intro to Drawing

CHAPTER I

Introduction to Drawing OBJECTIVES: At the end of the chapter, the student is expected to: 1. fully understand the many uses and principles of drawing and drafting, 2. know and identify the different drawing materials, tools, and instruments, 3. demonstrate the proper use of drawing tools and instruments, 4. identify the various types of lines and how they are used, 5. perform the required activities by using the needed tools and instruments, 6. appreciate the importance of each tool in drawing objects, and 7. draw with speed and accuracy in performing the required activities. Drawing – is a graphic representation of an idea, a concept, or a thing which actually or potentially exists in life. It is a way of communicating all necessary information about an idea or a concept, or it could be a graphic representation of a real entity, such as a machine part, a house, a tool or a proposed design. In engineering and technical work, being a universal language, drawing is called the language of the industry. 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. This drawing should convey all the needed information for its construction otherwise, the projected outcome or may not be accurately produced.

1. 2. 3.

TYPES OF DRAWING Artistic Drawings- range in scope from the simplest line drawings to the most famous paintings. These drawings are used to express the feelings, beliefs, philosophies, or abstract ideas of the artist. Technical Drawings- means of clearly and concisely communicating all of the information necessary to transform an idea or a concept into reality. It contains more than just a graphic representation of its subject, where it contains dimensions, notes, and specifications. Illustrations or Renderings- sometimes referred to as the third type of drawing because they are neither completely technical, nor completely artistic; because they combine some elements of both the artistic and technical drawings.

Drafting - is the process of representing an object or idea by means of lines having various thickness and makeup. It is an industrial art because it helps in the production of economically useful articles. This is a subject that deals mostly with the drawing of lines. The major kinds of drafting are identified as: 1. furniture drafting – design of various types of furniture and the making of its working drawings. 2. architectural drafting – refers to the making and production of working drawings/ documents of either residential, commercial, industrial, recreational, religious, storage and other structures for evaluation and construction purposes, 3. mechanical or machine drafting – preparation of detail and assembly working drawings of machines and their parts, 4. electrical and electronics drafting – pertains to the production of schematic wiring diagrams for either house wiring connections and radio and television receivers and transmitters or the installation of electrically- operated machines, 5. topographical drafting – the making of plots or maps for various purposes, 6. airplane drafting – the preparation of working drawings of aircraft, including helicopters, planes, rockets, and spaceships, 7. ship or naval drafting – making of working plans for all types of ship for either commercial or naval purposes,

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8. structural drafting – refers to the making of working drawings of buildings, bridges, towers, dams, and the like, and 9. sheet-metal drafting – development of surfaces of various objects made of galvanized iron, steel, aluminum, or copper sheets. Technical Drawing - also known as drafting is the practice of creating accurate representations of objects for technical, architectural and engineering needs. It is the process of producing engineering drawings, and the skill of producing them. A practitioner of the craft is known as a draftsman Engineering Drawing – type of drawing that is technical in nature, used to fully and clearly define requirements for engineered items, and is usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component. Common Features of Engineering Drawing

1. Geometry - the shape of the object; represented as views; how the object will look when it is 2. 3. 4. 5.

1. 2. 3. 4.

viewed from various standard directions, such as front, top, side, etc. Dimensions - the size of the object is captured in accepted units. Tolerances - the allowable variations for each dimension. Material - represents what the item is made of. Finish - specifies the surface quality of the item, functional or cosmetic. For example, a massmarketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery. Objectives in Drawing Students should attain the following objectives in drawing: Accuracy - a drawing is of maximum usefulness if it is accurate. Speed – is not attained by hurrying, but a byproduct of intelligent and continuous work which comes with study and practice. Legibility – as a means of communication to others, a drawing must be clear and legible to serve its purpose. Neatness – if a drawing is accurate and legible, it must also be clean. DRAWING TOOLS, INSTRUMENTS AND EQUIPMENT

Students must be acquainted with the different tools, instruments and equipment frequently used in drawing subjects. Drawing instruments are implements that help a draftsman in drawing geometric forms and figures (compass, divider, etc.). Tools are those which a draftsman manipulates when drawing which include the drafting items used directly to produce drawings (T-square, pencil, etc.). Drafting equipment are devices which also help in making drawings but are bigger and heavier compared to tools and instruments (drawing table, stool, etc.). Drawing board – a light and portable working table which is very handy for beginners. It has a slanting surface similar to a drawing table. Drawing table – like the drawing board, it is a device where drawing paper is fastened. It has a raised, flat surface and with sides that are squared and unbroken. This is a special table with an adjustable top so that it can be tilted to a desired angle, and is where the t-square is laid. Lighted table – a special table that is designed with a glass surface and a fluorescent lamp beneath it. This table is built especially for tracing purposes. Drafting machine – commonly used by professionals. This drawing table has a built-in T-square, triangle and protractor that are attached to it. T-square (or Tee Square) – a drawing tool used as a guide in drawing parallel horizontal lines and as a support for the triangles when drawing inclined lines. 2


