0.5M 25-28T Spur Gears Steel Pinion Gears Metal Spur Transmission Gear 45 Steel

The tooth count determines your gear ratio. A smaller pinion (25T) paired with a larger driven gear gives more torque reduction; a larger pinion (28T) gives a higher output speed for the same driven gear. Calculate your target ratio by dividing the driven gear's tooth count by the pinion tooth count, then select the option that gets you closest to your design goal.

Measure your motor or drive shaft diameter with calipers. These gears are available in 4 mm, 5 mm, and 6 mm bore. For a secure fit, the bore should match the shaft diameter exactly; you can then use a set screw, adhesive, or press fit depending on your application. If your shaft is between sizes, choose the next size up and use a shaft collar or sleeve.

Yes. 45 steel offers significantly higher shear strength than the nylon or plastic pinions commonly found in entry-level RC vehicles. They are well-suited for 1:10 to 1:18 scale RC cars, small robot joints, and light industrial automation where moderate torque and continuous rotation are required. For very high-shock or high-RPM applications, consider whether additional surface hardening is needed.

45 steel is not stainless and will oxidize if exposed to moisture without protection. For indoor or dry-environment use, a light coat of machine oil or grease on the tooth faces is sufficient. For outdoor or humid environments, apply a corrosion-inhibiting grease regularly, or consider a stainless steel alternative if long-term corrosion resistance is a priority.

Any gear with a matching 0.5 module and the same pressure angle (20°) will mesh correctly — including other 0.5M spur gears, 0.5M racks, and 0.5M pinions regardless of material. Module and pressure angle must both match; tooth count only affects the gear ratio, not compatibility.

For a single-axis drive with one pinion and one driven gear, a quantity of 1 or 2 is sufficient. For multi-axis robots or production runs, the 10–50 piece packs offer better per-unit value. Workshop builders who perform regular maintenance often stock the 20–30 piece packs to have spares on hand without over-ordering.

Yes. A 0.5M spur gear meshes directly with a 0.5M rack of the same pressure angle, making these pinion gears suitable for rack-and-pinion linear actuators in small CNC machines, camera sliders, or drawer mechanisms. Ensure the rack's tooth profile and pressure angle match before assembly.