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When a stripped or undersized gear brings your CNC router, conveyor, or robotic arm to a halt, finding a dimensionally accurate replacement fast is critical. Engineers, makers, and machine builders who need a reliable 3 Mod spur pinion gear with a consistent 30 mm face width will find this series covers tooth counts from 12T all the way to 55T in a single product line.
Each gear is machined from #45 medium-carbon steel and heat-treated for surface hardness. The tooth profile follows standard Module 3 (Mod 3) geometry with a 20° pressure angle. Face width is fixed at 30 mm (1.18 in), and outer diameters range from approximately 42 mm (1.65 in) for the 12T up to approximately 171 mm (6.73 in) for the 55T. Bore diameter varies by tooth count — see variant options for the exact bore of your selected size.
Typical applications include CNC rack-and-pinion linear drives, gearbox input stages for industrial conveyors, rotary indexing tables, and DIY motorized gate openers. The standardized Mod 3 pitch makes these gears interchangeable with any mating rack or gear of the same module, simplifying multi-axis machine builds and replacement sourcing.
| Module | 3 (Mod 3) |
|---|---|
| Pressure Angle | 20° |
| Tooth Count Range | 12T – 55T |
| Face Width | 30 mm (1.18 in) |
| Material | #45 Medium-Carbon Steel |
| Surface Treatment | Heat-treated (surface hardened) |
| Outer Diameter | See variant options |
| Bore Diameter | See variant options |
| Tooth Profile Standard | DIN / ISO Module 3 |
| Finish | Natural steel (uncoated) |
Determine your required gear ratio by dividing the driver tooth count by the driven tooth count. For a rack-and-pinion linear drive, the linear travel per revolution equals π × Module × Tooth Count (in mm). Select the tooth count that delivers your target speed or travel distance at your motor's operating RPM.
Bore diameter varies by tooth count. Please check the variant option label for the bore size of your selected tooth count before ordering. If your shaft diameter differs from the listed bore, the gear can typically be re-bored by a local machine shop.
#45 medium-carbon steel with surface hardening offers a good balance of toughness and surface wear resistance, suitable for moderate-to-high torque drives in CNC machines, conveyors, and automation equipment. For very high-shock or heavy-industrial loads, consult a mechanical engineer to verify the gear's rated torque against your application requirements.
The gears are supplied with a natural steel finish and are not coated or plated. For outdoor or humid environments, apply a light machine oil or grease to the tooth flanks and bore. For corrosive environments, consider a zinc-phosphate primer or a compatible gear lubricant with rust-inhibiting additives.
Yes. Any Mod 3 rack with a matching 20° pressure angle will mesh correctly with these pinions. The linear travel per pinion revolution is calculated as: Travel (mm) = π × 3 × Tooth Count. For example, a 20T pinion produces approximately 188.5 mm of travel per revolution.
Module (M) is the metric gear sizing standard: M = Pitch Diameter ÷ Tooth Count. Diametral Pitch (DP) is the imperial equivalent: DP = Tooth Count ÷ Pitch Diameter (in inches). Module 3 is approximately equivalent to 8.47 DP. These two systems are not directly interchangeable — always match module to module or DP to DP when selecting mating gears.
The gears are supplied with a plain bore. Shaft retention method (set screw, keyway, interference fit, or shaft collar) is determined by your application design. If a keyway is required, the bore can be broached by a local machine shop to your specified key size.
