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When your CNC router stalls mid-cut or your stepper motor drive slips under load, the culprit is almost always a weak or mismatched gear. Makers, robotics builders, and mechanical engineers who need a reliable, drop-in Module 2 spur gear will find this 45# carbon steel pinion gear engineered to handle real torque without play or premature wear.
Each gear is machined from 45# medium-carbon steel and finished with a blackened oxide surface for corrosion resistance. The range covers 12 to 24 teeth (12T–24T) with an outer diameter that scales proportionally per Module 2 geometry (OD = (T + 2) × 2 mm, typically 28–52 mm / 1.10–2.05 in). Bore options span 8 mm to 25 mm; larger bores (12 mm and above) include a precision-cut keyway (4 mm or 5 mm or 6 mm or 8 mm depending on bore size) for positive shaft locking.
Typical use cases include stepper motor pinion drives in CNC machines and 3D printer extruder gearboxes, reduction gear trains in robotic arms and automated conveyor systems, and replacement gears for DIY go-karts, winches, and small industrial drives where a Module 2 standard pitch is specified.
Machined from medium-carbon 45# steel for a balance of hardness and toughness, resisting tooth deformation under sustained radial and tangential loads.
True Mod 2 geometry ensures accurate meshing with any compatible Module 2 gear — no backlash shimming required when paired correctly.
Thirteen tooth-count options let you dial in your exact gear ratio for stepper motor drives, reduction stages, or direct-drive pinion applications.
Bore diameters from 8 mm to 25 mm, with precision keyways on 12 mm+ bores (4–8 mm keyway width), provide a positive, slip-free shaft connection.
The oxide treatment adds a layer of corrosion resistance and reduces light reflection — suitable for indoor mechanical assemblies and light-duty outdoor enclosures.
Bore and keyway dimensions are sized to fit common NEMA 17, NEMA 23, and equivalent stepper motor shaft diameters, making these gears a direct fit for CNC and robotics builds.
| Material | 45# Medium-Carbon Steel |
|---|---|
| Surface Finish | Blackened Oxide |
| Modulus (Module) | 2 (Mod 2) |
| Pressure Angle | 20° |
| Number of Teeth | 12T – 24T (see variant options) |
| Outer Diameter | (T + 2) × 2 mm — typically 28–52 mm (1.10–2.05 in) |
| Bore Diameter | 8 mm – 25 mm (see variant options) |
| Keyway Width | 4 mm (12 mm bore) / 5 mm (14–17 mm bore) / 6 mm (18–20 mm bore) / 8 mm (22–25 mm bore) — plain bore for 8 & 10 mm |
| Hub Width / Face Width | See variant options |
| Gear Type | External Spur Gear (Pinion) |
| Application | CNC drives, stepper motor gearboxes, robotics, DIY mechanical drives |
| Sold As | 1 piece per order |
The gear ratio is determined by dividing the driven gear tooth count by the driving (pinion) gear tooth count. For example, pairing a 12T pinion with a 24T gear gives a 2:1 reduction. Choose a lower tooth count for higher speed output and a higher tooth count for more torque. Always verify that the center distance between shafts matches the sum of the two gears' pitch radii: center distance = (T₁ + T₂) × Module / 2.
Measure your motor shaft diameter precisely with calipers. Common stepper motor shaft diameters are 5 mm (NEMA 17 small), 6.35 mm, 8 mm (NEMA 17 standard), 10 mm, and 12–14 mm (NEMA 23). Select the bore that matches your shaft. For shafts 12 mm and above, the included keyway provides a positive lock — pair it with a matching key stock for zero-slip transmission.
45# carbon steel offers a tensile strength of approximately 600–800 MPa after standard heat treatment, making it well-suited for the moderate loads found in CNC router axis drives, 3D printer extruder gearboxes, and similar light-to-medium industrial applications. For very high-cycle or heavy-load environments, consider whether a hardened or case-hardened gear grade is required for your specific duty cycle.
Yes — any two gears of the same module and pressure angle will mesh correctly regardless of tooth count. These gears use Module 2 with a standard 20° pressure angle, which is the most common metric spur gear standard. Confirm your existing gear's module (often stamped on the hub or listed in its datasheet) before ordering.
Black oxide provides mild corrosion resistance suitable for dry or lightly oiled indoor environments. It is not a substitute for galvanizing or stainless steel in wet, outdoor, or chemically aggressive conditions. For best results, apply a light machine oil or grease to the gear teeth and bore during installation and re-lubricate periodically.
Yes. The 8 mm and 10 mm bore variants are plain bore (no keyway). They can be secured to a shaft using a set screw through the hub, a press fit, or a shaft collar. For applications with reversing loads or high torque, a keyed bore variant is recommended to prevent rotational slippage.
For a Module 2 spur gear, the outer diameter (addendum circle diameter) is calculated as: OD = (Number of Teeth + 2) × Module. For example, a 20T Mod 2 gear has an OD of (20 + 2) × 2 = 44 mm (approximately 1.73 in). Use this formula to verify the gear will fit within your housing or clearance envelope before ordering.
