Gears, belts, and chains

Spur gears — set the module (mm) or diametral pitch (teeth per inch; module = 25.4 / DP), the tooth counts, the pressure angle (20° is standard; 14.5° on older and many imperial gears), and optionally a profile shift, backlash, a bore, and a keyway. You get the pitch, outside, root, and base diameters, the tooth thickness, the centre distance, the working pressure angle, and the transverse contact ratio (aim for 1.2 or more), with warnings for undercut (fewer than about 17 teeth at 20°) and pointed tips. Export either gear as SVG or DXF for a laser, router, or CAD.

Gear train — enter a ratio (7.5 or 60/8) and a tooth range; the tool lists the closest single pairs and two-stage compound trains (A drives B, C on B’s shaft drives D).

Timing belt — choose the profile, the pulley teeth, and an approximate centre distance; the tool picks the nearest belt (whole teeth), gives the exact centre distance for it, pulley pitch and outside diameters, the wrap and teeth in mesh, belt speed, and travel per turn (for 3D printer and CNC steps/mm).

V-belt and roller chain — length, nearest standard size (even chain links), exact centres, ratio, wrap angle, and speed, with the usual rules of thumb.

⛶ Full screen (or F) gives the drawing on the open tab (the meshing gears, the belt or the chain) the whole screen — the browser’s full screen where it is allowed, otherwise a full-window layer (iPhone); it is redrawn as the window changes, and ◫ Panels hides the figures beside it. Escape leaves.