CNC Machining Gears

Unlike a laser, a rotary cutting tool (router bit, end mill) has a real, non-negligible diameter, which sets a hard limit on how small a concave feature it can resolve. On an involute gear, the tightest concave feature is almost always the root fillet between two adjacent teeth — if your cutter diameter is larger than that fillet's effective radius, the tool simply can't reach into the full gap, and the root comes out shallower (and the tooth base thicker/stronger, but the tooth gap narrower) than the nominal profile.

As a rough guide, coarser modules (1–2) tolerate ordinary router/end-mill diameters (3–6 mm) without much trouble; module 0.3–0.5 gears usually need a cutter under 1–2 mm to clear the tooth gaps cleanly, which pushes toward smaller CNC routers, engraving-class mills, or a different process (laser or waterjet) entirely for very fine teeth.

Workflow

Every gear page's DXF download is a closed polyline of the exact involute profile plus a circle for the bore — import it into CAM software (Fusion 360, VCarve, Mastercam, or similar) as a 2D profile and generate an outside-offset toolpath for the gear's outer boundary and an inside-offset toolpath for the bore, compensating for your actual cutter diameter the same way kerf is compensated for laser cutting.

Waterjet and plasma

Both follow the same DXF-import workflow as milling, with kerf compensation handled like the laser-cutting case rather than a fixed cutter-diameter limit — waterjet in particular can resolve much finer internal features than a rotary cutter, since the "tool" is a narrow jet rather than a rigid bit. See Gear Materials for metal choices, or CNC Gears for a condensed practical checklist.