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When a gear skips a tooth under load or wears out mid-project, the whole build stops. DIY builders, robotics engineers, and machine designers who need a reliable 2.5 module spur gear know that tooth count and material both matter. These 45# steel pinion gears are stocked in a wide 10T–79T range so you can match the exact gear ratio your drivetrain demands without compromise.
Each gear is machined from 45# medium-carbon steel with a 2.5 mm module (pitch), a 25 mm (approximately 0.98 in) face width, and a standard 20° pressure angle. The tooth profile follows the involute standard, and the bore diameter varies by tooth count — see variant options for the specific bore of your chosen size. Overall outer diameter scales from approximately 30 mm (1.18 in) for the 10T up to approximately 202.5 mm (7.97 in) for the 79T.
Typical use cases include CNC router axis drives where consistent backlash control is critical, motorized conveyor and indexing tables that run continuous duty cycles, and custom robotics or automation rigs where a compact 2.5 mod gear train saves space without sacrificing torque capacity. The wide tooth-count selection also makes these gears a go-to for replacement parts on existing machinery that specifies a 2.5 module standard.
Machined from 45# steel, these gears deliver a solid balance of tensile strength and machinability — capable of handling moderate-to-heavy torque loads without the brittleness of cast iron alternatives.
The involute tooth profile conforms to the ISO/DIN 2.5 module standard with a 20° pressure angle, ensuring smooth meshing and predictable load distribution across the full tooth face.
At 25 mm (≈0.98 in) thick, the gear face is wider than many catalog equivalents, spreading contact stress over a larger area and extending service life under sustained or cyclic loading.
With 65 tooth-count options from 10T through 79T, you can dial in gear ratios from roughly 1:1 up to nearly 8:1 in a single product family — reducing the need to source gears from multiple suppliers.
Each gear is bored to a finished diameter sized for its tooth count. The hub is suitable for further machining to add a keyway or set-screw flat, giving you flexibility for shaft retention without special tooling.
Whether you are replacing a worn pinion on an existing machine or building a new drive from scratch, these gears slot directly into any 2.5 module gear train — no custom modification required for standard mesh applications.
| Module | 2.5 mm |
|---|---|
| Pressure Angle | 20° |
| Tooth Count (T) | 10T – 79T (see variant options) |
| Face Width (Thickness) | 25 mm (≈0.98 in) |
| Material | 45# Medium-Carbon Steel |
| Outer Diameter | See variant options |
| Bore Diameter | See variant options |
| Tooth Profile | Involute (ISO/DIN standard) |
| Surface Finish | Machined, natural steel |
| Quantity per Order | 1 Pcs (per variant) |
Start with your required gear ratio. Divide the driven gear tooth count by the driving (pinion) gear tooth count to get the ratio. For example, pairing a 20T pinion with a 60T gear gives a 3:1 reduction. Also consider center distance: multiply the sum of both tooth counts by half the module (1.25 mm) to get the theoretical center distance between shafts.
Yes — as long as your existing gears are also 2.5 module with a 20° pressure angle, they will mesh correctly regardless of brand. The involute tooth form is standardized. Do not attempt to mesh these with Module 2, Module 3, or any Diametral Pitch (DP) gears, as the tooth geometry is incompatible.
Bore diameter varies by tooth count and hub size. Because there are 65 variants in this listing, bore dimensions are not listed individually here. Please contact us to confirm the bore diameter for your specific tooth count before ordering, especially if you have a fixed shaft diameter requirement.
45# medium-carbon steel has a tensile strength of approximately 600–800 MPa in the normalized condition, making it suitable for moderate-to-heavy duty gear applications. It is also heat-treatable: quench-and-temper processes can raise surface hardness to approximately 45–55 HRC, significantly improving wear resistance for high-cycle or abrasive environments. Consult a heat treatment specialist for your specific load and duty cycle.
Yes, all steel spur gears benefit from lubrication to reduce friction and extend tooth life. For open gear drives running at low-to-moderate speeds, a lithium-based grease (NLGI Grade 1 or 2) applied to the tooth flanks works well. For enclosed gearboxes, an ISO VG 220 or VG 320 gear oil is appropriate. Re-lubricate at regular intervals based on your duty cycle and operating environment.
Yes. The hub is machined to a finished bore diameter and has sufficient wall thickness on most tooth counts to allow a standard keyway to be broached or a set-screw flat to be milled. We recommend confirming hub wall thickness for your specific tooth count before machining. For very small tooth counts (10T–14T), contact us to verify hub dimensions before modifying.
For two standard involute spur gears with the same module, center distance = (T1 + T2) × Module / 2. For example, a 20T and a 40T gear with 2.5 module: center distance = (20 + 40) × 2.5 / 2 = 75 mm. This is the theoretical value; allow for a small amount of backlash clearance in your housing design.
