LEARNING OBJECTIVES After completing this unit, you will be able to: ❯ ❯❯ Define the alphabet of lines. ❯❯ Identify the most common types of lines: visible, hidden, and center. ❯❯ Identify the types of lines used in dimensioning. ❯❯ Identify the types of lines used in sectional views. ❯ Understand the ways in which dashes, arrows, and line thickness are used with various lines. ❯ ❯❯ Describe the types of lines by appearance and purpose. ❯ Identify the style of lettering recommended for standard industrial drawings. TECHNICAL TERMS alphabet of lines break line center line chain line convention cutting-plane line dimension dimension line extension line hidden line leader line lettering phantom line section line stitch line symmetry line viewing-plane line visible line Copyright Goodheart-Willcox Co., Inc. 17 UNIT 2 Line Conventions and Lettering By definition, a convention is a generally accepted way of doing something. Before computers, prints were created by drafters with pencils and pens, and lettering was primarily a freehand craft. Lines were made with lead pencils, and the ability to create a line of an exact width was a skill that took time to develop. The ASME Y14.2 Line Conventions and Lettering standard sets forth the recommended appearance of lines, although in our current age of computers the guidelines no longer specify dash length and line width as precisely as in years past. Because drawings can easily be printed at a variety of scales and sizes, there is more flexibility today.