Design Guide: Threads in 3D Printed Parts (NPT & NPS CAD Tutorial)

Printing threads directly into 3D printed parts is not only possible — it works remarkably well, even in high-load, end-use applications, as shown in the testing video below. At F3DP, we’ve successfully printed NPS (National Pipe Straight) threads as small as 6-32 or M3 into parts with excellent performance. If you need to route compressed air, water, fuel, or other gases or liquids through your 3D printed components, we also offer a proven workflow for modeling NPT (National Pipe Taper) threads. This guide will walk you through how to design both NPS (straight) and NPT (tapered) threads into your 3D printed parts.

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Straight Thread (NPS) Strength Testing: Nylon 12 Material

Tensile strength test of MJF parts with larger printed in threads

Tensile strength test of MJF parts with smaller printed in threads

Straight Thread (NPS) Testing: TPU Rubber Material

Tensile strength test of TPU Rubber MJF parts, helicoil thread insert vs. printed in thread

Now that we’ve covered what and when you can print threads, let’s look at how—starting with CAD design.

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How to design Straight Thread (NPS)?

Our in-house engineering team is proficient with all major CAD platforms, but SolidWorks stands out as the easiest when it comes to adding threads to 3D printed parts. That’s because SolidWorks includes built-in tools that automatically apply the correct thread profiles, streamlining the design process. For this reason, the guide below is based on SolidWorks, and the following video will walk you through how to model threads specifically for 3D printing.

How To Design 3D Printable Straight Thread – NUT

How To Design 3D Printable Straight Thread – BOLT

Here is a really good tap / drill chart for reference.

For those not using Solidworks for their CAD design software we have also collected thread design how to video’s for a lot of the other major CAD design platforms on the market:

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How to Design Tapered Threads (NPT)

SolidWorks does not include a built-in tool for adding tapered (NPT) threads to your designs. However, our engineering team has developed a reliable workflow using pre-modeled NPT thread bodies to accomplish this. The video below provides a step-by-step walkthrough of the process:

To get started, download the complete library of NPT thread bodies. If you’re not using SolidWorks, we’ve also included Parasolid (.X_T) versions of each NPT size so you can replicate our workflow in the CAD software of your choice.

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What 3D Printing Technologies is it possible to print threads into parts with?

This guide has been specifically written around designing threads for 3D printed parts coming off of the HP MJF technology. The MJF machine is unique in that it allows for very fine features to be printed in any orientation without the need for support while still being able to use high strength materials like Nylon. The next closest technology that would be able to produce threads would be SLS, but these machines can’t capture the same level of detail as the MJF so they are limited to 1/4-20 or M6 threads or bigger. Then there are the liquid polymer machines like Polyjet, SLA, DLP, ect. These machines can absolutely print threads down to 8-32 or M4, but the hole must be oriented in the vertical direction from the print bed. If the hole is horizontal it will end up with support in it and the 3D printed thread will not turn out. Lastly, FDM technology is not suited to print in any threads under 1/2-13 or M12, and they have to be oriented vertically from the machines print bead.

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Click here to go to the 3D Printing Machines & Materials page

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