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When a stripped plastic gear or an undersized pinion brings your project to a halt, you need a drop-in replacement that won't let you down again. Whether you're a robotics builder, a CNC hobbyist, or a mechanical engineer prototyping a new actuator, these 45# carbon steel spur gears give you the tooth count and module precision to match virtually any existing drivetrain.
Each gear is machined from 45# medium-carbon steel — a material known for its balanced hardness and machinability — and finished with a natural steel surface. Available in two module sizes: Module 1 (tooth pitch circle diameter typically 12–160 mm / 0.47–6.30 in) and Module 2 (tooth pitch circle diameter typically 24–200 mm / 0.94–7.87 in), with tooth counts ranging from 12 to 160 teeth across the full selection.
These spur gears suit a wide range of applications: small DC motor pinion drives in robotics and automation, rack-and-pinion linear motion systems for CNC routers and 3D printers, and reduction gear stages in DIY winches, conveyor drives, and power-transmission assemblies requiring a precise 20° pressure angle involute tooth profile.
| Material | 45# Medium-Carbon Steel |
|---|---|
| Surface Finish | Natural steel (uncoated) |
| Pressure Angle | 20° |
| Tooth Profile | Standard involute |
| Available Modules | Module 1, Module 2 |
| Tooth Count Range | 12–160 teeth (Module 1); 12–100 teeth (Module 2) |
| Pitch Circle Diameter (Mod 1) | 12–160 mm (0.47–6.30 in) |
| Pitch Circle Diameter (Mod 2) | 24–200 mm (0.94–7.87 in) |
| Bore Diameter | See variant options |
| Face Width | See variant options |
| Hub Style | See variant options |
| Keyway | Contact us to confirm |
| Applicable Standards | ISO metric module system |
The module number defines the tooth size — a Module 2 gear has teeth twice as large as a Module 1 gear of the same tooth count. Choose Module 1 for compact, light-duty drives (small motors, robotics, 3D printers) and Module 2 for heavier loads requiring larger, stronger teeth (CNC routers, conveyor drives, reduction gearboxes). Always match the module of the mating gear exactly; gears of different modules will not mesh correctly.
Divide the number of teeth on the driven gear by the number of teeth on the driving gear to get your gear ratio. For example, a 60-tooth driven gear paired with a 20-tooth pinion gives a 3:1 reduction. Both gears must be the same module. Use our wide tooth count range (12–160 for Mod 1, 12–100 for Mod 2) to achieve ratios from approximately 1:1 up to 13:1 in a single stage.
45# carbon steel has a typical tensile strength of approximately 600–800 MPa and yield strength of around 355 MPa, making it significantly stronger than cast zinc alloy or nylon gears. Actual load capacity depends on tooth count, face width, speed, and lubrication. For high-torque or high-speed applications, we recommend consulting a gear load calculation before finalising your selection.
45# carbon steel has moderate corrosion resistance. For indoor or dry environments, the natural steel finish is adequate with periodic light lubrication. For outdoor, humid, or washdown environments, we recommend applying a rust-inhibiting grease or considering a surface treatment such as zinc plating or black oxide after purchase. These gears are not stainless steel.
The pre-bored centre hole may or may not match your shaft diameter exactly. In many cases, the bore will need to be enlarged on a lathe or drill press to match your shaft. A keyway can also be cut for positive torque transmission. We recommend confirming the bore diameter for your chosen variant before ordering, and having a local machine shop finish the bore if needed.
No. Gears of different modules have different tooth sizes and pitches and will not mesh correctly. Always pair gears of the same module. If you need to connect two shafts with different speed ratios, use a gear train where all meshing pairs share the same module throughout each stage.
For most applications, a medium-viscosity gear grease (NLGI Grade 1 or 2) applied to the tooth faces is sufficient. For high-speed, low-load applications, a light machine oil works well. Re-lubricate periodically based on operating hours and environmental conditions. Avoid dry running, which accelerates tooth wear significantly.
