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When your CNC machine, robotic arm, or automation rig demands a gear that fits a specific shaft diameter without slipping or wobbling, a standard flat gear often falls short. Engineers, makers, and machine builders who need a secure, stepped bore interface will find this 1 Module step spur gear an exact-fit solution for demanding drive trains.
This stepped pinion gear is machined from 45# medium-carbon steel, offering a balance of toughness and machinability suited to moderate-to-high load transmission. The gear body features a raised step hub that provides additional axial support and a positive shaft shoulder for set-screw or keyway retention. Tooth counts range from 15 T to 44 T (including 40 T variants with 25 mm, 30 mm, and 35 mm step heights), with bore diameters spanning 4 mm to 25 mm (approximately 0.16 in to 0.98 in). Overall outer diameters scale from approximately 17 mm (0.67 in) for the 15 T up to approximately 46 mm (1.81 in) for the 44 T.
Typical use cases include DIY CNC router Z-axis drives requiring a compact 1 Mod pinion gear, small robotic joint actuators needing a 45 steel stepped spur gear for shaft retention, and tabletop automation conveyor systems where a 1 module transmission gear pairs with a matching rack or larger wheel gear.
| Module | 1 (M1) |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Tooth Count Range | 15 T – 44 T (see variant options) |
| Bore Diameter Range | 4 mm – 25 mm (see variant options) |
| Outer Diameter Range | Approx. 17 mm – 46 mm (scales with tooth count) |
| Step Hub Height | 25 mm / 30 mm / 35 mm / 38 mm (varies by variant) |
| Tooth Profile | Standard Involute, 20° Pressure Angle |
| Surface Finish | See variant options |
| Quantity per Order | 1 Piece |
Select the tooth count based on your required gear ratio. Divide the driven gear's tooth count by the driving gear's tooth count to get the ratio. For example, pairing a 15 T pinion with a 30 T wheel gives a 2:1 reduction. Smaller tooth counts produce higher speed ratios; larger tooth counts reduce speed and increase torque output.
Measure your motor shaft or drive shaft diameter with a caliper. Choose the bore size that matches exactly — a bore that is too large will cause runout and vibration. If you plan to use a set screw, the bore should match the shaft closely. Imperial shaft users should note that 6.35 mm = ¼ in and 12.7 mm = ½ in options are available.
The step hub is a raised cylindrical boss that extends beyond the gear face, providing a shoulder for axial positioning and additional bearing surface for the shaft. Choose the step height (25 mm, 30 mm, or 35 mm) based on the available axial space in your gearbox or motor mount. A longer step gives more shaft engagement; a shorter step suits tighter assemblies.
45# medium-carbon steel has a tensile strength of approximately 600–800 MPa in its normalized state, making it suitable for moderate-torque, moderate-speed drives such as CNC axis feeds, small conveyor drives, and robotic joints. For very high-torque or high-cycle applications, consider whether heat treatment or a higher-alloy steel would be more appropriate for your specific load case.
Yes. All gears in this listing use the standard Module 1 involute tooth profile with a 20° pressure angle, which is the international standard for M1 components. They will mesh correctly with any M1-compatible rack, ring gear, or spur gear from any manufacturer that follows the same standard.
45# steel is not inherently corrosion-resistant. For indoor, dry environments this is typically not a concern with normal lubrication. For humid, outdoor, or wash-down environments, apply a light machine oil or grease to the gear teeth and bore, or consider a zinc-plated or stainless alternative if long-term corrosion resistance is critical.
Yes. Many desktop 3D printers and CO₂ laser cutters use Module 1 drive systems on their X/Y axes. These steel step spur gears can replace worn plastic or aluminum M1 pinions, offering improved durability. Verify the bore matches your stepper motor shaft (commonly 5 mm or 6.35 mm) and that the step height clears your motor face plate before ordering.
