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When a motion-control build demands consistent tooth engagement and reliable torque transfer, undersized or poorly machined gears become the weak link. Engineers, makers, and machine builders working on CNC routers, robotic arms, conveyor drives, and automation rigs need spur gears that hold tight tolerances across the full operating range — these 45# steel pinion gears are designed exactly for that purpose.
Each gear is machined from 45# medium-carbon steel, offering a balance of hardness and machinability suited to moderate-to-heavy drive applications. The range covers three module sizes — 3M (face width typically 30 mm / 1.18 in), 4M (face width typically 35–40 mm / 1.38–1.57 in), and 5M — with tooth counts spanning 10T through 56T, giving you fine control over gear ratio selection. Bore diameter and keyway dimensions vary by tooth count and module; see variant options for confirmed bore specs.
Typical use cases include: gear-rack linear drive systems for CNC gantries, stage-1 reduction stages in servo-driven robotic joints, and open-gear drive trains on light industrial conveyor equipment. The wide tooth-count range supports both high-speed low-torque and low-speed high-torque configurations within a single product family.
| Material | 45# Medium-Carbon Steel |
|---|---|
| Module Options | 3M / 4M / 5M |
| Tooth Count Range | 10T – 56T (varies by module; see variant options) |
| Face Width — 3M | Approximately 30 mm (1.18 in) |
| Face Width — 4M | Approximately 35–40 mm (1.38–1.57 in) |
| Face Width — 5M | See variant options |
| Pressure Angle | 20° (standard metric) |
| Bore Diameter | See variant options |
| Keyway | See variant options |
| Surface Finish | Machined, natural steel |
| Quantity per Order | 1 Pcs (per variant selected) |
The module must match your mating gear or rack exactly — a 3M pinion will only mesh correctly with a 3M rack or gear. As a general rule, higher module numbers indicate larger, stronger teeth suited to higher torque loads. Choose 3M for lighter-duty or space-constrained drives, 4M for medium-load applications, and 5M for heavier torque requirements. Always verify the module of your existing components before ordering.
Gear ratio is determined by dividing the driven gear tooth count by the driving pinion tooth count. For example, pairing a 10T pinion with a 40T gear gives a 4:1 reduction. With tooth counts from 10T to 56T available across all three modules, you can achieve a wide range of ratios. Calculate your required ratio first, then select the tooth count combination that fits your shaft center distance.
These gears are machined from 45# medium-carbon steel, which provides a good balance of tensile strength and wear resistance for moderate-to-heavy drive applications. They are suitable for CNC routers, robotic joints, and light industrial conveyor drives under continuous operation. For very high shock loads or extreme-duty cycles, consider heat-treated or alloy-steel alternatives and consult a mechanical engineer for load calculations specific to your application.
45# carbon steel has limited inherent corrosion resistance. For outdoor, humid, or washdown environments, we recommend applying a suitable gear lubricant or grease to the tooth faces and bore, and considering a protective coating or periodic maintenance schedule. If corrosion resistance is a primary requirement, stainless steel or plastic gears may be more appropriate for your application.
Bore diameter and keyway dimensions vary by module and tooth count. Please refer to the variant options on this page or contact us to confirm the bore specification for your selected variant before ordering. If you need a custom bore size, the 45# steel material is machinable and can be bored to your required diameter by a local machine shop.
No — gears of different modules are not interchangeable and will not mesh correctly. The module (tooth size) must be identical across all mating components in a gear pair or rack-and-pinion system. Mixing modules results in incorrect tooth engagement, accelerated wear, and potential drive failure. Always confirm that all components in your drive train share the same module.
These gears are manufactured to a standard 20° pressure angle, which is the most widely used metric gear standard globally. This ensures compatibility with the vast majority of metric racks, pinions, and gearboxes designed to DIN or ISO standards. If your application requires a 14.5° pressure angle, please contact us before ordering.
