Red Seal Machinist Practice Exam

How is the tolerance of a part defined?

1. The required finishing process for the part

2. The time taken to manufacture the part

3. The permissible limits of variation in a dimension

4. The strength of the material used

The correct answer is: The permissible limits of variation in a dimension

The tolerance of a part is defined as the permissible limits of variation in a dimension. This concept is crucial in machining and manufacturing as it establishes the acceptable range within which a dimension can deviate from the nominal value. Tolerances ensure that parts will fit together properly, operate effectively, and meet design specifications despite the inherent variations that can occur during the manufacturing process. In practice, establishing tolerances allows engineers and machinists to balance precision and cost. A tighter tolerance often requires more advanced machines, more time for setup and machining, and may lead to a higher scrap rate, thus increasing production costs. Conversely, looser tolerances might lead to parts that don’t fit correctly and thus require further finishing work or adjustments. Regarding the other choices, the required finishing process for the part relates to the methods employed to achieve the desired surface finish or dimensional accuracy, rather than defining the limits of variation. The time taken to manufacture the part is a factor in production efficiency but does not pertain to dimensional accuracy or variability. The strength of the material used is concerned with the material's ability to withstand loads and stresses rather than with dimensional tolerances. Thus, the definition of tolerance focuses specifically on the acceptable range of variation in a part's dimensions.