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When a stripped plastic gear or an undersized pinion brings your build to a halt, you need a drop-in replacement that holds up under load. Hobbyists, robotics engineers, and small-machine builders who demand dimensional accuracy and corrosion resistance turn to the 0.5 mod brass pinion spur gear as their go-to transmission component.
This spur gear is machined from solid brass, offering a balance of machinability, low friction, and natural corrosion resistance without surface coatings. The module is 0.5 (metric), with 22 teeth, and is available in five bore diameters — 4 mm (0.157 in), 5 mm (0.197 in), 6 mm (0.236 in), 6.35 mm (0.250 in / 1/4 in), and 8 mm (0.315 in) — to suit a wide range of motor shaft sizes. Outer diameter is approximately 12 mm (0.47 in) based on the formula (T + 2) × module.
Typical applications include RC car and truck drivetrains requiring a compact 0.5 mod pinion, tabletop robotics gearboxes pairing with a matching 0.5 mod spur gear, and small automation or clock-mechanism assemblies where a low-backlash brass transmission gear is essential for consistent torque transfer.
Machined from brass for inherent corrosion resistance, smooth meshing, and a longer service life compared to plastic alternatives in demanding environments.
Standard metric 0.5 module pitch ensures accurate meshing with any compatible 0.5 mod gear, rack, or pinion without custom modification.
Select the bore that matches your motor or drive shaft — including the common 1/4-inch (6.35 mm) shaft used in many hobby and light-industrial motors.
Brass-on-steel or brass-on-brass meshing produces minimal friction and heat, supporting continuous-duty cycles in robotics and automation rigs.
Available in 1, 2, 5, or 10-piece packs — order a single replacement or stock up for a full project build without overpaying for bulk minimums.
Standardized 0.5 mod tooth profile means this pinion gear slots directly into existing gearboxes designed for Mod 0.5 components, minimizing downtime.
| Module | 0.5 |
|---|---|
| Number of Teeth | 22T |
| Bore Diameter | 4 mm / 5 mm / 6 mm / 6.35 mm / 8 mm (see variant options) |
| Outer Diameter (approx.) | ~12 mm (0.47 in) |
| Material | Brass |
| Tooth Profile | Standard involute spur |
| Pressure Angle | 20° |
| Face Width | See variant options |
| Hub / Boss | See variant options |
| Finish | Natural brass (uncoated) |
| Packing Quantity | 1 / 2 / 5 / 10 PCS (see variant options) |
Measure your motor or drive shaft diameter with a caliper. Match it to the available bore options: 4 mm, 5 mm, 6 mm, 6.35 mm (1/4 in), or 8 mm. If your shaft is slightly undersized, a set screw or shaft collar can secure the gear; if oversized, the gear will not fit and must not be forced.
"Mod" (module) is the metric standard for gear tooth size. A 0.5 module gear will only mesh correctly with other 0.5 module gears of the same pressure angle (20°). It is not interchangeable with DP (diametral pitch) gears used in some imperial systems without conversion verification.
Brass offers good strength for light-to-medium torque applications such as RC car pinions, small robot joints, and clock mechanisms. For high-torque or high-RPM industrial drives, consider steel gears. Brass excels where corrosion resistance, low noise, and smooth meshing matter more than maximum load capacity.
Brass is naturally corrosion-resistant and does not rust. It may develop a patina (surface oxidation) over time in humid environments, but this does not significantly affect mechanical performance. No additional coating or treatment is required for typical indoor or light-outdoor use.
For a single motor drive, 1 PCS is sufficient. For a dual-motor or mirrored drivetrain, select 2 PCS. The 5 PCS and 10 PCS packs offer better per-unit value for multi-axis robots, batch builds, or keeping spares on hand for maintenance.
The outer (tip) diameter of a spur gear is calculated as (Number of Teeth + 2) × Module = (22 + 2) × 0.5 = 12 mm (approximately 0.47 inches). This is the maximum envelope diameter to account for in your housing or gearbox design.
Yes. A 0.5 mod spur pinion meshes correctly with a 0.5 mod rack of the same pressure angle (20°), making it suitable for compact linear actuators, camera sliders, and small CNC axis drives where a rack-and-pinion arrangement is preferred.
