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3D Printing Threads and Adding Threaded Inserts to 3D Printed Parts (With Video)

Two 3D printed test parts, plus screws, taps, and inserts scattered on a concrete background.

There are many ways to attach screws to 3D printed parts, including inserts, tapping, and even 3D printed screw threads.

Screws are among the most popular fasteners in any material. Can you use off-the-shelf screws with your 3D printed parts? The answer is a clear yes, for both stereolithography (SLA) and selective laser sintering (SLS) parts.

In this article, we explore different methods of using metal screws with 3D printed parts, and provide some tips for incorporating screw threads directly into your 3D design.

Watch our application video about 3D printing threads and threaded inserts for 3D printed plastics.

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Design Options for 3D Printed Screw Threads

Let’s take a look at the various design options for 3D printed threads, which we’ve collected over the years within Formlabs and based on feedback from our customers. Our test part is designed to showcase all these methods at once:

Illustration showing the different negative features on the test part used for photography in this article, labeled with corresponding hardware.

We’ve grouped these options based on the type of fastening, with pros and cons of each option listed for different use cases.

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Metal Screws to Metal Threads

In this section, we look at three ways to incorporate inserts and nuts into your completed 3D prints for strong, long-lasting fastening that stands up to multiple cycles of assembly and disassembly.

Screw-to-Expand Inserts

Test part with a machine screw installed in a screw-to-expand insert.
Closeup of a brass screw-to-expand insert.


  • Very good hold into 3D printed parts

  • Metal threads are strong and wear-resistant

  • Installs with a simple press fit


  • Inserts may loosen at elevated temperatures

Screw-to-expand inserts are cylindrical, with a slight taper and knurling on the exterior surfaces. During the design stage, incorporate a boss with a depth and diameter based on the insert’s specs into your part. Print and post-process the part as normal, following the usual steps for SLA or SLS post-processing, taking care to make sure no extra material remains inside the cavity, and install the insert with a simple press fit. Adding a screw will press the knurled surface into the surrounding printed material, creating a strong friction fit.

Tip for using screw-to-expand inserts with 3D printed parts made with SLA 3D printing: Wash the part as normal, insert the screw-to-expand insert, install a screw, and post-cure the part with the screw in place. Saving this step for last reduces the chance that the insert will crack the surrounding material when expanded.

Heat-Set Inserts

Test part with a machine screw installed in a heat-set insert.
Closeup of a brass heat-set insert.


  • Best hold into 3D printed parts

  • Metal threads are strong and wear-resistant


  • For thermoplastic (SLS) parts: requires a soldering iron and cooling time

  • For thermoset (SLA) parts: requires glue and curing time

Heat-set threaded inserts are designed to be installed into thermoplastics using a soldering iron with an installation tip. They can also be used as glue-in inserts in thermoset materials, such as SLA parts. 

To install in a thermoplastic part, like one printed with SLS Powders, follow the installation instructions for your particular hardware. The typical process is to use a soldering iron, with or without a special attachment, to heat the insert, which conducts heat into the surrounding plastic. The surrounding material softens and, by pressing down with the soldering iron, you can gently press the insert into the printed part. Be sure to allow enough time for the material to cool down and regain strength before installing a screw.

To install in a thermoset part, like one printed with SLA Resins, glue can be used to hold a heat-set insert in place. Unlike with traditional installation, make sure to design your boss to match the widest diameter of the insert, and use a bead of cyanoacrylate (CA) glue or epoxy to hold it in place when installed. Be sure to allow enough time for your glue to fully cure before installing a screw.

Note: In the SLS 3D printed part photographed for this article, the boss is sized for a press-fit, as we recommend here for thermoset plastics. This also works, with a drop of glue or epoxy, for thermoplastic parts, but won’t have as strong a hold as a true heat-set installation.

Although an additional step of soldering or gluing is required, heat-set threaded inserts for both SLS and SLA parts offer improved security and strength compared to screw-to-expand inserts With either method, these are a great option to gain a little extra security and strength compared to screw-to-expand inserts, although the additional step and equipment may be inconvenient.

