In the world of machinery, transmitting power efficiently and smoothly is paramount. However, traditional spur gears often fall short, leading to vibration, noise, and reduced load capacity. This is where herringbone gears shine.

With their unique double helical design, herringbone gears offer a game-changing solution. In this comprehensive guide, we’ll dive deep into the intricacies of herringbone gears, exploring their design principles, material choices, and where they fit across industrial drives. We’ll also compare them to other gear types, highlighting their superior performance.

What Is a Herringbone Gear

A herringbone gear is a type of double helical gear that consists of two helical gears mounted side-by-side on the same shaft, with the teeth set in a V-shape pointing outward. The two sets of teeth are angled in opposite directions, typically at 30-45 degrees to the shaft axis.

The “herringbone” name comes from the zig-zag tooth pattern that resembles the skeleton of a herring fish. The interlocking V-shaped teeth maintain contact on both sides, balancing the axial forces within the gear mesh. This self-centering action eliminates the need for thrust bearings to support the gears.

Herringbone gears are used in a wide range of power transmission applications, from heavy machinery and vehicles to precision instruments and robotics. Their unique properties make them an excellent choice for high-load, high-speed applications that require smooth, efficient power transfer with minimal noise and vibration.

Design of Herringbone Gears

Helix Angle

The helix angle is the angle between the tooth face and the gear axis. In herringbone gears, the two gear halves have equal but opposite helix angles, typically ranging from 30 to 45 degrees. Higher helix angles provide smoother operation and greater load capacity but also increase axial forces and manufacturing complexity.

Pressure Angle

The pressure angle is the angle between the tooth profile and a line perpendicular to the pitch circle. Standard pressure angles for herringbone gears are 14.5, 20, and 25 degrees, with 20 degrees being the most common. Higher pressure angles increase the gear’s strength and load capacity but may cause greater noise and wear.

Module and Diametral Pitch

The module (metric) or diametral pitch (imperial) determines the size of the gear teeth relative to the pitch diameter. A larger module or smaller diametral pitch results in stronger, wider teeth but also increases the overall gear size and weight.

Materials of Herringbone Gears

· Steel: The most widely used material for herringbone gears, offering high strength, toughness, and wear resistance. Various grades and heat treatments can be applied to optimize the gear properties.

· Cast iron: A lower-cost alternative to steel, suitable for moderate loads and speeds. Gray and ductile cast irons are commonly used, with graphite flakes or nodules providing lubrication and damping.

· Brass and bronze: Non-ferrous alloys used for gears requiring corrosion resistance or low friction. They have good machinability but lower strength compared to steel.

· Plastics: Polymers such as nylon, acetal, and PEEK can be used for lightweight, low-load applications. They offer low noise, self-lubrication, and resistance to corrosion and chemicals.

· Sintered metals: Powder metallurgy can produce near-net-shape herringbone gears with complex geometries. Sintered steels and alloys have good strength and wear resistance but may have lower toughness than wrought materials.

Whichever material is chosen, herringbone gears are unusually demanding to cut. A true herringbone has no central relief groove, so a standard hobbing cutter would run into the far half of the gear, and a dedicated shaper is needed instead.

Grinding the flanks afterward is nearly inaccessible, so cutting accuracy has to be achieved on the first pass — a constraint explored in how double helical and herringbone gears are manufactured.

Applications of Herringbone Gears

Industrial Machinery

Herringbone gears are widely used in heavy-duty industrial equipment such as compressors, pumps, blowers, and machine tools. Their high load capacity, smooth operation, and compact design make them suitable for power transmission in constrained spaces and demanding environments.

In mining and steel applications, the same self-centering behavior helps them carry the shock loads of crushers, grinders, rolling mills, and heavy conveyor drives without the thrust-bearing penalty that single-helical gears impose.

High-Torque and Turbine Drives

Herringbone gears are the standard choice for the highest-torque industrial drives. Rolling mills, crane and hoist gearing, bulk-handling conveyors, and the large gear units that step down industrial steam turbines and process compressors all put continuous high torque and repeated shock loading through the mesh.

The opposing helixes cancel each other’s axial thrust internally, so these gears carry that load without a substantial thrust bearing to absorb end forces. A single-helical gear in the same duty would need one.

The long, inclined tooth length gives high load-carrying capacity, and the absence of net axial thrust extends drivetrain and bearing life under sustained duty. That mix of capacity and durability is what heavy-industrial drives depend on.

Robotics and Automation

In robotic and automated systems, herringbone gears are used for precise motion control and power transmission. Their low backlash, high stiffness, and smooth operation enable accurate positioning and repeatable movements in robotic arms, grippers, and joints.

Advantages and Disadvantages of Herringbone Gears

The defining advantage of a herringbone gear is that its two opposing helixes generate equal and opposite axial forces. These cancel out within the mesh, so no separate thrust bearing is needed to react end loading.

The long, inclined teeth let the gear transmit high torques. Because more than two teeth stay enmeshed at any moment, engagement is also smoother and quieter than a spur gear can manage.

Those gains come at a cost. Herringbone gears are harder to manufacture and more expensive than equivalent spur or helical gears.

They cannot be cut on a simple hobbing machine, since the cutter would run into the far half of the gear. Post-cut grinding is nearly impossible too, because the tooth flanks are so difficult to reach. That is why a double helical gear, whose central relief groove lets the tool exit, is often cheaper to produce and chosen in its place.

Comparison with Other Types of Gears