Systems of Dimensioning

SYSTEMS OF DIMENSIONING

Two different systems of dimensioning are recommended by Bureau of Indian Standards as i) Aligned system and ii) Unidirectional system

1. Aligned System

In this system of dimensioning, dimensional values are so placed that they may be read from the bottom or the right-hand edges of the drawing sheet and satisfying the following conditions. 

i) Dimensional values should be placed parallel to the dimension line. 

ii) Dimensional values should be placed above the dimension line. 

iii) Dimensional values should not touch the dimension line. 

iv) Dimensional values should be placed at the middle of the dimension line.

Linear dimensioning drawn in aligned system is shown in Fig. 3.10(a).

Oblique dimensioning and angular dimensioning in aligned system of dimensioning are shown in Fig. 3.10(b) and 3.10(c) respectively.

2. Unidirectional System

In this system of dimensioning, dimensional values are so placed that they may be read from the bottom edge of the drawing sheet and satisfying the following conditions. 

i) Dimensional values for horizontal lines should be placed at the middle of the horizontal dimension lines with interrupting the dimension line. 

ii) Dimensional values for non-horizontal lines (Vertical and Oblique) should be placed at the middle by interrupting the dimension line so that it can be read from the bottom edge of the drawing sheet

Dimensional values in linear dimensioning, obligue dimensioning and angular dimensioning in Unidirectional system of dimensioning are shown in Fig. 3.11(a), (b) and (c) respectively.

Note : In a drawing only one system either Aligned system (or) Unidirectional system to be followed. Both the system should not be used in any drawing.