Nuts Incorporated Into Design

Test part with a machine screw installed in an embossed nut.
Test part with a machine screw installed in a nut that has been inserted into a pocket in the side of the part.


  • Very good hold into 3D printed parts

  • Metal threads are strong and wear-resistant


  • Pocket or boss needs to be designed into the part, and accessible after printing

  • Depending on geometry, may require glue and curing time

Designing a pocket or boss that securely holds a nut into the part itself is another method to get metal-on-metal contact. Hexagonal or square nuts can be used, and even locking nuts are possible to accommodate. There are many design variations for this method—just make sure your pocket or boss is easily accessible (i.e. not on an interior surface) so that the nut can be installed. For extra security, a drop of cyanoacrylate (CA) glue will hold the nut in place.

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Metal Screws to 3D Printed Parts

For speed and simplicity, it might be preferable to forego inserts and nuts in favor of screwing directly into a 3D printed part. Whether tapping threads or using a self-tapping screw, off-the-shelf hardware designed for use with plastics work well with 3D printed materials like resins and thermoplastic powders.

Tapping Screw Threads in 3D Printed Parts

Test part with a screw installed in a pocket without an insert. The hole has been tapped.


  • Good hold into 3D printed parts

  • Simple and quick to execute


  • Won’t hold up as well as metal to cycles of assembly and disassembly

  • May add work time to parts with many negative features

Using a thread tap designed for plastic is a quick, economical way to add screw threads to 3D printed parts. It doesn’t require any extra design steps, and most shops that work with plastics will already have the equipment required.

Thread-Forming or Self-Tapping Screws

Test part with a self-tapping screw installed in a pocket without an insert.


  • Good hold into 3D printed parts

  • Extremely simple and quick to execute


  • Won’t hold up as well as metal to cycles of assembly and disassembly

Self-tapping screws, also called thread-forming screws, can be inserted into a negative feature with no preparation work done to the part. Follow the manufacturer’s guidelines for boss dimensions. 

It’s suggested to use these with materials that are ductile, or have high elongation. Formlabs Nylon 11 Powder or Nylon 12 Powder are both suitable for this, as are the Tough and Durable Resins in the Formlabs SLA material family. Brittle materials, or those with low elongation (such as the Rigid Resins in the Formlabs SLA material family), may crack when used with self-tapping screws, so take caution and wear eye protection when using these materials.

3D Printed Threads

Directly 3D printed screw thread or 3D printed screw hole


  • Can custom design both positive and negative features


  • Won’t hold up as well as metal to cycles of assembly and disassembly

  • Only works with larger thread sizes

Including threaded geometries in your printed part can be effective if you follow certain guidelines. Stick to larger thread sizes, at least  ¼”–20 (imperial) or M6 (metric) or larger; reduce stress concentrations with fillets; and use thread profiles that are designed for plastics. For smaller screws, the threads should be customized to create a better fastener. For example, printing a semi-circular thread profile (on screw and nut) and using a 0.1 mm offset gives better thread engagement with improved wear characteristics. 

SLA and SLS 3D printing are generally preferable for this method over FDM, because they are more precise and can create parts with a smoother surface finish. Any material with particularly low surface friction, such as Durable Resin, is less likely to show wear over multiple cycles of assembly and disassembly.

When preparing your part for printing, it's important to minimize support structures on any threaded surfaces to ensure your parts will come together smoothly without additional post-processing.

Combine Multiple Components With 3D Printed Threads and Threaded Inserts

There are many options for combining multiple 3D printed components using screws and threaded fasteners. From directly 3D printing threads to using off the shelf inserts, you can choose any of the methods outlined above, based on the chosen material, the number of cycles of assembly and disassembly you anticipate, the strength required, and the amount of extra steps your workflow can accommodate.

Curious to see what 3D printing material might be right for your application? Use our interactive wizard to choose the best 3D printing material or request a free 3D printed sample part to see the quality firsthand.