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Triangles – tools used for measurements and for drawing vertical and inclined lines with the aid of a Tsquare. There are two kinds of triangles: the 90°x30°x60° and the 90°x45°x45°. With the two triangles and a T-square, other angles or inclined lines can be drawn such as 15°, 75°, 105°, 135°, and 165° (Figures 1.1 & 1.2). Protractor – a tool used for the measurement of angles. Pencil - considered as the most important tool of a draftsman because one cannot start his drawing without it. There are three grades of pencils, examples of which are: H, HB or F and B. H stands for hard, which is a pencil grade used in lay-outing and mechanical drawing. HB or F stands for medium, which are used for lettering and sketching. A B-grade pencil is a soft pencil used in freehand drawing specifically in charcoal painting and pencil rendering. HARD – The hard leads are used for construction lines on technical drawings. MEDIUM – The medium grades are used for general use on technical drawings. The harder grades are for instrument drawings and the softer for sketching. SOFT – Soft leads are used for technical sketching and artwork but are too soft for instrument drawings.

Figure 1.1. A Combination of the Two Triangles

Technical Pens – these are special pens used by engineers and architects for “inking” lines (outlining lines with ink) and lettering. They come in different grades. Compass – an instrument used to draw large arcs and circles in pencil. Mechanical Pencil – use of this type of pencil can save time spent in sharpening, since the lead can be fed from the mechanical pencil as needed. Divider – a tool used for dividing lines and angles; also used for transferring measurements. The two sharp ends of a divider’s needle points make transferring easier even without the use of pencils. Bow instruments – these include the bow compass and the bow divider and could be bought in sets. A bow compass is used for drawing circles and arcs with a diameter that is smaller than 2 cm. and a bow divider is used for transferring very small measurements. French curve – a tool used as an aid in drawing irregular curved lines. It is also used for connecting series of dots to produce smooth curved lines.

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Ruling pen – an instrument used solely for inking lines, which is not widely used anymore. Technical pens are now the preferred instruments. Scale or Rule – needed for measuring sizes and distances and for transferring measurements from it to the drawing paper. A scale or rule can also be used to divide a line into any number of equal parts with the help of the T-square and a triangle. The two kinds of triangular scale are the architect’s scale (English) and the engineer’s scale (Metric). Both scales are used to enlarge or reduce the size of objects drawn. Erasing shield – a tool used in erasing inked or penciled lines, blots, slurs, and so forth. Located in areas where there are other lines. Adjustable triangle – may take the place of both the 30°-60° and 45° triangles because this tool is used to draw angles that cannot be made with the aforementioned triangles. Eraser – a satisfactory eraser should be capable of completely removing pencil and ink lines without roughing the surface of the paper or leaving colored marks.

Figure 1.2. Methods of Placing Triangles to Draw Parallel Lines Proper Use and Care of Tools, Instruments, and Equipment As beginners, one must learn some work habits to extend the life of the drawing tools, instruments and equipment. In mechanical drawing, it is necessary to know and be acquainted with the different instruments, supplies and materials and equipments to be used. This also involves knowledge of how to use and properly care for these instruments. REMINDERS ON THE PROPER USE OF DRAWING TOOLS, MATERIALS, AND INSTRUMENTS 1. The scale should not be used as a ruler. 2. Do not use the head of the T-square as a hammer. 3. Do not put oil on joints of a compass. 4. Do not sharpen a pencil over the drawing board. 5. Tightly cap the ink bottle all the time. 6. Never put away instruments without relieving the spring tension. 4


7. 8. 9. 10.

11. 12. 13. 14. 15. 16.

