Answer:
1. All dimension, extension, and leader lines should be thin, sharp, dark lines (.5mm/2H).
2. Extension lines indicate the points between which the dimension figures apply. They
are drawn perpendicular to the dimension lines, start with a visible gap (~1/32") between
them and the object, and terminate 1/8" (3.2 mm) beyond the last arrowhead.
3. Each dimension should be terminated by arrowheads touching the extension lines and
pointing in opposite directions. Arrowheads are drawn freehand with .7mm/HB lead. The
line should be broken only at the approximate center for the dimension figures.
4. Dimensions shown with dimension lines and arrowheads should be placed to be read
from the bottom of the drawing (unidirectional system).
5. All dimensions should be given in decimal format. When dimensions are given in
inches, leading zeros are omitted from dimension values less than 1.00
6. When all dimensions on a drawing are given in inches, the inch marks (") are omitted,
the same applies to millimeters. If metric units are used, the word METRIC will appear
boxed in a spot toward the lower portion of the drawing sheet.
7. A dimension line should never coincide with an object line or a center line, nor should
it be an extension of these lines. Both, however, may be used as extension lines.
8. Crossing of extension lines or dimension lines should be avoided if possible. Where
such crossings are unavoidable, there should be no break in either of the lines. However,
if extension lines cross dimension lines through the arrowheads, the extension line may
be broken.
9. Dimensions should be at least 3/8" (10 mm) from the object outline, then equally
spaced at least 1/4" (6 mm) apart. A continuous series of dimensions should be aligned
rather than staggered. Standard practice is to place the shortest dimensions nearest to the
object and space adjacent parallel dimension lines further away from the object in order
of their length.
Explanation: