How to Include Hardware Features in CNC Machined Part Designs


Did you know that Protolabs can ready your machined part for hardware insertions? As part of the machining process, we can incorporate machined features that ensure your part is set up perfectly for hardware like Helicoils®, Keenserts®, PEM® fasteners, and dowel pins. For the first three, you should use the manufacturer’s suggested parameters when designing your CAD file. There’s a ton of related information online that will ensure that your model is prepped correctly. Here are some extra design tech tips for you to keep in mind as you work out your model.

If hardware is required, we suggest that you don’t include the intended hardware in your CAD file.  Instead, build your CAD file to accept the appropriate hardware.

Including Helicoil Features in Your CAD Files

If you’re designing a part that requires a ¼-20 Helicoil, simply look up the minor diameter for the required drill size, and apply it to your CAD file. For example, a 0.266 in. (6.7564mm) diameter hole is required for a ¼-20 Helicoil.  This will allow our software to recognize these features. Adding the threads or the hardware to your CAD file as a cosmetic feature doesn’t improve design for manufacturability.

Dowel Pins and Machined Parts

Let’s say that your design requires a 0.25 in. (6.35mm) press fit dowel pin. You should design this feature with a 0.2495” (6.3373mm) diameter. We recommend adding a range of +0.000 in./-0.0005 in. (+0.0mm/-0.01397mm) in your model. For a 0.25 in. (6.35mm) slip fit dowel pin feature, you would want to design your CAD file with a 0.2505 in. diameter feature. Here, too, it helps to add a +0.0005”/-0.000” (+0.01397mm/-0.0mm) callout in your CAD file.

Best Practices Working with Hardware and Machined Parts

In the end, how you incorporate hardware into design files for machined parts has a ripple effect. Doing it right can speed up the manufacturing process and ensure that you get the part you need. Using available resources, like our free CNC Machining Design Guide, can ensure a smooth transition from model to part.

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