How to 3D Print Nuts and Bolts

3D Model of printer friendlu bolt and nut

I recently tried to 3D print a bolt and nut, thinking it couldn’t be that hard, it’s a trap and here’s why.

Standard metric bolt and nut 3D models are everywhere. There’s a really cool Thingiverse customizer to make any size bolt or nut you need. Another option is to download the STEP file from a standard hardware site. After a few clicks the trap has been laid.

The next obvious step is to slice on high quality settings and print the bolt and nut out. After 10 minutes you will be elated with two nice looking parts. Try to tighten them down and GOTCHA. The nut will bind and won’t tighten properly. The problem is too much interference.

It should have been obvious but the metal parts were never intended to be printed out in plastic. The 3D printer can’t match the precision of mass produced metal bolts. I set off to find the right geometry for 3D printed hardware, here is what I came up with.

Improved vs metric standard bolt and nut cross-sections

3D printer optimized bolt and nut, compared to the standard M6 bolt and nut.

In the 3D printer optimized hardware the threads are chunkier and the pitch is wider. It threads much easier and won't bind when tightened down.

Tips for making 3D printed bolts and nuts that actually work:

1. Don’t go smaller than 6mm in dia. anything smaller and the pieces lose too much detail.

2. Start with at least a 2mm pitch, for a 6mm bolt the ISO standard would be 1 mm. This is too fine and unnecessary, 2 mm is the way to go.

3. The standard 60 degree open angle works fine.

You will need this 'trick' - HELIX

3D printed bolts and nuts can be made in any CAD package but require a tool that you probably haven't used before - The HELIX

FreeCAD helix

I use FreeCAD, here is the input prompt for building a helix. It will make a nice wireform that will become the sweep path for the threads. Next make a sketch with these reference dimensions and sweep a solid.

3D printer bolt dimensions

Solid helix to cut threads from shaft

There you have the threads to cut away from a solid shaft. I have glossed over some of the basic steps to create a shaft and hex head, and align the parts properly, each one varies with CAD package but I assume if you are trying to make a bolt you already have the basics down.

If you need some help, email me and I will send you the FreeCAD design file, so you can see every step.

Here is a link to the the model files, let me know if they work just as well for you.