Alphabet of Lines Mountain Crest Agriculture （字母的行陡峭的山峰农业）.pdfVIP

Alphabet of Lines 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. Alphabet of Lines Alphabet of Lines  The American National Standards Institute (ANSI) drafting standard applies. • An approximate 2:1 line width ratio is used for manually drawn thick and thin lines. • For CAD drawings, a single line width is acceptable.  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. Alphabet of Lines Construction Lines  Used to initially lay out a drawing.  Drawn very light and thin so they are barely visible.  Drawn with a 0.3 mm pencil or a sharpened drafting pencil with a hard lead. Visible Lines  Used to represent the visible edges of an object.  Also called object lines.  Drawn thick and dark.  Drawn with a 0.7 mm or 0.9 mm drafting pencil with a soft lead. Hidden Lines  Used to represent edges hidden from view.  Drawn as thin, dark lines.  Drawn as 3 mm dashes about 1.5 mm apart.  Spacing can vary slightly. Centerlines  Used to show the center of circles and arcs.  Drawn as thin lines.  Drawn using two long dashes and a short dash separated by a 1.5 mm gap.  The short dash is drawn about 3 mm long at the center point.  The long dash extends beyond the circle. Dimension Lines  Used for dimensioning and notes.  Drawn as thin lines.  Drawn with arrowheads on each end and placed between extension lines.  A line break provides space for the dimension. Extension Lines  Used to extend dimensions fro