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When a slipping or worn gear brings your build to a halt, you need a replacement that fits precisely and holds up under load. Whether you are a mechanical engineer, CNC hobbyist, or robotics builder, finding a Module 3 spur gear in the exact tooth count you need — without waiting weeks for a custom order — is a constant challenge. These Module 3 C45 steel spur gears are stocked in 12 through 120 tooth configurations so you can get the right cogwheel and keep your project moving.
Each gear is machined from C45 medium-carbon steel and surface-hardened for improved wear resistance. The module (pitch) is 3 mm, meaning the tooth pitch diameter equals 3 × tooth count (e.g., a 20-tooth gear has a 60 mm pitch diameter / ~2.36 in). Bore diameter and face width vary by tooth count — see variant options for exact dimensions. The flat (no hub) profile keeps the overall axial footprint compact.
Typical use cases include DC motor pinion drives in conveyor systems, rack-and-pinion linear actuators for CNC router axes, and reduction gear trains in robotic arm joints — all applications where a consistent module 3 pitch is required for correct meshing with mating gears or racks.
| Material | C45 Medium-Carbon Steel |
|---|---|
| Surface Treatment | Hardened (tooth flanks) |
| Module (Pitch) | 3 mm |
| Pressure Angle | 20° |
| Tooth Count Range | 12 – 120 Teeth (see variant options) |
| Pitch Diameter | Module × Tooth Count (e.g., 20T = 60 mm / 2.36 in) |
| Face Width | See variant options |
| Bore Diameter | See variant options |
| Hub Style | Flat (no hub) |
| Gear Type | External Spur Gear |
| Quantity per Order | 1 pc |
The tooth count determines your gear ratio and pitch diameter. Divide the desired gear ratio by the number of teeth on your mating gear to find the required tooth count on this gear. For example, a 4:1 reduction with a 15-tooth pinion requires a 60-tooth wheel. Use the pitch diameter formula (Module × Teeth = PD in mm) to confirm the center distance fits your housing.
"Module" (abbreviated M or Mod) is the metric standard for gear tooth size. Module 3 means the pitch diameter equals 3 mm × tooth count. These gears will mesh correctly with any other Module 3 external spur gear or Module 3 rack, regardless of brand, as long as the pressure angle is also 20°. They are NOT compatible with Module 2, Module 4, or imperial DP (diametral pitch) gears.
C45 steel with surface-hardened teeth provides solid load capacity for moderate-to-heavy duty drives. Exact torque ratings depend on tooth count, face width, speed, and lubrication. For critical load calculations, apply AGMA or ISO 6336 gear strength standards using the actual face width and material hardness values. These gears are well-suited for CNC drives, conveyor systems, and robotic joints operating at typical hobby-to-light-industrial torque levels.
C45 steel is not inherently corrosion-resistant. For outdoor or humid environments, we recommend applying a light machine oil or grease coating regularly, or considering a protective surface treatment such as zinc plating or painting after purchase. For fully corrosion-resistant applications, stainless steel or plastic gears would be a better choice.
Bore diameter varies by tooth count — please check the variant options or contact us to confirm the bore size for your selected tooth count before ordering. If the bore is slightly undersized for your shaft, it can typically be bored out or reamed to the required diameter by a machine shop. A keyway or set-screw can then be added for positive shaft retention.
Yes — the flat profile and available small tooth counts (12–20 T) make these gears well-suited as drive pinions on DC motors, stepper motors, and servo motors. Verify that the bore diameter matches your motor shaft diameter. If needed, the bore can be machined to size. Ensure the face width aligns with your mating gear or rack for full tooth engagement.
Yes, lubrication is recommended for all steel spur gear drives. Apply a light machine oil or gear grease to the tooth flanks before initial operation. For continuous-duty applications, re-lubricate every 200–500 operating hours or whenever you notice increased noise or heat. Proper lubrication significantly extends tooth life and reduces wear.
