0135090520_ppt02

C H A P T E R T WO

LAYOUTS

AND 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.

OBJECTIVES

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





PROJECTIONSBehind 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

4





Types of ProjectionsThere are two main types of projection: perspective and parallel.

These are broken down into subtypes, as shown below:

5





Drawing Vocabulary

• Drawing Lines

• Lettering

• Measurement Systems

• Scale

• Title Blocks

A B C A B C

Title Block

mmInch

6





ALPHABET OF LINES

Thick and Thin Drawing Lines

Freehand line technique

Line styles

7





FREEHAND LINESThe 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.

8





MEASUREMENT SYSTEMS

U.S. Customary Units

The Metric System

Dual-Dimensioned

9





DRAWING 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.

10





SPECIFYING THE SCALE ON A

DRAWING

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'

11





SCALES

Scales are measuring

tools used to quickly

enlarge or reduce

Drawing

measurements.

Types of Scales

12





METRIC 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

13





ENGINEERS’ 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.

14





MECHANICAL 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.

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.

15





Architects’ ScaleThe 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.

16





LETTERINGLettered 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

17





LETTERING 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.

18





Vertical

Capital

Letters and

Numerals

The proportions

of vertical capital

letters and numbers

are shown

19





Vertical 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.

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.

20





Inclined

Capital

Letters and

Numerals

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.

21





FRACTIONS

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.

22





USING 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.

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.

23





SPACING 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.

24





LETTERING 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

25





DRAWING 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.

26





Style 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.

27





THE COMPUTER

AS 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.

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.

28





SKETCHING 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

29





STANDARD 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 Borders

• Margins and Borders

• Zones

31





Title 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 OR

SKETCH

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

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