Unit 2: Drafting Instruments (Chapter2: Layouts and Lettering)

Technical Drawing with Engineering Graphics, 15th edition

Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman 1

Unit 2: Drafting Instruments

(Chapter2: Layouts and Lettering)

DFTG-1305 Technical Drafting

Instructor: Jimmy Nhan



OBJECTIVES

1. Identify the line patterns used in technical drawings and describe how they are used.

2. Identify standard drawing media and sheet sizes.

3. Label drawing scale information.

4. Identify drafting equipment and describe its usages

5. Fill in a standard title block with the appropriate information.

6. Lay out a drawing sheet.



DRAWING PENCILS

High-quality drawing pencils help produce good quality technical

sketches and drawings.

Hard

The hard leads in thisgroup (left) are usedwhere extremeaccuracy is required,as on graphicalcomputations andcharts and diagrams.The softer leads in thisgroup (right) aresometimes used forline work onengineering drawings,but their use is limitedbecause the lines areapt 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.



ALPHABET OF LINES

Thick and Thin Drawing Lines

Freehand line technique

Line styles



More

LINES



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.



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.



Typical Sheet Sizes and Borders

• Margins and Borders

• Zones



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.



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.



MEASUREMENT SYSTEMS

U.S. Customary Units

The Metric System

Dual-Dimensioned

Today’s metric system is the International System of Units, commonly referred to as SI



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.



SPECIFYING THE SCALE ON A DRAWING

List the predominant drawing scale in the titleblock. (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'

Map scales are indicated in terms of

proportions such as Scale 1:62500,

fractions such as Scale 1∙62500, or

graphically, such as:

For machine drawings, the scale indicates

the ratio of the size of the drawn object to

its actual size, regardless of the unit of

measurement used. Expansion or

enlargement scales are given as 2:1, 4:1;

5:1, 10:1, and so on.



SCALES

Scales are measuring tools

used to quickly enlarge or

reduce

Drawing measurements.

Types of Scales



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



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.



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.



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 architecturalunits and entering lengths, keep in mind that a value of 1 is one inch, not one foot.



TEMPLATES

Templates are available for a great variety of specialized needs. Templates may be found for drawing almost any ordinary drafting symbol or repetitive feature.



Drafting Equipment and its Usage

Adjustable drafting table is used to draw parallel, perpendicular

or oblique lines.



Drafting Equipment and its Usage (cont.)

Portable Drafting Board is used to draw parallel

Courtesy of Keuffel & Esser Co.

Documents

Unit 2: Drafting Instruments (Chapter2: Layouts and Lettering)