Orthographic Projections, Continued
Isometric scale
An isometric scale measures foreshortened lines with uniform accuracy.
Drawings made using an isometric scale create isometric projections by
rendering the object exactly as seen on the plane of projection.
You can
make an isometric scale on paper or cardboard to aid you in laying out
measurements. All distances in an isometric scale are 2/3 times true length
or approximately 80 percent of true size.
To make an isometric scale, use this table:
Step
1
Action
Along a horizontal line, mark off equal increments with any
standard scale (figure 6-15, view A).
2
Using a 45° triangle, lay off lines from each of the increments.
3
Using a 45° and a 30°/60° triangles, form a 75° angle with the
horizontal and lay off a line intersecting the diagonal lines.
4
Align a piece of paper, acetate, or cardboard, with the 75° line
indicating equal increments. These increments form the isometric
scale.
Continued on next page
6-18
