Isometric Scale

ISOMETRIC SCALE

It was explained in the previous section that the length of line parallel to the isometric lines is shortened than its true length. Hence the true length of isometric lines are to be converted, shorter in lengths to draw the isometric projection.

The scale which is used to convert the true length into isometric length is called as `Isometric Scale'. 

Refering the Fig. 17.4, the top face ABCD is sloping away from the observer and hence the edges of the top face will appear foreshortened. The true shape of the triangle BAD is represented by the triangle BPD.

To determine the extent of reduction of an isometric line `Isometric scale' is constructed as below.

Therefore the reduction of true length can be obtained by multiplying it by a factor 0.816.

(Aliter)

The reduction of true length can also be obtained by construction of simplified isometric scale as shown in Fig. 17.5 (ii).

1. Draw the true length AB. 906

2. Draw a line AC at an angle of 15° to AB to intersect another line inclined at 45° to horizontal, drawn from B.

3. Mark the divisions 0', 1', 2' etc. on true length AB.

4. Draw inclined lines at 45° through these divisions to obtain the corresponding isometric lengths, A-0, A-1, A-2 etc on the line AC.

(ie., A-0' is the true length and A-0 is the isometric length).