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When a loose gear slips mid-run or a mismatched module throws off your entire drivetrain, the cost is more than downtime — it's a rebuild. Engineers, robotics builders, and CNC hobbyists who need a reliable 3 mod spur gear with a stepped hub design can stop searching: this gear is machined to hold position, transfer torque cleanly, and drop into standard 3M gear trains without shimming or modification.
Each gear is machined from 45# carbon steel — a medium-carbon alloy known for its balance of hardness and machinability — and features a stepped (shouldered) bore hub that seats securely against a shaft shoulder or retaining collar. The tooth range spans 15T to 40T (module 3), with pitch diameters ranging from approximately 45 mm (1.77 in) at 15T to 120 mm (4.72 in) at 40T. Face width and hub step dimensions vary by tooth count; see variant options for exact per-SKU measurements.
Typical use cases include: CNC router axis drives requiring repeatable backlash-free engagement; robotic arm joint gearing where the stepped hub prevents axial creep under cyclic load; and DIY power transmission rigs — conveyor drives, winch mechanisms, and motorized camera sliders — where a standard 3M gear train is the design baseline.
| Module | 3 (Mod 3 / 3M) |
|---|---|
| Pressure Angle | 20° |
| Tooth Count Range | 15T – 40T (26 variants) |
| Pitch Diameter Range | 45 mm – 120 mm (1.77 in – 4.72 in) |
| Material | 45# Carbon Steel |
| Hub Style | Stepped (shouldered hub) |
| Bore Diameter | See variant options |
| Face Width | See variant options |
| Hub Step Diameter | See variant options |
| Surface Treatment | Oxidation-resistant machined finish |
| Gear Type | External spur gear |
| Packing Quantity | 1 pc per order |
Gear ratio is determined by dividing the driven gear tooth count by the driving gear tooth count. For example, pairing a 15T motor gear with a 30T output gear gives a 2:1 reduction — half the speed, double the torque. Map out your required input/output RPM and torque, then select the tooth counts that achieve that ratio within your available center distance.
Bore diameter varies by tooth count variant. Please check the bore size listed in the variant options before ordering. If your shaft is slightly undersized, the bore can typically be enlarged by a machinist. Do not force-fit a gear onto an oversized shaft as this will crack the hub.
Yes — any Module 3 gear with a matching 20° pressure angle will mesh correctly with this gear. This includes Module 3 racks, pinions, and other spur gears regardless of brand, as long as the module and pressure angle match. Confirm both parameters on your existing components before ordering.
45# carbon steel (roughly equivalent to AISI 1045) has a tensile strength of approximately 600–800 MPa in its normalized state, making it well-suited for moderate-to-high torque gear applications. It is commonly used for machine tool gears, conveyor drives, and robotic joints. For extreme shock loads or very high RPM applications, consider heat-treated variants or consult a mechanical engineer.
The machined steel surface has a basic oxidation-resistant finish suitable for dry indoor and light workshop environments. For outdoor use, high-humidity enclosures, or washdown environments, we recommend applying a gear lubricant or protective coating (e.g., grease, zinc spray, or black oxide treatment) after installation to extend service life.
Yes. Module 3 spur gears are widely used in CNC router axis drives, laser cutter gantries, and large-format 3D printer extruder/drive systems. The stepped hub is particularly useful in these builds as it provides a positive axial stop, reducing the chance of the gear walking along the shaft during repeated bidirectional motion.
A plain-bore gear has a straight cylindrical bore and relies entirely on set screws or keys for axial and rotational retention. A stepped-hub gear adds a machined shoulder that seats against a shaft collar, bearing face, or housing wall — providing positive axial location without additional hardware. This reduces assembly complexity and improves positional repeatability in precision drive systems.
