A Cog 4 Your Machine

Involute gear template generator · offline · print at 100 % scale

Train

Tooth spacing (mm along pitch circle)

Contact (pressure) angle °

Drive speed (rev/min)

The driver ▶ turns clockwise at this speed; each gear’s row shows what it does in response. Readout only — templates are the same at any speed.

Gears

Gear properties

Select a gear to edit its properties.

Display Pitch circles Line of contact + base circles Center marks 1 cm grid

Show rotated (% of one tooth)

Print & calibrate

Paper

Measured length of the printed 100 mm bar

Prints a cover sheet (assembly + parts list), then true-scale cut sheets. Every gear is printed whole — only a gear too big for one sheet is tiled, on its own, with crop marks (8 mm overlap). Print once, measure the bar, type the result, print again. Turn OFF “fit to page” in the print dialog.

Project

Saves the whole train — gears, positions, colours, holes and display settings — as a .cog4 file you can keep next to the app on the stick. Older .json projects still open. Ctrl+S saves, Ctrl+Shift+S saves as. Your current design is also kept in this browser and comes back next time you open the app.

Export

STL: gear exports the selected gear flat, at the origin, for slicing. STL: assembly exports every visible gear merged at its solved position, for Blender. Extrusion only makes flat spur gears — the same kind this app draws; bevel/crown gearing and 3D assembly mock-ups are out of scope.

scroll = zoom · drag bg = pan · drag gear = move (+ shaft stack) + snap · del = remove · esc = deselect