Understanding Alphabet of Lines in Technical Drafting: Visible, Hidden, Center, Dimension, Assignments of Construction

Download Understanding Alphabet of Lines in Technical Drafting: Visible, Hidden, Center, Dimension and more Assignments Construction in PDF only on Docsity! EDT 300/306 - Basic Technical Drafting 1 Alphabet of Lines Chapter 3 Sacramento City College EDT 300/ ENGR 306 2 Alphabet of Lines The design industry has agreed on a set of standard lines that are used to represent various objects. The American Society of Mechanical Engineers (ASME) has developed this standard which is accepted throughout the industry. Written down in a standards manual. 5 Alphabet of Lines The Alphabet of Lines Object Hidden Center Dimension Extension Phantom Break Datum Construction 6 Alphabet of Lines Refer to Handout The Alphabet of Lines Available on Blackboard APPLICATION OF LINES TH VIEWING-PLANE LINE EXTENSION LINE ree LINE a CENTER LINE HIDDEN LINE BREAK LINE CUTTING-PLANE LINE VISIBLE LINE CENTER LINE \ {PATH OF MOTION) LEADER a LINE PHANTOM LINE — ” SECTION LINE SECTION A-A VIEW B-B (ANS! Y14.2M, 1982) EDT 300/306 - Basic Technical Drafting 10 Visible Lines 11 Object/Visible Lines Object/Visible Lines Show the object. Show the outline of the the visible edges or contours of an object that can be seen by an observer. 12 Object/Visible Lines Object/Visible Lines Should stand out sharply when contrasted with other lines on the drawing. Object/Visible Lines - Spacing and Size. Medium width. Continuous line (no dashes) Dense black. 15 Hidden Lines Hidden Lines Show Edges Surfaces Corners of an object that are concealed from the view of the observer. 16 Hidden Lines Hidden Lines Spacing and Size Thin lines. Evenly space short dashes Approximately 1/8” long, Spaces 1/32” long. Dense black. 17 Hidden Lines Hidden Line “Rules” 1. Start and end with a dash. 2. If a hidden line is a continuation of a visible line then a gap is shown. 3. A gap is also shown when a hidden line crosses but does not intersect another line. Hidden lines should be omitted when they are not needed for clarity. 20 Center Lines Center Lines Show 1. Axes of symmetrical parts 2. Centers of circles and 3. Paths of motion. 21 Center Lines Center Lines - Spacing and Size. Thin lines. Alternating long and short dashes. The long dash (3/4” to 1-1/2”) The short dash (1/16” to 1/8”) Dense black. 22 Center Lines Center Lines “Rules” 1. Center lines intersect at the short dashes. 2. Center lines extend only a short distance past the object. 3. Center lines start and end with a long dash. 25 Dimension Lines, Extension Lines and Leaders Dimension lines Indicate the size and direction of dimensions. Are terminated by arrowheads. Dimension Lines - Spacing and Size Thin lines. Continuous. Dense black. 26 Dimension Lines, Extension Lines and Leaders 27 Dimension Lines, Extension Lines and Leaders Extension lines Indicate the termination of a dimension. Extend from approximately 1/16 inch from the object to 1/8 inch beyond the last arrowhead. Extension Lines - Spacing and Size Thin lines. Dense black. Continuous lines. 30 Leader Lines EDT 300/306 - Basic Technical Drafting 31 Cutting Plane Lines 32 Cutting Plane Lines Cutting Plane Lines Indicate the location of the edge view of the cutting plane. Cutting Plane Lines - Spacing and Size Thick line. Dense black. Two forms are approved for general use. EDT 300/306 - Basic Technical Drafting 35 Section Lines 36 Section Lines Section Lines Represent surfaces exposed by a cutting plane passing through an object. Sometimes called “cross-hatching”. “hatching” Drawn at an angle of 45o with a sharp 2H pencil. 37 Section Lines Section Lines - Spacing and Size Thin lines Continuous lines. Dense black. Space about 1/8” apart. small drawings - 1/32 Space lines close together large drawings - 3/16” Space lines further apart. Make line spacing uniform. 40 Break Lines Break lines Show the limit of a partial view of a broken section. For short breaks, a thick line is drawn freehand. Usually used for mechanical work. For large breaks A long, thin line joined by freehand “zig-zags”. Usually used for architectural work. 41 Break Lines Break Lines - Spacing and Size Thick. Dense black. Freehand. Continuous. Thin Dense black Straight line with freehand “zig” Continous. CENTER LINE DIMENSION LINE /-—HIODEN LINE -—BREAK LINE VIEWING-PLANE LINE EXTENSION LINE Cee LINE \ 75 tpHantom LINE ~ — CECTINN 1 INF EDT 300/306 - Basic Technical Drafting 46 Datum Lines 47 Datum Dimensions Datum Lines Show Lines points surfaces that are assumed to be accurate. Are placed on drawings as datum dimensions since they may be used for exact reference and location purposes. 50 Construction Lines Construction Lines Used to lay out all work PRIOR to drawing ANY object lines. Drawn very light so they will not reproduce when making a blue print. (They should not be visible when viewing beyond an arm’s length from the drawing.) Construction Lines - Spacing and Size Thin lines. Light gray lines. Draw with very hard pencil 2H, 3H, 4H. EDT 300/306 - Basic Technical Drafting 51 Border Lines 52 Border Lines Border lines Are the “frame” of the drawing. Spacing and Size Thickest lines. Dense black. Continuous. Border lines are the heaviest of all lines.