2.5/3/4/5 Mod Spur Gear 10T to 45T Flat Gear Motor Transmission Gear 45# Steel

The module must match the mating gear or rack exactly — a 3 Mod gear will only mesh correctly with other 3 Mod components. As a rule of thumb, higher modules (larger tooth size) handle more torque but result in a larger pitch diameter for the same tooth count. If you are replacing an existing gear, measure the pitch diameter and divide by the tooth count to confirm the module before ordering.

Divide the driven gear tooth count by the driving gear tooth count to get the ratio. For example, a 30T gear driven by a 10T pinion gives a 3:1 reduction. This listing covers 10T through 45T, so you can achieve ratios from approximately 1:1 up to 4.5:1 within a single module family without sourcing from multiple suppliers.

45# medium-carbon steel has a typical tensile strength of 600–800 MPa in the normalized or quenched-and-tempered condition, making it significantly stronger than cast iron or nylon gears and suitable for moderate continuous loads. It is not as hard as case-hardened alloy steel (e.g., 20CrMnTi), so for very high-cycle or shock-load applications you may want to consider surface hardening after machining.

45# steel is not stainless and will oxidize if left unprotected in humid or wet conditions. For indoor or enclosed gearbox use with periodic lubrication, surface rust is not typically a concern. For outdoor or high-humidity environments, apply a light grease or anti-corrosion coating, or consider specifying a stainless or zinc-plated alternative for your application.

Yes — as long as the rack shares the same module and pressure angle (20°). A 3 Mod spur gear from this listing will mesh directly with a standard 3 Mod steel or nylon rack, making it a straightforward choice for CNC router gantries, 3D printer Z-axis drives, and linear actuator stages.

Bore diameter varies by tooth count and module — please refer to the variant detail or contact us to confirm the bore for your specific selection. Because the gears are machined from 45# steel, the bore can be enlarged on a lathe and a keyway or set-screw flat can be added without risk of cracking, giving you flexibility to fit a range of motor shaft diameters.

Yes. The flat spur profile and standard metric module sizing make these gears compatible with stepper and servo motor output shafts commonly used in CNC and robotics applications. Verify the bore diameter matches your motor shaft, or plan to machine the bore to size. The straight-tooth geometry produces no axial thrust, which simplifies motor bearing loads in direct-drive configurations.