Copyright Goodheart-Willcox Co., Inc. Unit 2 Line Conventions and Lettering 25 Stitch lines are included in the ASME standard. These lines simply represent the path of a sewing or stitching process. They are comprised of either short dashes with spaces that are the same length, or a series of dots approximately 1/8″ apart. The chain line is used to indicate an area on the drawing wherein something special applies, as il- lustrated by the NO PAINT note in Figure 2‑2. For example, if the last inch of a rod is to be heat-treated, a 1″ chain line is drawn next to that area of the part, Figure 2-11. A local note can point to the chain line. A chain line appears somewhat similar to a center line, with short and long dashes alternating, but it is thick instead of thin. Standardized Lettering In engineering drawings, the text and numeric infor- mation is referred to as lettering. Within the context of drafting, “lettering” is not only the letters and numerals themselves, but also the process of creating those characters. In the past, when drawing and let- tering were both done by hand, it was of the utmost importance that the lettering be legible, uniform, and standard. Even today, for any documents created by hand, such as preliminary sketches, legible lettering helps avoid potentially costly mistakes. Within the context of print reading, lettering is covered in this unit to establish the definition and standard expression recommended by the ASME standard. Lettering on an industrial print is to be uppercase lettering, unless lowercase lettering is spe- cifically required. The recommended minimum height for lettering is 1/8″ (3 mm), with exceptions for draw- ing block headings, zone letters and numerals, section and view letters, and other information in the title block, such as part name and number. For additional discussion on title block information, see Unit 3. By definition, engineering drawings created by hand use a font referred to in most drafting resources as “single-stroke Gothic lettering,” Figure 2‑12. “Single-stroke” does not imply each letter is created with a single stroke, but rather refers to the freehand technique of forming each letter from a series of single strokes. Gothic means simple, “sans serif” (without serifs) lettering, as opposed to a Roman font, which contains serifs. Serifs are the small tails that make letters appear fancier. As CAD technologies and com- puter fonts were developed, not everyone used the same terminology. For example, one popular CAD system has a font called GOTHIC, but it appears like a traditional “old English” font. The same system has a font called ROMAN SIMPLEX that matches the engineering Gothic style rather well, but also a ROMAN DUPLEX font that is a truly Roman-style lettering, complete with serifs. This can be confus- ing when establishing CAD template drawings and standard CAD management protocols. However, CAD lettering is consistent and accurate, and there are many fonts and styles from which to choose. In summary, it is critical that industrial prints have clear and concise lettering, and computer applica- tions have helped to meet that goal. Goodheart-Willcox Publisher Figure 2‑10. Phantom lines are used to show (A) alternate positions of moving parts, (B) adjacent positions of related parts, and (C) repeated detail. NEW GIRDER A B C Goodheart-Willcox Publisher Figure 2‑11. A chain line indicates something special applying to an area of a part, such as the heat treatment detail noted here. EXISTING