DRAFTING

THE UNIVERSAL LANGUAGE

SKETCHINGRough 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.

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.

Refined Sketches are refined design ideas. They may not look anything like the original rough sketches.

Developing 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.

Oblique Sketches

Isometric Sketches

Perspective Sketches

OBLIQUE SKETCHES

The easiest pictorial sketches to produce.

Show 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.

Cavalier oblique drawings cause the sides and top to look deeper than they are.

Cabinet oblique drawings shorten the lines that project back from the front to one-half their original length.

ISOMETRIC SKETCHES

Isometric means equal measure. Angles formed by

the lines at the upper right corner are equal to 120 degrees.

Object is shown as if viewed from one corner.

PERSPECTIVE SKETCHES

Show how the human eye and camera would see it.

Realism is obtained by

having parallel lines meet at a

distance vantage point.

Most realistic, yet, most difficult of the

three sketches.

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.

Detail DrawingsMost are prepared using the multi-view method.

This method places one or more views of the object in one drawing.

Generally, a top, right side, and end view are shown.

Multi-view drawings use orthographic projection to project information at the right angles to new views.

Front view is drawn in the lower left quadrant of the paper.

Projection lines are extended to the top and right of a front view to form the top and side views.

DRAWING LINESDifferent lines are used to show the outlines and major details on an object.

Hidden lines are dotted lines used to show outlines which are not visible in a certain view.

Object lines are the darkest lines which show the outlines and major details.

Center lines locate holes in a part. These lines pass through the center of the hole.

Extension lines, used in dimensioning, indicate the points from which the measurements are taken.

Between the extension lines are the dimension lines. These have arrows pointing to the extension lines that indicate the range of the dimension.

GLOSSARYRough sketches- incomplete and unrefined design ideas.

Refined sketches- refined design sketches.

Detailed Sketches- communicate size, in addition to the shape and proportion communicated in the first two drawings.

Oblique sketches- Shows the front view as if you were looking straight at it, and the sides extend back from the front. Parallel lines drawn to 45 degrees to the front view.

Isometric sketches- shows object as if viewed from one corner. Angle measures in upper right corner are equal to 120 degrees.

Perspective sketches- realistic sketches that have parallel lines that meet at a distance vantage point.

GLOSSARYOne-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.

Multi-view method- a method that places one or more views of the object in one drawing.

Orthographic projection- top and side views are projected up to the right of the front view.

Object lines- are the darkest lines which show the outlines and major details.

Hidden lines- dotted lines used to show outlines which are not visible in a certain view.

Center lines- lines that locate holes in a part and pass through the center of the hole.

Extension lines- lines used in dimensioning, indicate the points from which the measurements are taken.

Dimension lines- lines that have arrows pointing to the extension lines that indicate the range of the dimension.

GLOSSARY