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When your project demands reliable torque transfer and tight meshing tolerances, a poorly matched gear becomes the weakest link in your drivetrain. Whether you're a robotics engineer, CNC hobbyist, or RC vehicle builder, the Mod 1.5 steel spur gear with 20 teeth gives you the dimensional accuracy and material strength needed to keep your transmission running smoothly under load.
This spur gear is machined from carbon steel, offering a solid balance of strength and machinability. The module (modulus) is 1.5, with 20 teeth and a pitch circle diameter of 30mm (approximately 1.18 inches). Bore sizes range from 5mm to 15mm (approximately 0.20 to 0.59 inches), with optional keyslot configurations (3×1.4mm, 4×1.8mm, or 5×2.3mm) available for positive shaft locking.
Typical use cases include DIY robotic arm joint drives requiring a compact Mod 1.5 spur gear set, CNC axis transmission systems needing a steel pinion gear with keyway, and RC vehicle gearbox builds where a 20-tooth steel spur gear with bore selection is essential for custom shaft fitment.
| Module (Modulus) | 1.5 |
|---|---|
| Number of Teeth | 20T |
| Pitch Circle Diameter | 30mm (approx. 1.18 in) |
| Outside Diameter | Typically 33mm (approx. 1.30 in) |
| Bore Diameter | 5 / 6 / 6.35 / 7 / 8 / 10 / 12 / 12.7 / 14 / 15mm — See variant options |
| Keyslot | None / 3×1.4mm / 4×1.8mm / 5×2.3mm — See variant options |
| Face Width (Hub Length) | See variant options |
| Material | Carbon Steel |
| Tooth Profile | Involute |
| Pressure Angle | 20° |
| Gear Type | Spur Gear (Pinion) |
| Finish | See variant options |
Measure your motor or drive shaft diameter with a caliper. Select the bore size that matches your shaft exactly — options range from 5mm to 15mm (including 6.35mm and 12.7mm for imperial shafts). If your shaft is slightly undersized, a keyslot variant with a set screw can compensate for minor play.
For light-duty or low-torque applications, a plain bore with a set screw is often adequate. For higher torque loads or applications where gear slippage would be critical (such as CNC axis drives or robotic joints), a keyslot version (3×1.4mm, 4×1.8mm, or 5×2.3mm) provides a positive mechanical lock between the gear and shaft.
This gear meshes with any other Mod 1.5 (Module 1.5) spur gear or rack with a matching 20° pressure angle. The module must match exactly — Mod 1.5 gears will not correctly mesh with Mod 1.0, Mod 2.0, or other module gears.
Carbon steel offers strong mechanical properties but has limited corrosion resistance compared to stainless steel. For outdoor or humid environments, we recommend applying a light machine oil or grease coating, or considering a surface-treated variant. For highly corrosive environments, contact us to confirm the best option for your application.
Gear ratio is calculated as the number of teeth on the driven gear divided by the number of teeth on the driving gear. For example, pairing this 20T pinion with a 40T gear gives a 2:1 reduction ratio. The Mod 1.5 standard ensures consistent center distance calculations: center distance = (T1 + T2) × Module / 2.
Yes. Mod 1.5 steel spur gears are commonly used in CNC axis transmission systems and extruder gear trains. Verify that your mating gear is also Mod 1.5 and that the bore size matches your stepper motor shaft. For extruder applications, confirm the face width is sufficient for your filament drive requirements.
Keyslot size should match the keyway cut into your shaft. Common pairings: 3×1.4mm keyslot for smaller shafts (typically 8–10mm bore), 4×1.8mm for mid-range shafts (typically 10–12mm bore), and 5×2.3mm for larger shafts (typically 12–15mm bore). Always verify against your shaft's actual keyway dimensions before ordering.
