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When a mismatched or undersized gear causes slippage, noise, or premature wear in your motor drive or CNC build, the root cause is almost always an incorrect module or bore size. Engineers, robotics builders, and machine tool hobbyists who need a dependable, drop-in spur pinion gear will find this Mod 1.5 steel 45# gear a straightforward solution — available in 12 to 50 teeth and bore sizes from 5 mm to 25 mm to match a wide range of motor shafts.
Each gear is machined from 45# medium-carbon steel in an unquenched (non-heat-treated) condition, offering good machinability for secondary operations such as keyway cutting or set-screw drilling. The module is 1.5 (metric), with a 20° pressure angle conforming to standard spur gear geometry. Tooth height is 12 mm across all variants. Outer diameter scales with tooth count — ranging from approximately 21 mm (0.83 in) for the 12T up to approximately 78 mm (3.07 in) for the 50T.
Typical use cases include DC motor pinion replacement in CNC router Z-axis drives, stepper motor output gears in 3D printer extruder assemblies, and small gearbox reduction stages in robotic arm joints — all applications where a standard Mod 1.5 metric spur pinion gear with a precise bore fit is required.
Machined from 45# carbon steel for a solid balance of strength and machinability — suitable for moderate-load motor and drive applications.
Eight tooth-count options let you dial in the exact gear ratio needed for your motor drive, CNC axis, or robotic joint without custom machining.
Thirteen bore sizes cover the most common motor shaft diameters, including the 6.35 mm (1/4 in) size popular in North American stepper motors.
Conforms to ISO metric spur gear standards, ensuring direct interchangeability with any mating Mod 1.5 gear from any source.
The unquenched (non-hardened) condition means you can drill set-screw holes, cut keyways, or turn the bore to a custom fit without specialist tooling.
Consistent face width simplifies stack-up calculations and allows mixing of different tooth-count gears on the same shaft centerline.
| Module | 1.5 (Metric) |
|---|---|
| Pressure Angle | 20° |
| Tooth Count Options | 12T / 15T / 20T / 25T / 30T / 35T / 40T / 50T |
| Bore Options | 5 / 6 / 6.35 / 7 / 8 / 10 / 12 / 14 / 15 / 16 / 17 / 20 / 25 mm |
| Tooth Height (Face Width) | 12 mm (0.47 in) |
| Outer Diameter Range | Approx. 21 mm – 78 mm (0.83 in – 3.07 in), varies by tooth count |
| Material | 45# Medium-Carbon Steel |
| Heat Treatment | Unquenched (non-hardened) |
| Gear Type | Spur (straight tooth) |
| Hub / Set Screw | See variant options |
| Weight | See variant options |
Select the tooth count based on your required gear ratio. Divide the driven gear's tooth count by the pinion's tooth count to get the reduction ratio. For example, pairing a 15T pinion with a 45T gear gives a 3:1 reduction. If you are replacing an existing gear, match the tooth count exactly.
Measure your motor shaft diameter with a caliper. Common sizes include 5 mm and 6 mm for small DC motors, 6.35 mm (1/4 in) for NEMA stepper motors, and 8–20 mm for larger servo or gearmotor shafts. Choose the bore that matches your shaft — a bore that is too large will require a bushing or set-screw fix.
Yes. Any two spur gears with the same module (1.5) and the same pressure angle (20°) will mesh correctly regardless of brand or tooth count. Verify both the module and pressure angle of your existing gear before ordering.
Yes. Because these gears are supplied in an unquenched (non-hardened) condition, the steel is soft enough to machine with standard HSS tooling. You can drill radial set-screw holes or mill a keyway without needing carbide tooling or EDM.
45# carbon steel has a tensile strength of approximately 600–700 MPa in the unquenched condition. For moderate-load motor pinion applications — such as CNC axis drives, 3D printer extruders, and light robotic joints — this is typically sufficient. For high-shock or continuous heavy-load applications, consider a quenched-and-tempered or case-hardened gear instead.
45# carbon steel has limited inherent corrosion resistance. For indoor or dry environments this is generally acceptable with light lubrication. For humid, wet, or outdoor environments, apply a rust-inhibiting grease or consider a stainless steel or zinc-plated alternative.
A light machine oil or gear grease applied to the tooth flanks is recommended for most applications. For enclosed gearboxes, an ISO VG 68–150 gear oil is suitable. Avoid dry running, which accelerates tooth wear on unquenched steel gears.
