Test: Toothed Gearing - 1 - Mechanical Engineering MCQ

Base circle radius = Pitch circle radius x cos φ

Due to ease of standadization, manufacturing and low cost of production, the use of involute te e th has becom e universal by e n tire ly superseding the cycloidal teeth shape.

• Circular Pitch: Circular pitch is the distance between corresponding points on adjacent teeth measured along the pitch circle. It is one of the parameters used to specify the size of gears.



• Addendum Circle Diameter: The addendum circle diameter is the diameter of the circle that passes through the tips of the gear teeth. It is another parameter that can be used to determine the size of gears.



• Pitch Circle Diameter: The pitch circle diameter is an important parameter that is commonly used to specify the size of gears. It is the diameter of the pitch circle, which is an imaginary circle that represents the point of contact between two gears.



• Base Circle Diameter: The base circle diameter is the diameter of the base circle, which is an imaginary circle from which the involute curve of the gear tooth is generated. While it is not as commonly used as the pitch circle diameter, it is still a parameter that can be used to specify gear size.

Among these options, the pitch circle diameter is usually the parameter that is used to specify the size of gears. It is a key dimension that helps in determining the overall dimensions and performance characteristics of the gear system.

For continuous transmission of motion, at least one tooth of one wheel must be in contact with another tooth of second wheel. Therefore, the contact ratio must be greater than unity.

• Module: The module refers to the size of the gear teeth. Gears with the same module will have teeth that are compatible with each other.


• Pressure Angle: The pressure angle is the angle at which the gears come into contact with each other. Gears with the same pressure angle will mesh correctly.


• Addendums and Dedendums: Addendums are the extensions of gear teeth beyond the pitch circle, while dedendums are the recesses. Gears with the same addendums and dedendums will fit together properly.


• Thickness: The thickness of the gears also plays a role in their interchangeability. Gears with the same thickness will be able to mesh correctly.

Therefore, for gears to be interchangeable, they must have the same module, pressure angle, addendums, dedendums, and thickness. This ensures that the gears will fit together properly and function smoothly.

• Reduction Ratio: A reduction ratio of 50 means that the output speed is 1/50th of the input speed.


• Worm and Worm Wheel Gearing: This type of gearing is known for its high reduction ratios, making it ideal for applications where a significant speed reduction is required.


• Efficiency: Worm and worm wheel gears have high efficiency due to the sliding action between the teeth, resulting in minimal energy loss.


• Quiet Operation: This type of gearing operates quietly, making it suitable for applications where noise is a concern.


• Compact Design: Worm and worm wheel gears have a compact design, making them suitable for applications where space is limited.

Gear drives use no intermediate link or connector and transmit the motion by direct contact. Hence, gears ensure definite velocity ratio and provide a positive drive.

Pair of teeth is at pitch point have pure rolling action. At away other position, they have sliding as well as rolling velocity.