68 Chapter 4
4.4 ANGULAR DIMENSIONS.
Angular dimensions are used for measuring and displaying inside and outside angles. These angles are
measured in degrees (Figure 4.1C). Where greater accuracy is required, the degree is divided into 60
minutes and the minute into 60 seconds. For reference, a circle has 360 degrees. Inch and millimeter
measurements both measure angles in degrees. Normally, angular dimensions are specified in decimal
degrees, degrees and minutes, or degrees, minutes, and seconds (For example, 24.5°, 24° 30', 24° 30'
16"). When the angle is less than 1 degree, a leading zero should be used (for example, 0.5°, 0° 30').
4.5 REFERENCE DIMENSIONS.
A reference dimension is used only for information purposes. The indication “REF” should be noted imme-
diately under or beside the dimension. Normally it is either a duplication of a dimension or the accumulated
value of other dimensions. Reference dimensions are typically located within parentheses. Reference di-
mensions do not have tolerances and should not be used to manufacture or inspect parts. The purpose of
reference dimensions is to provide additional information. Some prints may not show reference dimensions
within parentheses and instead show “REF” or “REFERENCE” after the dimension (Figure 4.10).
4.6 NOMINAL SIZE AND ACTUAL SIZE.
In architecture, “nominal size” refers to the dimensions of sawn lumber before it is dried or surfaced.
Nominal dimensions are essentially approximate or rough-cut dimensions by which a material is
generally called or sold in trade but which differs from the actual dimension. In the lumber trade, for ex-
Figure 4.9 A diagram showing “not to scale” dimension (A) and “not complete” dimension (B).