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When your RC car, robotic arm, or small-scale drive system demands consistent torque transfer without slop or premature wear, finding a correctly sized pinion gear becomes critical. Hobbyists, makers, and mechanical engineers who work with compact gear trains know that a mismatched bore or wrong module can derail an entire build. This 0.5 module 25-tooth brass spur gear is engineered for those who need dimensional accuracy and dependable mesh engagement across a range of shaft sizes.
Each gear is machined from brass, offering a balance of machinability, moderate corrosion resistance, and low-friction meshing against steel or plastic mating gears. The module is 0.5 (metric), with 25 teeth and bore options spanning 4 mm, 5 mm, 6 mm, 6.35 mm (1/4 inch), and 7 mm — covering the most common motor shaft diameters in this class. The 6 mm with-step variant accommodates shaft shoulder designs. Overall gear diameter is approximately 13.5 mm (0.53 in), with a face width typically in the 3–5 mm range depending on variant.
Typical use cases include RC car transmission pinion replacement, small servo-driven robotic joints requiring a 0.5 mod spur gear for robotics, and compact automation mechanisms where a brass pinion gear 25 teeth configuration provides quiet, smooth power delivery compared to plastic alternatives.
| Module | 0.5 (Metric) |
|---|---|
| Number of Teeth | 25T |
| Pitch Diameter | 12.5 mm (0.49 in) |
| Outside Diameter | Approx. 13.5 mm (0.53 in) |
| Bore Diameter | 4 / 5 / 6 / 6.35 / 7 mm (see variant options) |
| Face Width | See variant options |
| Material | Brass |
| Pressure Angle | 20° |
| Gear Type | Spur Gear (Pinion) |
| Finish | Natural brass (uncoated) |
| Packing Quantity | 1 / 2 / 5 / 10 PCS (see variant options) |
| Weight (per piece) | Approx. 2–5 g (varies by bore) |
Measure your motor or drive shaft diameter with calipers before ordering. Common sizes: 4 mm and 5 mm suit micro gear motors; 6 mm fits many standard DC and brushless motors; 6.35 mm (1/4 in) matches North American hobby motor shafts; 7 mm suits larger servo or stepper shafts. If your shaft has a shoulder step, select the "6 mm with Step" variant.
Module (Mod) is the metric standard for gear tooth size — it equals the pitch diameter divided by the number of teeth. Two gears mesh correctly only when they share the same module and pressure angle. This gear is Mod 0.5 with a 20° pressure angle, compatible with any other Mod 0.5 spur gear, rack, or pinion regardless of tooth count.
Brass offers tensile strength in the 300–500 MPa range depending on alloy, making it suitable for light-to-medium torque applications such as RC car transmissions, robotic joints, and small automation mechanisms. For high-shock or continuous heavy-load drives, consider steel gears. Brass excels where quiet operation and corrosion resistance matter more than maximum load capacity.
Brass has inherent corrosion resistance against moisture and mild chemicals, making it suitable for indoor robotics, hobby builds, and light outdoor use. It is not recommended for prolonged saltwater or highly acidic environments. If corrosion is a primary concern, consider stainless steel alternatives or apply a light machine oil coating for added protection.
Yes. Brass-on-plastic pairings are common in RC and robotics because the softer plastic acts as the sacrificial wear component, protecting the brass pinion. Ensure the plastic gear is also Mod 0.5 with a 20° pressure angle. Avoid pairing brass with very soft plastics under high RPM, as the plastic teeth may wear rapidly.
For prototyping or a single repair, the 1 PCS option is ideal. If you are building multiple robots, running a small production batch, or want spares on hand, the 5 PCS or 10 PCS packs offer better per-unit value. The 2 PCS pack suits differential or dual-motor drive setups that require matched pinions.
The bore is a plain through-hole. Set screw, keyway, or D-bore configurations are not included in this listing. For secure shaft attachment, use a shaft collar, adhesive retainer (e.g., Loctite 638), or have a machinist add a set screw hole. Contact us to confirm if a specific bore modification is available.
