What do limit dimensions indicate?

• A. An exact size only
• B. Upper and lower limits
• C. The necessary tolerance only
• D. Size variations only

Answer: (B)

Limit dimensions are used to specify a range of permissible sizes for a feature, indicating both an upper limit and a lower limit. This means that the feature can vary between these two specified dimensions but must not exceed either boundary. This method provides flexibility in manufacturing while ensuring that the part will function correctly within its assembly and meet design intent.

Using limit dimensions helps to define acceptable variations in the size of the part, allowing for tolerances that reflect the manufacturing processes that may introduce variability. This is crucial in engineering design, as it ensures that while the part can differ within specified limits, it will still fit properly with other components and maintain the required functionality.

Other options, such as an exact size only or a focus solely on necessary tolerance or size variations, do not capture the comprehensive purpose of limit dimensions, which is to establish both the maximum and minimum allowable sizes for a feature on a part.