How to Add Threads to 3D Printed Parts: Easy Methods Explained

To add threads to a 3D printed part, you can either design the threads directly into the model, use heat-set threaded inserts, or tap threads into the printed hole after printing. Heat-set inserts provide strong metal threads, while tapping creates threads by cutting into the plastic. Designing threads in the model works best for coarse threads and larger sizes.

Syntax

Here are the common methods to add threads to 3D printed parts:

• Design Threads: Model the thread shape directly in your CAD software.
• Heat-Set Inserts: Insert metal threaded sleeves into holes using heat.
• Tapping: Drill a hole and use a tap tool to cut threads into the plastic.

Each method requires specific preparation and tools.

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Method 1: Design Threads
- Use CAD software to create a helical thread profile on the part.

Method 2: Heat-Set Inserts
- Print a hole slightly smaller than the insert.
- Heat the insert with a soldering iron.
- Press the insert into the hole until flush.

Method 3: Tapping
- Print a hole slightly smaller than the desired thread size.
- Use a tap tool to cut threads manually after printing.

Example

This example shows how to use heat-set inserts to add threads to a 3D printed part.

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1. Design a hole in your 3D model with a diameter 0.1-0.2 mm smaller than the insert's outer diameter.
2. Print the part with your usual settings.
3. Heat a soldering iron to about 250°C (482°F).
4. Place the heat-set insert on the soldering iron tip.
5. Press the insert gently into the hole until it is flush with the surface.
6. Let it cool to secure the insert in place.

Output

The metal insert is securely embedded in the plastic, providing strong, reusable threads for screws.

Common Pitfalls

• Designing Threads Too Small: Threads may not print cleanly or fit screws properly.
• Incorrect Hole Size for Inserts: Too large holes cause loose inserts; too small holes can crack the part.
• Overheating Inserts: Can deform the plastic or damage the insert.
• Skipping Thread Tapping: Without tapping, screws may strip the plastic threads.

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Wrong hole size for insert:
- Hole diameter = insert outer diameter + 0.2 mm (too large)
Right hole size for insert:
- Hole diameter = insert outer diameter - 0.1 mm (recommended)

Quick Reference

Method	Hole Size	Tools Needed	Strength	Best Use
Design Threads	Exact thread profile in CAD	CAD software	Moderate	Large coarse threads, simple screws
Heat-Set Inserts	0.1-0.2 mm smaller than insert	Soldering iron, inserts	High	Strong, reusable metal threads
Tapping	Slightly smaller than tap size	Tap tool, drill	Moderate	Custom thread sizes, post-print modification

Key Takeaways

Use heat-set inserts for strong, durable metal threads in plastic parts.

Designing threads in CAD works but may print poorly for small sizes.

Tap holes after printing to create clean threads if inserts are not used.

Always size holes carefully to match the threading method for best fit.

Avoid overheating inserts to prevent damage to the plastic part.