Engineering Drawing for Beginners

Line-Drawing Quality

• Engineering drawings require precise, clean lines. A beginner should practice drawing with a graphite pencil before starting to draft. Graphite is able to produce different line weights with varying pressure of the lead on the drawing sheet. Dark lines are used for profiles, section cuts and important elements, whereas lighter lines are for detail, texture and minor elements. Furthermore, there are different line types, including continuous, used for most drawings; dashed, for objects overhead; dotted, for objects hidden behind surfaces; centerlines, for denoting the center of objects and spaces; and numerous other lines, for delineating the locations of pipes, wires and property lines. In drafting, all drawn lines should be crisp, without smudges or stray marks.

Orthogonal Projections

• Orthogonal projections are plans, sections and elevations of objects or buildings that are drawn with correct angles of elements and accurate dimensions to scale. People may understand a plan is a horizontal cut through an element or structure, showing the spatial floor or horizontal layout, but they may not know about section and elevation drawings. Section drawings are similar to plan drawings, except sections are cut vertically through an element or structure. Elevations show vertical faces or facades of of elements or structures.

Isometric Drawings

• Similar to orthogonal projections, isometric drawings are drawn dimensionally accurate to scale, but unlike orthogonal projections, the angles of elements in isometric drawings are skewed to represent an object three-dimensionally on a two-dimensional surface. The angles used on drawn vertical and horizontal surfaces, denoting length, height and depth, are continuous throughout the drawing, though they're not accurate in relation to the real objects' angular relationships. Video game players may be familiar with isometric projections, because video games often use isometric views to convey three-dimensional space.

Perspective Drawings

• Perspective drawings are three-dimensional projections that depict an object or structure as the eye would see it. In perspective drawings, objects that are farther away are smaller, and all lines showing depth converge toward one, two or three vanishing points. One-point perspectives depict interior spaces with the vanishing point on a horizon line that's considered to be at eye level. Two-point perspectives show complex or multiple objects arrayed in space with two vanishing points on a horizon line that's considered to be an infinite distance away. Finally, three-point perspectives are similar to two-point perspectives, but a third vanishing point is moved vertically relative to the two horizon-line vanishing points. The third vanishing point expresses extreme height, with all vertical lines converging toward that point.