Gear types
Bevel gears
These gears have teeth cut on a cone instead of a cylinder blank. They are used in pairs to transmit rotary motion and torque where the bevel gear shafts are at right angles (90 degrees) to each other. An example of two bevel gears are shown below.
Bevel gears
Crossed helical gears
These gears also transmit rotary motion and torque through a right angle. The teeth of a helical gear are inclined at an angle to the axis of rotation of the gear.
The diagram below shows how the axis of rotation of two helical gears are crossed at right angles. Helical gears are smoother running than spur gears and are more suitable for rotation at high velocities. An example of two crossed helical gears are shown below.
Crossed helical gears
Worm and worm wheel
A gear which has one tooth is called a worm. The tooth is in the form of a screw thread. A worm wheel meshes with the worm. The worm wheel is a helical gear with teeth inclined so that they can engage with the thread – like worm. Like the crossed helical gears, the worm and worm wheel transmit torque and rotary motion through a right angle. The worm always drives the worm wheel and never the other way round. The mechanism locks if the worm wheel tries to drive the worm. Worm mechanisms are very quiet running. An example of a worm and worm wheel is shown on the right hand side below. An application of the worm and worm wheel used to open lock gates is shown on the left hand side below.
Worm and worm wheel
application
The helical gear
This gear is used for applications that require very quiet and smooth running, at high rotational velocities.
Parallel helical gears have their teeth inclined at a small angle to their axis of rotation. Each tooth is part of a spiral or helix. The helical gears shown below have splines cut in their center holes. The gears can move along a splined (grooved) shaft, although they rotate with the shaft. An example of a helical gear is shown below.
Double helical gears give an efficient transfer of torque and smooth motion at very high rotational velocities. An example of a double helical gear is shown below.
Single helical gear
Double helical gear
Spiral bevel gears
When it is necessary to transmit quietly and smoothly a large torque through a right angle at high velocities, spiral bevel gears can be used. Spiral bevel gears have teeth cut in a helix spiral form on the surface of a cone. They are quieter running than straight bevel gears and have a longer life. Spiral bevel gears are used in motorcar rear axle gearboxes. An example of spiral bevel gears are shown below.
Spiral bevel gears
Face cut gears
It is possible to cut gear teeth on the face of a gear wheel. Also, gear teeth can be cut on the inside of a gear ring an example of which is shown in the top figure below. Internal gears have better load carrying capacity than external spur gears. They are safer in use because the teeth are guarded. An example of an external face cut gear is shown below.
Internal face cut gear
External face cut gear
Bevel gears
These gears have teeth cut on a cone instead of a cylinder blank. They are used in pairs to transmit rotary motion and torque where the bevel gear shafts are at right angles (90 degrees) to each other. An example of two bevel gears are shown below.
Bevel gears
Crossed helical gears
These gears also transmit rotary motion and torque through a right angle. The teeth of a helical gear are inclined at an angle to the axis of rotation of the gear.
The diagram below shows how the axis of rotation of two helical gears are crossed at right angles. Helical gears are smoother running than spur gears and are more suitable for rotation at high velocities. An example of two crossed helical gears are shown below.
Crossed helical gears
Worm and worm wheel
A gear which has one tooth is called a worm. The tooth is in the form of a screw thread. A worm wheel meshes with the worm. The worm wheel is a helical gear with teeth inclined so that they can engage with the thread – like worm. Like the crossed helical gears, the worm and worm wheel transmit torque and rotary motion through a right angle. The worm always drives the worm wheel and never the other way round. The mechanism locks if the worm wheel tries to drive the worm. Worm mechanisms are very quiet running. An example of a worm and worm wheel is shown on the right hand side below. An application of the worm and worm wheel used to open lock gates is shown on the left hand side below.
Worm and worm wheel
application
The helical gear
This gear is used for applications that require very quiet and smooth running, at high rotational velocities.
Parallel helical gears have their teeth inclined at a small angle to their axis of rotation. Each tooth is part of a spiral or helix. The helical gears shown below have splines cut in their center holes. The gears can move along a splined (grooved) shaft, although they rotate with the shaft. An example of a helical gear is shown below.
Double helical gears give an efficient transfer of torque and smooth motion at very high rotational velocities. An example of a double helical gear is shown below.
Single helical gear
Double helical gear
Spiral bevel gears
When it is necessary to transmit quietly and smoothly a large torque through a right angle at high velocities, spiral bevel gears can be used. Spiral bevel gears have teeth cut in a helix spiral form on the surface of a cone. They are quieter running than straight bevel gears and have a longer life. Spiral bevel gears are used in motorcar rear axle gearboxes. An example of spiral bevel gears are shown below.
Spiral bevel gears
Face cut gears
It is possible to cut gear teeth on the face of a gear wheel. Also, gear teeth can be cut on the inside of a gear ring an example of which is shown in the top figure below. Internal gears have better load carrying capacity than external spur gears. They are safer in use because the teeth are guarded. An example of an external face cut gear is shown below.
Internal face cut gear
External face cut gear
Distributed by Abu-Iyad
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