'Recognizing the need is the primary condition for design.'

The following rules should be considered while dimensioning:

1. Standard sizes of letters and figures should be used.

2. All dimensions should be specified in mm. The use of mm should be avoided by giving a general note “All dimensions are in mm”.

3. As far as possible dimensions should be placed outside the views.

4. Dimension lines should not run in the direction included in the hatched area.

5. Dimensions should be taken from visible outlines rather than from dashed lines.

6. Dimensions should be given from a base line, a centre line, an important hole, or a finished surface which may be readily established.

Dimensions should be quoted only once in one view.

8. Overall dimensions should be placed outside the intermediate dimensions.

9. Dimensions should be placed outside a sectional view.

10. Zero should precede the decimal point when the dimension is less than unity.

11. Dimension line should not cross. Also dimension lines and extension lines should not cross.

12. When there are several dimension lines, the shorter dimension should be nearer the view.

13. Leaders should not be drawn curved or made free hand.

14. Do not use outlines for dimensions.

15. Same method of dimensioning should be used for all dimension lines.

Dimensioning Task

There are two Methods of Dimensions. (1) Uni-directional System  (2) Aligned System.

Procedure: UNIDIRECTIONAL METHOD OF DIMENSIONING

Step-1 Draw an example drawing as given into the above figure.  Drawing should be drawn as per the given dimensions.

Step-2 In Unidirectional Method of  Dimensioning the dimension line should be cut at center and dimensions should be placed in the middle of dimension lines as shown into the figure.

Step-3 At the ends of dimension lines filled arrow heads should be placed.

Procedure: ALIGNED METHOD OF DIMENSIONING

Step-1 Draw an example drawing as given into the above figure.  Drawing should be drawn as per the given dimensions.

Step-2 In Aligned Method of Dimensioning the dimension line should be continuous and dimensions should be placed in the middle of dimension lines as shown into the figure.

Step-3 At the ends of dimension lines filled arrow heads shouldbe placed.

Ref: http://www.engineeringdrawing.org/dimensions-methods.html 06/10/2017