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When a stripped plastic gear or an imprecise metal pinion causes your motor drive to slip, stall, or lose positional accuracy, the downstream cost in downtime and rework adds up fast. Hobbyists building RC vehicles, robotics engineers prototyping compact actuators, and makers assembling precision motion systems all need a spur gear that holds its mesh under load without play or wobble. This 0.5 module 42-tooth brass pinion spur gear is machined to deliver consistent tooth engagement and shaft fit across repeated duty cycles.
Each gear is machined from brass, offering a balance of machinability, moderate corrosion resistance, and low-friction meshing against steel or aluminum mating gears. The module is 0.5 (metric pitch standard), with 42 teeth and a bore diameter available in 4 mm (0.157 in), 5 mm (0.197 in), 6 mm (0.236 in), or 8 mm (0.315 in) to suit a range of motor shaft sizes. Overall gear diameter is approximately 21–22 mm (0.83–0.87 in) based on standard 0.5 mod geometry.
Typical applications include RC car and truck motor pinion replacement, small robotic joint actuators requiring a 0.5 mod gear train, and DIY CNC or 3D printer extruder drive assemblies where a compact 42-tooth spur gear reduces speed and multiplies torque from a brushed or brushless motor shaft.
Machined from brass for reliable tooth strength, low-friction meshing, and moderate corrosion resistance in indoor and light-outdoor drive applications.
Conforms to the metric 0.5 mod gear standard, ensuring accurate tooth profile and pitch for correct mesh with any compatible 0.5 mod mating gear.
42 teeth provide a defined gear ratio reference point for motor-to-output speed and torque calculations in RC, robotics, and automation builds.
Available in 4 mm, 5 mm, 6 mm, and 8 mm bore diameters to fit a wide range of brushed and brushless motor shaft sizes without adapter sleeves.
Order as 1, 2, 5, or 10 pieces per pack — ideal for single-build prototyping, small-batch production runs, or stocking spares for ongoing projects.
Approximately 21–22 mm outer diameter keeps the gear train compact for space-constrained enclosures in robotics joints, RC drivetrains, and miniature actuators.
| Module | 0.5 (Metric) |
|---|---|
| Number of Teeth | 42T |
| Bore Diameter | 4 mm / 5 mm / 6 mm / 8 mm (see variant options) |
| Outer Diameter (approx.) | ~21–22 mm (~0.83–0.87 in) |
| Material | Brass |
| Gear Type | Spur Gear (Pinion) |
| Tooth Profile | Standard involute, 0.5 mod |
| Hub / Face Width | See variant options |
| Finish | Natural brass (uncoated) |
| Pack Quantity | 1 / 2 / 5 / 10 PCS (see variant options) |
| Compatible Gear Module | Mod 0.5 only |
| Typical Applications | RC vehicles, robotics, CNC, 3D printer drives |
Measure your motor shaft diameter with a caliper. This gear is available in 4 mm, 5 mm, 6 mm, and 8 mm bore diameters. Select the bore that matches your shaft exactly — a loose fit will cause slippage under load, while an oversized shaft will not insert. If your shaft falls between sizes, a set-screw hub or shaft adapter may be needed.
Module (Mod) is the metric standard for gear tooth size, defined as the pitch diameter divided by the number of teeth. Two gears must share the same module to mesh correctly. This gear is Mod 0.5, meaning it will only mesh properly with other Mod 0.5 gears — not Mod 0.4, Mod 0.8, or any other module. Always verify your mating gear's module before ordering.
Brass offers good machinability and adequate strength for light-to-moderate torque applications such as RC car pinions, small robotic joints, and hobby CNC drives. It is softer than steel, so in high-torque or high-RPM applications where a steel pinion meshes against a brass gear, wear rates should be monitored. For heavy industrial loads, a steel spur gear may be more appropriate.
Brass has moderate natural corrosion resistance and performs well in indoor environments and light outdoor use. In consistently wet, salt-spray, or chemically aggressive environments, periodic lubrication with a compatible gear grease will extend service life. For harsh outdoor conditions, consider stainless steel or anodized aluminum alternatives.
Gear ratio depends on the tooth count of the mating pinion. For example, if your motor pinion has 14 teeth and this gear has 42 teeth, the reduction ratio is 42 ÷ 14 = 3:1, meaning the output shaft turns at one-third the motor speed with three times the torque. Adjust your pinion tooth count to achieve your target ratio.
Yes. The 0.5 mod 42T brass spur gear is well-suited for compact 3D printer extruder gear trains and small CNC axis drives where a Mod 0.5 gear train is specified. Verify that your existing drive gear or rack is also Mod 0.5, and select the bore size that matches your stepper motor or drive shaft diameter.
For a single prototype or repair, the 1 PCS option is sufficient. If you are building multiple units or want spares on hand, the 2, 5, or 10 PCS packs offer a lower per-unit cost. For small-batch production runs, the 10 PCS pack provides the best value per gear.
