29-10-2014, 12:29 PM
Abstracts: Gears are toothed wheels used for transmitting motion of power. If the teeth are cut parallel to the axis on a cylindrical surface, then they are called spur gears and if the tooth are inclined to the axis with a definite inclination they are called helical gears. These are used for transmitting motion with their rotational axes commonly used in machine tools. The profile can be modified to get the required properties. Then the gears are said to be corrected. Changing the distance slightly will only give rise to a different working pressure angle without affecting the uniformity of motion transmission. In a helical gear pair the hands of helix are always opposite. The teeth of spur and helical gears may fail due to a bad design, weak material, deviations from normal service or improper hear treatment. The typical failures are breaking off, pitting, seizure, surface abrasion, etc. Each gear pair is to be checked for safety in bending and wear load acting on them.