Machine Drawing 0135090520 ppt02

C H A P T E R T WO
LAYOUTSLAYOUTS
AND LETTERINGAND LETTERING

2
Technical Drawing with Engineering Graphics, 14/e
Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman
© 2012, 2009, 2003, Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
OBJECTIVESOBJECTIVES
1. Identify six types of technical drawings based on the projection
system they use.
2. Identify the line patterns used in technical drawings and describe
how they are used.
3. Read and measure with the architects’ scale, engineers’ scale, and
metric scale.
4. Identify standard drawing media and sheet sizes.
5. Add lettering to a sketch.
6. Fill in a standard title block

3
PROJECTIONSPROJECTIONS
Behind every 2D drawing of an object is a space relationship involving the object
and three “imagined” things:
1. The observer’s eye, or station point
2. The plane of projection
3. The projectors (also called visual
rays or lines of sight).
Perspective Projection
Parallel Projection

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Types of ProjectionsTypes of Projections
There are two main types of projection: perspective and parallel. These are
broken down into subtypes, as shown below:

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Drawing VocabularyDrawing Vocabulary
• Drawing Lines
• Lettering
• Measurement Systems
• Scale
• Title Blocks
A BC 
Title Block
mm
Inch

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ALPHABET OF LINESALPHABET OF LINES
Thick and Thin Drawing Lines
Freehand line technique
Line styles

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FREEHAND LINESFREEHAND LINES
The main difference between an instrument or CAD drawing and a freehand sketch is
in the appearance of the lines. A good freehand line is not expected to be precisely
straight or exactly uniform, as is a CAD or instrument-drawn line. Freehand lines show
freedom and variety.
Freehand construction lines are very light, rough lines. All
other lines should be dark and clean.

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MEASUREMENT SYSTEMSMEASUREMENT SYSTEMS
U.S. Customary Units
The Metric System
Dual-Dimensioned

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DRAWING SCALEDRAWING SCALE
Drawing scale is the reduction or enlargement of the drawn object
relative to the real object
Reduced and Enlarged Scale. Many drawings must be shown at reduced scale for the
object to fit on the paper.

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SPECIFYING THE SCALE ON ASPECIFYING THE SCALE ON A
DRAWINGDRAWING
List the predominant drawing scale in the title
block. (Courtesy of Dynojet Research, Inc.)
For a part that is shown on
the paper at half its actual
size, the scale is listed in one
of these three ways:
SCALE: 1:2
SCALE: 1/2
SCALE: .5
Architectural drawings list
the scale based on the number
of fractions of an inch on the
drawing that represent one
foot on the actual object.
Example:
SCALE: 1/8" 1'

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SCALESSCALES
Scales are measuring tools
used to quickly enlarge or
reduce
Drawing measurements.
Types of Scales

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METRIC SCALESMETRIC SCALES
The triangular scales have
one full-size scale and five
reduced-size scales, all fully
divided.
Using these scales, a drawing
can be made full size,
enlarged sized, or reduced
sized.
Full Size 1:1 scale
Half Size 1:2 scale

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ENGINEERS’ SCALESENGINEERS’ SCALES
An engineers’ scale (also called a civil engineers’ scales) is a decimal scale
graduated in units of 1 inch divided into 10, 20, 30, 40, 50, and 60 parts.
Because the engineers’ scale divides inches into decimal units, it is convenient
in machine drawing to set off inch dimensions expressed in decimals.

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MECHANICAL ENGINEERS’ SCALESMECHANICAL ENGINEERS’ SCALES
Triangular combination scales are available that
include full- and half-size mechanical engineers’
scales, several architects’ scales, and an
engineers’ scale all on one stick.
Triangular combination scales are available that
include full- and half-size mechanical engineers’
scales, several architects’ scales, and an
engineers’ scale all on one stick.
Mechanical engineers’ scales are divided into units representing inches to full
size, half size, quarter size, or eighth size.
To draw an object to a scale of half size, for example, use the mechanical
engineers’ scale marked half size, which is graduated so that ever ½” represents
1". In other words, the half-size scale is simply a full-size scale compressed to half
size.

