ALPHABET OF LINES

1. ALPHABET OF LINES

2. OBJECTIVES – Standard VI & Standard VII • Interpret plans, diagrams, and working drawings. • Apply appropriate technical and graphic communication in the technological systems. • Identify Line Types for the Alphabet of Lines • Construct lines properly on drawings. • Hierarchy of lines

3. ESSENTIAL QUESTIONS • Why is drafting considered a universal language? • Why is it important to recognize the alphabet of lines? • What is the hierarchy of lines?

4. Drafting as a Language • Drafting is called a “universal language” • Symbols (lines and figures) have specific meaning are used. • The symbols accurately describe the shape, size, material, finish, and fabrication or assembly of a product.

5. Drafting as a Language • Drafting is also known as the “language of industry” • Industry uses this precise language because the drawings must communicate the information the designer had in mind to those who produce the product.

6. Why Study Drafting? • Drafting is a form of graphic communication. • “A picture is worth a thousand words.” • Meaning - A picture tells a story just as well as a large amount of descriptive text.

7. “A picture is worth a thousand words.”

8. ALPHABET OF LINES • Industry standard classifying the different types of lines used in drawings. • Developed by the American Society of Mechanical Engineers (ASME). • Lines are classified by line thickness and drawn thin or thick. • Thick lines are typically drawn with a 0.7 mm or 0.9 mm mechanical pencil. • Thin lines are typically drawn with a 0.3 mm or 0.5 mm mechanical pencil.

9. LINE TYPES

10. CONSTRUCTION • Used to initially lay out a drawing. • Used for guide lines for lettering. • Draw very light and thin so they are barely visible. • Draw with a 0.5 mm pencil.

11. VISIBLE/OBJECT These lines are thick and dark solid (unbroken) lines that are used on drawings to indicate the edges and details of an object. These lines should be the most prominent on the drawing as they are drawn thicker (wider) than most other lines. We will use the 0.9 mm pencil.

12. HIDDEN These lines are medium dashed lines used to indicate a surface, edge, or contour of an object that cannot be seen, or is hidden from view. The dashed lines are 1/8” long with a 1/16” space. Hidden lines will be drawn with a 0.7 mm pencil.

13. CENTER These lines are thin lines made up of alternating long and short dashes. They are used to indicate the center of circles and of symmetrical features. Also as an aid in dimensioning. The short dashed lines are 1/8” long, the space is 1/16”, & the long line ranges from 3/4” to 1 ½”. Lines will be drawn with 0.5 mm pencil

14. SECTION Section lines are thin “cross hatching” lines used in sectional views to symbolize different parts of an object or different materials from which an object is manufactured. Section lines are normally drawn at a 45° with a 0.5 mm pencil.

15. DIMENSION, EXTENSION, & LEADER These lines are thin lines (0.5 mm)used for dimensioning purposes. Dimension and leader lines generally end with arrowheads and are accompanied by a number indicating a size or location dimensions. Extension lines aid dimension lines by extending the surface of the object so it can be dimesioned.

16. CUTTING PLANE OR VIEWING PLANE These lines are very thick lines (0.9 mm) that indicate where an imaginary cutting plane passes through an object, for viewing or sectioning purpose. Arrowheads on both ends of the line point to the surface to be viewed.

17. BREAK These lines are used to shorten a view, or to eliminate repetitive details when an entire view is not necessary. Short break lines are thick wavy freehand lines. Long break lines are thin straight zigzags.

18. PHANTOM These lines are thin lines used to indicate alternate positions of moving parts, lines of motion, adjacent parts and repetitive details. They are similar in style to a Cutting Plane Line, but much thinner in weight.

19. Hierarchy of Line • It is not uncommon for line types to coincide or overlap in a drawing. • When visible lines, hidden lines, or center lines coincide in the same view, a preferred line is illustrated. • That chosen line is determined by what is called the Precedence of Lines.

20. Hierarchy of Line • This list ranks the line type precedence from highest to lowest: • Object or visible line • Hidden line • Cutting plane line • Center line • Break line • Dimension and extension lines • Sectioning lines

21. Hierarchy of Line In the example you can see where lines coincide with one another line from the front view to the side view.

22. Hierarchy of Line The “X” lines are object lines which overlap the hidden line of the circles (holes). The object line has precedence over the hidden line which means the object line is drawn.

23. Hierarchy of Line The “Y” line is an object line which overlaps the center line of the large circle. The object line has precedence over the center line which means the object line is drawn.

24. Hierarchy of Line The “Z” line is a hidden line. Although the center line for the small circle (hole) is in front of the hidden line, the hidden line has precedence over the center line and is therefore shown instead of the center line.

25. REVIEW • Why is drafting considered a universal language? • Even though people around the world speak different languages, the graphic language (symbols & line types) has remained common. • Why is it important to recognize the alphabet of lines? • The lines in the Alphabet of Lines are used to describe shape, size, hidden surfaces, interior detail, and alternate positions of parts. • Each conveys a particular meaning on the drawing. • What is the hierarchy of lines? • The order in which lines are drawn when more than one line type is located in the same location on a drawing.

26. REVIEW • What line starts and ends with a dash? • HIDDEN LINE • What lines should be the most prominent on the drawing? • OBJECT LINE • What line is drawn the lightest and thinnest for laying out the drawing? • CONSTRUCTION LINE