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When a slipping or undersized gear derails your build mid-project, the frustration is real. Makers, robotics hobbyists, and small-machine builders who need reliable, repeatable motion transfer demand a gear that holds its bore tight and meshes cleanly under load. These Mod 0.5 brass pinion spur gears are engineered for exactly that — delivering consistent torque transmission in compact drive trains where accuracy matters.
Each gear is machined from brass with a hardened tooth profile, available in 20 to 60 teeth and bore diameters from 4 mm to 15 mm (approximately 0.16 in to 0.59 in). A captive set screw locks the gear firmly to the shaft, eliminating axial slip. The module (Mod) rating of 0.5 defines the tooth pitch, making these gears directly interchangeable with any other Mod 0.5 spur gear in your drivetrain.
Typical use cases include CNC pen plotters and engravers requiring fine-pitch gear reduction, small robotic arm joints where a compact Mod 0.5 pinion gear meshes with a rack or larger spur, and DIY automation projects such as conveyor indexers, camera sliders, and clock mechanisms that rely on a hardened brass spur gear for long service life.
Each gear includes a captive M2 or M3 set screw (size varies by bore) that clamps directly onto the shaft, preventing rotational and axial slip under dynamic loads.
Choose from 20 T up to 60 T to dial in your gear ratio. Finer ratios for speed, larger tooth counts for torque — all in the same Mod 0.5 pitch family.
The tooth flanks are hardened for wear resistance, extending service life in continuous-duty applications such as CNC routers, 3D printer extruder drives, and robotic joints.
Brass offers a favorable combination of machinability, moderate corrosion resistance, and low friction against steel mating gears — ideal for indoor automation and light-industrial use.
Module 0.5 is a globally standardized tooth pitch. These gears mesh directly with any Mod 0.5 rack, pinion, or spur gear, simplifying drivetrain design and part sourcing.
Bore sizes span 4 mm, 5 mm, 6 mm, 6.35 mm (1/4 in), 7 mm, 8 mm, 10 mm, 12 mm, 14 mm, and 15 mm, covering the most common hobby and light-industrial motor shaft diameters.
| Module (Mod) | 0.5 |
|---|---|
| Material | Brass (hardened tooth profile) |
| Tooth Count Range | 20 – 60 Teeth (see variant options) |
| Bore Diameter Range | 4 mm – 15 mm (see variant options) |
| Bore Type | Round bore with set screw; stepped bore available on select variants |
| Pitch Diameter | Mod × Teeth (e.g., 0.5 × 20 = 10 mm; 0.5 × 60 = 30 mm) |
| Pressure Angle | 20° (standard) |
| Hub / Face Width | See variant options |
| Fastener Included | Set screw (M2 or M3, varies by bore size) |
| Finish | Natural brass |
| Weight | See variant options |
| Quantity per Order | 1 PCS (per variant listing) |
The gear ratio is determined by dividing the driven gear tooth count by the driving (pinion) gear tooth count. For example, pairing a 20-tooth pinion with a 40-tooth spur gives a 2:1 reduction — halving speed and doubling torque. Choose a lower tooth count for higher speed output and a higher tooth count when you need more torque or a larger pitch diameter to match a specific center distance.
NEMA 17 stepper motors typically have a 5 mm output shaft. Select the 5 mm bore variant. If your motor has a D-flat shaft, the set screw will seat against the flat for a more secure grip. For NEMA 23 motors (6.35 mm / 1/4 in shaft), choose the 6.35 mm bore variant.
"No step" bore variants have a straight-through cylindrical bore with no shoulder or counterbore — the shaft passes fully through the hub. Standard bore variants may include a stepped counterbore that positions the gear at a fixed axial depth on the shaft. Choose "No step" when you need to adjust the gear's axial position freely; choose the stepped variant when a fixed seating depth is required for your assembly.
Brass Mod 0.5 spur gears are well-suited for light-to-medium duty continuous operation in CNC pen plotters, camera sliders, small robotic joints, and similar applications. The hardened tooth profile improves wear resistance compared to standard brass. For high-torque or high-speed industrial drives, consider a steel Mod 0.5 gear instead. If you are unsure whether brass meets your load requirements, contact us to confirm.
Brass is inherently corrosion-resistant and will not rust. In humid or mildly corrosive indoor environments, brass performs reliably without surface treatment. For outdoor or high-humidity applications, a light coating of machine oil or grease on the tooth flanks will further extend service life and reduce friction against mating steel gears.
Yes. Any Mod 0.5 gear — regardless of material — will mesh correctly with these brass pinion gears, provided the pressure angle is 20° (the industry standard for Mod 0.5). Brass-on-steel pairings are common in precision instruments and light automation because the softer brass acts as a sacrificial wear surface, protecting the harder steel rack or spur from accelerated wear.
Center distance = (Pitch Diameter of Gear 1 + Pitch Diameter of Gear 2) ÷ 2. For Mod 0.5 gears, Pitch Diameter = Module × Tooth Count. Example: a 20-tooth pinion (PD = 10 mm) meshing with a 40-tooth spur (PD = 20 mm) requires a center distance of (10 + 20) ÷ 2 = 15 mm.
