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When a stripped or undersized gear brings your build to a halt, finding an exact-spec replacement fast is everything. Whether you are a robotics engineer, a CNC hobbyist, or a maker building a custom drive train, these Mod 2.5 steel spur gears give you a reliable, drop-in solution across a wide tooth-count range — all in one listing.
Each gear is machined from carbon steel, delivering solid strength and wear resistance for demanding mechanical applications. The Mod 2.5 (2.5 mm per tooth) pitch standard means consistent meshing with any other M2.5 gear in your system. Outer diameters span approximately 30 mm (1.18 in) for the 10-tooth variant up to 105 mm (4.13 in) for the 40-tooth variant, with bore dimensions varying by tooth count — see variant options for exact bore specs.
Typical use cases include DC motor pinion drives for robotics and automation, rack-and-pinion linear actuators in CNC router builds, and reduction gear stages in electric go-karts or conveyor systems — anywhere a durable, standard-pitch flat spur gear is required.
| Module (Mod) | 2.5 |
|---|---|
| Tooth Count Range | 10T – 40T (31 variants) |
| Outer Diameter Range | ~30 mm – ~105 mm (1.18 in – 4.13 in) |
| Material | Carbon Steel |
| Gear Type | Spur Gear (Flat / Straight Tooth) |
| Pitch | Mod 2.5 (metric) |
| Pressure Angle | 20° (standard) |
| Bore Diameter | See variant options |
| Hub / Keyway | See variant options |
| Surface Finish | See variant options |
| Weight | See variant options |
Select your tooth count based on the gear ratio you need. Divide the driven gear teeth by the driving gear teeth to get the ratio. For example, pairing a 10T pinion with a 30T gear gives a 3:1 reduction. Use a smaller tooth count on the motor shaft for speed reduction and torque multiplication.
"Mod" (Module) is the metric standard for gear tooth size — Mod 2.5 means each tooth occupies 2.5 mm of pitch diameter per tooth. These gears will mesh correctly with any other Mod 2.5 gear, rack, or pinion regardless of brand, as long as the pressure angle is also 20°.
Carbon steel spur gears in Mod 2.5 are well-suited for moderate-to-high torque applications at typical motor speeds. Exact load capacity depends on tooth count, shaft fit, lubrication, and operating speed. For very high-shock or continuous heavy-load environments, ensure proper lubrication and shaft alignment to maximise service life.
Carbon steel has moderate corrosion resistance. For outdoor or humid environments, we recommend applying a light machine oil or grease coating during installation and re-lubricating periodically. If your application requires higher corrosion resistance, consider stainless steel alternatives.
Bore diameter varies by tooth count. Please check the variant detail or contact us to confirm the bore size for your selected tooth count before ordering. Measure your motor shaft diameter with calipers to ensure a proper fit — a loose bore will cause slippage under load.
Yes. Mod 2.5 spur gears are commonly used in CNC router Z-axis drives, rack-and-pinion linear actuators, and rotary indexing tables. Pair with a matching Mod 2.5 rack for linear motion, or with a mating spur gear for rotary reduction stages.
Hub configuration (set screw, keyway, or plain bore) varies by variant. Please refer to the variant specifications or contact us to confirm the hub style for your selected tooth count before purchasing.
