What does a reference dimension indicate in engineering drawings?

A reference dimension is used in engineering drawings to provide additional information regarding the size or location of a feature without implying a requirement for manufacturing or assembly. Specifically, it serves informational purposes, helping designers and engineers to understand relationships between features while not being a critical dimension that must be met during the manufacturing process.

Since reference dimensions do not encompass tolerances, they help clarify design intent without constraining manufacturing processes. While dimensions with defined tolerances dictate allowable variations and are essential for precise fabrication, reference dimensions are purely supplementary, making them vital for design clarity without the pressure of compliance. This distinguishes reference dimensions from mandatory specifications, which impose strict requirements on dimensions that must be adhered to during production.