Line Weights And Types

Line weights are generally subject to the following conventions:

1. For manual pencil drafting using drawing boards, finished work includes bold object lines (2H to B pencils), light dimension lines, center lines, section lines, and so on (3H to 5H pencils). Temporary construction lines, guidelines for lettering, and other types should be kept very light (7H or 8H). Border lines for the drawing sheet and title block should be made bold (3B to 6B).

2. For inked or computer-plotted drawings different pen widths are used to achieve similar effects (see Figure 3.1). When plotting (printing) using a laser or inkjet printer from a computer drawing in

AutoCAD, these line-boldness conventions are replicated by configuring each line color as certain line widths.

3. Border lines are roughly twice as bold as object lines, which in turn are roughly twice as bold as dimension lines. In addition, AutoCAD drafting uses colors to emulate each thickness (black or white for objects, green for dimensions, blue for borders, etc.). In AutoCAD's print-dialogue box you are allowed to designate different line widths for each different color.

Line Types: The major line types and line thicknesses using pens or plotter machines are outlined below. It becomes obvious from the table below that larger sheets require the use of thicker lines than smaller sheets.

Object Lines

Object lines, also known as visible lines, are solid lines used mainly to define the shape and size of a structure or object. They are continuous prominent lines representing the edges of surfaces or the intersection of two surfaces, as shown in Figure 3.2. An object/visible line is typically drawn thick (dark) and solid so that the outline or shape of the object (e.g., wall, floor, elevation, detail, or section) clearly stands out on the drawing with a definite contrast between these lines and secondary lines on the drawing. They are heavier than hidden lines, dimension lines, center lines, and broken lines. As we shall see later in the chapter, blueprint drawings often contain different solid line types that are not object lines.

Dashed Lines

Dashed or hidden lines serve more than one purpose in construction drawings. They are comprised of medium- or light-weight, uniformly sized broken lines consisting of evenly spaced short dashes and are generally intended to represent hidden surfaces or intersections of an object. On floor plans they may be used to represent features that lie above the plane of the drawing, such as high wall cabinets in a kitchen. You may vary the lengths of the dashes slightly in relation to the size of the drawing.

On remodeling-job drawings, they are also used to indicate the position of preexisting construction. In some cases they are used for relationship clarification or to show alternative positions of a movable component. To be complete, a drawing must include lines that represent all the edges and intersections of the surfaces in the object. Many of these lines are invisible to the observer because they are covered by other portions of the object. For example, in Figure 3.3A the dashed lines indicate the location of blocking hidden behind the wall.

In architectural drafting dashed lines may be applied in different weights to reflect their purpose (e.g., to reflect importance or distance from the main view) while showing drawing features that are not visible in relationship to the view or plan. These dashed features can be subordinated to the main emphasis of the drawing. Hidden lines should typically begin and end with a dash, in contrast with the visible lines from which they start, except when a dash would form a continuation of a visible line. Dashes should be joined at comers; likewise, arcs should begin with dashes at tangent points. Hidden lines should be omitted when not required for the clarity of the drawing. Although features located behind transparent materials may be visible, they should be treated preferably as concealed features and shown with hidden lines. Examples of dashed-line representations include beams and headers, upper kitchen cabinets, un-dercounter appliances (e.g., dishwasher or refrigerator), or electrical circuit runs, as shown in Figure 3.3B. Figure 3.3C is another example of hidden-line use.


Type of Line

^Recommended Line Thickness in mm.

(inch equivalent in brackets)




A2 A3 A4


Continuous - thick

0.7 {0.028}

0.5 (0.020)

0.35 (0.014)

• •

Object Visible) outline lines Border line


Continuous - thin

0,35 (0.014}


• ■ • • • • • •

Dimension lines Leaders

Imaginary Intersection of surfaces

Extension lines, and intersection lines Section lines & Hatching Adjacent parts and tooling Short center lines Contour lines


Continuous -thin, freehand or ruled with zig-zag

0,35 (0.014)

0.25 (0.010)

0.18 (0.007)


Indication of repeated detail Break lines (other than on an axis)


Dashed - medium p Space 13}3 1 mm minimum J L A » 23 to 4S

0.50 (0.020}

0.35 (0.014)

0.25 (0.010)

• •

Hidden surfaces Surfaces above plane

1 I A-TAtnl.1 a J ""A B s 2A [0 10A

0.35 (0.014)

0.25 (0.010)

0.16 (0.007)

• • ■ * • •

Centerlines Pitch lines

Alternative position of moving part

Path lines for indicating movement

Features in front of a cutting plane

Developed views Material to be removed


0.25 (0.010)

0.35 (0.014) 0.18 (0.007)

Cutting planes

* AO = 1189mm x 841mm (46.8 in x 33.1 in); A1 = 841 mm x 594 mm (33.1 in x 23.4 in); A2 = 594 mm x 420 mm (23.4 in x 16.5 in); A3 = 420 mm x 297 mm (16.5 in x 11.7 in) A4 = 297 mm x 210 mm (11.7 in x 8.3 in); AS = 210 mm x 149 mm (8.3 in x 5.9 in).

Figure 3.1 Major types of line used in construction drawings. Line weights are clearly impacted by sheet size. The larger the sheet being used, the heavier the line weight required. An object line on an AO sheet for example should be twice as thick as an object line drawn on an A2, A3, or A4 sheet.

Line Weights Architecture
Figure 3.2 Object lines identify and describe the shape of an object. For example, in this drawing object lines are used to portray the furniture as well as the various architectural elements in the design (e.g., stairs, elevators, walls, etc).

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  • jouni
    What weight should a hidden line be?
    6 months ago

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