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When a slipping or undersized pinion gear stalls your project, every minute of downtime costs you. Whether you're a robotics builder, RC hobbyist, or automation engineer, finding a dimensionally accurate Mod 1 spur gear with the right bore size shouldn't be a bottleneck. These Mod 1 Steel Spur Gears with 12 teeth are engineered for builders who need consistent mesh quality and dependable torque transfer across a range of shaft diameters.
Each gear is machined from carbon steel, offering a balance of strength and machinability suited to motor-driven transmission systems. The module (Mod 1) defines the tooth pitch, ensuring direct compatibility with any other Mod 1 gear in your drivetrain. Available bore sizes range from 4mm to 7mm (~0.157" to ~0.276"), covering the most common motor shaft diameters used in small-to-medium power transmission applications. Tooth count is fixed at 12T, with an outer diameter typically in the 14mm range (~0.55").
These pinion gears are well-suited for DC motor gearbox assemblies, 3D printer extruder drives, and light CNC axis drives where a compact, low-tooth-count spur gear is required for speed reduction or torque multiplication. Long-tail use cases include "Mod 1 12 tooth pinion gear for NEMA 17 motor", "steel spur gear bore 5mm for robot drivetrain", and "replacement transmission gear for RC crawler gearbox".
Machined from carbon steel for reliable strength in motor transmission and drivetrain applications without excessive weight.
Module 1 tooth geometry ensures direct mesh compatibility with any Mod 1 gear, rack, or pinion in your system — no custom adaptation needed.
Choose from 4mm, 5mm, 6mm, 6.35mm (1/4"), or 7mm bore to match your motor shaft precisely. Each variant is machined to tolerance for a secure fit.
A 12T pinion paired with a larger driven gear delivers effective speed reduction and torque increase — ideal for compact gearbox stages.
Accurately cut tooth flanks promote consistent contact ratio and reduced backlash, contributing to quieter operation in precision motion systems.
Dimensionally consistent with standard Mod 1 pinion gears, making these a straightforward replacement for worn or damaged gears in existing assemblies.
| Module | Mod 1 (Module 1) |
|---|---|
| Number of Teeth | 12T |
| Bore Size Options | 4mm / 5mm / 6mm / 6.35mm / 7mm |
| Outer Diameter | See variant options |
| Face Width | See variant options |
| Material | Carbon Steel |
| Finish | See variant options |
| Pressure Angle | 20° |
| Gear Type | Spur Gear (Pinion) |
| Hub / Set Screw | See variant options |
| Quantity per Pack | 1 piece |
Measure your motor shaft diameter with a caliper. Common sizes are 4mm, 5mm, 6mm, 6.35mm (standard 1/4" imperial shaft), and 7mm. Select the bore that matches your shaft exactly — a loose fit will cause slippage under load, while an oversized shaft will not insert. If your shaft is between sizes, a 6.35mm bore with a set screw can sometimes accommodate a 6mm shaft with shimming.
"Mod 1" (Module 1) is a standardized metric tooth size designation. It means the pitch diameter equals the number of teeth in millimeters (so a 12T Mod 1 gear has a 12mm pitch diameter). Any two Mod 1 gears with the same pressure angle (20° is standard) will mesh correctly regardless of tooth count. Do not mix modules — a Mod 1 gear will not mesh properly with a Mod 0.8 or Mod 1.5 gear.
These gears are machined from carbon steel, which provides good tensile strength for light-to-medium duty motor transmission tasks such as robotics, 3D printer drives, and small CNC systems. For heavy industrial loads or continuous high-torque applications, consult the torque rating of your specific motor and verify the gear's face width and material grade are appropriate. Contact us to confirm suitability for demanding use cases.
Carbon steel has moderate corrosion resistance. For indoor, dry environments these gears perform well without additional treatment. If your application involves moisture, humidity, or occasional exposure to liquids, applying a light machine oil or grease to the gear teeth will extend service life. For outdoor or wet environments, consider stainless steel alternatives.
Yes. A Mod 1 spur gear meshes directly with a Mod 1 gear rack, making this 12T pinion suitable for linear motion systems such as small CNC gantries, camera sliders, or drawer actuators. Ensure the rack's pressure angle matches (20° standard) and that the gear is mounted at the correct center distance from the rack surface.
Securing method depends on the variant. Many pinion gears of this type include a set screw (grub screw) on the hub that tightens against the shaft — check the product images for your selected variant. For shafts with a flat (D-shaft), align the set screw to the flat for maximum grip. If no set screw is present, a press fit or adhesive retaining compound (e.g., Loctite 638) can be used for permanent installation.
Gear ratio = driven gear teeth ÷ driving gear teeth. With this 12T pinion driving a 36T gear, you get a 3:1 reduction (output speed is 1/3 of input, torque is 3× input). Pair it with a 24T gear for 2:1, or a 60T gear for 5:1. The 12T count makes it well-suited as the first stage in a multi-stage gearbox where significant speed reduction is needed.
