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When your motor shaft needs a reliable, accurately cut gear that won't slip under load, a poorly matched pinion is the first thing to fail. Whether you're building a CNC router, a robotic arm, or a custom drive train, engineers and makers need a spur gear that holds tight tolerances across a wide range of tooth counts and bore sizes — all from a single trusted source.
These 1 Module spur pinion gears are machined from 45# medium-carbon steel, offering a solid balance of strength and machinability. Each gear is cut to Module 1 (1M) standard, with tooth counts ranging from 32T to 150T and bore diameters from 6 mm (0.24 in) up to 30 mm (1.18 in). Select step-diameter variants are also available with hub steps of 25 mm, 30 mm, 38 mm, 40 mm, 50 mm, 60 mm, and 70 mm for applications requiring a shoulder stop or spacer integration.
Typical use cases include DC motor pinion replacement in 3D printers and CNC machines, gear reduction stages in robotics and automation rigs, and custom drive assemblies for RC vehicles, conveyor systems, and educational mechatronics projects. Long-tail searches like "1 mod steel spur gear with keyway bore" and "45 steel motor pinion gear metric" describe exactly what this product delivers.
| Module | 1M (Metric Module 1) |
|---|---|
| Tooth Count Range | 32T – 150T (see variant options) |
| Bore Diameter Range | 6 mm – 30 mm (see variant options) |
| Step Diameter Options | 25 / 30 / 38 / 40 / 50 / 60 / 70 mm (select variants) |
| Material | 45# Medium-Carbon Steel |
| Pressure Angle | See variant options |
| Gear Face Width | See variant options |
| Surface Finish | See variant options |
| Quantity per Order | 1 piece |
| Tooth Profile Standard | Module 1 (ISO/DIN metric) |
The tooth count determines your gear ratio and pitch circle diameter. For a given Module 1 gear, the pitch circle diameter (PCD) in mm equals the tooth count (e.g., 40T = 40 mm PCD). Match the tooth count to your required gear ratio: divide the driven gear teeth by the driving gear teeth to get the reduction ratio. For motor pinions, smaller tooth counts (32T–40T) are common for higher-speed, lower-torque outputs; larger counts (80T–150T) suit slower, higher-torque stages.
Measure your motor or drive shaft outer diameter (OD) precisely with calipers. Select the bore that matches your shaft OD exactly — a loose bore will cause runout and noise. Common motor shaft sizes include 6 mm, 8 mm, and 10 mm for small DC and stepper motors; 14 mm–20 mm for larger servo and gearbox outputs. The 6.35 mm bore suits 1/4" imperial shafts and the 12.7 mm bore suits 1/2" shafts.
A step (or hub step) is a machined shoulder on the gear hub that is larger than the bore but smaller than the gear OD. It acts as a locating feature or spacer stop, preventing the gear from sliding axially along the shaft. If your assembly requires a shoulder reference — for example, to maintain consistent axial position against a bearing face — choose a step-diameter variant. If no axial stop is needed, the standard (non-step) variant is sufficient.
Yes. All gears in this listing are cut to Module 1 (1M) standard, which means they will mesh correctly with any other Module 1 spur gear, rack, or pinion regardless of tooth count, as long as the pressure angle matches (typically 20° for standard metric gears). Do not attempt to mesh Module 1 gears with Module 0.8, Module 1.25, or other module sizes — the tooth profiles are incompatible.
45# steel (equivalent to AISI 1045 medium-carbon steel) offers a tensile strength of approximately 600–800 MPa in the normalized condition, making it significantly stronger than aluminum or plastic gears and suitable for moderate-to-high load applications. It is not as hard as case-hardened or alloy steel gears (e.g., 40Cr), but it provides a good balance of machinability, toughness, and wear resistance for most motor drive and automation applications. For very high-cycle or high-impact loads, consider surface treatment options.
These gears are supplied with a plain bore (no keyway pre-cut) unless otherwise noted in the variant description (e.g., "within grub screw" variants include a set screw hole). For most motor pinion applications, a set screw (grub screw) tightened against a flat on the shaft is the standard retention method. If your shaft has a keyway, you will need to have a matching keyway broached into the bore by a local machine shop. Contact us to confirm bore details for your specific variant before ordering.
45# steel is susceptible to surface oxidation (rust) if exposed to moisture without protection. For outdoor or humid environments, apply a light machine oil, grease, or corrosion-inhibiting coating to the gear surfaces. Alternatively, consider pairing with a sealed gearbox housing. These gears are not stainless steel and are not intended for submerged or highly corrosive environments without additional surface treatment.
