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When your CNC router, robotic arm, or automation drive train demands consistent torque transfer without slippage or premature wear, the gear material and tooth geometry make all the difference. Engineers, makers, and machine builders who rely on metric spur gears need components that hold tight tolerances across thousands of operating cycles — these 2.5 modulus spur gears are machined to meet that standard.
Each gear is manufactured from 45# medium-carbon steel, offering a balanced combination of machinability and mechanical strength. The module is 2.5 (pitch diameter = module × tooth count), with a circular pitch of approximately 7.85 mm (~0.309 in). Tooth count options span from 12T to 100T, and every gear in this series features a uniform face width (thickness) of 25 mm (~0.984 in). Bore diameter and keyway dimensions vary by tooth count — see variant options for exact bore specs.
Typical use cases include: CNC gantry and rack-and-pinion drive systems requiring repeatable positioning; robotic joint actuators where compact gear reduction is needed; industrial conveyor and indexing mechanisms using metric gear trains; and DIY automation projects pairing these pinion gears with matching 2.5 mod rack sections or mating spur gears.
45# Medium-Carbon Steel Construction — Delivers the tensile strength and surface hardness needed for sustained load-bearing in drive and reduction gear applications, with better wear resistance than mild steel alternatives.
Module 2.5 / 7.85 mm Circular Pitch — Conforms to the ISO metric gear standard, ensuring accurate meshing with any Mod 2.5 mating gear or rack. Pitch diameter scales linearly with tooth count (PD = 2.5 × T mm).
25 mm Uniform Face Width — A consistent 25 mm (~0.984 in) tooth thickness across the entire range provides stable load distribution and simplifies gear train alignment in multi-stage assemblies.
Wide Tooth Count Selection (12T – 100T) — Choose from 12 to 100 teeth in a single product listing to achieve your target gear ratio without sourcing from multiple suppliers.
20° Pressure Angle for Smooth Engagement — The standard 20° involute tooth profile minimizes backlash and noise while maximizing load-carrying capacity across the full tooth contact zone.
Machined Bore with Keyway — Each gear includes a machined center bore sized to the tooth count, with a keyway slot for positive shaft locking. Confirm bore diameter against your shaft diameter before ordering.
| Module | 2.5 |
|---|---|
| Pressure Angle | 20° |
| Circular Pitch | 7.85 mm (~0.309 in) |
| Tooth Count Range | 12T – 100T (see variant options) |
| Face Width (Thickness) | 25 mm (~0.984 in) |
| Material | 45# Medium-Carbon Steel |
| Bore Diameter | See variant options |
| Keyway | Included (dimensions vary by tooth count) |
| Pitch Diameter Formula | PD = Module × Tooth Count (mm) |
| Outside Diameter Formula | OD = Module × (Tooth Count + 2) (mm) |
| Surface Finish | Machined, natural steel |
| Quantity per Order | 1 pc |
Divide the driven gear tooth count by the driver gear tooth count to get your reduction ratio. For example, pairing a 20T pinion with a 60T gear gives a 3:1 reduction. Use the pitch diameter formula (PD = 2.5 × T) to verify center distance: center distance = (PD₁ + PD₂) / 2.
45# medium-carbon steel has a typical tensile strength of approximately 600–800 MPa in the normalized condition. It is well-suited for moderate-to-high load gear applications such as CNC drives, robotic joints, and industrial indexing. For very high-shock or high-speed applications, consider whether a heat-treated or alloy steel variant is required.
45# carbon steel is not inherently corrosion-resistant. For outdoor or humid environments, apply a light machine oil or grease coating during operation, or consider adding a protective surface treatment. These gears are designed for enclosed or lubricated drive systems.
Yes — any gear or rack with Module 2.5 and a 20° pressure angle will mesh correctly with this series. Verify that the face width of your mating component is compatible (25 mm or wider) and that the center distance matches the calculated value based on pitch diameters.
Bore diameter varies by tooth count in this series. Check the product images or contact us to confirm the exact bore size for your selected tooth count before ordering. The keyway slot allows a key to be used for positive torque transmission — match the key dimensions to your shaft's keyway spec.
Yes. Because all gears in this listing share the same module (2.5) and pressure angle (20°), they can be combined in multi-stage configurations. Calculate the center distance for each stage using the pitch diameter formula, and ensure adequate shaft support and alignment for each mesh point.
A light gear oil (ISO VG 68–150) or lithium-based grease is suitable for most applications. For low-speed, high-load applications, use a heavier grease. For high-speed applications, a splash or drip oil lubrication system is recommended to maintain the oil film across the tooth contact zone.
