Explain terms and procedures utilized in technical drafting Objective 4.03 Explain terms and procedures utilized in technical drafting

Drafting is: The process of accurately representing three (3) dimensional objects and structures on a two (2) dimensional surface, usually paper.

SKETCHING Rough Sketches are the most common recording method. The term “rough” describes the state of the design ideas. It suggests that the designs are incomplete and unrefined. Refined Sketches are refined design ideas. They may not look anything like the original rough sketches. Both rough and refined sketches communicate shape and proportion. It does not communicate size. Pictorial sketches try to show the artifact much like the human eye would see it. Therefore, a single view is used to show how the front, sides, and top would appear. Detailed Sketches communicate size, in addition to the shape and proportion communicated in the first two drawings. It also communicates the information needed to build a model of the product or structure

Kinds of Pictorial Sketches: Different techniques are used to show the artifact as the human eye would see it. Therefore, a single view is used to show how the front, sides, and top would appear. 1. Oblique Sketches 2. Isometric Sketches 3. Perspective Sketches

OBLIQUE SKETCHES: The easiest pictorial sketches to produce. Shows the front view as if you were looking straight at it. Sides extend back from the front view. Sides shown with parallel lines that are generally drawn at 45 degrees to the front view.

Two types of Oblique Sketches A cabinet oblique’s depth is drawn at the half the original length. A cavalier oblique’s depth is drawn at the original length.

Types of Oblique Drawings Oblique Pictorials Introduction to Engineering DesignTM Unit 1 – Lesson 1.2 – Intro to Technical Sketching Types of Oblique Drawings Oblique Cavalier Oblique Cabinet The difference in the two is the depth of the object. Project Lead The Way, Inc. Copyright 2007

ISOMETRIC SKETCHES Object is shown as if viewed from one corner. Isometric means equal measure. Angles formed by the lines at the upper right corner are equal to 120 degrees. Isometric sketches Object is shown as if viewed from one corner.

ISOMETRIC SKETCHES 3” 3” 2” Object is shown as if viewed from one corner.

Isometric of a Cube

Isometric Dimensioning

PERSPECTIVE SKETCHES Show how the human eye and camera would see it. Usually drawn to one or two point vanishing points Depict real life appearances

TYPES OF PERSPECTIVE VIEWS Three major types: one-point, two-point, and three-point. One-point perspective shows an object as if you were directly in front of it. Two-point perspective shows how an object would appear if you stood at one corner. Three-point perspective shows how the eye sees the length, width and height of an object.

PERSPECTIVE SKETCHES

Three Point Perspective

Detail Drawings This drawing method places one or more views of the object in one drawing.(Figure 12-4 pg.226) Most detail drawings are prepared using the multi-view method.(Figure 12-5,pg.227) One view drawing Two view drawing Three view drawing Multiview drawing use orthographic projection to project information at right angles to new views drawings. The surface with the most detail is chosen to be shown in the front view. Three view drawings consist of a front, top, and side view are shown. 16

The Alphabet of Lines (Fig. 12-7 pg. 230) Object lines Hidden lines Center lines Extension lines Dimension lines 17

____________________________ Object lines The lines that outline the object and its major details must stand out. These solid lines are called object lines and are the darkest on all drawings. 18

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Hidden lines Some details are hidden in one or more views. Therefore, they are shown but with lighter, dashed lines called hidden lines. 19

Center lines ______ _ ______ _ _____ A third type of line locates holes and arcs on a part. These lines pass through the center of the hole and are thus called center lines. 20

l<—————————————>l Extension lines First, the extension lines indicate the points from which the measurements are taken. 21

l<——————2 ½”—————>l Dimension lines Between the extension lines are dimension lines. These have arrows (or other terminators) pointing to the extension lines that indicate the range of the dimension 22

The symbol used to represent the word PERPENDICULAR is:

Orthographic Projection The front view needs to be sketched first. Any side of the object can be considered the front view. The side that shows the most detail and the fewest hidden lines should be the first choice. The front view consists of width and height. All of the views should be sketched actual size or the same scale. 24

Orthographic Projection The lines that define the right side of the object need to be projected to the right side of the paper. The vertical lines that define the width of the object need to be sketched next. 25

Orthographic Projection The side view is now completed. The top view can be done without any further measuring. Above the side view sketch a line at a 45 degree angle. Sketch construction lines from the sides of the side view up to the angled line. 26

Orthographic Projection At the points where the vertical construction lines intersect the angled line, sketch horizontal lines over the top of the front view. Sketch vertical construction lines from the front view at the points that define the top view up through the horizontal lines. 27

Orthographic Projection Darken all of the lines that define the object in each view and erase all of the construction lines. The width dimension for the top view is projected from the front view. 28