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When your motion-control build demands dimensional accuracy and repeatable torque transfer, undersized or poorly machined gears become the weakest link. Engineers, robotics hobbyists, and CNC builders who rely on stepper motors need spur gears that hold tight tolerances across every tooth — and that is exactly what these 0.5 module 45# steel spur gears are designed to deliver.
Each gear is machined from 45# medium-carbon steel, offering a balance of hardness and machinability suited to precision drive applications. The module is 0.5 (Module = 0.5 mm per tooth pitch), with tooth counts ranging from 20T to 60T and bore diameters from 4 mm (~0.157 in) to 12 mm (~0.472 in). Outer diameters scale with tooth count: a 20T gear measures approximately 11 mm OD (~0.43 in), while a 60T gear reaches approximately 31 mm OD (~1.22 in). Face width is typically 5–8 mm depending on the model variant.
Typical use cases include stepper motor pinion drives in 3D printers and CNC routers, compact robotic joint actuators requiring low-backlash gear reduction, and educational or prototyping platforms where interchangeable 0.5M gear sets are needed for rapid iteration.
| Module | 0.5M |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Tooth Count (T) | 20T, 22T, 24T, 25T, 28T, 30T, 32T, 35T, 40T, 50T, 60T |
| Bore Diameter | 4 mm / 5 mm / 6 mm / 7 mm / 8 mm / 10 mm / 12 mm |
| Outer Diameter (OD) | See variant options (scales with tooth count; approx. 11–31 mm) |
| Face Width | See variant options (typically 5–8 mm) |
| Pressure Angle | 20° |
| Gear Type | Spur Gear (Pinion) |
| Pack Quantity | 1 / 2 / 3 / 5 pcs (select above) |
| Surface Finish | See variant options |
| Weight (per piece) | See variant options |
Select your tooth count based on the gear ratio you need. Divide the driven gear tooth count by the driving gear tooth count to get the reduction ratio. For example, pairing a 20T pinion with a 60T gear gives a 3:1 reduction. All variants in this listing share the same 0.5M module, so any two gears from this range will mesh correctly with each other.
Standard NEMA 17 stepper motors typically have a 5 mm output shaft. Select the 5 mm bore variant for a direct fit. If your motor has a D-cut shaft, you may need to add a set screw or use a shaft coupler for a secure connection. NEMA 11 motors commonly use a 5 mm shaft as well, while NEMA 8 motors often use a 4 mm shaft.
45# steel provides a tensile strength of approximately 600–700 MPa in the normalized condition, making it suitable for moderate-load drive applications such as 3D printer extruder drives, CNC axis drives, and light robotic joints. For very high-torque or high-speed applications, consider whether a heat-treated or hardened gear grade is more appropriate for your load cycle.
45# carbon steel has limited inherent corrosion resistance compared to stainless steel. For indoor, dry environments these gears perform well without additional treatment. If your application involves moisture, humidity, or outdoor exposure, applying a light machine oil or grease to the gear teeth is recommended to prevent surface oxidation and extend service life.
Yes. All gears with the same module (0.5M) and the same pressure angle (20°) will mesh correctly regardless of tooth count, as long as the center distance is set appropriately. The center distance between two meshing gears equals half the sum of their pitch diameters: C = (D1 + D2) / 2, where D = Module x Tooth Count.
For a 0.5M gear, the pitch diameter equals 0.5 x tooth count (in mm), and the outer diameter is approximately (0.5 x T) + 1 mm. Examples: 20T gives ~11 mm OD, 30T gives ~16 mm OD, 40T gives ~21 mm OD, 50T gives ~26 mm OD, 60T gives ~31 mm OD. Refer to the variant selector for confirmed dimensions.
Each variant in this listing represents a specific combination of tooth count, bore diameter, and pack quantity. To order multiple combinations, add each desired variant to your cart separately. The pack quantity options (1, 2, 3, or 5 pcs) let you right-size each line item for your build.
