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When your project demands repeatable, low-backlash power transmission in a compact footprint, undersized or poorly finished gears become the weak link. Makers, robotics engineers, and CNC hobbyists who need reliable 0.5 module spur gears will find this range covers the most common tooth counts and bore sizes in a single listing — eliminating the frustration of sourcing multiple SKUs.
Each gear is machined from 45# medium-carbon steel, offering a balance of hardness and machinability suited to moderate-load drive trains. The 0.5M (module 0.5) pitch standard means an outer diameter that scales linearly with tooth count: the 25-tooth gear measures approximately 13 mm (0.51 in) OD, while the 60-tooth gear reaches roughly 31 mm (1.22 in) OD. Bore options span 4 mm through 15 mm (0.16–0.59 in) to accommodate common motor and shaft diameters. Tooth count options run 25, 26, 28, 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, 50, 52, 55, 58, and 60 teeth.
Typical use cases include small-scale robotic arm joints requiring a 0.5M pinion drive gear, desktop CNC axis drives where a straight-cut spur gear minimises noise at low speeds, and DIY automation rigs pairing a 45-steel spur gear with a stepper motor shaft for consistent torque transfer.
| Module | 0.5M |
|---|---|
| Tooth Count Options | 25, 26, 28, 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, 50, 52, 55, 58, 60 teeth |
| Bore Diameter Options | 4 mm / 5 mm / 6 mm / 6.35 mm / 8 mm / 10 mm / 12 mm / 14 mm / 15 mm |
| Outer Diameter (approx.) | (Teeth + 2) × 0.5 mm — e.g., 25T ≈ 13.5 mm; 60T ≈ 31 mm |
| Pressure Angle | 20° (standard) |
| Gear Type | Straight-cut spur gear (pinion drive) |
| Material | 45# medium-carbon steel |
| Finish | See variant options |
| Hub Width / Face Width | See variant options |
| Pack Quantity | 1 pc / 5 pcs / 10 pcs (select above) |
Divide the driven gear tooth count by the driver (pinion) tooth count to get your ratio. For example, pairing a 25-tooth pinion with a 50-tooth gear gives a 2:1 reduction. Select the tooth counts that produce your target ratio while keeping both gears within the 0.5M module family.
Match the bore to your shaft diameter exactly. Common stepper and DC motor shafts are 4 mm, 5 mm, 6 mm, or 8 mm. The 6.35 mm bore suits ¼-inch imperial shafts. If you plan to use a set screw or keyway, choose the bore that matches the shaft and add your own retention method — the gears ship without set screws unless otherwise noted.
Yes, provided the other gear is also Module 0.5 with a 20° pressure angle — the international standard for this pitch. Module and pressure angle must match for proper mesh; tooth count only affects the gear ratio and centre distance, not compatibility.
45# steel is significantly stronger than brass or engineering plastics in bending and surface fatigue. It is well-suited to moderate-load, moderate-speed applications such as robotics joints, small CNC axes, and automation rigs. For very high-speed or heavy-load applications, consider hardened or alloy steel gears instead.
45# carbon steel has limited inherent corrosion resistance. For indoor, dry environments this is generally acceptable. If your application involves moisture, humidity, or chemical exposure, apply a light machine oil coating for protection, or consider stainless steel gears for your use case.
The 1-pc option is ideal for prototyping or replacing a single failed gear. The 5-pc pack suits small production runs or builds requiring multiple identical gears (e.g., a multi-axis robot). The 10-pc pack offers the best per-unit value for larger builds or when you want spares on hand. All pack sizes ship the same gear specification.
Centre distance = (Teeth on Gear A + Teeth on Gear B) × Module / 2. For a 25T and 50T pair: (25 + 50) × 0.5 / 2 = 18.75 mm. Use this formula to set shaft spacing accurately in your design.
