How to Do CNC Machining Surface Finish? Choose Finishes for CNC

CNC machining surface finish is essential in many manufacturing and production processes. It is creating a smooth, polished, and even surface on a material or object. CNC machining offers greater advantages over traditional methods of machining such as higher accuracy and repeatability, less waste, and improved quality control. In this article, I will elaborate on why CNC machining surface finish is important and how it can benefit businesses in terms of product quality and efficiency. I will also put a look at the different types of CNC machining surface finishes available, their advantages, and any potential drawbacks may have.

CNC Machining Surface Finish

Why CNC Machining Surface Finish Is Needed?

In the manufacturing industry, CNC machining surface finish is essential to ensure the quality and accuracy of production parts. It is a specialized process that provides more detail and smoother surfaces for critical components. The need for precision and accuracy in manufacturing processes has never been more relevant than it is today. As such, the importance of a good CNC machining surface finish cannot be overstated. Achieving a high-quality surface finish requires special attention to detail and careful consideration of the machined material type. The surface finish can have an impact on both functionality and aesthetics, making it critical to a successful final product.

CNC Machining Surface Finishes You May Use For Your Project

When it comes to the surface finishes for cnc, there are several options available depending on your project requirements. CNC machining can produce surfaces with different textures and finishes depending on the type of cutting tool used in the process. Each type of CNC finish has its own advantages which makes them suitable for different types of projects. 

Bead Blasting


  • Bead blasting is used to produce an even, matte, or satin surface finish on CNC machined parts with no stress induced by the process. This makes it a great option for components that require precise dimensions and shapes such as medical fixtures or aerospace equipment.
  • The low pressure used in bead blasting also means that any internal threads or intricate details are not impacted during the process, preserving their functionality and accuracy.
  • Bead-blasted surfaces are less prone to corrosion due to their increased porosity which helps to increase the overall lifespan of components.


  • The most obvious disadvantage of glass beads blasting is that it typically leaves average surface roughness and uneven surface textures. This can present problems if you’re working with precise measurements or trying to achieve tight tolerances between components.
  • Excess particles left over from the bead blast process can increase wear and tear on your parts and cause them to deteriorate more quickly compared to other finishing techniques.
  • While bead blasting may be relatively inexpensive compared to other CNC machining surface finishes, it also tends to be less durable than other methods like chemical etching or anodizing.


Passivation is an important process in CNC machining surface finishes. It involves treating the surface with a chemical compound that will protect it from contamination and oxidization, while also improving its lifespan. Passivation plays an integral role in both small- and large-scale machining operations, as it ensures that finished products meet the highest quality standards. 


  • The process of passivation involves removing any impurities on the metal’s surface that could cause premature corrosion or rusting.
  • It also helps fill in any microscopic pores or crevices in the surface finish which could accumulate debris or moisture and lead to further damage down the line.
  • By reducing these imperfections, manufacturers are able to achieve smoother finishes with greater accuracy during their CNC machining operations.

Cons: This process has its drawbacks that must be accounted for before proceeding. 

  • It is great for preventing rust and oxidation of the metal surfaces but it also removes any lubricants already in place, reducing the part’s ability to function properly.
  • If there are defects on the surface of the part such as burrs or scratches, passivation may not completely remove them which can lead to further problems down the line.
  • Passivated parts require more attention when it comes to maintenance as they need regular cleaning and lubricating to work at their peak performance levels.

Anodizing (Type II and III) 

Anodizing, commonly used in the aerospace and automotive industries, is a process of electrolytically depositing oxide films on CNC-machined surfaces. This process can improve the durability and corrosion resistance of these components, as well as creating aesthetically pleasing finishes. Type II and Type III anodizing are two common methods used to finish CNC machining surfaces today. 

Type II: Type II anodizing creates a thicker protective layer of hard coating that provides superior protection against wear and tear over time. It also has good insulation properties, making it an ideal choice for electrical components that need to be protected from short circuits or other damage caused by

conducted electricity. The most common color for this type of surface finish is black, although it can also be applied in other colors with additional chromic acid treatments.

Type III: The Type III hard coat anodize process is typically used when higher levels of corrosion protection and abrasion resistance are desired. This type of anodize uses a diluted sulfuric acid solution to create a thicker oxide layer on the surface of many functional applications and metals like aluminum or titanium alloys, making them resistant to corrosion and scratching in harsh environments.

cnc machining surface finish(anodizing)


As-machined CNC Machining Surface Finish is a process by which the surface of a part or component can be improved for enhanced performance and durability. This process involves the use of CNC machining to create precise and repeatable surfaces, which are then refined using abrasives or other special tools to create the desired finish. As-machined CNC machining provides superior results compared to traditional manual machining processes, allowing for tighter tolerances and exacting specifications that can’t be replicated with hand power alone. By using this method, parts, and components are created with uniformity and consistency time after time, resulting in smoother finishes that have greater resistance to wear and tear over time. The highly automated nature of as-machined CNC machining also ensures quality assurance standards are met while keeping costs low by reducing the need for manual labor.

What Are the Issues You Should Consider for CNC Machining Surface Finish?

CNC machining is a method of manufacturing that uses computers to control the motion of tools and cutting surfaces. CNC machining aims to produce parts with accurate dimensions and surface finish. While CNC machining offers many benefits, it also has some inherent issues when it comes to achieving a good surface finish on the finished product. Here are some of the key issues you should consider for CNC machining surface finish: 

  • The first issue is material selection. Different materials require different cutting tools and processes in order to achieve an acceptable surface finish. This means that the right material must be selected to ensure a good result.
  • Selecting an appropriate feed rate is important as too high or low can lead to poor results or damage the workpiece altogether.
  • Surface roughness is one issue that is particularly important with CNC machining projects. Your design should take into account any potential interference between components or surfaces due to variations in surface roughness caused by different levels of accuracy during manufacturing processes.
  • Also, you can consider any additional finishing work required after machining like polishing or grinding which will also impact surface finish expectations.


Understanding and achieving the desired surface finish with CNC machining can be challenging. Using quality cutting tools, adhering to precise speed and feed rates, consistent monitoring of machine conditions and tool life, and applying suitable lubrication or coolant can help you reach the desired result in an efficient manner. If additional surface finish is needed post-machining treatments such as polishing can be used to achieve higher accuracies.