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When a stripped or undersized gear stalls your CNC router, 3D printer, or automated drive system, every minute of downtime costs you. Engineers, makers, and machine builders who demand repeatable torque transmission need a spur gear that holds tolerance under load — not one that wears out after a few hundred cycles. These 4 Mod 45# steel spur gears are engineered for exactly that workload.
Each gear is machined from 45# medium-carbon steel, a material known for its balanced hardness and machinability. The tooth profile follows the standard 4-module (Mod 4) metric pitch, with a uniform face width of 35 mm (approximately 1.38 in). Tooth counts span 10 through 25 teeth, giving pitch circle diameters ranging from approximately 40 mm (1.57 in) for the 10T up to 100 mm (3.94 in) for the 25T variant.
Typical use cases include: rack-and-pinion CNC gantry drives requiring a 4 Mod steel pinion gear, open-frame 3D printer Z-axis or extruder reduction stages, and light industrial conveyor or rotary indexing systems where a metric spur gear with 35 mm face width provides the necessary contact ratio.
| Module (Mod) | 4 |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Face Width (Thickness) | 35 mm (≈1.38 in) |
| Tooth Count Options | 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 Teeth |
| Pitch Circle Diameter Range | 40 mm (10T) – 100 mm (25T) |
| Pressure Angle | 20° (standard metric) |
| Bore Diameter | See variant options |
| Keyway | See variant options |
| Surface Finish | See variant options |
| Compatible Gear Standard | Mod 4 metric spur gear / rack |
| Quantity per Order | 1 piece |
Select the tooth count based on your required gear ratio and available shaft center distance. For a rack-and-pinion CNC drive, fewer teeth (10–14T) give faster linear travel per motor revolution; more teeth (20–25T) increase torque and reduce speed. Use the formula: center distance = (T1 + T2) × Module / 2 to verify mesh with a mating gear.
Pitch circle diameter (PCD) = Teeth × Module. For Mod 4: 10T = 40 mm, 12T = 48 mm, 15T = 60 mm, 18T = 72 mm, 20T = 80 mm, 24T = 96 mm, 25T = 100 mm. Intermediate values follow the same formula.
45# medium-carbon steel has a typical tensile strength of approximately 600–800 MPa in the normalized condition. It is well-suited for moderate-to-heavy torque transmission in CNC routers, 3D printer drives, and light industrial machinery. For very high-shock or continuous heavy-duty cycles, consider a hardened or alloy-steel alternative.
45# carbon steel has limited inherent corrosion resistance. For indoor or dry environments this is generally acceptable. If your application involves moisture, coolant, or outdoor exposure, apply a rust-inhibiting oil or grease to the gear teeth, or contact us to confirm whether a coated variant is available.
Yes — any gear or rack manufactured to the standard Mod 4 metric profile with a 20° pressure angle will mesh correctly with these spur gears. Verify that your existing component is labeled "Module 4" or "Mod 4" (not DP or CP pitch systems, which are not compatible).
Bore diameter varies by tooth count and is listed in the variant selector. Please check the variant options above before ordering to confirm the bore fits your motor or drive shaft. If you need a custom bore size, contact us to confirm availability.
Yes. These 4 Mod steel spur gears are commonly used in open-frame CNC gantry rack-and-pinion drives, 3D printer Z-axis reduction stages, and extruder gear trains where a robust metric pinion gear is required. Confirm the tooth count and bore diameter match your motor shaft and mating rack specification before purchasing.
