Bevel Gear

Bevel Gears are gears which instead of being a cylinder with straight teeth (like a spur gear), it is formed into a cone (essentially a tapered spur gear). The teeth at the bottom of the bevel (the large end) taper down to smaller gear teeth at the top of the bevel gear (small end). Bevel gears usually run on shafts that are 90 degrees to one another whose axis intersect at some point above the gear teeth. Bevel gears can also be designed on most shaft angle less than or greater than 90 degrees as required.

Bevel Gear

Bevel Gear Design

Around the perimeter of the disk’s face are the teeth – elevated segments of equal length that protrude in the Z-axis and are shaped like straight lines or waves.

Depending on the gear’s configuration, the teeth may be higher toward the middle and lower toward the gear’s perimeter; if viewed from the side, the gear would look like a ridged, truncated cone.

A bevel gear’s axis extends from its middle in the Z-axis. That axis intersects with the axis of at least one other bevel gear, and it is this axial intersection that distinguishes bevel gears from different gear varieties.

Bevel gears range in their possible tooth shape, pitch surface, pitch angle, and other properties. This quality of customizability makes bevel gears attractive to professionals in all kinds of industries. While bevel gears are most often configured at a 90° angle, they can also be designed to work at other tips. Four bevel gears in a square make a differential gear, transmitting power to two axles spinning at different speeds, such as in an automobile.

Bevel gears are industrial gears that are characterized by gear axis intersection. A gear is a machined wheel, the circumference or face of which features specially shaped teeth. When those teeth interact with similarly shaped teeth on other gears, torque can be transferred between the two gears as they turn.

What is a Straight Bevel Gears?

This is the simplest form of a bevel gear. The teeth are in a straight line which intersects at the axis of the gear when extended. The teeth are tapered in thickness making the outer or heel part of the tooth larger than the inner part or toe. Straight bevel gears have instantaneous lines of contact, permitting more tolerance in mounting. A downside in using this type is the vibration and noise. This limits straight bevel gears to low-speed and static loading applications. Common application of straight bevel gears are differential systems in automotive vehicles.


  • Axial force is only generated in the direction of the opposing gears
  • Don’t worry about left-hand and right-hand gear pairings


  • Tooth surface grinding is not possible, so high-precision gears cannot be produced
  • Less strength than spiral bevel gears

Materials Used in Bevel Gears

Important considerations in selecting a bevel gear are power transmission requirements, design life, the possibility of exposure to corrosive elements, and noise and heat generation. All of these factors determine the success of the gear in a particular application.
Bevel gears are typically constructed from metal or plastic. Bevel gears can be made of various types of materials with differing properties, such as aluminum, bronze, cast iron, brass, steel, hardened steel, and stainless steel. Plastic materials used to make bevel gears include Delrin, nylon, and polycarbonate.

Types of Bevel Gears

There are different types of bevel gears according to their tooth profile and orientation. The more complicated types such as the spiral and hypoid bevel gears resulted from further development of manufacturing processes such as CNC machining.

Spiral Bevel Gears

This is the most complex form of bevel gears. The teeth of spiral gears are curved and oblique, in contrast to the teeth orientation of straight bevel gears. This results in more overlap between teeth which promotes gradual engagement and disengagement upon tooth contact. This improved smoothness results in minimal vibration and noise produced during operation.

Hypoid Bevel Gears

This is a special type of bevel gears where the axes of the shafts are not intersecting nor parallel. The distance between the two gear axes is called the offset. The teeth of hypoid bevel gears are helical, similar to spiral bevel gears. A hypoid bevel gear designed with no offset is simply a spiral bevel gear. Manufacture and shaping of hypoid types are similar to spiral bevel gears.

Miter Bevel Gears

This is a type of bevel gear with a gear ratio of 1:1, meaning the driver and driven gears have the same number of teeth. The purpose of this type is limited to changing the axis of rotation. It does not produce any mechanical advantage. Usually, miter gears have axes that intersect perpendicularly. In some assemblies, the shafts are aligned to cross at any angle. These are known as angular miter bevel gears. Shaft angles of angular miter bevel gears can range from 45° to 120°. Miter bevel gear teeth cuts can be straight, spiral, or Zero.

Bevel Gears

Main Applications of Bevel Gears

The bevel gear has many different applications such as marine applications, locomotives, printing presses, automobiles, cooling towers, steel plants, power plants, railway track inspection machines, etc.

(1) Bevel gears are employed in differential drives, which can transfer energy to two axles rotating at different velocities, such as those on a cornering automobile.
(2) Bevel gears are used as the basic function for a hand drill. As the handle of the drill is rotated in a vertical form, the bevel gears modify the spinning of the chuck to a horizontal motion.
(3) The gears in a bevel gear planer allow for minor regulation during assembly and permit some displacement based on the deflection under operating powers without concentrating the force on the end part of the tooth.
(4) Spiral bevel gears are essential parts of rotorcraft drive arrangements.

The Advantages of Bevel Gears

The biggest advantage of bevel gears is their ability to change mechanical advantage. They are suitable for use in situations requiring high load capacity, but smooth and quiet gear operations. The uneven number of teeth in the mating faces of a bevel gear can help alter the rotational drive and torque, either by increasing speed and decreasing torque or by decreasing speed and increasing torque. Miter gears cannot be used to change speed. However, the 90° intersecting axes of miter gears result in highly efficient operations, and hence these gears are used in applications that demand high efficiency.

Spiral bevel gears and hypoid bevel gears are two types of spiral bevel gears. Furthermore, unlike worm gearboxes, self-locking is not possible with bevel gears. Bevel gearboxes are a low-cost alternative to hypoid gearboxes when a right-angle transmission is required. However, due to the lack of self-locking, bevel gearboxes cannot achieve high efficiency like hypoid gearboxes during low speed operation.

– Are bevel gears self-locking?

Spiral bevel gears are often used instead of straight bevel gears when space is at a premium or when aesthetics are important. For example, they are common in steering wheels, where their compound shape provides good coverage of the wheel while still allowing room for brake lights and other accessories. Another use for spiral bevel gears is as reduction gears in transmissions.

– Which bevel gear is most commonly used?

A spiral bevel gear is a helical-toothed bevel gear. The most common application is in a car differential, where the direction of drive from the drive shaft must be rotated 90 degrees to drive the wheels. A spiral bevel gear system is more efficient than a standard bevel gear system because it does not require as much space for its size, and it can transmit more power with less friction.

– Where are spiral bevel gears used?

Bevel gears contain three types of spaces: internal, external, and semi-external. The number and size of these spaces determine how much power can be transmitted from one gear to the next. This is the only type of gear allowed in water mills. External gears have diameters that are equal on both sides of their ring frames. Semi-external gears are halfway between internal and external gears.

– What is the function of the bevel gear in the water mill?

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