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When a stripped or undersized gear brings your 3D printer, CNC router, or custom drive system to a halt, finding an exact-spec replacement fast is critical. These 1 Mod 45# steel spur gears are engineered for makers, machine builders, and hobbyists who need reliable, dimensionally accurate pinion gears without compromise.
Each gear is machined from 45# medium-carbon steel, offering a solid balance of hardness and toughness. The tooth profile follows the standard Module 1 (Mod 1) metric system, with a consistent face width of 10mm (approx. 0.39 in). Outer diameter scales with tooth count — ranging from approximately 14mm (0.55 in) for the 12T variant up to approximately 162mm (6.38 in) for the 160T variant, following the standard formula OD = (T + 2) × Module.
These 1 Mod spur gears are widely used as replacement pinion gears in FDM 3D printer extruder drives and Z-axis lead screw couplings, as motion-transfer gears in DIY CNC router spindle and axis assemblies, and as drive gears in custom robotics, automation rigs, and RC vehicle gear trains requiring metric module compatibility.
| Module | 1 (Mod 1) |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Face Width (Thickness) | 10 mm (approx. 0.39 in) |
| Tooth Count Range | 12T – 160T (78 variants) |
| Outer Diameter | (T + 2) × 1 mm — e.g. 14 mm for 12T, 162 mm for 160T |
| Pitch Diameter | T × 1 mm — e.g. 12 mm for 12T, 160 mm for 160T |
| Pressure Angle | 20° |
| Tooth Profile | Standard Involute |
| Bore Diameter | See variant options |
| Hub Diameter | See variant options |
| Surface Finish | See variant options |
| Weight | See variant options |
Your gear ratio determines the tooth count you need. Divide the driven gear teeth by the drive (pinion) gear teeth to get the ratio. For example, pairing a 20T pinion with a 60T gear gives a 3:1 reduction. If you are replacing an existing gear, count the teeth on the worn part or measure the pitch diameter in mm — for Mod 1 gears, pitch diameter equals tooth count in millimetres.
Module (Mod) is the metric standard for gear tooth size. Module 1 means the pitch diameter equals the tooth count in millimetres. Two gears mesh correctly only if they share the same module and pressure angle. These gears are Mod 1 with a 20° pressure angle — they will mesh with any other Mod 1, 20° involute spur gear or rack, regardless of brand, as long as the tooth counts are compatible with your desired ratio.
45# medium-carbon steel (equivalent to SAE 1045) offers a tensile strength of approximately 600–700 MPa in its normalised state, making it well-suited for moderate-load drive applications such as 3D printer extruder gears, CNC axis drives, and light-duty robotics. For very high-torque or high-speed industrial applications, consider whether a hardened or alloy steel variant is more appropriate for your load requirements.
45# carbon steel is not inherently corrosion-resistant. For outdoor, humid, or wet environments, we recommend applying a light machine oil or grease coating to the gear teeth and bore, or considering a stainless steel alternative if prolonged moisture exposure is expected. For indoor CNC and 3D printer use, standard lubrication practice is sufficient to prevent surface oxidation.
Bore diameter varies by tooth count variant — please check the variant detail or contact us to confirm the bore size for your selected tooth count before ordering. Common bore sizes for small pinion gears (12T–20T) are typically in the 4–8 mm range, while larger gears (50T+) often have bores of 10 mm or more. If your shaft diameter differs from the standard bore, the gear can often be bored out by a local machine shop.
Yes. Module 1 spur gears mesh directly with Module 1 gear racks, making them a common choice for CNC router X/Y axis drives, laser cutter carriages, and similar rack-and-pinion linear motion systems. Select a tooth count that gives you the desired linear travel per motor revolution — for Mod 1, each tooth on the pinion corresponds to π mm (approx. 3.14 mm) of linear travel per revolution divided by tooth count.
Yes, lubrication extends gear life significantly. Apply a thin layer of lithium-based grease or machine oil to the tooth faces during installation. For 3D printers running continuously, re-lubricate every 3–6 months or when you notice increased noise. For CNC routers and intermittent-use machines, inspect and re-lubricate every 6–12 months depending on duty cycle and operating environment.
