3 Module Spur Gear Pinion Gears #45 Steel 10T to 68T Metal Spur Transmission CNC

Determine your required gear ratio first: divide the driver tooth count by the driven tooth count to get the ratio. For example, a 10T pinion driving a 30T gear gives a 3:1 reduction. Match the tooth counts to your motor speed and output torque requirements. If you are replacing an existing gear, count the teeth on the worn part and select the same number.

"Module" (abbreviated M or Mod) is the metric standard for gear tooth size. Module 3 means the pitch diameter equals 3 mm multiplied by the number of teeth. Two gears mesh correctly only when they share the same module and pressure angle. These gears are Module 3 with a 20° pressure angle — they will mesh with any other standard Mod 3 / 20° spur gear or rack, regardless of brand.

#45 steel (equivalent to AISI 1045) has a tensile strength of approximately 600–800 MPa in the normalized condition. It is suitable for moderate-load applications such as CNC axis drives, conveyor pinions, and motorized hobby projects. For very high-torque or high-speed industrial applications, consider whether a hardened or alloy steel gear would be more appropriate for your specific load cycle.

These gears are made from carbon steel and are supplied with a natural (uncoated) finish, which means they are not inherently corrosion resistant. For use in humid or outdoor environments, we recommend applying a light machine oil or grease to the tooth surfaces and bore, or using a rust-inhibiting coating. If corrosion resistance is a primary requirement, consider stainless steel or plastic gears instead.

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. #45 steel is machinable, so a qualified machine shop can re-bore or add a keyway if the standard bore does not match your shaft. Always confirm wall thickness is sufficient before enlarging the bore.

Yes. Module 3 metal spur gears are commonly used in DIY CNC router axis drives, extruder gear trains, and motorized linear stages. The smaller tooth counts (10T–20T) are popular as motor pinions, while larger counts serve as driven gears in reduction stages. Verify that the bore matches your motor shaft diameter and that the face width suits your belt or gear alignment requirements.

Apply a thin film of gear grease or machine oil to the tooth flanks before first use. For enclosed gearboxes, an ISO VG 220 gear oil is typical. For open drives, a lithium-based grease works well. Re-lubricate periodically based on operating hours and environment. Keep the gear mesh free of debris to prevent accelerated tooth wear.