Drafting TechniquesIntroductionYou should know the techniques of pencil drawing, tracings, and ink tracingbefore you attempt to create or revise technical drawings.Pencil drawingsBy far the greater part of all drafting is done in pencil. Most prints orphotocopies are made from pencil tracings; all ink tracings are made frompencil drawings. There are two types of pencils: those with conventionalwood-bonded cases known as wooden pencils and those with metal or plasticcases known as mechanical pencils.Figure 3-1 shows an example of a conventional and mechanical pencils.Figure 3-1.—Conventional and mechanical pencils.Pencil manufacturers market three types of lead used to produce engineeringdrawings; graphite, plastic, and plastic-graphite.GRAPHITE: Graphite is conventional lead composed of graphite, clay, andresins. It is available in varying degrees of hardness. The hardest grades are9H, 8H, 7H, and 6H. Mediums grades are 5H, 4H, 3H, and 2H. Mediumsoft grades are H and F. The soft grades are HB, H, and 2B; and the softestgrades are 6B, 5B, 4B, and 3B. The softer grades are not suitable for precisetechnical drawing or drafting, but may suffice for freehand technicalsketches.PLASTIC: Plastic lead was developed particularly for drawing or drafting ondrafting films such as Mylar or vellums. They are available in a limitednumber of grades, which do not closely correspond to the degrees ofhardness in conventional graphite leads. Plastic lead has good microformreproduction characteristics.Continued on next page3-6
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