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When your CNC router, robotic arm, or automation drive train demands consistent torque transfer and zero-slip engagement, a poorly matched gear becomes the weakest link in the system. Engineers, makers, and small-batch manufacturers who need reliable, dimensionally accurate motion components will find these 45# steel spur gears with step bore a dependable solution for both prototyping and production builds.
Each gear is machined from 45# medium-carbon steel, offering a balance of hardness and machinability suited to moderate-to-high load applications. The module is Mod 1 (1M), with tooth counts ranging from 10T to 80T and bore diameters from 4 mm (0.157 in) to 25 mm (0.984 in). Step diameters span 0 to 40 mm depending on the selected variant, allowing direct shaft mounting without additional spacers in many configurations.
Typical use cases include 1M spur gear sets for DIY CNC gantry drives, Mod 1 pinion gear replacements in stepper motor assemblies, and metal motor gears for 3D printer extruder or axis drive upgrades where plastic gears have failed under load.
Machined from 45# steel for a reliable combination of tensile strength and wear resistance, suitable for continuous-duty motion control applications.
Module 1 tooth profile ensures direct interchangeability with any Mod 1 rack, pinion, or spur gear in your drivetrain without custom adaptation.
Select from 10T through 80T to dial in your gear ratio precisely — from high-speed, low-torque pinion configurations to high-torque reduction stages.
The integrated step bore accommodates shaft shoulders and retaining features, reducing the need for additional collars or spacers in many standard shaft configurations.
Available bore diameters from 4 mm (0.157 in) to 25 mm (0.984 in) cover the most common stepper motor, servo, and DC motor shaft sizes used in CNC and robotics builds.
Machined to Mod 1 tooth profile tolerances to ensure smooth meshing, reduced backlash, and predictable performance across the full tooth count range.
| Module | Mod 1 (1M) |
|---|---|
| Tooth Count | 10T – 80T (see variant options) |
| Bore Diameter | 4 mm – 25 mm (see variant options) |
| Step Diameter | 0 – 40 mm (see variant options) |
| Material | 45# Medium-Carbon Steel |
| Gear Type | Spur Gear (straight tooth) |
| Pressure Angle | 20° (standard Mod 1) |
| Surface Finish | See variant options |
| Shaft Compatibility | See variant options |
| Application | CNC, robotics, automation, motor drives |
The tooth count determines your gear ratio. Divide the driven gear tooth count by the driving gear tooth count to get the ratio. For example, pairing a 20T pinion with a 60T gear gives a 3:1 reduction — tripling torque while reducing speed by the same factor. Select a smaller tooth count (10T–20T) for high-speed, lower-torque output, and a larger count (40T–80T) for higher torque at reduced speed.
Match the bore diameter to your motor or drive shaft diameter. Common stepper motor shaft sizes are 5 mm and 6.35 mm (1/4 in); servo motors often use 6 mm, 8 mm, or larger. Measure your shaft with calipers before ordering. If your shaft has a shoulder or step feature, also check the step diameter option to ensure clearance.
The step diameter refers to the outer diameter of the stepped (recessed) section of the bore. This step allows the gear to seat against a shaft shoulder or housing face, providing axial location without a separate collar. A step diameter of "0" indicates a plain (non-stepped) bore. Select the step diameter that matches your shaft shoulder or housing recess dimension.
Yes. All gears in this listing follow the Mod 1 (Module 1) standard, which defines tooth pitch and profile geometry. They will mesh correctly with any other Mod 1 spur gear, rack, or pinion regardless of brand, as long as the pressure angle is also 20° (the standard for Mod 1 components). Do not attempt to mesh Mod 1 gears with different module sizes (e.g., Mod 0.8 or Mod 1.5) as they are not interchangeable.
45# medium-carbon steel offers significantly higher tensile strength and wear resistance than engineering plastics (such as POM/Delrin or nylon) and is harder than most aluminum alloys used in gears. This makes them suitable for applications with sustained loads, higher RPM, or environments where plastic gears have previously stripped or worn prematurely. For very high-speed or corrosive environments, consider whether additional surface treatment is needed.
45# steel has moderate corrosion resistance. For indoor, dry environments typical of CNC machines and robotics, standard lubrication (grease or oil) is generally sufficient to prevent surface oxidation. For outdoor, humid, or chemically exposed environments, consider applying a rust-inhibiting coating or selecting a stainless steel alternative. Regular lubrication will also extend service life and reduce wear.
Yes. These Mod 1 steel spur gears are commonly used as direct replacements for plastic extruder drive gears or axis drive gears in 3D printers. Select the bore size matching your motor shaft (typically 5 mm for NEMA 17 steppers) and the tooth count that matches your existing gear ratio. The steel construction resists the stripping and deformation that can occur with plastic gears under high retraction loads or prolonged use.
