Tolerances in machined parts

It is necessary to maintain machined part tolerances to fit parts properly. They lay down the limits within which a part’s dimension can vary. This gets even worse in such precise situations as aerospace and medical devices.

An example would be jet engines that require parts with minimal tolerances to ensure efficient operation and safety. When any deviation occurs, it may cause engine failure. This shows how significant accurate tolerances are in terms of dependability and efficiency.

On the other hand, garden tools may have wider tolerances since they are not critical applications. This will reduce the cost of production but still keep them functional. The choice of tolerances should rely on the role played by each component and the implication of dimensional deviations.

Tolerance LeverOverall Dimension Range
Specifications<<3 & >0.5<<6 & >3<<30 & >6<<120 & >30<<400 & >120<<1000 & >400<<2000 & >1000

How do you outsource machined parts?

In your search for a supplier for your machining needs, it is important to take into account several factors that guarantee the quality of your parts. The market is full of machining factories, but when choosing one, you need to look at their experience, technology, and track record in manufacturing high-quality components. Making an informed decision will enable you to achieve the projected outcomes of your project.

  • Certifications: While ISO certifications are good indicators of a Machining company, they are not the whole story of what a company can do. Such certifications would help in selecting effective machining partners.
  • Word of Mouth: Talking with other hardware companies that use machined parts manufacturers can give valuable insights into how to go about outsourcing.
  • Demand Information: Manufacturers must be asked many questions, and if their answers do not satisfy you, think twice before committing yourself.
  • Request for Quotes (RfQs): Comparing quotes from various machining companies allows finding out the most cost-effective one among them for your project.
  • Visit Factories: Attending manufacturers’ plants makes you see things as they happen and the equipment they use. Hiring an agent to organize these visits will be helpful in some cases.

When arranging the manufacture of outsourced machined parts, consider a few key tips.

  • Adhere to DfM Guidelines: Ensure digital designs are manufacturable by following design for manufacturing guidelines closely so that there are no extremely deep holes or thin walls that may cause difficulty in the manufacturing process.
  • Use Universal Standards: Give full technical drawings with digital files to avoid confusing people. Use universal standards instead, which may lead to miscommunication.
  • NDA: When signing non-disclosure agreements, all designs remain confidential and are not shared by anyone else.
  • Factor in Shipping Times: Especially if working under tight deadlines, consider longer delivery times for outsourced parts
  • Prepare for Payment: For first-time orders, manufacturers may require upfront payments, while credit terms could be provided on later projects.


On-demand CNC Machining prototyping and parts with Custom Finishes and low volume manufacturing.

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