Hilfsbemaßung

Hilfsbemaßung, a German term often translated as "auxiliary dimension" or "reference dimension," is a specific type of dimension used in technical drawings. Its primary purpose is to provide additional information without affecting the manufacturing or inspection of a part. Unlike standard dimensions, which define critical geometric features and tolerances, auxiliary dimensions are informational only.

These dimensions are typically derived from other existing dimensions on the drawing. They are useful for providing context, indicating the location of features relative to a datum, or clarifying the overall size or proportions of a component. For example, an auxiliary dimension might show the overall length of a complex shape, even though the individual segments that make up that length are already dimensioned.

Auxiliary dimensions are usually enclosed in parentheses or marked with a specific symbol, such as an "X" or "REF," to clearly distinguish them from driving dimensions. This visual cue signals to engineers, machinists, and inspectors that the dimension is for reference and does not impose a manufacturing requirement. Consequently, if an auxiliary dimension is slightly off due to variations in the primary dimensions, it does not constitute a drawing error or a part rejection. Their presence simplifies understanding the design intent and aids in measurement verification without creating ambiguity in production.