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When your motion-control build demands a gear that fits precisely, transmits torque reliably, and holds up under continuous load, a loose-tolerance blank simply won't do. Engineers, makers, and machine builders working on CNC routers, conveyor drives, robotic arms, and industrial automation rigs need a spur gear that arrives ready to mount — with a finished bore, a matching keyway, and a hub that keeps the gear centered on the shaft.
These Module 3 spur gears are machined from C45 medium-carbon steel and surface-hardened for wear resistance. The gear body spans a tooth count range of 12 to 40 teeth, with an outer diameter that scales accordingly — from approximately 42 mm (1.65 in) for the 12-tooth up to approximately 126 mm (4.96 in) for the 40-tooth. Bore options run from 8 mm pilot-hole roughing blanks up to 40 mm finished bores with keyways sized to DIN 6885 standards (4 mm, 5 mm, 6 mm, 8 mm, 10 mm, or 12 mm depending on bore diameter). The integrated hub adds axial support and simplifies shaft-collar or set-screw retention.
Typical use cases include motor-pinion drives on CNC gantry systems, stage-1 reduction gears in servo-driven conveyor lines, and replacement gears for industrial automation equipment requiring Module 3 pitch. The hardened tooth surface makes these gears well-suited for continuous-duty applications where a standard mild-steel gear would wear prematurely.
Machined from C45 steel (equivalent to 1045 carbon steel), offering a tensile strength of approximately 600–800 MPa — a reliable balance of machinability and load-bearing capacity for power-transmission gears.
Tooth flanks are hardened to extend service life under repetitive mesh loading, reducing pitting and surface fatigue compared to through-soft gears in the same material class.
The raised hub provides additional axial bearing surface and simplifies clamping with shaft collars or set screws, keeping the gear concentric and reducing wobble under dynamic loads.
Keyed bore variants are finish-machined to H7 tolerance and include a keyway sized to DIN 6885 — ready to mount on a keyed shaft without additional machining. Pilot-hole variants are available for custom boring.
Sixteen tooth-count options from 12T to 40T let you dial in your gear ratio precisely. All share the same Module 3 pitch, so mixing tooth counts within a stage is straightforward.
Bore options from 8 mm up to 40 mm cover the most common motor and gearbox output shaft diameters used in servo, stepper, and AC induction motor applications.
| Module | 3 |
|---|---|
| Pressure Angle | 20° |
| Tooth Count Range | 12 – 40 Teeth |
| Material | C45 Medium-Carbon Steel |
| Surface Treatment | Surface Hardened |
| Bore Range | 8 mm – 40 mm (Pilot Hole or Finished with Keyway) |
| Keyway Standard | DIN 6885 (where applicable) |
| Outer Diameter (OD) | See variant options (scales with tooth count) |
| Face Width | See variant options |
| Hub Included | Yes |
| Quantity per Order | 1 pcs (default); multi-pack options available |
Select tooth counts based on your required gear ratio. Divide the driven gear teeth by the driving gear teeth to get the ratio. For example, a 12-tooth pinion meshing with a 36-tooth gear gives a 3:1 reduction. All gears in this listing share Module 3 pitch, so any two tooth counts can mesh together as long as center distance and face width are compatible.
Pilot Hole (Roughing) variants have a small center hole and require finish boring on a lathe or machining center to your exact shaft diameter. Keyed bore variants are already finish-machined to a specific bore diameter with a DIN 6885 keyway, ready to mount on a matching keyed shaft without additional machining.
C45 steel with surface-hardened teeth is suitable for moderate to heavy continuous-duty applications. The hardened tooth flanks resist pitting and surface fatigue. For very high shock loads or extreme-duty cycles, consider specifying a higher alloy steel or a heat-treated variant. Contact us if you need load-capacity calculations for your specific application.
C45 carbon steel is not inherently corrosion-resistant. For humid, wet, or outdoor environments, apply a rust-inhibiting coating, grease, or oil film after installation. If corrosion resistance is a primary requirement, consider stainless steel or plastic gears instead.
Spur gears and helical gears of the same module and pressure angle can mesh, but only if the helical gear has a helix angle close to 0° (i.e., effectively spur). Standard helical gears have a helix angle that changes the effective pitch and prevents direct meshing with spur gears. For best results, mesh Module 3 spur gears with other Module 3 spur gears.
Keyway dimensions follow DIN 6885 standards and are determined by bore diameter. For example, a 12 mm bore uses a 4 mm key, a 16–22 mm bore uses a 5–6 mm key, and a 25–32 mm bore uses an 8 mm key. Check the variant name for the bore + keyway combination (e.g., "16mm + 5mm Keyway") and match it to your shaft key dimensions before ordering.
For enclosed gearboxes, use an ISO VG 220 or VG 320 gear oil. For open drives or light-duty applications, a lithium-based grease (NLGI Grade 2) applied to the tooth flanks is sufficient. Re-lubricate at regular intervals based on operating speed and load. Avoid running the gears dry, as this accelerates tooth wear.
