Gear+generator+stl

While primarily a 2D tool that exports SVG and DXF files, it is widely used by makers who import those shapes into Tinkercad or Inkscape to create 3D models.

A highly popular web tool specifically designed for 3D printing. It supports over 10 gear variants, including helical, spur, and double helical gears. gear+generator+stl

A robust online tool that generates precise involute tooth forms. It provides real-time visualization and exports directly to STL for 3D printing. While primarily a 2D tool that exports SVG