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When a stripped or undersized gear brings your CNC router, 3D printer, or robotic arm to a halt, finding a dimensionally accurate replacement fast is critical. Engineers, makers, and automation integrators who need reliable motion-control components rely on a consistent, well-documented gear selection — and that is exactly what this 1 Mod spur gear series delivers.
Each gear in this series is machined from 45# medium-carbon steel, offering a solid balance of hardness and machinability. The module is 1 (Mod 1), with a tooth pitch of 3.14 mm (approximately 0.124 in). Tooth counts span from 12T through 150T, giving pitch circle diameters that range from roughly 12 mm (0.47 in) for the 12T up to 150 mm (5.91 in) for the 150T. Bore diameter and keyway dimensions vary by tooth count — see variant options for exact bore specs.
Typical use cases include DIY CNC machine axis drives, stepper and servo motor output stages, small conveyor and indexing mechanisms, and educational robotics platforms where a standardised Mod 1 gear train is required. Long-tail search terms that describe this product well: "1 module steel spur gear for NEMA stepper motor", "Mod 1 metal gear 45 steel CNC", and "replacement spur gear 3.14mm pitch motor shaft".
Machined from 45# steel for a reliable combination of surface hardness and core toughness, suitable for continuous-duty motor drive applications.
Module 1 is one of the most widely used metric gear standards. These gears mesh directly with any other Mod 1 spur gear or rack, simplifying system design and replacement.
87 tooth-count options in a single product listing let you dial in the exact gear ratio you need without sourcing from multiple suppliers.
Each variant is bored to fit common motor shaft diameters. The hub length provides adequate face width for set-screw or key retention on stepper and servo shafts.
A light oxide or phosphate treatment on the steel surface helps resist surface rust during storage and light-duty operation in indoor environments.
Gear teeth are cut to standard involute profile tolerances, reducing backlash and noise when paired with a properly aligned Mod 1 pinion or rack.
| Module (Mod) | 1 |
|---|---|
| Tooth Pitch | 3.14 mm (0.124 in) |
| Pressure Angle | 20° |
| Tooth Count Range | 12T – 150T (87 variants) |
| Pitch Circle Diameter | 12 mm – 150 mm (0.47 in – 5.91 in), varies by tooth count |
| Material | 45# Medium-Carbon Steel |
| Bore Diameter | See variant options |
| Hub Length | See variant options |
| Face Width | See variant options |
| Surface Treatment | Oxide / phosphate finish |
| Gear Type | External spur gear |
| Application | CNC, robotics, motor drive, automation |
Divide the desired gear ratio by the tooth count of your driving gear (pinion) to find the required driven gear tooth count. For example, a 3:1 reduction with a 20T pinion requires a 60T gear. The centre distance between shafts equals (T1 + T2) × module / 2, so for a 20T and 60T Mod 1 pair the centre distance is 40 mm.
Yes. Any gear or rack with Module 1 and a 20° pressure angle will mesh correctly with these gears. Confirm the module and pressure angle of your existing components before ordering — mixing modules (e.g., Mod 1 with Mod 1.25) will result in incorrect meshing and rapid wear.
Bore diameter varies by tooth count and is listed in the variant options on this page. Smaller tooth-count gears (12T–20T) typically have bores in the 4–6 mm range, while larger gears (60T and above) commonly have bores of 8–12 mm or more. Select your model and check the variant detail for the exact bore size before ordering.
45# medium-carbon steel has a tensile strength of approximately 600–800 MPa in the normalised condition and can be heat-treated to higher hardness if needed. For most hobby CNC, 3D printer, and light industrial stepper/servo applications running at moderate speeds and loads, 45# steel provides adequate strength and wear resistance. For high-speed or heavy-load industrial drives, consider specifying a heat-treated or alloy-steel gear.
The oxide/phosphate surface treatment provides basic corrosion resistance for indoor storage and dry operating environments. For humid or outdoor environments, apply a light machine oil or grease to the tooth faces and bore. Avoid prolonged exposure to water or corrosive chemicals without additional protective coating.
Yes, provided the bore diameter matches your motor shaft diameter. Most variants include a set-screw hole in the hub for shaft retention. If your shaft has a flat (D-cut) or keyway, verify the bore style of the specific variant. For a secure fit, the bore should match the shaft diameter within standard H7/h6 tolerance — use a reamer or broach if a tighter fit is required.
Larger tooth-count gears have a greater pitch circle diameter and wider tooth root, which generally allows them to transmit higher torque at the same module. However, the face width (gear thickness) is the primary driver of load capacity. For high-torque applications, select a variant with a wider face width or consider stacking two gears on the same shaft. Contact us if you need load-capacity calculations for your specific application.
