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When your drivetrain demands a precise 90° direction change without the noise and vibration of straight-cut bevel gears, engineers and makers alike turn to spiral bevel gears. Whether you are building a CNC axis, a robotic joint, or a custom gearbox, mismatched or poorly paired bevel gears cause backlash, premature wear, and frustrating alignment headaches. This listing solves that problem by supplying a factory-matched left-spiral and right-spiral pair, guaranteed to mesh at the correct 90° angle with a 1:1 ratio right out of the box.
Each set consists of two spiral bevel gears machined from alloy steel, featuring a helical tooth profile for gradual engagement and reduced operating noise. Available in 1.5 modulus and 2 modulus configurations, with tooth counts of 20T, 25T, and 30T. Bore diameters range from 10 mm (0.39 in) to 25 mm (0.98 in), and each bore is precision-cut with a standard keyway — 4×2 mm, 5×2.5 mm, 6×3 mm, or 8×3.5 mm depending on the bore size — for positive, slip-free shaft engagement.
Typical applications include 90° right-angle gearboxes for CNC router Z-axes, robotic arm wrist joints requiring compact torque redirection, custom agricultural or industrial machinery where spiral bevel gear sets replace worn OEM components, and DIY power transmission projects demanding low-noise, high-efficiency direction change at a 1:1 speed ratio.
| Gear Type | Spiral Bevel Gear (Matched Pair) |
|---|---|
| Spiral Direction | Left Spiral + Right Spiral (1 set) |
| Shaft Angle | 90° |
| Gear Ratio | 1:1 |
| Available Modulus | 1.5 / 2 |
| Available Tooth Count | 20T / 25T / 30T |
| Bore Diameter Range | 10 mm – 25 mm (0.39 in – 0.98 in) |
| Keyway Dimensions | 4×2 mm / 5×2.5 mm / 6×3 mm / 8×3.5 mm (varies by bore) |
| Material | Alloy Steel |
| Surface Finish | Natural Metallic (uncoated) |
| Tooth Profile | Spiral (Helical Bevel) |
| Weight | See variant options |
Modulus determines the physical size of each tooth — a higher modulus means larger, stronger teeth capable of transmitting more torque. Choose 1.5 modulus for lighter-duty or space-constrained applications (e.g., small robotics, hobby CNC), and 2 modulus for heavier loads or larger shaft diameters. Tooth count affects the outer diameter of the gear: 20T produces the most compact gear, while 30T gives a larger pitch circle and smoother load distribution. Match the modulus to your existing gearbox design or calculate based on your torque and speed requirements.
Select the bore diameter that matches your shaft diameter exactly. The keyway dimensions are determined by the bore size: 10–12 mm bores use a 4×2 mm keyway, 14–16 mm bores use 5×2.5 mm, 18–20 mm bores use 6×3 mm, and 22–25 mm bores use 8×3.5 mm. These follow standard DIN 6885 keyway dimensions. If your shaft has a pre-cut keyway, verify the width and depth match before ordering.
The two gears in each set are mirror images of each other — one is left-hand spiral and the other is right-hand spiral. They share the same modulus, tooth count, and outer dimensions, but their tooth helix directions are opposite so they mesh correctly at 90°. Do not attempt to pair two left-spiral or two right-spiral gears, as they will not mesh properly.
These gears are machined from alloy steel, which provides significantly higher tensile and shear strength compared to carbon steel or cast iron alternatives. The spiral tooth profile distributes load across multiple teeth simultaneously, further increasing load capacity versus straight-cut bevel gears of the same modulus. Exact torque ratings depend on operating speed, lubrication, and mounting precision. For critical load calculations, consult standard gear engineering references using the modulus, tooth count, face width, and material properties.
Yes, spiral bevel gears require proper lubrication for optimal performance and longevity. For enclosed gearboxes, use a gear oil with viscosity appropriate for your operating speed and load (ISO VG 150–220 is common for moderate-speed applications). For open or semi-open installations, apply a consistent grease such as NLGI #2 lithium-complex grease to the tooth flanks. Inspect and replenish lubrication at regular intervals based on your duty cycle.
Yes, provided the replacement gears match the original modulus, tooth count, bore diameter, and keyway dimensions of the OEM parts. Measure the original gears carefully — modulus can be calculated from the outer diameter and tooth count (OD = modulus × (tooth count + 2) for standard gears). If the original gears are imperial (diametral pitch), note that metric modulus and imperial DP gears are not interchangeable even if they appear similar in size.
Straight-cut bevel gears have teeth that run straight across the face of the gear cone, causing all tooth contact to occur simultaneously — this produces more noise and vibration, especially at higher speeds. Spiral bevel gears have curved, helical teeth that engage gradually along the tooth length, spreading the load over a larger contact area. The result is quieter operation, higher load capacity for the same gear size, and smoother torque transmission. Spiral bevel gears are the preferred choice for applications where noise, vibration, or continuous-duty performance is a concern.
