Lines used in drafting are lines whose appearance and meaning are determined by international agreements. Geometric Lines

Technical Drawing – Part of the Design Process Before something can be produced, it needs to be imagined by someone. A drawing is a graphic representation of the real thing or idea to be produced. Emphasize that the design process is part of the program in C1 and C2 in both programs- though more in the applied path due to the heavy emphasis on technology in the 2nd competency. 2

Three Ways of Producing Technical Drawings Sketch – freehand showing as much detail as possible Drafting Instruments – precise drawings done entirely by hand with manual drafting instruments CAD – Computer Assisted Design, softwares created starting in the 1960’s

CONVENTIONAL LINES FACING DEEP In a technical drawing, each type of line has its own significance. Each is distinguished from the other by a particular thickness or shape. The object above is drawn in isometric projection. It is portrayed on the left by three views. We will use this object to illustrate the principal lines found in technical drawing on the slides which follow. 4

CONVENTIONAL LINES TOP side Front A OBJECT LINE OR VISIBLE OUTLINE 5

CONVENTIONAL LINES OBJECT LINE OR VISIBLE OUTLINE The object line or visible outline is made of a continuous line that portrays the visible forms of the object. It is a thick line, its thickness chosen to clearly show the shape. OBJECT LINE OR VISIBLE OUTLINE 6

CONVENTIONAL LINES B HIDDEN FEATURE LINE 7

CONVENTIONAL LINES HIDDEN FEATURE LINE B The hidden feature line is made of a dashed line that portrays surfaces and edges that are hidden from view. The line is medium sized, half the width of the one chosen for the visible outline. B HIDDEN FEATURE LINE 8

CONVENTIONAL LINES C C THE CENTER LINE 9

CONVENTIONAL LINES THE CENTER LINE The center line is made from phantom lines. It is used to designate the axes of circular or cylindrical shaped objects. The line is half the width of the one used for hidden features. It is a fine line. THE CENTER LINE 10

CONVENTIONAL LINES SUMMARY A B C D E F G H J LINE NAME PURPOSE THICKNESS 100 % Thick A Object line or visible outline Portrays visible forms. B Hidden feature line Portrays surfaces and edges that are Medium 50 % hidden from view C Portrays the center of a round or circular Fine 25 % Center line object. D Is used to indicate the dimension. Extension line Fine E Is used to indicate the dimension. Dimension line Fine F Cutting plane line Indicates the placement of an Very thick imaginary cut. G Indicate the surface imagined to have Section lines Fine been cut. H Used to shorten the view of a part. Break line Fine J Indicates the part of a drawing to which Fine Leader a note refers 11

Dimensioning

Ø 8 FACING Ø14 X 3 DEEP 80 50 45 40° 13 20 40 Technical drawings must not only faithfully reproduce the shape of objects, but also serve as a guide to their construction or manufacturing. Dimensioning an object means giving all the necessary dimensions to build a technical object.

Lines To enter dimensions and specify their place we use a fine line, called a dimension line, ending in arrows. The dimension is placed in the center of the dimension line. Its value is given in millimetres. Units are not shown. 36 The extension line is a fine line that connects the measured part of the object to the dimension line.

Dimensioning cylindrical shapes Objects with rectangular shapes are dimensioned differently than those with cylindrical shapes. The shapes of rectangular objects are dimensioned in relation to surfaces. Round or cylindrical shapes are dimensioned in relation to their center.

Dimensioning cylindrical shapes The leader line may be drawn at 30º, 45º or 60º. The line touches the circle and points to the center. Ø 25 DIA 25 The Ø symbol or abbreviation DIA precedes the diameter to be dimensioned. Ø 20 R18 Cylindrical holes are dimensioned by a note specifying the diameter and depth, if necessary. Curves composed of arcs of a circle are dimensioned by their radius.

Summary Ø 8 Leader line FACING Ø14 X 3 DEEP Shape dimension 50 40 13 80 50 45 Ø 8 FACING Ø14 X 3 DEEP 40° 13 20 40 Shape dimension Position dimension Dimension Extension line Dimension line

Representations of 3-D objects as two dimensional. Projections

Space Occupied by Objects Concept Explanation Dimension Occupies three dimension: length, width, height Measurement Typically in mm, units of measurement correspond to numbers Side or face Flat surface with two dimensions Edge Limit of a side or border between two sides, only one dimension Vertex A point, no dimensions. Where two or more edges meet.

Orthographic parallel projections In this type of drawing, the observer is infinitely far away. The lines of vision then appear to be parallel. The projection is said to be orthographic to the viewer’s line of vision. (orthographic being the fancy term for perpendicular) Orthogonal is a fancy word to mean perpendicular… Origin is Greek for Right Angles. 20

Multi-view orthographic projections . The observer can only see one side at a time. That is why, in most cases, one must draw several views of the object to portray it completely. 21

Multi-view orthographic projections In technical drawing, the views are flat figures (two dimensions) that we see from directly in front of each object. Width Height 22

Multi-view orthographic projections In the type of projections used in North America, we imagine the object being drawn in the center of a transparent box. The different views of the object are projected onto the sides of this box. 23

Multi-view orthographic projections One of these views is designated as the front view of the object. We usually choose the face that best portrays the object. The choice of the front view determines the placement of the other views. 24

Multi-view orthographic projections The projection box and its six views are spread in such a way as to place all the views on the same plane. BOTTOM VIEW LEFT SIDE VIEW REAR VIEW FRONT VIEW RIGHT SIDE VIEW TOP VIEW The other views pivot around the front view. 25

Multi-view orthographic projections REAR vIEW Among the six possible views, we will choose to portray those necessary to the description of the shape of the object. LEFT VIEW FRONT VIEW RIGHT SIDE VIEW TOP VIEW BOTTOM VIEW 26

Multi-view orthographic projections TOP VIEW Here is the usual representation of views in multi-view orthographic projections. This type of drawing is used in technology because it allows description without deforming the faces of objects. 27 FRONT VIEW RIGHT SIDE VIEW