Which of the following dimensions typically do not require a tolerance?

• A. Reference dimensions
• B. Nominal dimensions
• C. Scaled dimensions
• D. Projected dimensions

Answer: (A)

Reference dimensions are typically included in engineering drawings to provide additional information about the design but are not meant to be controlled during the manufacturing process. These dimensions serve to indicate the size or location of other features and are often shown in parentheses. Since they do not directly impact the function or assembly of the component, they are not assigned tolerances.

In contrast, nominal dimensions are standard measurements from which tolerances are derived, making them inherently linked to the manufacturing process. Scaled dimensions, often used in models or drawings to achieve accurate representation rather than functional sizes, also require care in interpretation, but they may involve tolerances depending on their application. Projected dimensions, often related to features that require proper placement for assembly or secure fit, typically do have specific tolerance requirements to ensure the components fit together correctly.