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Never fill up a pen over the drawing board. Always clean the instruments and the drawing table before beginning your work. Do not fold drawing or tracing paper. Do not use the divider as pincers or picks. Never use the divider in making pin holes. Do not use the edge of the T-square as a guide in cutting the edge of paper. Rub the eraser only on the surface to be erased. Never jab the dividers on the drawing board. Always use the upper edge of the T-square as guide in drawing lines. Always clean your instruments after using them. FREEHAND DRAWING

Freehand drawings are drawings made without the use of any drawing instrument or straightedges. Such drawings are made in preliminary sketches and perspectives, which are pictorial drawings as seen by the artist’s eyes. Sketch is the synonym of freehand drawing. A freehand sketch should not look like an instrumental drawing with perfectly straight and accurate lines. The unevenness of a properly sketched line is more attractive and interesting than a mechanically perfect line. The weight, direction, and proportions of sketched lines are important in freehand drawing. Freehand sketching only requires paper, pencil, and eraser. Pencil Strokes and Techniques Sketches, as with drawings, consist of straight and curved lines. With practice, drafters can become skilled in creating neat, sharp, clear examples – straight or curved – of all the various line types which will be introduced later. In order to attain the desired result, the following should be followed:

1. Soft pencils, such as HB or F, should be used for freehand sketching with point slightly rounded 2. 3.

4. 5. 6. 7. 8.

9. 10.

rather than needle-sharp, Hold the pencil naturally, about 1 ½” back from the point, and approximately at right angles to the line to be drawn, To sketch a line, rest your hand on the drawing surface and pivot only the fingers, Draw horizontal lines from left to right with a free and easy wrist-and-arm movement (figure 1.3), parallel to the lower edge of the drawing paper, Draw vertical lines downward with finger and wrist movements, Draw inclined lines from left to right, Short lines are drawn with finger movement while long lines are made with arm movement, Sketch lines longer than 1” in short intervals, with a small gap between each interval. Do not omit these gaps for they add a professional touch to a sketch, Circles and arcs are best drawn by inscribing them inside a square of light construction lines (figure 1.4), and Ellipses are drawn best by sketching first the center lines with light lines and then the enclosing rectangle with very light construction lines (figure 1.5).

Vertical lines

Horizontal lines

Inclined lines

a. Short lines drawn with finger movement

b. A long line drawn with arm movement c. A long line drawn in segments

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Figure 1.3. Pencil Techniques in Drawing Straight Lines


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Radii Method

One or two-stroke Method

Figure 1.4. Pencil Techniques in Drawing Circles and Arcs in Sketching

Parallelogram Method

One or two-stroke Method

Figure 1.5. Pencil Techniques in Drawing Ellipse Pencil points may be sharpened into different shapes, as shown in figure 1.6, depending on the purpose. For sketching, the first two shapes are preferred.

Figure 1.6 Pencil point Shapes 6


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NOTE: To avoid developing a flat portion and to reduce the number of necessary sharpening of pencil, slightly twist the pencil when sketching a line. ALPHABET OF LINES These are conventional lines, each with definite purpose, which must be properly drawn or sketched in order not to be misinterpreted. On a technical drawing, line is the most fundamental and perhaps the most important entity. Lines help to illustrate and describe the shape of objects that will later become real parts. LINE

SYMBOL

Border Lines

LINE WIDTH Very thick

Object/ Visible Lines

Thick

Hidden Lines

Thin

Center Lines

Thin Thin

Long Break Lines Thick

Short Break lines

Thin

Phantom Lines

Stitch Lines

Thin or

Extension Lines

Thin

Dimension Lines

Thin

Leader Lines/ Reference Lines

Thin

Cutting Plane Lines

or

Thick

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USES/ DESCRIPTION Serve as boundary of the drawing. Used in drawing templates. To show the main outline or edges or contours of an object . View visible lines so that the views they outline stand out clearly on the drawing with a definite contrast between these lines and secondary lines. To show areas that are not visible on the surface but which exist behind the plane of projection. To indicate symmetry about an axis and location of centers. This line consists of alternating long and short dashes. Thin, solid ruled lines with freehand zigzags which are used to reduce or shorten the view of long uniform sections or when only a partial view is needed. Solid freehand lines used to indicate a short break in a detail and assembly drawing. To show alternate positions of related parts, adjacent positions of related parts, and repeated detail. They consist of long dashes separated by pairs of short dashes. The short dashes may vary in length, depending on the size of the drawing. To show a sewing and stitching process. This is made of short thin dashes and spaces of equal lengths of approximately 0.016, and the second is made of dots spaced at 0.12 inch apart. Thin unbroken lines used to indicate extent of dimensions To indicate distance measured Leaders are used to connect a note or dimension to part of an object; to indicate part, dimension or other reference To designate where an imaginary cutting took place; to indicate direction of sight when a partial view is used or to show the location of cutting planes for sectional views.


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Thin

Used to indicate the surface in the section view imagined to have been cut along the cutting-plane line. Used as horizontal and vertical guides in lettering.

