Unidirectional System:

(a) Dimensional values shall be indicated hence such they may be read from the bottom of the drawing-sheet. Non-horizontal dimension lines are preferably near the middle, interrupted, hence the value may be inserted.

(b) Angular dimensional values may be oriented also like in diagram.

(c) The positioning of dimensional values frequently requires adapting to different conditions. Hence, for example where values may be:

(i) Close to a termination to ignore having to follow a long dimension line whereas only part of the dimension line requires to be displayed.

(ii) Above the extension about the dimension line beyond one of the terminations, and space is limited as shown in diagram.

(iii) on the ending of a dimension line that is too short for dimensional value to be indicated in the common way

(iv) On top of a horizontal extension of a leader line such terminates on a dimension line whereas space does not permit a placement at the interruption of a non-horizontal dimension line.

(v) The given indications are used along with dimensions to display applicable shape identification and to develop drawing interpretation. The applicable indication or symbol shall precede for dimension the value.

f              :               Diameter

Sf            :               Spherical diameter

SR           :               Spherical Radius

R             :               Radius n               :               Square