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When your motor drive, robotic joint, or RC drivetrain demands tight mesh tolerances and consistent torque transfer, undersized or poorly machined gears become the weakest link. These 0.5 module spur gears are engineered for hobbyists, makers, and small-machine builders who need reliable, repeatable power transmission in compact gear trains.
Each gear is machined from 45# medium-carbon steel, offering a balance of machinability and wear resistance suited to moderate-load applications. The range covers 20, 22, 24, and 26 teeth at 0.5 module, with bore options of 4 mm, 5 mm, 6 mm, and 6.35 mm (1/4 in). Outer diameters span approximately 11–14 mm (0.43–0.55 in) depending on tooth count, keeping the footprint minimal for space-constrained assemblies.
Typical use cases include DC motor pinion drives in 3D printer extruder gearboxes, small servo reduction stages in robotic arms, and speed-reduction gear pairs in DIY CNC axis drives — all scenarios where a 0.5 mod spur gear with a precise bore fit is critical to backlash control and long service life.
| Module | 0.5 |
|---|---|
| Tooth Count Options | 20T / 22T / 24T / 26T |
| Pressure Angle | 20° (standard) |
| Bore (Hole) Size | 4 mm / 5 mm / 6 mm / 6.35 mm (1/4 in) |
| Pitch Diameter (approx.) | 10 mm / 11 mm / 12 mm / 13 mm (by tooth count) |
| Outer Diameter (approx.) | 11 mm / 12 mm / 13 mm / 14 mm (by tooth count) |
| Face Width | See variant options |
| Material | 45# Medium-Carbon Steel |
| Surface Finish | See variant options |
| Hub Style | See variant options |
| Pack Quantity | 1 / 2 / 5 / 10 / 20 Pcs |
| Gear Type | Spur (straight tooth) |
The gear ratio is determined by dividing the driven gear tooth count by the driving gear tooth count. For example, pairing a 20T pinion with a 26T gear gives a reduction ratio of approximately 1.3:1. Choose a higher tooth count on the driven gear for speed reduction and torque multiplication, or a lower count for speed increase. All four options (20T, 22T, 24T, 26T) share the same 0.5 module, so they mesh with each other and with any other 0.5 mod gear.
Match the bore to your motor or servo shaft diameter. Common DC hobby motors use 3–6 mm shafts — select 4 mm, 5 mm, or 6 mm accordingly. The 6.35 mm option is equivalent to 1/4 inch and suits motors with imperial shaft standards common in North American hobby applications. If your shaft is slightly undersized, a set screw or shaft collar can compensate; if oversized, the bore cannot be reduced without machining.
45# steel offers moderate tensile strength (typically 600–800 MPa depending on heat treatment) and is well-suited for light-to-medium duty motor transmission tasks such as 3D printer extruders, small robotic joints, and RC drivetrains. For heavy industrial loads or continuous high-torque applications, consider gears made from alloy steel or with surface hardening. If in doubt, calculate the tangential load against the gear's face width and module to verify adequacy.
45# carbon steel is susceptible to surface oxidation in humid or wet environments. For indoor, dry-environment use (typical of electronics enclosures, desktop robots, and 3D printers), bare steel is generally acceptable with light lubrication. For outdoor or high-humidity applications, apply a thin coat of grease or consider a corrosion-inhibiting lubricant. If corrosion resistance is a primary requirement, look for stainless steel or brass gear alternatives.
Yes. All gears in this listing share the same 0.5 module and 20° pressure angle, which means any combination of 20T, 22T, 24T, and 26T gears will mesh correctly with each other and with any other 0.5 mod external spur gear. The center distance between two meshing gears equals (T1 + T2) × module / 2. For example, a 20T and 26T pair requires a center distance of (20 + 26) × 0.5 / 2 = 11.5 mm.
For prototyping or one-off builds, the 1 Pcs option lets you validate fit and function before committing to more. For production runs, educational kits, or keeping spares on hand, the 5, 10, or 20 Pcs packs offer better per-unit value. If you are building a gear train that requires multiple identical gears (e.g., an idler stage), ordering a multi-pack in a single transaction ensures all gears come from the same production batch for consistent tolerances.
A light machine oil or white lithium grease applied to the tooth flanks is sufficient for most hobby and light-duty applications. Avoid heavy greases that can attract dust and debris in open-gear configurations. For enclosed gearboxes, a gear oil with an appropriate viscosity grade (ISO VG 68–150) works well. Re-lubricate periodically based on run time and operating conditions.
