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When a slipping or undersized gear brings your build to a halt, you need a drop-in replacement that holds torque without play. Engineers, CNC builders, and robotics makers who demand repeatable mesh accuracy turn to module-standard spur gears machined from structural-grade steel — not zinc alloy or plastic that deforms under load.
These straight spur gears are machined from 45# medium-carbon steel, delivering a balance of hardness and machinability suited to moderate-to-high load transmission. The gear module is 2 (Mod 2), with tooth counts ranging from 12T to 60T (tooth counts available: 12–60T in single increments). Pitch diameter scales linearly with tooth count: PD = Module × Teeth, giving a range of approximately 24 mm (0.94 in) at 12T up to 120 mm (4.72 in) at 60T. Face width and bore diameter vary by specification — see variant options for exact dimensions.
Typical use cases include DC motor output shafts in tabletop CNC routers, gear-reduction stages in robotic arm joints, and speed-matching drives in conveyor or actuator assemblies. Long-tail applications: "Mod 2 spur gear for NEMA 23 motor", "45 steel transmission gear 20 tooth", "cylinder gear pair for DIY gearbox".
| Material | 45# Medium-Carbon Steel |
|---|---|
| Gear Module | 2 (Mod 2) |
| Tooth Count Range | 12T – 60T (see variant options) |
| Pitch Diameter | Module × Teeth (24 mm at 12T → 120 mm at 60T) |
| Tooth Profile | Involute, full-depth, straight (spur) |
| Pressure Angle | 20° |
| Face Width | See variant options |
| Bore Diameter | See variant options |
| Surface Finish | See variant options |
| Pack Quantity | 1 / 2 / 4 / 10 (see variant options) |
| Weight (per piece) | See variant options |
Determine your required gear ratio first: ratio = driven teeth ÷ driving teeth. For example, a 3:1 reduction pairing a 12T pinion with a 36T gear. Then confirm the center distance: C = (Module × (T1 + T2)) / 2. With Mod 2, a 12T + 36T pair gives C = (2 × 48) / 2 = 48 mm. Select tooth counts that satisfy both your ratio and your available center distance.
45# steel has a typical tensile strength of 600–800 MPa and yield strength around 355–490 MPa in normalized condition. Actual load capacity depends on tooth count, face width, speed, and lubrication. For high-cycle or shock-load applications, consider whether a heat-treated or alloy steel variant better suits your duty cycle.
45# carbon steel has limited inherent corrosion resistance. For outdoor, humid, or washdown environments, apply a compatible gear lubricant or grease, or consider a surface treatment such as zinc plating or black oxide after purchase. For fully corrosion-resistant requirements, a stainless steel gear may be more appropriate.
Yes — any two gears of the same module and pressure angle will mesh correctly. These gears use Mod 2 with a 20° pressure angle, which is the most common standard. Verify that your existing gear is also Mod 2 / 20° PA before ordering. Module is not interchangeable with DP (diametral pitch) used in inch-standard gears.
Use a digital caliper to measure the outer diameter of your shaft at the mounting point. The gear bore must be equal to or slightly larger than the shaft diameter to allow fitting (typically an H7 tolerance fit). If a keyway is required, confirm the keyway width and depth match your shaft's key. Bore and keyway dimensions for each tooth count are listed in the variant options.
If you are replacing a worn gear in an existing drive, a single gear is usually sufficient — provided the mating gear is still within tolerance. For new gearbox builds, ordering a matched pair (or full gear train) from the same batch ensures consistent tooth geometry and surface finish, which reduces break-in wear and noise. Use the Pack of 2 or Pack of 4 options for multi-gear assemblies.
For moderate-speed, moderate-load applications, an ISO VG 220 gear oil or a lithium-based grease (NLGI #2) applied to the tooth flanks is suitable. For high-speed or enclosed gearbox use, circulating gear oil is preferred. Avoid dry running — even brief unlubricated operation accelerates tooth surface wear on carbon steel gears.
