Line Conventions

Line conventions convey information as

succinctly as a physical example of the

object itself.

The appropriate use of standard line

conventions enables fabricators to

replicate objects based solely on your

drawing

Line Conventions

Any lines visible in a view that define edges or outlines of objects are drawn with lines referred to as object lines. Object lines are drawn as solid, thick lines. In drawings that do not have cutting planes, visible lines will be the thickest lines drawn.

Object Lines

Lines not readily apparent in a view of an object are hidden lines. Hidden lines are evenly-spaced, short dashes that begin and end as a dash in contact with the line from which it starts and stops.

Hidden Lines

Center lines are used to indicate the center of a circle, arc, or any symmetrical object. Center lines are composed of long and short dashes, alternately and evenly spaced, with a long dash at each end. At intersecting points, center lines should be drawn as short dashes

Center lines

To give a clearer view of obscure or oblique planes and interior or hidden features of an object that cannot be clearly observed in a conventional outside view, use viewing or cutting plane lines respectively. Viewing or cutting plane lines are the thickest of all lines.

Viewing or Cutting Plane Lines

Viewing or Cutting Plane Lines

Cutting plane lines, together with arrowheads and letters, make up the cutting plane indications.

Arrowheads at the end of cutting plane lines indicate the direction from which you view the section.

The cutting plane may be a simple, continuous plane, or it may be offset to show the interior detail to better advantage.

Lines that define the parameters of a dimension are

called dimension lines. Dimension lines are thin lines

terminating in arrowheads.

Place dimension lines no closer than 3/8" from the

object outline. Parallel dimension lines should be a

minimum of 1/4" apart.

Dimension lines

You may place parallel dimension lines more than 1/4" apart

so long as the spacing between dimension lines is uniform

throughout the drawing.

Dimension lines are generally broken in the center of the line

to provide a space for the dimension figure.

Dimension figures for parallel dimension lines are staggered.

Dimension lines

Extension lines are thin lines that extend from the object outline or

point on the object to a place outside the image area.

Extension lines define areas for dimensions.

You should leave a 1/16" gap between the object outline or point

on the object and the beginning of the extension line.

Extension lines project 1/8" beyond the outermost dimension line.

Extension and dimension lines are drawn at right angles to each

other.

Extension lines

Notes or dimensions that pertain to surfaces or parts are lead to that surface or part by leader lines.

Leader lines are thin, solid lines that terminate in an arrowhead or dot.

Use arrowheads when leader lines terminate at the outline of an object.

Use dots when leader lines terminate within the outline of the object or on the surface of the object

Leader lines

Arrowheads indicate the extent of the dimension. All arrowheads on a drawing should be uniform in size and style. Carelessly drawn arrowheads make drawings look unfinished and unprofessional.

When indicating the radius of an arc or circle, place the arrowhead at the end of the dimension line that touches the object outline. The end of the dimension line terminates at the centerline of the arc or circle.

Arrowheads

When an extended part of an object has a continuous shape

and size, you can save space by abbreviating the object using

zigzag or wavy lines.

These zigzag or wavy lines are called break lines because you

figuratively break away an unimportant segment of an object.

LONG BREAK LINES: Long break lines are ruled lines with

freehand zigzags that reduce the size of the drawing required to

delineate an object and reduce detail.

Break Lines

SHORT BREAK LINES: To indicate a short break in an

object, use thick, solid, wavy freehand lines.

Rods, tubes, and bars have additional conventions that

not only break their length but also imply the material or

texture of the object.

Break Lines

To indicate alternate positions of parts, repeated detail, or to indicate a datum plane, use phantom or datum lines.

Phantom or datum lines consist of a medium weight series of one long dash and two short dashes evenly spaced and terminating in a long dash.

Phantom or datum lines

Though these standards relate to

technical drawing, which is far more

precise than freehand sketching,

their conventions should be used as

a guide when sketching.

In Review

References

http://www.tpub.com/content/draftsman/