Two gears can only mesh if they share the same Module (or Diametral Pitch).

): The number of teeth on the gear. A minimum of 13 teeth is recommended for a 20° pressure angle to avoid "undercutting".

| Symptom | Likely Cause | Fix | | :--- | :--- | :--- | | Loose, wobbles on shaft | Hole is too big | Add a tolerance modifier in CAD or use a metal insert | | Won't mesh at all | Different Modules | Measure pitch diameter; ensure both gears use Mod 1 or Mod 2 | | Turns for 1 sec, then jams | Zero backlash | Regenerate STL with 0.2mm backlash | | Teeth snapping off | Too fast print speed / low temp | Print slower (30mm/s) and hotter (+5°C) for layer adhesion |

An intuitive 3D modeling software that includes a built-in gear generator tool, allowing users to adjust diameters and widths before exporting to STL. Common Gear Types for 3D Printing

Look at the 2D preview. Ensure the tooth tips (addendum) and roots (dedendum) look smooth. Ensure the shaft hole is not intersecting the root circle (you may need to add a hub).

For Elias, this wasn’t just about mechanical advantage; it was about the "Perfect Fit." He wasn’t printing toys; he was restoring a 1920s clockwork telescope he’d found in a basement in Prague. The original brass gears were long gone, dissolved by rust and time.