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
• Not cross each other
• Not excessively long
• Not parallel to
dimension lines,
extension lines, or
section lines
• Avoid 75°or less than
15°angles from
horizontal
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 Elements
Minimum Letter
Letter Heights Drawing Sizes
Drawing Sizes INCH
Heights INCH
METRIC (mm)
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
All other characters
.10
.12
All sizes
All sizes
2.5
3
All sizes
All sizes
Lettering Notes