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When your motion-control build demands smooth, low-noise power transfer, a mismatched or poorly machined gear becomes the weakest link in the entire drivetrain. These left-spiral helical gears are engineered for makers, automation integrators, and small-batch manufacturers who need reliable stepped transmission components without sourcing from industrial distributors.
Each gear is machined from 45# medium-carbon steel and features a 45° left-hand helix angle with a precision-cut step bore. Available in Modulus 2.5 and Modulus 3, with tooth counts ranging from 10 to 30 teeth. Outer diameter varies by modulus and tooth count — typically 27.5 mm to 96 mm (approx. 1.08 in to 3.78 in). Face width is typically 20–30 mm (approx. 0.79–1.18 in).
Typical use cases include CNC router Z-axis drives, stepper and servo motor gearboxes, robotic joint transmission assemblies, and custom left-hand helical gear pair replacements in industrial equipment.
Machined from 45# steel for a balance of machinability, tensile strength (typically 600–800 MPa), and wear resistance suited to continuous motor transmission loads.
The 45° left-spiral geometry distributes tooth load across a wider contact area than spur gears, reducing vibration and operating noise in high-speed motor drives.
Choose Modulus 2.5 for compact, lighter-duty assemblies or Modulus 3 for higher torque applications. Both series share the same 45° helix for easy pairing.
The stepped bore profile allows secure shaft seating and simplified axial positioning without additional spacers, saving assembly time in tight gearbox housings.
Eight tooth-count variants per modulus let you dial in your gear ratio precisely. Pair with a matching right-spiral gear of the same modulus to achieve ratios from 1:1 to 3:1 and beyond.
Gear flanks are finished to reduce surface roughness, supporting consistent lubrication film retention and extending service intervals in enclosed gearbox environments.
| Material | 45# Medium-Carbon Steel |
|---|---|
| Helix Angle | 45° |
| Spiral Direction | Left Spiral (Left-Hand) |
| Available Modulus | 2.5 / 3 |
| Tooth Count Options | 10, 12, 13, 15, 18, 20, 26, 30 Teeth |
| Bore Type | Stepped Bore |
| Outer Diameter | See variant options |
| Face Width | Typically 20–30 mm (0.79–1.18 in) |
| Bore Diameter | See variant options |
| Surface Finish | Precision-machined, reduced surface roughness |
| Hardness | See variant options |
| Weight | See variant options |
| Quantity | 1 PCS per order (multi-pack options available) |
Modulus 2.5 gears are smaller and lighter, making them suitable for compact assemblies and lighter torque loads. Modulus 3 gears have larger teeth and a higher load-carrying capacity, making them the better choice for higher-torque motor drives and heavier-duty gearboxes. Both share the same 45° left-hand helix angle, so they can be paired with matching right-spiral gears of the same modulus.
Left-spiral helical gears mesh with right-spiral helical gears of the same modulus and helix angle (45°). The mating gear must have the same modulus (2.5 or 3) and a matching tooth profile. Confirm the center distance and gear ratio you need, then select the appropriate tooth count for the driven gear.
Bore diameter and keyway dimensions vary by tooth count and modulus. Please refer to the variant detail images or contact us to confirm the exact bore size before ordering to ensure compatibility with your shaft.
45# medium-carbon steel offers a tensile strength typically in the range of 600–800 MPa and is widely used in general-purpose gear manufacturing. It is suitable for moderate-speed, moderate-torque motor transmission applications. For very high-load or high-speed environments, consider whether a heat-treated or alloy steel variant would better suit your requirements.
45# steel has moderate corrosion resistance. For applications in humid or mildly corrosive environments, we recommend applying a light machine oil or grease coating during installation and maintaining regular lubrication. For highly corrosive environments, a stainless steel or coated gear may be more appropriate.
Yes. These left-spiral helical gears are well-suited for CNC router axis drives, stepper motor gearboxes, and similar precision motion-control applications where smooth, low-backlash power transfer is important. Ensure the modulus, tooth count, and bore diameter match your existing drivetrain components.
Gear ratio is determined by dividing the tooth count of the driven gear by the tooth count of the driving gear. For example, pairing a 10-tooth driving gear with a 20-tooth driven gear gives a 2:1 reduction ratio. Select your tooth counts based on the input/output speed ratio your application requires.
