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When a slipping or undersized gear brings your motor drive, CNC router, or robotics project to a halt, you need a replacement that holds tolerance under load. These Module 2.5 spur gears are engineered for hobbyists, makers, and small-scale machine builders who demand repeatable, low-backlash power transmission without sourcing industrial minimums.
Each gear is machined from 45# medium-carbon steel — a material known for its balance of hardness and machinability — and finished to Module 2.5 (pitch = 2.5 mm per tooth) geometry. The tooth count range spans 10T through 120T, with pitch circle diameters scaling from approximately 25 mm (0.98 in) at 10T up to 300 mm (11.81 in) at 120T. Face width is typically 20–25 mm (0.79–0.98 in) depending on variant; bore diameter varies by tooth count — see variant options for exact bore specs.
Typical use cases include DC motor gearbox reduction stages for 3D printer extruder drives, stepper-motor-driven linear actuators in DIY CNC machines, and open-frame gear train assemblies in educational robotics platforms where a standard Module 2.5 pitch is specified.
| Module | 2.5 |
|---|---|
| Tooth Count Range | 10T – 120T (see variant options) |
| Material | 45# Medium-Carbon Steel |
| Gear Type | Spur (straight-cut, flat) |
| Pitch Circle Diameter | Module × Teeth (e.g., 2.5 × 20T = 50 mm / 1.97 in) |
| Face Width | Typically 20–25 mm (0.79–0.98 in); see variant options |
| Bore Diameter | See variant options |
| Pressure Angle | 20° |
| Surface Treatment | See variant options |
| Packing Quantity | 1 PCS per order |
Determine your required gear ratio first: divide the driver tooth count by the driven tooth count to get the ratio. For example, a 20T pinion driving a 60T gear gives a 3:1 reduction. Select tooth counts that achieve your target ratio while keeping pitch circle diameters within your available centre-distance envelope. Use the formula: Centre Distance = (T1 + T2) × Module / 2.
45# steel spur gears at Module 2.5 are suited for light-to-medium duty applications — typical for DC motor drives, stepper-driven CNC axes, and educational robotics. Exact torque capacity depends on tooth count, face width, operating speed, and lubrication. For heavy industrial loads or continuous high-RPM service, consult an engineer and consider hardened or alloy steel alternatives.
45# steel has moderate corrosion resistance suitable for dry indoor environments. For humid, wet, or outdoor use, apply a consistent film of gear grease or anti-rust oil, or consider stainless steel or nylon gear alternatives. Regular maintenance will significantly extend service life in challenging conditions.
Yes — Module 2.5 is an internationally standardised pitch. Any two Module 2.5 spur gears with a 20° pressure angle will mesh correctly regardless of brand, provided the bore and shaft dimensions are compatible. Verify the pressure angle of your existing gears before mixing.
Yes. 45# steel is machinable on a lathe or with a drill press. Many makers bore out the hub to their required shaft diameter and add a keyway or set-screw flat. Ensure sufficient hub wall thickness remains after boring — typically keep at least 3–5 mm of material around the bore for structural integrity.
Pitch Circle Diameter (PCD) = Module × Number of Teeth. For Module 2.5: a 20T gear has PCD = 2.5 × 20 = 50 mm (1.97 in); a 60T gear has PCD = 150 mm (5.91 in). The outside diameter (OD) = PCD + 2 × Module = PCD + 5 mm for Module 2.5 gears.
Lubrication is strongly recommended for all steel spur gear applications. Apply a light gear grease or lithium-based grease to the tooth flanks before first use. Re-lubricate every 50–100 operating hours or whenever you notice increased noise or heat. Proper lubrication reduces wear, noise, and the risk of surface fatigue on the tooth flanks.
