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When a stripped or mismatched pinion gear stalls your build, every minute of downtime costs you. Whether you are a robotics engineer, RC hobbyist, or CNC machine builder, finding a Mod 1 spur pinion gear in the exact tooth count and bore diameter you need — without waiting weeks — is the real challenge. These steel 45# spur pinion gears are stocked across a wide range of configurations so you can get back to building fast.
Each gear is machined from 45# medium-carbon steel, offering a solid balance of toughness and machinability. The tooth profile follows the standard Mod 1 (Module 1) specification, with an outer diameter that scales linearly with tooth count — typically ranging from approximately 12 mm (0.47 in) for 10T up to approximately 41 mm (1.61 in) for 39T. Bore options span 4 mm to 20 mm (0.16 in to 0.79 in), with step-bore variants available on larger tooth counts to accommodate shaft shoulders. A radial set screw is included for secure shaft retention.
Typical applications include DC motor pinion drives in mobile robotics platforms, gearbox input stages on RC cars and crawlers, and spindle or axis drive trains on small CNC routers and 3D printer extruder assemblies. The standardised Mod 1 pitch makes these gears interchangeable with any other Mod 1 rack, gear, or gearbox component.
| Module (Mod) | 1 |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Tooth Count Range | 10T – 39T (28 options) |
| Bore Diameter Range | 4 mm – 20 mm (0.16 in – 0.79 in) |
| Step Bore Options | Available on select tooth counts (Step 17 mm, 20 mm, 22 mm, 26 mm, 28 mm, 30 mm) |
| Pressure Angle | 20° (standard involute) |
| Outer Diameter (approx.) | See variant options |
| Face Width | See variant options |
| Shaft Retention | Radial set screw (included) |
| Finish | Natural machined steel |
| Gear Type | External spur (straight tooth) |
| Unit Sold | 1 piece per order |
The tooth count determines your gear ratio. Divide the tooth count of the driven gear by the tooth count of this pinion to get the reduction ratio. For example, pairing a 10T pinion with a 30T driven gear gives a 3:1 reduction. Choose a lower tooth count for higher torque output and a higher tooth count for higher speed output.
Measure your motor shaft diameter with a calliper. Select the bore that matches exactly — a bore that is too large will cause runout even with the set screw tightened. Common motor shaft sizes include 4 mm, 5 mm, 6 mm, 6.35 mm (1/4 in), 8 mm, and 10 mm. Step-bore variants are designed for shafts that have a shoulder or collar at a specific depth.
A step bore has two diameters: a smaller bore at the front face and a larger counterbore at the rear. This allows the gear to seat against a shaft shoulder or motor face plate, providing axial location without a separate spacer. If your motor shaft has a shoulder or if you need the gear to sit flush against a mounting face, choose the step-bore variant. If your shaft is a plain cylinder, the standard bore is sufficient.
45# steel (equivalent to SAE 1045) has a tensile strength of approximately 600–700 MPa in the normalised condition. For typical hobby and light industrial motor drives — RC vehicles, robotics, small CNC machines — this is more than adequate. For heavy industrial or shock-load applications, consider a hardened steel or alloy gear instead.
45# carbon steel is not inherently corrosion resistant. The gears are supplied with a natural machined finish. For outdoor or humid environments, apply a light machine oil or grease to the tooth faces and bore after installation. For highly corrosive environments, consider stainless steel or plastic gears instead.
Yes. All gears in this listing follow the standard Mod 1 involute tooth profile with a 20° pressure angle, which is the most common Mod 1 standard worldwide. They will mesh correctly with any other Mod 1 external spur gear, rack, or gearbox component of the same module, regardless of brand or country of manufacture.
Each order includes one (1) gear plus one set screw. If you need multiple gears, simply increase the quantity at checkout or add multiple variants to your cart.
