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When a stripped or undersized gear brings your build to a halt, you need a replacement you can trust. These 1 Mod 45# steel spur gears are engineered for makers, robotics builders, CNC hobbyists, and RC enthusiasts who demand consistent tooth engagement and long service life from every component in their drivetrain.
Each gear is machined from 45# medium-carbon steel and features a hardened tooth profile for wear resistance. The bore diameter ranges from 5 mm (0.197 in) to 16 mm (0.630 in), and tooth counts span 12T to 42T, giving you a wide selection to match your gear ratio requirements. A radial set screw is included on every gear to lock the bore securely onto the shaft.
These 1 mod pinion spur gears suit a broad range of applications: compact robot joint actuators requiring a specific reduction ratio, DIY CNC axis drives where backlash must be minimised, and RC car or truck transmission upgrades where a harder tooth surface extends gear life under load.
Machined from 45# steel for a balance of toughness and machinability, delivering reliable torque transmission without brittle failure under shock loads.
The tooth surface is hardened to resist wear and pitting, extending service intervals in continuous-duty or high-cycle applications such as CNC drives and robotic joints.
Eighteen tooth-count options let you dial in the exact gear ratio your drivetrain needs, from high-speed pinion configurations to torque-multiplying reduction stages.
Ten bore diameter options (5, 6, 6.35, 7, 8, 10, 12, 14, 15, 16 mm) cover the most common shaft sizes used in hobby motors, stepper motors, and servo output shafts.
Each gear ships with a radial set screw pre-tapped into the hub, allowing tool-free alignment and a firm, slip-resistant connection to the drive shaft.
Conforms to the international Module 1 standard, ensuring direct interchangeability with Mod 1 racks, idler gears, and mating pinions from any compatible source.
| Module | 1 (Mod 1) |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Tooth Profile | Hard Tooth (surface hardened) |
| Number of Teeth | 12T, 15T, 16T, 18T, 20T, 22T, 24T, 25T, 26T, 28T, 30T, 32T, 33T, 35T, 36T, 38T, 40T, 42T |
| Bore Diameter | 5 mm / 6 mm / 6.35 mm / 7 mm / 8 mm / 10 mm / 12 mm / 14 mm / 15 mm / 16 mm |
| Bore Diameter (inches) | 0.197" / 0.236" / 0.250" / 0.276" / 0.315" / 0.394" / 0.472" / 0.551" / 0.591" / 0.630" |
| Pressure Angle | 20° |
| Shaft Locking Method | Radial set screw (included) |
| Gear Type | External spur gear (pinion) |
| Pitch Diameter | See variant options |
| Face Width | See variant options |
| Finish | See variant options |
The gear ratio between two meshing gears equals the driven gear tooth count divided by the driving (pinion) gear tooth count. For example, pairing a 12T pinion with a 36T gear gives a 3:1 reduction. Choose a lower tooth count for higher speed output and a higher tooth count for more torque. Always verify that both gears share the same module (Mod 1) so the teeth mesh correctly.
Measure your motor or shaft diameter with a calliper before ordering. Common stepper motor shafts are 5 mm or 6.35 mm (1/4"), hobby DC motor shafts are typically 3–6 mm, and servo output shafts vary by brand. Select the bore that matches your shaft exactly — a loose bore will cause slippage even with the set screw tightened.
These gears are machined from 45# medium-carbon steel with a hardened tooth surface, making them significantly more durable than plastic or sintered-metal alternatives. They are suitable for moderate-duty continuous operation in robotics, CNC, and RC applications. For very high-torque or shock-load environments, consider a larger module or a helical gear design.
45# steel has moderate corrosion resistance. For indoor or dry environments, the bare steel finish is adequate with periodic light lubrication. For humid, outdoor, or wash-down environments, apply a thin coat of grease or consider a corrosion-inhibiting lubricant to extend service life. If corrosion resistance is a primary requirement, stainless steel or plastic gears may be more appropriate.
Yes — any gear or rack labelled Module 1 (Mod 1) with a 20° pressure angle will mesh correctly with these gears. Module 1 is an international standard, so compatibility is determined by the module number, not the brand. Do not mix with Mod 0.8, Mod 1.25, or other module sizes, as the tooth profiles will not engage properly.
Slide the gear onto the shaft so the set screw hole aligns with a flat on the shaft (if present) or positions over the desired locking point. Use an appropriate hex key (Allen key) to tighten the set screw firmly. For shafts without a flat, tightening the set screw against the round shaft surface is sufficient for light-to-moderate loads; adding a shaft flat with a file improves holding strength for higher torques.
Yes. Because all gears in this listing share the same Mod 1 standard, you can combine different tooth counts across multiple stages to achieve compound gear ratios. Ensure adequate centre-distance spacing between each gear pair and use appropriate shaft supports (bearings or bushings) to maintain alignment under load.
