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When your CNC router, robotic arm, or automation drive demands precise, repeatable torque transfer, a poorly matched gear becomes the weakest link in the entire system. Engineers and makers who need a dependable module 3 spur gear with a keyed bore — one that won't slip under load or corrode in a workshop environment — will find this 45# steel pinion motor gear a straightforward, no-compromise solution.
Each gear is machined from 45# medium-carbon steel, offering a balanced combination of tensile strength and machinability. The module (pitch) is 3, giving a circular pitch of 9.42 mm (0.371 in). Tooth counts span 14 through 30 teeth, with outside diameters ranging from approximately 48 mm (1.89 in) for the 14T up to 96 mm (3.78 in) for the 30T. Bore diameters are available from 12 mm to 40 mm, each paired with a matching DIN 6885 parallel keyway to lock the gear firmly onto the shaft.
Typical use cases include: replacing worn pinion gears on CNC rack-and-pinion axes, building custom gearbox stages for stepper or servo motor drives, and constructing speed-reduction or torque-multiplication assemblies in industrial automation rigs and DIY robotics projects.
Machined from 45# steel for a tensile strength typically in the 600–800 MPa range, delivering the rigidity needed for continuous-duty motor and drive applications without excessive weight.
Strict Mod 3 tooth geometry ensures accurate mesh with any standard Mod 3 mating gear, minimising backlash and noise in precision motion-control systems.
Every bore includes a machined keyway (4×2 mm up to 12×4 mm depending on bore size) so the gear locks positively to the shaft — no set-screw slippage under reversing or shock loads.
Nine tooth counts (14 T through 30 T) combined with bore diameters from 12 mm to 40 mm give you the flexibility to match virtually any motor shaft and gear-ratio requirement in a single product family.
The keyed bore accommodates standard stepper and servo motor output shafts, making these gears a direct fit for NEMA 23/34 motor builds and custom CNC axis drives.
Tooth flanks are finish-machined for smooth engagement. Apply a light gear grease or oil for extended service life in enclosed or semi-enclosed gearbox housings.
| Module (Mod) | 3 |
|---|---|
| Circular Pitch | 9.42 mm (0.371 in) |
| Pressure Angle | 20° |
| Tooth Count Options | 14T, 15T, 16T, 18T, 20T, 22T, 24T, 25T, 30T |
| Outside Diameter Range | ~48 mm – 96 mm (1.89 in – 3.78 in) |
| Bore Diameter Options | 12, 14, 15, 16, 18, 20, 22, 24, 25, 28, 30, 32, 35, 40 mm |
| Keyway Dimensions | 4×2 mm / 5×2.5 mm / 6×3 mm / 8×3.5 mm / 10×4 mm / 12×4 mm (matched to bore) |
| Material | 45# Medium-Carbon Steel |
| Gear Face Width | See variant options |
| Hub Diameter | See variant options |
| Surface Treatment | See variant options |
| Quantity per Order | 1 pc |
The tooth count determines the gear ratio when paired with a mating gear. Divide the driven gear's tooth count by the driving gear's tooth count to get the ratio. For example, a 14T pinion driving a 28T gear gives a 2:1 reduction. Choose a smaller tooth count for higher speed output and a larger tooth count for more torque.
Measure your motor shaft diameter with a calliper and select the matching bore. Common stepper motor shaft sizes are 6.35 mm, 8 mm, 10 mm, 12 mm, and 14 mm. If your shaft is metric, choose the bore that matches exactly. The included keyway requires a corresponding key on the shaft for a positive drive connection.
Yes — any gear or rack manufactured to the Module 3 standard with a 20° pressure angle will mesh correctly with these gears. Confirm the module and pressure angle of your existing components before ordering. Mixing modules (e.g., Mod 2 with Mod 3) will result in incorrect mesh and rapid wear.
45# medium-carbon steel has a typical tensile strength of 600–800 MPa and yield strength around 355–490 MPa in the normalised condition. It is well-suited for moderate-to-high torque drives in CNC, robotics, and general machinery. For very high-shock or high-cycle fatigue applications, consider heat-treated or alloy-steel alternatives.
Yes. Apply a suitable gear grease (e.g., NLGI #2 lithium-based grease) or gear oil to the tooth flanks before operation. Regular re-lubrication extends service life significantly, especially in enclosed gearboxes or high-cycle applications. In open-drive configurations, a light machine oil applied periodically is sufficient.
45# steel is not inherently corrosion-resistant. For outdoor or humid environments, apply a rust-inhibiting coating, grease, or paint to exposed surfaces. Alternatively, consider stainless-steel or plastic gears for corrosion-critical applications. Regular inspection and re-greasing will help maintain performance in damp conditions.
The keyways follow the DIN 6885 parallel key standard, which is widely compatible with metric motor shafts. The keyway width and depth are matched to the bore diameter: 4×2 mm for 12 mm bore, 5×2.5 mm for 14–16 mm bore, 6×3 mm for 18–22 mm bore, 8×3.5 mm for 24–28 mm bore, 10×4 mm for 30–35 mm bore, and 12×4 mm for 40 mm bore.
A 14T pinion produces a higher gear ratio (more torque multiplication) when paired with a larger gear, but generates more tooth stress per engagement. A 30T pinion runs more smoothly and quietly with lower contact stress, but provides less ratio range. For most CNC and robotics drives, a 14T–20T pinion paired with a larger driven gear is a common and effective choice.
