Core one belt calibration tool.

Calibrating the belts on the Prusa Core One can be tricky — especially when the wizard gives you “turns,” or when you simply want a precise visual reference for the tightening angle you apply each time. This tool makes that process easier by giving you a clear indicator for the rotation angle of the tension screw.

What it helps you do:

• Apply the exact number of turns required by the wizard.
• Quickly and consistently see how far you’ve rotated the tension screw.

Assembly:

•  Insert two cube neodim magnets 5mm or place a double-sided sticky tape.

How to use it:

1. Attach the tool to the tension screw — the two magnets keep it securely in place.
2. Slide the arrow onto the hex key. It should be a snug, friction fit: able to rotate, but not spin freely. If needed, slightly adjust the hole with a file after printing.
3. Rotate the screw to your desired angle and align the arrow with the markings (each mark = 10°).

Using it with the belt tuning wizard:

Following the belt tuning wizard:
https://help.prusa3d.com/de/article/belt-tuning-wizard_973716

When the wizard shows values in turns, you can convert them to degrees with:
(x / y turns) × 360 = degrees

Example:

2/8x360=0.25x360=90

This tool removes all the guesswork and helps you dial in your Core One’s belt tension with confidence and repeatability.

Upload includes:

STL file for printing

Recommended print settings:

Filament type-PLA
Nozzle diameter-0.4 mm
Layer height-0.15 mm
Infill density-15%
Support material-no

A small tool — but surprisingly useful for anyone who enjoys a perfectly tuned machine.