Spex Logo

What Are Secondary Machining Processes?

BlogSecondary Processes


What Are Secondary Machining Processes?​

Depending on the type of part being manufactured, there are many steps in the process from raw material to finished part. Parts with various surface features or unique shapes often use multiple machines and machining processes. 

For example, a CNC machine might cut and form the general shape of the part. Then another machine may form threads on the parts. Then a grinder machine durburrs the part. And after that, the parts are washed and engraved.

Modern CNC machines have advanced capabilities, but they can’t do everything.

Secondary machining processes form the features that weren’t done in the initial machining of the part. This includes things like deburring, engraving, sub-assembly, and surface treatments like anodizing, heat treatment, and powder coating.

The secondary processes are less extensive than the initial machining. They’re used to add the specific final touches to the parts and components. 

Here are four examples of common secondary processes that we provide.


Parts are engraved for a variety of reasons. One of the most common reasons is to keep track of different lot numbers and help identify parts that look similar. Engraving parts can also help identify different metal alloys since they usually look the same.

After parts are machined, we use in-house CNC engravers and laser engravers to add part numbers, lot numbers, AISI numbers, and more to parts.

Laser engravers are more accurate and can be used for smaller text, or more complex designs like a QR code. The CNC engraver will provide a more durable engraving.


Deburring is a secondary process used to remove small imperfections from parts. Deburring isn’t always necessary, but sometimes the machining process creates small burrs on parts—especially when there are small slots, threads, or sharp edges.

During the deburring process, a spinning brush, grinding wheel, or belt is used to remove the burrs and smoothen out the part. 

A burr is a small protrusion on a part and they’re usually sharp. For certain parts, deburring is a necessary process for parts to function properly and ensure safe handling.


Sub-assembly is a process where two or more separate parts are attached together by the manufacturer. The term “sub-assembly” refers to components that are first assembled together and then integrated into a larger assembled unit. So, a sub-assembly isn’t the final product. Some more complex parts or components are machined as separate parts to speed up the production process, and then assembled.

In some cases, the assembled parts are two different materials, like attaching a rubber o-ring to a metal part.

When sub-assembly operations are outsourced to the manufacturer, it saves time and allows the customer to scale their operations.

Surface treatments

Various things can be done to the surface of the part. This includes heat treatment, anodizing, plating, and powder coating. These are usually to add durability to the part.

Different surface treatments are used for different types of parts and use cases. Metals that are more susceptible to rust or scratches are more likely to benefit from surface treatments.

Steel parts are the most common for plating, when a thin layer of zinc, nickel, or chromium is added to the part. Many steel parts are also heat treated, which makes the steel harder and stronger, but also more brittle.

Aluminum parts are often anodized, which adds a thin layer of oxidized aluminum so that its surface is no longer reactive. The layer of oxidation offers protection from scratches and mechanical wear, as well as chemical protection from water and oxygen.

Spex has served as a local manufacturer since 1946. We provide a wide range of manufacturing services. If you want to learn more about our precision machining capabilities or secondary machining services, reach out to one of our team members to get a custom quote.

Related content

Contact us

Fill out the form to learn more about our precision machining services.

We would love to hear from you! Please fill out this form and we will get in touch with you shortly.

  • Max. file size: 256 MB.
  • This field is for validation purposes and should be left unchanged.
Spex Logo

Phone: (585) 467-0520

Email: sales@spex1.com

85 Excel Drive
Rochester, NY 14621