What is it for ?

With this kit, you can test how much clearance you need for your 3D-printed metric screw threads, bolts, and nuts to fit smoothly.

You can also test how the allen key and spanner work with your print, and assess how durable your material of choice is for tightening bolts and nuts.

Testing with steel-manufactured bolts and nuts is also possible.

How was the clearance achieved ?

The bolts and nuts are marked with three numbers: 0, 0.1, and 0.2. These represent how much the thread gap has been enlarged.

• 0 means that the screw/nut model was made exactly according to the ISO 68-1, ISO 261, and ISO 724 standards.
• 0.1 and 0.2 indicate the amount by which the thread gap was increased.

Here are pictures showing how the other models were made:

(+0.2 bolts and all nuts were made the same way.)

The .3mf file

I printed 3 kits with different layer heights: 0.08 mm, 0.12 mm, and 0.16 mm, using PLA. This was done to test how screw threads perform with different layer heights. I used a Bambu Lab A1 printer, and it showed that the 0.08 mm layer height worked the best for screw threads (requiring the least clearance to fit smoothly).

The .stl files

I’ve also included .stl files so you can test different layer heights, materials, and printing settings.

The prints

For the bolts, you will need a size 8 allen key, and for the nuts, a size 15 spanner. Alternatively, you can use your hands or pliers.

If you apply too much torque while tightening the bolts and nuts, they may break. This can be useful for testing the strength of your material and printing technique.

! Update 14.42026 !

Consider decreasing the largest diameter on bolt thread a bit when designing screws . It helps a lot for easy assembly of screw connections. Alternatively you may increase the smallest diameter of bolt thread for the same result.

If you find this tool usefull in designing screw threads please leave a rating.