Engineering Drawings: Line Styles

Standard engineering drawing line types

A variety of line styles graphically represent physical objects. Types of lines include the following:
Visible – are continuous lines used to depict edges directly visible from a particular angle.
Hidden – are short-dashed lines that may be used to represent edges that are not directly visible.
Center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features.
Cutting plane – are thin, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views.
Section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."

Engineering Drawings: Common Features

Drawings convey the following critical information:

Geometry – the shape of the object; represented as views; how the object will look when it is 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 mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery.

Hands-On AutoCAD LT

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Incompleted Shelby on Sketchup

This is the incompleted 67' Ford Mustang Shelby I made on Google Sketchup. It was a good idea for a project, however Sketchup was not the right program to build it. It was fairly inaccurate and hard to line-up due to the inconvient snap function. Finding the blueprints for the car was very easy; a website supplied all the drawings and you simply had to download the picture. Once downloaded, to converted the image to a JPEG image on Photoshop then imported the JPEG image into Sketchup.

Isometric Projection

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Isometric drawing is way of presenting designs/drawings in three dimensions. The example below has been drawn with a 30 degree set square. Designs are always drawn at 30 degrees in isometric projection. It is vital that drawing equipment such as T-squares and 30/60 degree set squares are used carefully. The drawing paper should be clip securely to a drawing board.

Oblique Projection

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Oblique projection is a method of drawing objects in 3 dimensions. It is quite a simple technique compared to isometric or even perspective drawing. However, to draw accurately in oblique projection traditional drawing equipment is needed, such as rulers, drawing boards, T-squares, set squares, etc.

Artistic/Perspective Drawing

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1. Single Point Perspective Drawing

Perspective drawing is a good style to use when drawing in 3D. There are different styles including single point and two point perspective. The basic example below shows how to construct a simple single point perspective drawing of a cube. Using the same skills more complex drawings/designs can be drawn, after a little practice.

2. Two Point Perspective Drawing

Perspective is a realistic way of drawing objects in 3D. We have already looked at single point perspective, two point perspective using two vanishing points and when an object is drawn in this way it is even more realistic than if it were to be drawn with a single vanishing point.