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Architects’ ScaleArchitects’ Scale
The architects’ scale is intended primarily for drawings of buildings, piping
systems, and other large structures that must be drawn to a reduced scale to fit on
a sheet of paper.
AutoCAD software users sometimes
become confused using architectural
units. When selecting architectural
units and entering lengths, keep in mind
that a value of 1 is one inch, not one foot.
AutoCAD software users sometimes
become confused using architectural
units. When selecting architectural
units and entering lengths, keep in mind
that a value of 1 is one inch, not one foot.

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LETTERINGLETTERING
Lettered text is often necessary to completely describe an object or to provide
detailed specifications. Lettering should be legible, be easy to create, and use styles
acceptable for traditional drawing and CAD drawing.
Engineering drawings use single-stroke
sans serif letters because they are highly
legible and quick to draw.
Sans serif means without serifs, or
spurs
Sans serif means without serifs, or
spurs

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LETTERING STANDARDSLETTERING STANDARDS
An Example of Lettering and Titles
Using CAD
• Most hand-drawn notes use lettering
about 3 mm (1/8") high.
• CAD notes are set using the
keyboard and sized to be in the
range of 3 mm (1/8") tall according
to the plotted size of the drawing.
• CAD drawings typically use a
Gothic lettering style but often use
a Roman style for titles.When adding lettering to a CAD
drawing, a good rule of thumb is
not to use more than two fonts
within the same drawing.
When adding lettering to a CAD
drawing, a good rule of thumb is
not to use more than two fonts
within the same drawing.

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VerticalVertical
CapitalCapital
Letters andLetters and
NumeralsNumerals
The proportions
of vertical capital
letters and numbers
are shown

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Vertical Lowercase LettersVertical Lowercase Letters
When large and small capitals are
combined, the small
capitals should be three fifths to
two thirds the height of the
large capitals.
When large and small capitals are
combined, the small
capitals should be three fifths to
two thirds the height of the
large capitals.
Lowercase letters are rarely used in engineering sketches except for lettering
large volumes of notes. Vertical lowercase letters are used on map drawings, but
very seldom on machine drawings.

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InclinedInclined
CapitalCapital
Letters andLetters and
NumeralsNumerals
Inclined (italic) capital
letters and numerals,
are similar to vertical
characters, except for
the slope. The slope of
the letters is about 68°
from the horizontal.

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FRACTIONSFRACTIONS
Do’s & Don’t
• Never let numerals touch the fraction bar.
• Center the denominator under the numerator.
• Avoid using an inclined fraction bar, except when lettering
in a narrow space, as in a parts list.
• Make the fraction bar slightly longer than the widest part
of the fraction.

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USING GUIDELINESUSING GUIDELINES
Use extremely light horizontal guidelines to keep letter height uniform…
Do not use vertical
guidelines to space the
distance from one letter
to the next within a word
or sentence.
Do not use vertical
guidelines to space the
distance from one letter
to the next within a word
or sentence.
For even freehand letters:
• Use 1/8" gridded paper for drawing to make lettering easy.
• Use a scale and set off a series of spaces, making both the
letters and the spaces between lines of letters 1/8" high.
• Use a guideline template like the Berol Rapidesign 925
• For whole numbers and fractions, draw five equally
spaced guidelines.

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SPACING OF LETTERS AND WORDSSPACING OF LETTERS AND WORDS
Spacing between Words
Space letters closely within words to make
each word a compact unit, but space words
well enough apart to clearly separate them
from adjacent words.
Spacing between Rows
Be sure to leave space between rows of lettering,
usually equal to the letter height.
Spacing between Letters
Uniform spacing between letters is done by
eye. Contrary to what might seem logical,
putting equal distances from letter to letter
causes them to appear unequally spaced.

