CHAPTER 6

Lines and Lettering

Learning Objectives

• Identify the lines found on a given industry drawing

• Draw ASME standard lines• Solve engineering given problems• Create ASME standard text• Answer questions related to lines

and lettering

Lines

• Must be of a quality that reproduces easily

• Dark, crisp, sharp, and of the correct thickness

• No variation in darkness• Variation in thickness• Thicker lines stand out clearly

• Thinner lines are subordinate

Mechanical Drafting Line Standards

• ASME Y14.2, Line Conventions and Lettering• Thick lines .02 in. (0.6 mm)

Twice as wide as thin lines• Thin lines .01 in. (0.3 mm)

Half as as wide as thick lines

• Military (MIL) standards (STD)• Thick• Medium• Thin

ASME Line Conventions

ASME Example

[Insert Figure 6.2]

Construction Lines

• Layout• Do not represent a specific

drawing feature• Not reproduced on the final

drawing

Visible Lines

• Object lines, or outlines• Visible surfaces or edges• Continuous (solid)• Thick• .02 in. (0.6 mm)

• ASME example

Hidden Lines

• Invisible edges• 125 in. (3 mm) dashes spaced .06

in. (1.5 mm) apart• Thin• .01 in. (0.3 mm)

• ASME example

Hidden Line Rules

Centerlines

• Centers of circles and arcs• Center axis of a circular or

symmetrical form• Centers in a bolt circle pattern• Paths of motion in a mechanism

Centerlines

• Series of alternating long and short dashes• Long dash .75 to 1.50 in. (19-35 mm)

• Spaces between dashes .062 in. (1.5 mm)

• Short dash .125 in. (3 mm)

Centerlines

• Extend .125 in. (3 mm) or .25 in. (6 mm) past objects

• Thin• .01 in. (0.3 mm)

• ASME example

Bolt Circle

• Polar coordinate dimensions• Rectangular coordinate

dimensioning

Symmetry

Extension Lines

• Establish the extent of a dimension• Begin with a .06 in. (1.5 mm)

space from the object• Extend .125 in. (3 mm) beyond the

last dimension• Thin• .01 in. (0.3 mm)

• ASME example

Extension Line Rules

• Can cross object lines, centerlines, hidden lines, other extension lines

• Should not cross dimension lines• Centerlines become extension

lines for dimensioning purposes

Dimension Lines

• Capped on the ends with arrowheads

• Broken to provide a space to indicate the length of the dimension

• Thin• .01 in. (0.3 mm)

• ASME example

Leader Lines

• Leaders• Connect a specific note to a

feature• Direct dimensions• Symbols• Item numbers• Part numbers

Leader Lines

• 45°, 30°, or 60° angles common• .125 to .25 in. (3-6 mm) shoulder

common• Pointing to a line: cap with an arrow• Pointing to a dimension line: no arrow• Pointing inside an object: cap with

a .05 in. (1.5 mm) dot

Leader Lines

• Continuous or hidden• Thin• .01 in. (0.3 mm)

• ASME example

Leader Line Rules

Arrowheads

• Terminate dimension lines and leader lines• Cutting plane lines and viewing plane lines• Twice as big as arrowheads on dimension and

leader lines• Three times as long as wide• .125 in. (3 mm) long for dimension lines and

leader lines• Consistent sizes• Open or filled• ASME example

Cutting-Plane and Viewing-Plane Lines

• Thick• .02 in. (0.6 mm)

• Takes precedence over the centerline

• ASME example

Cutting-Plane and Viewing-Plane Lines

Section Lines

• Appear in the view of a section• Show where the cutting-plane line

cuts through material• 45°, 30°, or 60°angles common• Thin• .01 in. (0.3 mm)

• ASME example

Section Line Rules

• Equally spaced• ASME minimum space .06 in. (1.5 mm)

• Avoid 75°or less than 15°angles from horizontal

• Not parallel or perpendicular to object lines• Opposite directions on adjacent parts• Thin parts can be shown without section

lining• Omit around text when necessary to have

text in a sectional view

Section Lines

• Outline section lining• Coded section lines• Thin parts shown without section

lining

Short Break Lines

• Shorten the length of a long object or part

• Provide a partial view of a feature• Thick• .02 in. (0.6 mm)

• ASME example

Long Break Lines

• Break long distances• Thin• .01 in. (0.3 mm)

Phantom Lines

• Alternate positions of moving parts• Adjacent positions of related parts• Repetitive details• Contour of filleted and rounded corners• Thin• .01 in. (0.3 mm)

• ASME example

Chain Lines

• Indicate specified treatment• Projected tolerance zone• Alternately spaced long and short

dashes• Thick• .02 in. (0.6 mm)

• ASME example

Stitch Lines

• Indicate the location of stitching or sewing

• Short thin dashes, or• .01 in. (0.3 mm) diameter dots

spaced .12 in. (3 mm) apart

Lettering

• Dimensions• Notes• Titles

Lettering

• Must be of a quality that reproduces easily

• Dark, crisp, sharp• CADD text• Font

ASME Lettering Standards

• ASME Y14.2, Line Conventions and Lettering• Opaque

• Clearly spaced

• Vertical or inclined

• One style

• Upper case letters

Lettering on Engineering Drawings

• Single-stroke Gothic• Vertical uppercase letters• Arial, Century Gothic, RomanS, or

SansSerif font

Lettering Numbers

Inclined and Lowercase Lettering Styles

• Inclined• 68°to the right from horizontal

• Structural drafting

• Civil drafting or maps

• Lowercase• Uncommon in mechanical drafting

• Engineering specifications

• Civil drafting or maps

Architectural Lettering

• Traditional freehand architectural lettering with an artistic flair• StylusBT, ArchiText, CountryBlueprint,

or CityBlueprint fonts

• United States National CAD Standard (NCS)• SansSerif font

Lettering Legibility

• Background area between letters:• Approximately equal

• Individual words clearly separated• Space between two numerals with a

decimal point between:• Minimum two-thirds the lettering height

• Vertical space between lines of lettering• No more than the lettering height, no less

than half the lettering height

ASME Letter Heights

Sheet ElementsMinimum

Letter Heights INCH

Drawing Sizes INCH

Letter Heights METRIC (mm)

Drawing Sizes

METRIC

Drawing title, sheet size, CAGE Code, drawing

number, revision letter in the title block

.24 D, E, F, H, J, K 6 A0, A1

Drawing title, sheet size, CAGE Code, drawing

number, revision letter in the title block

.12 A, B, C, G 3 A2, A3, A4

Zone letters and numbers in borders

.24 All sizes 6 All sizes

Drawing block headings .10 All sizes 2.5 All sizesAll other characters .12 All sizes 3 All sizes

Lettering Notes