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SECTION VIEWS C H A P T E R S E V E N. Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012,

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Presentation on theme: "SECTION VIEWS C H A P T E R S E V E N. Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012,"— Presentation transcript:

1 SECTION VIEWS C H A P T E R S E V E N

2 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. OBJECTIVES 1.Understand sections and cutting-plane lines. 2. Apply correct section-lining practices. 3. Recognize and draw section lining for 10 different materials. 4. Draw a section view given a two-view drawing. 5. Demonstrate correct hidden-line practices for section views. 6. Identify seven types of sections. 7. Apply section techniques to create clear, interpretable drawings. 8. Demonstrate the proper techniques for sectioning ribs, webs, and spokes. 9. Use hatching when using conventional breaks to show elongated objects. 10. Interpret drawings that include section views.

3 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. UNDERSTANDING SECTIONS Section views are used for three main purposes: To document the design and manufacture of single parts that are manufactured as one piece. To document how multiple parts are to be assembled or built. To aid in visualizing the internal workings of a design. When the part is cut fully in half, the resulting view is called a full section.

4 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. THE CUTTING PLANE The cutting plane appears edgewise as a thick dashed line called the cutting-plane line. The arrows at the ends of the cutting-plane line indicate the direction of sight for the sectional view. The Cutting Plane

5 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. VISIBLE EDGES ON CUTTING PLANES Newly visible edges cut by cutting plane are crosshatched with section lining.

6 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. LABELING CUTTING PLANES Note that each section (A-A and B-B) is completely independent.

7 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. RULES FOR LINES IN SECTION VIEWS Show edges and contours that are now visible behind the cutting plane. Omit hidden lines in section views. A sectioned area is always completely bounded by a visible outline—never by a hidden line. A visible line can never cross a sectioned area in a view of a single part.

8 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. CUTTING-PLANE LINE STYLE It is made up of equal dashes, each about 6 mm (1/4“) long ending in arrowheads. This form works especially well for drawings. The alternative style, uses alternating long dashes and pairs of short dashes and ends with arrowheads. This style has been in general use for a long time, so you may still see it on drawings. Both lines are drawn the same thickness as visible lines. The arrowheads at the ends of the cutting plane line indicate the direction in which the cutaway object is viewed. Alternative Methods for Showing a Cutting Plane A and B.

9 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. VISUALIZING CUTTING-PLANE DIRECTION Correct and Incorrect Cutting-Plane Line Placement

10 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SECTION-LINING TECHNIQUE Uniformly spaced by an interval of about 2.5 mm Not too close together Uniformly thin, not varying in thickness Distinctly thinner than visible lines Neither running beyond nor stopping short of visible outlines

11 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SECTION-LINING TECHNIQUE CONTINUED….

12 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SECTION-LINING SYMBOLS Section-lining symbols may be used to indicate specific materials. These symbols represent general material types only, such as cast iron, brass, and steel. Symbols for Section Lining

13 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SECTION-LINING IN CAD CAD programs usually include libraries that allow you to select from a variety of section-lining patterns, making it easy to use different patterns, angles, and scales for the spacing of the pattern.

14 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. HALF SECTIONS Symmetrical objects can be shown effectively using a special type of section view called a half section. A half section exposes the interior of half of the object and the exterior of the other half. This is done by removing one quarter of the object. Half section Cutting plane

15 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. BROKEN OUT SECTIONS It often happens that only a partial section of a view is needed to expose interior shapes. Such a section, limited by a break line, is called a broken out section.

16 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. REVOLVED SECTIONS The shape of the cross section of a bar, arm, spoke, or other elongated object can be shown in the longitudinal view by using a revolved section. To create a revolved section, first imagine a cutting plane perpendicular to the centerline or axis of the object. Next, revolve the plane 90° about a centerline at right angles to the axis. 90°

17 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. REMOVED SECTIONS A removed section is one that is not in direct projection from the view containing the cutting plane — that is, it is not positioned in agreement with the standard arrangement of views.

18 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. OFFSET SECTIONS In sectioning complex objects, it is often desirable to show features that do not lie in a straight line by “offsetting” or bending the cutting plane. These are called offset sections. Note the offset cutting plane line

19 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. RIBS IN SECTION To avoid giving a false impression of thickness and solidity, ribs, webs, gear teeth, and other similar flat features are not hatched with section lining even though the cutting plane slices them. Thin features are not hatched even though the cutting plane passes lengthwise through them.

20 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ALIGNED SECTIONS When parts with angled elements are sectioned, the cutting plane may be bent to pass through those features. The plane and features are then imagined to be revolved into the original plane. Aligned Section The angle of revolution should always be less than 90° for an aligned section.

21 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PARTIAL VIEWS If space is limited on the paper or to save time, partial views may be used with sectioning. Another method of drawing a partial view is to break out much of the circular view, retaining only those features that are needed for minimum representation.

22 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. INTERSECTIONS IN SECTIONS Whenever an intersection is small or unimportant in a section, it is standard practice to disregard the true projection of the figure of intersection. Larger intersections may be projected Note that the larger hole K is the same diameter as the vertical hole. In such cases the curves of intersection (ellipses) appear as straight lines.

23 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. CONVENTIONAL BREAKS AND SECTIONS Conventional breaks are used to shorten the view of an object that is too long to show clearly at one scale on the drawing sheet.

24 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. ASSEMBLY SECTIONS Section views are often used to create assembly drawings. Notice that the hatching on different parts has different hatch patterns or hatch at different angles. When used on the same part, the hatching is always at the same angle to help you recognize the parts easily.