Section Lines Guide Lines

Very Thin

All required lines should be clean-cut, dark, uniform throughout the drawing, and properly spaced for legible reproduction by all commonly used methods. Spacing between parallel lines may be exaggerated to a maximum of 3 mm (.12”) so there is no fill-in when the drawing is reproduced. The use of line types on a drawing are used to describe the various features of an object to the person reading the print.

Cutting-plane lines

Object Lines

Hidden Line

Leader Lines

Phantom Line

Section Line

Dimension and

Center Lines 8


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Extension Lines

Stitch Line

Short-Break Line

Long-Break Line

It is very important to understand the different use of lines. The alphabet of lines is the common language of the technician and the engineer. In drawing an object, the draftsman arranges the different views in a certain way, and then uses different types of lines to convey information.

SKETCHING GEOMETRICAL FIGURES A line is the movement of a point and the latter only indicates position. In art or in drafting, a pointed mark made by a pencil or drawing pen is assumed to be a point, and an extension or prolongation of the pencil or pen point as a line. Therefore, a point represents a corner or the intersection of two edges of an object, while a line may represent an edge or the intersection of two plane surfaces of the same object.

Figure 1.7 Points and Lines 9


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Figure 1.8 Angles Plane Figures

Figure 1.9 Curved Figures

Figure 1.10 Quadrilaterals

Figure 1.11 Triangles

10 Figure 1.12 Regular Polygons


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Solid Figures

Figure 1.13 Cones

Figure 1.14 Pyramids

Figure 1.15 Cylinders

Figure 1.16 Spherical Figures

11 Figure 1.17 Prisms


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Quadrilateral - a plane figure with four (4) sides. Some quadrilaterals are the trapezoid, square, rectangle, and parallelogram. Parallelogram - a quadrilateral with two opposite sides parallel and equal. Examples of parallelograms are: square, rhombus, and rectangle. Rectangle - has four (4) right angles and two (2) of its opposite sides are equal and parallel. Rhombus – has four equal sides, but its angles are not right angles. Trapezoid – a quadrilateral with two opposite sides parallel. Its other two sides are not parallel and are unequal in length. Trapezium – a quadrilateral with no equal sides and angles. Cone – a geometrical solid with a circular base and with sides tapering to a point., called the vertex. If a cone is cut parallel to its base, the bottom portion is called a frustum of the cone and the upper part is a smaller cone. If the cutting plane is oblique or inclined, the resulting cone is truncated. Pyramid – a solid figure whose base is either square, triangular, rectangular, or polygonal in shape. It can also be cut to form a frustum or truncated pyramid. Prism – a solid figure with a base either square, rectangular, or polygonal in shape. A prism with a square-shaped base is called a square prism. Cube – figure whose other five sides (f a square prism) are equal in size to its base. SKETCHING EXERCISES Sketch the following with the use of a soft pencil. 1. Freehand Drawing of Lines (Paper size is 9” x 12 “).

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2. Freehand Drawing of Curves

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3. Freehand Drawing of Geometric Figures/ Solids

INSTRUMENTAL DRAWING Instrumental drawing or mechanical drawing - is a term that applies only to a drawing made with drawing instruments. One has to be familiar with the instruments to be used in drawing objects. How to Locate the Center of the Paper’s Drawing Area In order to center objects in the drawing paper, with reference to the border lines, the following must be considered: 1. Connect the opposite corners of the drawing paper/ template’s borders with the aid of any straight edge (1 & 2, and 3 & 4), 2. Lightly mark the approximate center of the paper with the use of a hard pencil, 3. If needed, draw vertical and horizontal lines passing through the center of the paper.

14 Figure 1.18 Center of the Paper


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Improper pen handling Holding pen nibs or reservoir pens to the paper surface incorrectly may result in undesirable lines that have defective resolution.

Figure 1.19 Result of improper pen handling Drawing over pencil lines in ink One can draw in ink over lines previously drawn in pencil. After the inked in portion of the drawing is complete, remove the graphite under drawing with a soft eraser. If the basic pencil drawing contains too much graphite, the ink will roll away from the pencil line. Should this occur, carefully remove some of the graphite with a soft eraser. INSTRUMENTAL DRAWING EXERCISES 1. With the aid of your drawing tools and instruments, draw the following in your drawing template: A. 45° parallel lines, E. The pyramids, B. The prisms, F. The triangles, C. The curved figures, G. The lines of Sketching Exercise no. 1, D. The quadrilaterals, H. The arcs/ curves of Sketching Exercise no. 2.

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intro to Drawing

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