Copyright Goodheart-Willcox Co., Inc. 18 Section 1 Introduction to Drafting and Print Reading Alphabet of Lines There are several types of lines commonly used in engineering drawings, depending on the field of study. The current ASME standard illustrates these and identifies each by name. On some occasions, more than one option for the appearance of the line is given. Each line has a particular meaning to an engineer, designer, or drafter. Individuals who are reading the print must recognize and understand the meanings of these lines in order to correctly inter- pret an industrial print used in the manufacturing environment. The list of types of lines, defined in many references as the alphabet of lines, is used throughout industry. See Figure 2‑1. Each line has a definite form or dash pattern and a standard line weight (width). In older standards, three line weights were recommended— thin, medium, and thick. Current standards rec- ommend two line weights—thick and thin. The standard thick line is recommended to be 0.6 mm in width. The standard thin line is recommended to be 0.3 mm in width. Of course, the actual width of these lines may vary depending on the size of the draw- ing and whether or not the drawing is reduced or enlarged. In all cases, however, the thin-to-thick ratio should remain 1:2. In most cases, CAD programs can be configured to print drawings at any size or scale while maintaining any desired line thickness. It is important to note that thinner lines should not be lighter. All linework should be black. Be aware, however, that many drawings through- out the years have been produced without attention to standard line weight. Many of the early CAD sys- tems could not easily print variations in line weight. With on-screen colors, some creators of drawings may not go to the trouble of establishing line weight. This often produces a drawing that is harder to read and interpret. Within your company, you have the opportunity to be the champion for conformance to industry standards, thus promoting drawings that “speak with the proper language.” Lines in a drawing convey information essential to understanding the print. Therefore, to understand the print, you must know and understand the alpha- bet of lines. Refer to Figure 2‑1 and Figure 2‑2 as you read the remainder of this unit. Primary View Lines Of primary importance to the print reader are the three lines in the alphabet that are used in multiview drawings. Discussed in Unit 5, multiview drawings Goodheart-Willcox Publisher Figure 2‑1. The alphabet of lines is a standardized list of lines from which the drafter can choose. Each line has a definite form or pattern and an intended purpose and meaning. Visible Line Hidden Line Center Line Symmetry Line Section Line Dimensioning Leader Cutting-plane or Viewing-plane lines Break Line Phantom Line Stitch Line Chain Line Thick (Width approximately 0.6 mm) (Width approximately 0.3 mm) Thin Thin Thin Thin All thin Thick Thick Thick Thick Thin Thin Thin Thin Thick EXTENSION LINE DIMENSION LINE