Sketching 
Types: Isometric Sketch The isometric projection is the basis for the typical threedimensional engineering sketch. The three axes of the isometric sketch form mutual 120 degrees angles with each other (see Figure 1). Alternatively, there is a left axis at 30 degrees upward from the horizontal, a right axis at 30 degrees upward from the horizontal, and a 90 degrees vertical axis. The proportions along each axis are in the ratio 1:1:1. The term Isometric means equal (iso) length (metric). Circles on the isometric planes appear as ellipses in isometric sketches. Isometric grids are a convenient aid in sketching isometric drawings with both straight edges (see Figure 2) and circular features (see Figure 3).

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