Computer Aided Drafting 2 (1)
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Transcript of Computer Aided Drafting 2 (1)
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 -