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When a loose-fitting or undersized pinion causes slippage, noise, or premature wear in your drive train, the root cause is almost always a mismatch between bore diameter and shaft size. Hobbyists building RC vehicles, engineers prototyping CNC actuators, and makers assembling small automation rigs all face the same challenge: finding a compact spur gear that fits the shaft exactly and holds up under continuous load.
This 0.5 Module brass spur gear features 45 teeth and is available with bore diameters of 4 mm (~0.157 in), 5 mm (~0.197 in), 6 mm (~0.236 in), 8 mm (~0.315 in), and 10 mm (~0.394 in). The gear body is machined from solid brass, offering a balance of machinability, corrosion resistance, and low-friction meshing. Outer diameter is approximately 23 mm (~0.906 in) based on the 0.5 mod × 45T formula (OD = (T+2) × module).
Typical use cases include: CNC router axis drives requiring quiet, low-backlash transmission; robotics joint actuators where a compact 45-tooth reduction stage is needed; and RC model gear trains where a brass pinion meshes with a nylon or steel rack for smooth, durable operation.
| Module | 0.5 |
|---|---|
| Number of Teeth | 45T |
| Outer Diameter | ≈ 23 mm (0.906 in) |
| Bore Diameter | 4 / 5 / 6 / 8 / 10 mm (see variant options) |
| Face Width | See variant options |
| Material | Brass |
| Pressure Angle | 20° |
| Tooth Profile | Involute |
| Finish | Natural brass (uncoated) |
| Packing Quantity | 1 / 2 / 5 / 10 PCS (see variant options) |
Measure your motor or drive shaft diameter with a caliper. Select the bore size that matches exactly — 4, 5, 6, 8, or 10 mm. A bore that is too large will cause runout and slippage; a bore that is too small cannot be pressed on without machining. If your shaft is an imperial size (e.g. 1/4 in = 6.35 mm), choose the next available metric bore and ream or sleeve to fit.
For a 0.5 Module gear with 45 teeth, the outer (tip) diameter is calculated as OD = (T + 2) × Module = (45 + 2) × 0.5 = 23.5 mm. In practice, finished OD is approximately 23–23.5 mm (~0.906–0.925 in) depending on machining tolerance.
Brass spur gears are well-suited for light-to-medium duty applications such as RC models, desktop CNC drives, and small robotic joints. Brass offers good machinability and low friction against steel or nylon mating gears. For heavy-load or high-speed industrial drives, consider steel gears instead. If in doubt, contact us with your torque and RPM requirements.
Brass has natural corrosion resistance in most indoor and light-outdoor environments. It does not rust like steel. However, in highly humid, salt-spray, or chemically aggressive environments, consider applying a light machine oil or grease to the tooth surfaces for added protection.
This gear meshes with any 0.5 Module gear or rack with a matching 20° pressure angle — regardless of material (brass, steel, nylon, or acetal). Ensure the mating component is also 0.5 Mod; mixing modules will result in incorrect meshing and rapid wear.
Yes. Each bore size is a separate variant. Add the desired bore size and quantity combination to your cart, then repeat for additional bore sizes. All items will be consolidated into a single order.
The packing quantity refers to the number of identical gears (same bore size) included in one purchase. Multi-piece packs offer a lower per-unit cost and are useful for prototyping with spares, building symmetric gear trains, or stocking your workshop.