25 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. COMPUTER TECHNIQUES FOR SECTIONS 2D and 3D sectional views are created using CAD. Most CAD systems have a “hatch” command to generate the section lining and hatch patterns to fill an area automatically. (Courtesy of PTC.)

26 C H A P T E R E I G H T AUXILIARY VIEWS

27 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. OBJECTIVES 1. Create an auxiliary view from orthographic views. 2. Draw folding lines or reference-plane lines between any two adjacent views. 3. Construct depth, height, or width auxiliary views. 4. Plot curves in auxiliary views. 5. Construct partial auxiliary views. 6. Create auxiliary section views. 7. Produce views to show the true length of a line, point view of a line, edge view of a surface, and true-size view of a surface. 8. Show the true size of the angle between two planes (dihedral angle). 9. Construct the development of prisms, pyramids, cylinders, and cones. 10. Use triangulation to transfer surface shapes to a development. 11. Create the development of transition pieces. 12. Graphically solve for the intersection of solids. 13. Apply revolution to show true-length edges and true-size surfaces.

28 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. UNDERSTANDING AUXILIARY VIEWS Auxiliary views are useful for both design and documentation. Many objects are shaped so that their principal faces are not parallel to the standard planes of projection. To show the true circular shapes, use a direction of sight perpendicular to the plane of the curve, to produce an Auxiliary View.

29 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. THE AUXILIARY PLANE To show the inclined surface (P) true size, the direction of sight must be perpendicular to the inclined plane. The auxiliary plane in this case is perpendicular to the frontal plane of projection and hinged to it. It is angled to the horizontal (top) and profile (side) viewing planes.

30 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PRIMARY AUXILIARY VIEWS A primary auxiliary view is projected onto a plane that is perpendicular to one of the principal planes of projection and is inclined to the other two.

31 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DEPTH AUXILIARY VIEWS All these views show the object’s depth and therefore are all depth auxiliary views.

32 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. HEIGHT AUXILIARY VIEWS The front view and all these auxiliary views show the height of the object. Therefore, all these auxiliary views are height auxiliary views.

33 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. WIDTH AUXILIARY VIEWS The front view and all these auxiliary views are width auxiliary views.

34 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SUCCESSIVE AUXILIARY VIEWS From a primary auxiliary view, a secondary auxiliary view can be drawn, then from it a third auxiliary view, and so on. Successive Auxiliary Views

35 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. SECONDARY AUXILIARY VIEWS A secondary auxiliary view is projected from a primary auxiliary view onto a plane that is inclined to all three principal projection planes. Second Auxiliary View, showing the True Size of the Top Oblique Surface

36 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. REFERENCE PLANES If you are using 2D CAD, you can draw half of the view and then mirror the object. Instead of using one of the planes of projection, you can use a reference plane parallel to the plane of projection that touches or cuts through the object.

37 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. Place two triangles together so that the 90° corners are on the outside. Slide them on your drawing until the outer edge of one triangle is along the line to which you want to sketch parallel. Hold down the triangle and slide the other along it. Draw parallel lines along one edge of the triangle. Draw perpendicular lines along the other edge. USING TRIANGLES TO SKETCH AUXILIARY VIEWS You can use two triangles to quickly draw parallel and perpendicular lines for “accurate” sketches.

38 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. CIRCLES AND ELLIPSES IN AUXILIARY VIEWS Circular shapes appear elliptical when viewed at an angle other than 90° (straight on to the circular shape). This is frequently the case when constructing auxiliary views.

39 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. HIDDEN LINES IN AUXILIARY VIEWS Your instructor may ask you to show all hidden lines for visualization practice, especially if the auxiliary view of the entire object is shown. Later, when you are familiar with drawing auxiliary views, omit hidden lines when they do not add needed information to the drawing. Generally, hidden lines should be omitted in auxiliary views, unless they are needed to clearly communicate the drawing’s intent.

40 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. PARTIAL AUXILIARY VIEWS Using an auxiliary view often makes it possible to omit one or more regular views, but auxiliary drawings are time consuming to create and may even be confusing because of the clutter of lines. Partial views are often sufficient and easier to read.

41 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. AUXILIARY SECTIONS An auxiliary section is simply an auxiliary view in section. Note the cutting-plane line and the terminating arrows that indicate the direction of sight for the auxiliary section. In an auxiliary section drawing, the entire portion of the object behind the cutting plane may be shown, or the cut surface alone may be shown.

42 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. VIEWING-PLANE LINES AND ARROWS When the drawing sheet is too crowded to show the auxiliary view in direction projection you can use a viewing-plane line or a viewing direction arrow to indicate the direction of sight for the auxiliary view.

43 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. DIHEDRAL ANGLES The angle between two planes is called a dihedral angle. Auxiliary views often need to be drawn to show dihedral angles true size, mainly for dimensioning purposes.

44 Technical Drawing with Engineering Graphics, 14/e Giesecke, Hill, Spencer, Dygdon, Novak, Lockhart, Goodman © 2012, 2009, 2003, Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. AXIS OF REVOLUTION The axis of revolution appears as a point in this view. The object revolves but does not change shape in this view. In the adjacent views in which the axis of revolution, if it were drawn, would show as a line in true length, the dimensions of the object that are parallel to the axis of revolution do not change. Revolution, like auxiliary view projection, is a method of determining the true length and true size of inclined and oblique lines and planes.


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