COMPUTER AIDED DRAFTING 2

Lesson 1: Drawing The universal language in engineering and

technical work. Any engineering construction whether it be

engine design, product design, construction design or any component part of any object requires a well prepared drawing or plan before it is constructed.

Types of Drawing Line Drawing Pictorial Drawing Perspective Drawing Isometric Drawing Oblique Drawing Working Drawing Detail and Assembly

Line Drawing One method of drawing is to construct an

object from lines out of geometric shapes or simple figure.

Pictorial Drawing Shows object as they would appear in a

photograph.

Perspective Drawing These drawings more nearly represent an

object as it would appear to the eye.

a. One Point Perspective A single point on the horizon where a subject

vanishes.

b. Two-Point or Angular Perspective The object is assumed to be a station directly

in front.

Vanishing Point

Vanishing Point

Ground Line

c. Two-Point Perspective The observer is assumed to be at a station

above the block.

Ground Line

d. Two-Point Perspective The observing station is low, placing the

ground line and horizon on the same phase.

Isometric Drawing Horizontal lines are drawn to recede 30 deg to

the right and 30 deg to the left.

Oblique Drawing The receding lines in oblique drawings do not

converge but remain parallel with each other.

Working Drawing To make an object as required, the craftsman

must have a clear representation of the shape and definite, accurate information about its size, details, special process, materials and finish.

Drawings with two or more vies are used to give complete information about the object.

Working Drawing 1. The general size, shape

and function (purpose of the product)

2. The material specifications that are required (type and the size of metal, wood, plastics, ceramics, papers, fabrics)

3. The fabrication technique to be used (joints, weld, adhesives)

4. The hardware that is required (hinges, locks, electrical parts etc.)

5. The finishing method

Working Drawing

Detail and Assembly Drawing Products which are complex and the

complexity will determine just how much information can be presented on one drawing.

Lesson 2: Lettering Lettering is important in any drawing because

it gives other pertinent information necessary to depict the object under construction with the drawing or the graphical representation fails to show.

Styles of Letters Single stroke gothic lettering style

Single stroke vertical upper case or caps Single stroke vertical lower case or small letters Single stroke inclined upper case Single stroke inclined lower or small letters

Roman Letters Italic Letters Text Letters

Single Stroke Gothic Lettering StyleSingle stroke vertical upper case or capsSingle stroke vertical lower case or small lettersSingle stroke inclined upper caseSingle stroke inclined lower or small letters

Roman Letters All letters having

“accented: strokes or consisting of heavy and lights or thick and thin lines.

Italic Letters All slanting letters are classified as Italics.

Sometimes they are referred to as either Roman Italics or Gothic Italics.

Text Letters Includes all kinds of old English German text,. This style is often used on diplomas and

certificates.

General Proportion of Letters 1. Normal Letters – when letters are drawn

neither too narrow nor too wide Letter I (capital) – the narrowest and the

foundation stroke of all letters W – widest letter O Q M – the second widest letter A C D G K U X Y – the third widest letters while

others are average width

General Proportion of Letters (cont’d) 2. Compressed Letters – these letters are

narrow in width in proportion to the height and are used when space is limited.

3. Extended Letters – these letters are wider than the normal letters and are used when the space is very wide.

Lesson 3: Drawing Instruments, materials and Equipment In mechanical drawing, it is necessary to know

and be acquainted with the different instruments, supplies and materials and equipment to be used.

1. T-square T-square is used as guide in drawing horizontal lines. They are usually permanent or fixed head and

movable adjustable head.

A. Fixed head T-square

1. T-square

Adjustable Head T-square

2. Triangles

30˚ x 60˚ 45˚ x 45˚

Used to guide vertical and inclined lines.

3. Scales or Rule

Flat Ruler

Steel Tape

Zigzag Ruler

Engineer’s scaleArchitect’s scale &

More.. Compass Protractor French Curve Drawing Pencil Drawing Pens

Lesson 4: Geometric ConstructionGeometric terms and figures: Point – this refers to a geometric figure

without any dimension. It only shows position.

Line – this is a figure made only by a moving point.

Perpendicular Line – lines drawn 90 deg in relation to a horizontal line.

Geometric terms and figures: (cont’d) Horizontal Lines – are lines parallel to the

horizon or the lower edge of the drawing paper. Vertical Lines – lines which are parallel to the

vertical edge of the paper.

Inclined Lines – neither vertical nor horizontal

Geometric terms and figures: (cont’d) Angles

Right Angle Acute Angle Obtuse Angle Reflex Angle Straight Angle

Triangle Scalene Isosceles Equilateral Right Angles

Parallel Lines Bisect

Trisect

Geometric terms and figures: (cont’d) Tangent Line Arc Circumferenc

e Radius Chord Sector Diameter Center

Geometric terms and figures: (cont’d) Polygon

Square Pentagon Hexagon Heptagon Octagon Nonagon Decagon And more

Lesson 5: Orthographic Projectio Is the graphical representation of the different

views of an object to show the necessary information needed.

6 Possible views (Front, top, right side bottom, rear, and left view)

Three Planes of Projection1. Frontal or Vertical plane – the front view is

projected2. Horizontal plane – plane where the

appearance of the object as viewed directly from above on top is projected.

3. Profile or Inclined plane – plane that will show the shape of an object when viewed from the side and the distance from the bottom to top and the distance from the front to rear.

Alphabet of Lines Visible or object line – Invisible line, hidden or dotted line

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Dimension line –

Center line – Extension, projection or witness line –

Leader line -

Alphabet of lines Cutting plane line –

Reference line

Short break line – Long break line -