Drafting and Drawing Instruments

• Drafting's origins trace back to ancient times, with cave paintings representing some of the earliest documented forms.
• Early drawings were created on animal hide and vellum, preceding the development of rice paper by the Chinese and papyrus by the Egyptians.
• Drawings serve as a visual means to communicate ideas through detailed illustrations.
• considered a universal language in industry and technology.
• Uses specialized lines and symbols for communication among technical experts.
• Prepares individuals to produce working drawings and simulations for engineering purposes.
• Primary communication tool for engineers.

Drawing Instruments

• Used for drawing and designing
• Quality is essential for good results
• Include T-squares, triangles, compasses, dividers, protractors, and scales

T-Square

• Used for horizontal lines and guiding triangles for vertical lines.
• Can be made of wood, plastic, or a combination.
• Three types: fixed head, movable head, and detachable head.

Triangle

• Typically has two equal sides meeting at a 90-degree angle.
• Made of plastic and comes in various sizes.
• Base must rest on the T-square when in use.
• Common types: 30 degrees X 60 degrees and 45 degrees X 45 degrees.

Compass

• Used for drawing arcs and circles.
• Pen leg and needlepoint leg are held together with a handle.

Divider

• Used for transferring measurements and dividing lines into equal parts.
• Divider points are easily adjusted to transfer accurate measurements.

Protractor

• A semi-circular instrument divided into 180 equal parts (degrees).
• Used for measuring arcs, angles, and circles.
• Usually made of plastic.

Drawing Tools and Materials

Drawing Paper

• Hard and soft surface drawing papers are best.
• Oslo paper is commonly used, but bond paper is also recommended.

Masking Tape

• Used to fasten drawing paper to surfaces without damage.

Pencil Sharpener

• Used to sharpen pencils when dull.

Eraser

• Used to clean drawings.
• Soft erasers remove smudges, harder erasers correct errors.

Drawing Pencil

• Comes in various grades.
• Hard pencils are for accuracy in graphs and diagrams.
• Medium pencils are for general use.
• Soft pencils are for artwork.

Triangular Scales

• Used to reproduce drawings in enlarged or reduced form.
• Architect's scale is most used for general drawing.
• Reproduces measurements in full, reduced, and enlarged sizes.

Erasing Shield

• Made of metal with irregular holes.
• Protects drawings when clearing smudges etc.

Lines

• Drawing: each line represents a specific element
• Use of different weights makes drawings easier to read and understand.
• Alphabet of Lines: set of line symbols in mechanical drawing

Artist's Drawing (Freehand Drawing)

• Done without specialized tools
• Synonymous with sketching

Freehand Drawing

• Built through practice
• Requires only pencil and eraser

Center Line

• Thin line consisting of long and short dashes drawn alternately with a gap of 2mm
• Indicates an imaginary cut

Dimension Line

• Thin line with an arrowhead
• Used to indicate measurements of an object.

Extension Line

• Extends from the object to show dimension limits

Hidden Line

• Medium thick line composed of short dashes about 2-3 millimeters long

Long-Break Line

• Medium thick line consisting of broken and straight lines drawn alternately
• Also known as the limiting line

Phantom Line

• Shows position/s of part of an object that moves
• Drawn by two short dashes and one long dash.

Section Line

• Thin line to show a surface that has been cut
• It is spaced evenly at 45 degrees

English System

• People measure a shorter distance on the ground with their feet. They measure shorter distance by their palm which is equal to an inch, yard, miles.

Metric System

• Decimal system of measurement, exists in several variations with different choices of base units
• Metric Units are widely used for personal, commercial, and scientific purposes.
• The basic SI unit is called the meter. The meter is divided into 100 centimeters. Each centimeter is divided into 10 millimeters.

Conversion of Fraction and Decimal

Changing Fraction To Decimal Form

• A fraction is a numerical quantity that is not a whole number.
• If a number is expressed in the form of where is not equal to zero.
• Metric measurements must be rounded to a convenient number of digits. To convert, divide the top number (numerator) with the bottom number (denominator)

Changing Decimal Form To Fraction

• Write down the decimal divided by 1.
• Multiply the numerator and denominator by 10 for every number after the decimal point.

Short-Break Line

• Thick line drawn in freehand
• Shows details that a part has been cut off/broken out

Visible Line

• Thick line that represents visible edges and the outline of an object

Leader Line

• Short, thin, and inclined line with an arrowhead at the end

Basic Line Sketching

• Horizontal: strokes are drawn from left to right (right-handed) and vice versa
• Vertical: strokes are drawn downward.
• Inclined: strokes drawn downward.
• Curved: strokes are drawn downward.

Principles of Orthographic Projection

Drawings: multi-view, orthographic projection, and orthographic view.

• Multi-view drawing show more than one view of an object
• Orthographic projection show a flat graphical representation
• Orthographic view shows three regular views viewed at 90 degrees.

Six (6) Principal Views of an Object

• include front, left-side, right-side, top, rear, and bottom views

Planes of Projection:

• Horizontal, frontal, and profile are used in orthographic drawing.
• The planes of projection join and form quadrants

Types of Pictorial Drawing

• Axonometric (Isometric, Dimetric, Trimetric)
• Oblique (Cavalier, Cabinet, General Oblique)
• Perspective (Parallel, Angular, Oblique)

Axonometric Pictorial Drawing

• Isometric: shows three surfaces, tilted 30 degrees
• Dimetric: displays a 3D cube with one side smaller than the other two
• Trimetric: axonometric and no axes or angles are equal

Oblique Pictorial Drawing

• Cavalier: depth axis lines are full scale/size.
• Cabinet: depth axis lines are drawn one-half scale
• General oblique: depth varies from one-half to full size.

Perspective Pictorial Drawing

One-point/Parallel:

• Using one vanishing point
• Front view is drawn in true shape

Two-point/Angular

• Using two vanishing points

Three-point/Oblique

• Using three vanishing points.

Scaling and Dimensioning

• Used to enlarge or reduce.
• Scales are ratios when used in furniture drawing
• Reducing: 1:1, 1:2, 1:5, 1:10
• Enlarging: 2:1

Overall Dimension

• Indicates the width, height, and depth

Detail Dimensions

• Indicates size or location
• Scaling helps fit a drawing onto a page or enlarge details for clarity.
• Tools include: proportion scale, scale rule, and calculator.

Dimensioning includes

• Numerical value that defines the size, or form of an object
• Dimensioning - process of using lines, numbers, and notes.

Using Dimensions

Size Dimension

• Overall size and details

Location Dimension:

• position of parts and features.

Full-size Scale

• Ratio of 1:1
• Each millimeter on paper is equal to one on the actual view

Reduced Scale

• 1:2- views are double size
• One value: each 1 mm is equivalent to two mm

Enlarged Scale (Scaled-up)

Scale 2:1

• 2mm represents 1 on the actual object

Undirectional

• Placed dimension can be read from the sheet

Aligned

• Horizontal dimensions can be read from the sheet, and dimensions can on the right side of the drawing.