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When a loose or undersized gear causes backlash, missed steps, or premature wear in your CNC router, 3D printer, or robotic arm, the root cause is almost always a mismatch between the gear module and the shaft bore. These Mod 1 45# steel pinion spur gears are engineered for makers, automation engineers, and machine builders who need a drop-in replacement or a reliable upgrade for their drive train.
Each gear is machined from 45# medium-carbon steel, offering a balance of hardness and machinability. The module is 1 (1M), with tooth counts ranging from 10 T to 60 T and bore diameters from 4 mm (0.16 in) to 25 mm (0.98 in). Step variants add a precision-turned shoulder — ranging from 14 mm to 45 mm — that seats directly against a motor face or bearing housing for axial alignment. Overall gear width is typically 10–15 mm depending on tooth count.
Typical use cases include stepper and servo motor pinion drives in CNC milling machines, rack-and-pinion linear actuators, gearbox reduction stages in robotics, and DIY automation projects requiring a standard Mod 1 spur gear interface.
Machined from 45# steel for a solid combination of surface hardness and core toughness — resisting tooth wear under continuous cyclic loading.
True Mod 1 tooth profile ensures interchangeability with any standard 1M rack, pinion, or mating gear in your drivetrain without custom modification.
Select from 10 to 60 teeth to dial in your gear ratio precisely — from high-speed, low-torque pinion drives to slower, higher-torque reduction stages.
Available in bore sizes from 4 mm to 25 mm to fit a wide range of motor shaft diameters, including common NEMA stepper and servo motor shafts.
Step variants (14 mm – 45 mm step diameter) provide a machined shoulder for axial positioning against motor faces or bearing housings, eliminating the need for separate spacers.
CNC-hobbed tooth flanks maintain consistent mesh with mating Mod 1 gears, keeping positional error low in closed-loop CNC and robotics applications.
| Module | 1 (Mod 1 / 1M) |
|---|---|
| Material | 45# Medium-Carbon Steel |
| Tooth Count | 10 T – 60 T (see variant options) |
| Bore Diameter | 4 mm – 25 mm (see variant options) |
| Step Diameter | 14 mm – 45 mm, or No Step (see variant options) |
| Pressure Angle | 20° |
| Gear Face Width | Typically 10–15 mm (varies by tooth count) |
| Surface Finish | Machined, natural steel |
| Quantity | 1 piece per order |
The gear ratio is determined by dividing the driven gear tooth count by the driving (pinion) gear tooth count. For a 3:1 reduction, pair a 15 T pinion with a 45 T gear. Lower tooth counts (10–15 T) suit high-speed, low-torque pinion drives; higher counts (40–60 T) are used where more torque multiplication is needed.
Measure your motor shaft diameter with calipers before ordering. Common NEMA 17 stepper shafts are 5 mm; NEMA 23 shafts are typically 6.35 mm or 8 mm; NEMA 34 shafts are often 12 mm or 14 mm. Select the bore that matches your shaft exactly — a loose bore will cause runout and backlash.
The step is a precision-turned shoulder on the back face of the gear that registers against a motor face plate or bearing housing for axial alignment. If your motor mount has a pilot bore or register, choose a step variant whose step diameter matches. If you are mounting the gear with a set screw or keyway only, the "No steps" variant is sufficient.
45# medium-carbon steel provides a tensile strength of approximately 600–800 MPa in the normalized condition, which is adequate for most light-to-medium duty CNC routers, 3D printer extruder drives, and robotic joint actuators. For heavy-duty industrial gearboxes or high-shock loads, consider case-hardened or alloy steel alternatives.
45# steel is not stainless and will oxidize if left unprotected in humid environments. Apply a light coat of machine oil or grease to the tooth flanks and bore during installation and during storage. For outdoor or wet environments, consider a zinc-plated or stainless alternative.
Yes. Module 1 is an internationally standardized tooth profile (ISO 54 / DIN 780). Any Mod 1 gear, rack, or pinion from any supplier will mesh correctly with these gears, provided the pressure angle is also 20°, which is the global standard for Mod 1 components.
The bore is a plain (smooth) bore. You will need to drill and tap a set screw hole, or use a shaft collar, to secure the gear to your shaft. For high-torque applications, a flat on the shaft combined with a set screw is recommended to prevent slipping.
