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When a stripped or undersized gear brings your build to a halt, you need a replacement that fits right the first time. Whether you're a robotics hobbyist, a CNC builder, or a mechanical engineer prototyping a custom drive train, finding a spur pinion gear with the exact tooth count and module specification can be frustrating. These 45# steel 2-module spur gears are stocked in a wide tooth range — 10T through 59T — so you can match your existing gear set without compromise.
Each gear is machined from 45# medium-carbon steel, offering a solid balance of hardness and machinability. The module (Mod) is 2, meaning the pitch diameter equals twice the tooth count in millimeters (e.g., a 20T gear has a 40 mm pitch diameter). Gear thickness is a consistent 20 mm (approximately 0.79 in), and bore diameter varies by tooth count — typically ranging from 5 mm to 12 mm (0.20 in – 0.47 in) across the series. Each listing is for 1 piece.
These gears are well-suited for DC motor pinion replacement in robotics and automation rigs, custom gearbox builds for RC vehicles and power transmission projects, and CNC router or 3D printer axis drive systems where a 2-module standard gear is required.
| Material | 45# Medium-Carbon Steel |
|---|---|
| Module (Mod) | 2 |
| Tooth Count (T) | 10T – 59T (select variant) |
| Gear Face Thickness | 20 mm (0.79 in) |
| Pitch Diameter | 2 × Tooth Count (mm) — e.g., 20T = 40 mm |
| Bore Diameter | See variant options |
| Pressure Angle | 20° |
| Surface Finish | See variant options |
| Quantity per Order | 1 piece |
| Compatible Gear Type | Mod 2 Spur / Rack |
Your gear ratio is determined by dividing the driven gear tooth count by the driving (pinion) gear tooth count. For example, if your motor pinion has 20T and your driven gear has 60T, the ratio is 3:1. Select the tooth count that achieves your target ratio when paired with your existing mating gear. If you are replacing a worn gear, match the tooth count exactly.
Module is the standardized unit of gear tooth size. A Mod 2 gear has a tooth pitch of 2 mm per tooth on the pitch circle. Two gears will mesh correctly only if they share the same module and pressure angle. These gears are Mod 2 with a 20° pressure angle — they will mesh with any other Mod 2, 20° spur gear or rack.
45# steel (equivalent to SAE 1045) is a medium-carbon steel with a tensile strength typically in the range of 570–700 MPa in its normalized state. It provides a good balance of toughness and hardness for moderate-load gear applications such as robotics, light automation, and hobby CNC machines. For heavy industrial loads or shock loading, consider heat-treated or alloy steel alternatives.
These gears have a treated surface finish that provides basic oxidation resistance for indoor storage and use. They are not recommended for prolonged outdoor exposure or wet environments without additional protective coating (e.g., grease, paint, or plating). For outdoor or high-humidity applications, consider stainless steel or coated alternatives.
Bore diameter varies by tooth count across the 10T–59T range, typically from approximately 5 mm for smaller tooth counts up to 12 mm for larger ones. Please check the variant detail or contact us to confirm the exact bore diameter for your selected tooth count before ordering, especially if you need to match a specific motor shaft diameter.
No. These are straight-cut spur gears and are designed to mesh only with other spur gears or Mod 2 racks on parallel shafts. They are not compatible with helical gears, bevel gears, or worm gears, which require different tooth geometry and shaft orientations.
Each order includes 1 piece of the selected tooth count variant. If you need multiple gears — for example, a matched pair for a gearbox stage — please adjust the quantity in your cart accordingly.
