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Finding a spur gear that fits your shaft exactly — without custom machining — is one of the most common frustrations for robotics builders, CNC hobbyists, and mechanical engineers. These 1 Module spur pinion gears with integrated step bore are engineered to solve that problem, offering a wide tooth count range (10T to 100T) and multiple bore diameters in a single product family, so you can match your motor shaft without compromise.
Each gear is machined from 45# medium-carbon steel, delivering a balance of toughness and machinability suited to moderate-to-high load drive applications. The step bore design — with hub depths ranging from 14 mm to 50 mm depending on tooth count — provides a secure, concentric seating surface for set-screw or keyway retention. Bore options span 4 mm to 25 mm (approximately 0.16 in to 0.98 in), covering the most common motor and shaft standards. Outer diameter scales with tooth count: a 10T gear measures approximately 12 mm (0.47 in) OD, while a 100T gear reaches approximately 102 mm (4.02 in) OD.
Typical use cases include DC motor gearboxes for mobile robotics and wheeled platforms, lead-screw drive stages in desktop CNC routers and laser cutters, and custom reduction stages in 3D printer extruder assemblies. The 1 Mod pitch standard ensures direct interchangeability with any other 1M gear in your drivetrain, making these gears a reliable long-tail choice for 1 module spur gear replacement, 45 steel pinion gear for stepper motor, and precision step bore gear for CNC build.
Medium-carbon steel provides solid load-bearing capacity and wear resistance for sustained gear mesh contact in drive and reduction applications.
A single product family covers small pinions for high-speed motor output stages through large driven gears for torque multiplication — no need to source from multiple suppliers.
The integrated hub step provides a concentric seating reference for set-screw or keyway retention, reducing runout and improving concentricity versus plain-bore gears.
Bore options cover the most common motor shaft standards, from small hobby motors (4 mm) to larger NEMA 23 and industrial shafts (up to 25 mm), eliminating custom boring in most builds.
Full interchangeability with any 1M rack, pinion, or spur gear. Drop-in replacement for existing 1 Mod drivetrains without recalculating center distances.
Gear teeth are machined to standard involute profile tolerances, ensuring smooth mesh engagement and consistent backlash across the full tooth count range.
| Module | 1M (1 Mod) |
|---|---|
| Tooth Count Range | 10T – 100T (see variant options) |
| Material | 45# Medium-Carbon Steel |
| Bore Diameter Range | 4 mm – 25 mm (0.16 in – 0.98 in) |
| Step Hub Depth | See variant options |
| Outer Diameter (OD) | See variant options (scales with tooth count) |
| Pressure Angle | 20° |
| Tooth Profile | Standard Involute |
| Surface Finish | See variant options |
| Quantity per Order | 1 Pcs |
Select tooth count based on your required gear ratio. Divide the driven gear tooth count by the driving pinion tooth count to get the reduction ratio. For example, pairing a 20T pinion with a 60T gear gives a 3:1 reduction. Higher tooth counts on the pinion reduce ratio and increase output speed; lower tooth counts increase torque multiplication.
Measure your motor shaft diameter with calipers before ordering. Common sizes: NEMA 17 steppers typically use 5 mm shafts; NEMA 23 steppers commonly use 6.35 mm (1/4 in) or 8 mm shafts; many DC hobby motors use 4–6 mm shafts. Select the bore that matches your shaft exactly — these are not adjustable after machining.
The step bore is a two-diameter bore design: a larger outer diameter provides a hub seating surface, while the inner bore matches your shaft. This step creates a concentric reference that reduces runout compared to a plain through-bore gear. It also allows the gear to be positioned axially on the shaft with a defined reference face, which is important for maintaining gear mesh alignment in multi-stage drivetrains.
Yes. All gears in this listing use the standard 1 Module (1M) pitch, which is fully interchangeable with any other 1M spur gear, rack, or pinion regardless of manufacturer. Center distance between two meshing 1M gears equals (T1 + T2) / 2 in millimeters, where T1 and T2 are the respective tooth counts.
45# steel (equivalent to SAE 1045 medium-carbon steel) offers a tensile strength of approximately 600–700 MPa in the normalized condition. For precision load ratings specific to your application (torque, speed, duty cycle), consult standard gear strength calculation methods (AGMA or ISO 6336). These gears are suited to moderate-load robotics, CNC, and maker applications; they are not rated for heavy industrial gearbox duty without engineering review.
45# steel has moderate corrosion resistance. For indoor, dry environments (typical robotics and CNC workshops), surface oxidation is minimal with normal handling. For humid or outdoor environments, apply a light machine oil or grease to the gear teeth and bore after installation. If corrosion resistance is a primary requirement, consider stainless steel or plastic gear alternatives for your application.
The step bore design is compatible with set-screw retention using a standard M3 or M4 grub screw tapped into the hub (not pre-drilled — you will need to drill and tap the hub for your set screw). Keyway retention requires machining a keyway slot into the bore, which is possible given the 45# steel material. Contact us to confirm hub wall thickness for your selected variant before machining.
