How to Avoid Stress Concentration in CNC Machined Parts

In the world of precision CNC machining, the structural integrity of a part is paramount. One of the most critical, yet often overlooked, factors affecting this integrity is stress concentration. Stress concentration occurs when stress is localized in a small area of a part, typically at sharp internal corners, sudden changes in crosssection, or surface imperfections. These "hot spots" can become initiation points for cracks and lead to premature part failure under load, compromising performance and reliability.


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For businesses relying on highquality machined components, understanding and mitigating stress concentration is not just an engineering best practice—it's a competitive advantage. Here are key strategies to avoid it in your CNC machined parts:

1. Incorporate Generous Fillet Radii
The most effective method to combat stress concentration is to eliminate sharp internal corners. Instead of a 90degree angle, design corners with a generous fillet radius. This smooth transition distributes stress over a larger area, significantly reducing the peak stress. A good rule of thumb is to use the largest feasible radius your design allows.

2. Utilize Chamfers and Tapers
Similar to fillets, chamfers and tapers can be used to gradually transition between different crosssections. Avoid abrupt changes in geometry. If a part must have a step or a notch, design it with a sloped transition to prevent a sharp stress riser.

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3. Optimize Hole Placement and Design
Holes are inherent stress concentrators. Avoid placing holes too close to the edges of a part or near other stressraising features. When possible, use counterbores or spot faces to create a flat, uniform surface around the hole, which helps in better load distribution.



4. Select the Right Material and Grain Direction
The material's inherent properties play a crucial role. Materials with higher ductility can better withstand localized stress. Furthermore, for processes like milling, consider the material's grain direction. Aligning the machining operations to work with, rather than against, the grain can improve fatigue life.

5. Specify Superior Surface Finishes
Rough surface finishes from machining can act as a series of tiny stress concentrators. Specifying a smoother surface finish, such as through polishing or grinding, can remove these micronotches and enhance the part's overall fatigue strength.

Partner with a Proactive Machining Expert

Avoiding stress concentration is a collaborative effort between design and manufacturing. As your onestop CNC machining partner, we don't just follow blueprints—we analyze them. Our engineering team proactively identifies potential stress concentration issues during the Design for Manufacturability (DFM) review phase. We provide expert recommendations on fillet sizes, optimal geometry, and material selection to ensure your parts are not only precise but also durable and reliable.

By designing for longevity and partnering with a manufacturer that understands structural mechanics, you reduce the risk of field failures, enhance product performance, and ultimately build a stronger, more trusted brand. Let us help you build parts that are built to last.