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ResourcesMachining DesignChoosing the Right Finish for Your CNC Machined Parts

Choosing the Right Finish for Your CNC Machined Parts

picture of Greg Paulsen
Written by
picture of Joel Schadegg
Updated by
 2 min read
Published September 25, 2020
Updated September 11, 2024

With the wide variety of surface finishes and treatments offered by Xometry, we've got your parts covered.

finished CNC part

Unless otherwise specified, a CNC machined part will have an “as-milled” surface finish. However, many parts require additional processing to achieve a desired surface characteristic or property for cosmetic, corrosion resistance, wear resistance, or other purposes. Xometry offers a wide variety of surface finishes and treatments to ensure that your parts meet all of their surface property requirements.

Some of the most common surface finishes and treatments here at Xometry are bead blasting, anodizing, and powder coating. Take a look at the images and their descriptions below for more detail on those finishes. We also offer chem-film (conversion coating), electroless nickel, gold, or silver plating, and custom finishes. If you require a surface finish or treatment that you don't see here, please reach out to our support team (support@xometry.com) and we will be happy to help!

Standard, As-Milled Finish

"As-Milled" is our standard finish which results in a surface roughness of 125 uin. Minor tool marks are visible on the part. Improving the surface finish (roughness) to 63, 32, or 16 uin will increase the number of manufacturing operations and likely increase costs.

part with standard finish

Standard, As-Milled Finish

Bead Blast Finish

A light texture with a matte finish is created by blowing small glass beads against the part in designated areas. Additional cost may occur if the design requires significant masking of surfaces or holes that do not require bead blasting.

part with bead blast finish

Bead Blast Finish

Anodizing, Type II (Sulfuric Acid Anodizing)

Type II coatings produce a uniform, corrosion resistant coating. Parts can be dyed in different colors after anodizing – black, red or gold are most common. The part shown here is not dyed. Anodizing is usually associated with aluminum parts. 

Reference MIL-A-8625 for additional information on anodizing.

anodized part

Anodizing, Type II (Sulfuric Acid Anodizing)

FREE CNC Metal Finishes E-Book

Anodizing, Type II (Sulfuric Acid Anodizing)

Type III coatings produce a wear resistant layer of specified thickness and the corrosion resistance achieved with Type II coatings. Parts can be dyed in different colors after anodizing – black, red or gold are most common. The part shown here is dyed black. Anodizing is usually associated with aluminum parts. 

Reference MIL-A-8625 for additional information on anodizing.

type ii anodized part

Anodizing, Type II (Sulfuric Acid Anodizing)

Powder Coat Finish

Powdered paint is sprayed onto a part that is then sent through an oven to bake the paint onto the part. This creates a strong, wear and corrosion resistant layer that is more durable than standard painting methods. A wide variety of colors are available to achieve the desired part aesthetic. A powder-coating finish is commonly used in military applications.

powder coated part

Powder Coat Finish

picture of Greg Paulsen
Greg Paulsen
They call me the Director of Application Engineering at Xometry. This means I not only get to produce great design-for-manufacturing content but also consult on various custom manufacturing projects using CNC machining, additive manufacturing, sheet metal, urethane casting, and injection molding. If you have a question, I'm your guy.

Read more articles by Greg Paulsen

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