The term 'Isometric' is derived from two words. 'iso' meaning equal and 'metric' meaning measure. So, isometric drawing and projection refers to the fact that the angles used to form the projection planes are equal or in mathematical terms, 360° divided by 3 equals 3 drawing planes of 120°.
Isometric drawing is a quick and effective method used for depicting the 3-dimensional form of an object. It differs from isometric projection because the depth and width of the drawing are not scaled. Although this means that the drawing is slightly larger than how it appears in real life, isometric drawing is generally preferred as it is efficient to draw.
The figures below model how to draw or project an isometric drawing using an orthogonal drawing.
Start by marking the bottom corner of the overall form you are intending to draw.
Using your T-square and an isometric set square, draw a line at 30°. Remember, you are acutally drawing a line at 120° (90° from the T-square + 30° from the set square). Do not worry about measuring the line just best guess the measurement required. It is important to ensure that you draw as lightly as possible. Ideally, your line work should not be able to be seen to anyone standing 1 -2 meters away from you.
Flip over the Set Square and repeat for depth (or width) of the object.
Using a ruler, measure and mark the depth of the object. Mark the line by accurately placing the pencil at the measurement and then spin and lift the pencil. Ensure that your pencil is always sharp!
Rotate the Set Square and draw a vertical line to represent the height of the object.
Repeat drawing the vertical lines for each edge of the object being drawn.
Measure and mark the overall height of the object you're drawing.
Using the t-square and isometric Set Square draw lines to complete the width and depth planes of your object.
Complete the isometric box by drawing the back edges of the object.
You can now begin to draw in the detail of the object.
Isometric projection is similar to isometric drawing in the way in which it is drawn. However, to make the drawing appear more realistic the depth of the drawing is scaled. This foreshortens the object being depicted making it appear smaller and a closer representation of the real life object. Isometric projection is less commonly used because of this.
Exploded views are 3-Dimensional assembly drawings. Usually drawn as isometric drawings, they show how each individual part of a product inter-connects with each other. They are extremely useful for inclusion in instruction manuals.