Brief Introduction Lecture F18_briefintroduction.docx Handout Page 1

Brief Introduction to Engineering Graphics

The use of drawings to convey

information.

Sketching

freehand

straight edge

CAD drawings

2D drafting

3D model to 2D drawings

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Orthographics◦ Multiviews

Pictorials

◦ Isometric - a special type

of axonometric which uses

120 degree angles for axis.

◦ Obliques-front faces similar

to orthographic: 90 axis

Perspectives

◦ Used in architecture, more

realistic but hard to use for

measuring.

Isometric Oblique

120

90

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Different Graphical Representation of objects.On pg 27:

See Fig. 3

and Table 1

Brief Introduction Lecture F18_briefintroduction.docx Handout Page 2

Engineering Lettering

Information that is hard to read is even harder to understand…use

GOOD ENGINEERING LETTERING

Class standard is VERTICAL and UPPERCASE (except in the case of

*metric units) as shown on pg. 39 Fig. 21of graphics text

Usually height of text is about 1/8” (3 mm) but don’t measure it…use

guidelines if provided.

Example of lettering expected for

all class assignments.

Fractions can vary from standard…don’t make too small

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*Note: 25.4 mm = 1 INCH

mm is millimeters, leave lowercase

10 mm = 1 centimeter

mm IS THE STANDARD METRIC UNIT

See pg. 30 Sec. 3 I inch

Examples of LetteringDecent Lettering – spaced a

bit too close together

Same here – needs to keep letters VERTICAL!!!

FLOATING letters – needs to use

the guidelines

Incorrect fraction (too small).

POOR form (one shouldn’t

have top or bottom plus

NON-UNIFORM height.

Good Form plus correct way to do millimeters (case-sensitive)

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Brief Introduction Lecture F18_briefintroduction.docx Handout Page 3

Expectations of LetteringGood – spacing of letterings could be improved upon

Fair to Poor – form is fine but not uniform height –FLOATING letters.

Poor to Fail – Not vertical, not uniform height, poor spacing.

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- Linetypes -

The type or appearance of a line depends on what it

is trying to represent.

Be familiar with the different types of lines found in

Fig. 7 on pg. 29.

Solid/Continuous indicates a

visible surface/edge

Dashed indicates a hidden

surface/edge

Centerline indicates symmetry

Each linetype has its own lineweight too.

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Centermark indicates center of circular

feature. Extends past actual diameter Ø

of circle of or radius of arc.

lide 7

Brief Introduction Lecture F18_briefintroduction.docx Handout Page 4

- RULES and EXPECTATIONS -

Use of straight edge is allowed.

Lettering templates, circle templates, compasses

and other “drafting” equipment is not allowed.

NEATNESS and ACCURACY do count!

Even Lineweight (LWT)

Sharp corners

Gaps (or no gaps) in important areas

Examples will be given showing both “good” and

“poor” work.

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- SKETCHING EXAMPLES -

FAIR (B work)• Uneven LW

• Visible Lines need to be darker

• Poor dashes

GOOD (A

work)

POOR (D

work)• overall

neatness

• used straightedge (sort of)

I suggest using a SHARP No. 2 pencil or a 0.7 mm HB lead mechanical pencil.

Don’t forget the straight edge.

Fig. 24 on page 70 shows examples of good totally freehand lines. You are allowed and expected to use a straight edge.

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Brief Introduction Lecture F18_briefintroduction.docx Handout Page 5

Examples

FAIR circle sketch – a bit too flatten bottom

See Methods for sketching circles

on page 73 for good circle

sketching technique.

Didn’t use straight edge

Circle form good –uneven

lineweight (LWT)

UnevenLWT

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-More Examples-10

• Hidden Lines

should not be

scaled

• Watch for

where gaps

should be

• Uneven linewt

• This is a better

hidden line

form.

• Follow

directions.

• Gaps should

be included

only when

needed.

• Uneven linewt

• Poor hidden

line form, this is

a stitch.

• Circle is poor

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INCHES

12 inches per foot

Usually in decimal inch

smallest unit is .02 inch

50 divisions within each inch

Otherwise 1/16 of an inch is typical “ruler” but

if fraction of inch increments are dividing by 2:

1/2 1/4 1/8 1/16 1/32 1/64 1/128

- Decimal Inch and Metric Scale-15

Typical Units for Mechanical Engineering

METRIC

Standard unit is millimeters

25.4 mm per inch

10 mm per centimeter

Case-sensitive, abbreviation is lower case mm.

Ø of circle:

Ø of different circle:

- Abbreviations used in grading -

LWT or LW for lineweight

GEL for good engineering lettering

^ for gap needed (or not needed)

NEAT for neatness

ACC for accuracy

WSS for where shape shows

FFS from finished surface

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