Machine Design Elements Board Practice Exam

When the width of a tooth space exceeds the thickness of each of the engaging teeth on the pitch circle, this phenomenon is known as backlash. Backlash occurs because there is a gap or space created between the engaging parts of gears, which can affect the precision with which they transfer motion and force. It can result in a delay in the engagement of teeth, leading to potential issues in the performance of mechanical systems.

Understanding backlash is crucial in machine design, particularly in applications where accurate positioning and consistent force transfer are critical. For instance, in high-precision machinery, excessive backlash can lead to increased wear, noise, and inefficiencies in operation. It is often a consideration when designing gear systems, as proper adjustment or compensation for backlash is necessary to achieve desired operational characteristics.

In contrast, terms like allowance, bottom land, and top land refer to other aspects of gear design or fitting tolerances, but they do not specifically address the concept of engaging tooth space width relative to tooth thickness in the context of motion transfer.