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LETTERING FOR TITLESLETTERING FOR TITLES
In most cases, the title and
related information are lettered
in title boxes or title strips
When lettering by hand, arrange
the title symmetrically
about an imaginary centerline

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DRAWING PENCILSDRAWING PENCILS
High-quality drawing pencils help produce good quality technical
sketches and drawings.
Hard
The hard leads in this
group (left) are used
where extreme
accuracy is required,
as on graphical
computations and
charts and diagrams.
The softer leads in this
group (right) are
sometimes used for
line work on
engineering drawings,
but their use is limited
because the lines are
apt to be too light.
Medium
These grades are for
general-purpose work in
technical drawing. The
softer grades (right) are
used for technical sketching,
lettering, arrowheads,
and other freehand work
on mechanical drawings.
The harder leads (left) are
used for line work on
machine drawings and
architectural drawings. The
H and 2H leads are widely
used on pencil tracings for
reproduction.
Soft
These leads are too
soft to be useful in
mechanical drafting.
They tend to produce
smudged, rough lines
that are hard to erase,
and the lead must be
sharpened continually.
These grades are used
for artwork of various
kinds, and for full-size
details in architectural
drawing.

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Style of PencilStyle of Pencil
You might be surprised how much your drawings benefit from finding a style of pencil
that suits your use. Soft pencils, such as HB or F, are mainly used in freehand
sketching.
Choose a pencil that:
• Is soft enough to produce clear black lines, but hard enough not to
smudge too easily.
• Is not so soft that the point breaks
easily.
• Feels comfortable in your hand.
• Grips the lead without slipping.

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THE COMPUTERTHE COMPUTER
AS A DRAFTING TOOLAS A DRAFTING TOOL
Most people who create technical drawings use CAD. The
advantages include accuracy, speed, and the ability to present
spatial and visual information in a variety of ways.
Even the most skilled CAD users need to
also be skilled in freehand sketching, to
quickly get ideas down on paper.
Even the most skilled CAD users need to
also be skilled in freehand sketching, to
quickly get ideas down on paper.
One benefit of CAD is the ability to draw perfectly straight uniform lines
and other geometric elements. Making changes to a CAD drawing takes
about a tenth the time that it takes to edit a drawing by hand.

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SKETCHING AND DRAWING MEDIASKETCHING AND DRAWING MEDIA
Many choices of media (paper and other) are available for particular
sketching or drawing purposes. Whether you are sketching or are plotting a
drawing from a CAD workstation, choose the type of sheet and size that suits
your needs.
Small notebooks or sketch pads are
useful when working at a site or when
it is necessary to quickly record
information.
Sketch on Graph Paper
Graph paper can be helpful in
making neat sketches

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STANDARD SHEETSSTANDARD SHEETS
There are ANSI/ASME standards for international and U.S. sheet sizes.
Note that drawing sheet size is given as height width. Most standard
sheets use what is called a “landscape” orientation.
* May also be used as a vertical sheet size at 11" tall by 8.5" wide.

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Typical Sheet Sizes and BordersTypical Sheet Sizes and Borders
• Margins and Borders
• Zones

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Title BlockTitle Block
The title block is located in the lower right corner of the format.
Standard areas in the title block provide the information as shown
below.

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PLANNING YOUR DRAWING ORPLANNING YOUR DRAWING OR
SKETCHSKETCH
When laying out a drawing sheet, you will
need to consider:
• the size and scale of the object you will
show
• the sheet size
• the measurement system (units) for the
drawing
• the space necessary for standard notes
and title block.The object you are drawing is the “star” of the sketch. Keep the object near the
center of the sheet. It should be boldly drawn, using
thick visible lines. Make it large enough to fill most of the sheet and so that
details show clearly

Machine Drawing 0135090520 ppt02

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