CHAPTER 16 Engineering Drawings and Symbols © 2011 Cengage Learning Engineering. All Rights Reserved. 16-1

Material to be Covered Chapter 16: Sections 1 – 5

Outline In this chapter we will Discuss the need for conventional engineering symbols and drawings Show how vital information for an object is communicated to others using Orthographic views Isometric views Sectional views © 2011 Cengage Learning Engineering. All Rights Reserved. 16-3

Outline In this chapter we will Introduce basic rules of an engineering drawing Showing dimensions Specifying material size Indicating finished surfaces Show some common symbols used in civil, electrical, and mechanical engineering © 2011 Cengage Learning Engineering. All Rights Reserved. 16-4

Objectives The objectives of this chapter are to Introduce engineering graphical communication principles To discuss why engineering drawings are important © 2011 Cengage Learning Engineering. All Rights Reserved. 16-5

Importance of Engineering Drawing “a picture is worth a thousand words” In engineering, a good drawing is worth even more than a thousand words © 2011 Cengage Learning Engineering. All Rights Reserved. 16-6

Importance of Engineering Drawing Engineering drawings are important in conveying useful information to other engineers and machinists Allow the readers to visualize what the proposed product would look like Provide information on dimensions and material used to make the proposed product Provide views from the top, the side, and the front © 2011 Cengage Learning Engineering. All Rights Reserved. 16-7

Orthographic Views Orthographic views show what an object’s projection looks like when seen from the top, the front, or the side © 2011 Cengage Learning Engineering. All Rights Reserved. 16-8

Orthographic Views Relative locations of the top, bottom, front, back, right-side, and left-side view © 2011 Cengage Learning Engineering. All Rights Reserved. 16-9

Orthographic Views Views needed to fully describe an object Top view Front view Right-side view © 2011 Cengage Learning Engineering. All Rights Reserved. 16-10

Orthographic Views Three types of lines used in orthographical views Solid lines represent Visible edges of the planes Intersection of two planes Hidden or dashed lines represent An edge of a plane Extreme limits of a cylindrical hole inside the object Intersection of two planes not visible from the direction you are looking © 2011 Cengage Learning Engineering. All Rights Reserved. 16-11

Orthographic Views Centerlines represent Line of symmetry Center of holes Center of cylinders visual edge hidden cylindrical hole centerline of cylinder © 2011 Cengage Learning Engineering. All Rights Reserved. 16-12

Orthographic Views Some objects can be fully described with one view or two views This object can be described by 2 views: front and top Washer can be described by 1 view and thickness © 2011 Cengage Learning Engineering. All Rights Reserved. 16-13

Example 16.1 – Orthographic Views Given: object as shown Find: draw the orthographic views Solution: Front view Top view Side view © 2011 Cengage Learning Engineering. All Rights Reserved. 16-14

Dimensioning and Tolerancing American National Standard Institute (ANSI) sets the standards for the dimensioning and tolerancing practice for engineering drawings Every engineering drawing must include Dimensions Tolerances Materials from which products will be made Finished surfaces marked Other notes such as part numbers © 2011 Cengage Learning Engineering. All Rights Reserved. 16-15

Dimensioning Two concepts when specifying dimensions Size Location Basic dimensioning practice Dimension lines Provide information on the size of the object Extension lines Lines that extend from the points to which the dimension or location is to be specified Lines are drawn parallel to each other with dimension line placed between them © 2011 Cengage Learning Engineering. All Rights Reserved. 16-16

Dimensioning Leaders Fillet Information box contains Arrows that point to a circle or a fillet for the purpose of specifying their sizes Fillet Rounded edges of an object Size, radius of roundness must be specified Information box contains Name of person who prepared the drawing Title of the drawing Date Scale Sheet number and drawing number © 2011 Cengage Learning Engineering. All Rights Reserved. 16-17

Basics of dimensioning practice leader centerline dimension line extension line Basics of dimensioning practice © 2011 Cengage Learning Engineering. All Rights Reserved. 16-18

Example 16.2 – Dimensioning Given: an object and its dimensions are shown below Find: show dimensions in the orthographic views Solution: 1” Side view Front view Top view Orthographic views © 2011 Cengage Learning Engineering. All Rights Reserved. 16-19

Tolerancing Engineered products generally consist of many parts Would everything fit correctly if the actual dimension of machine part is off from the specified value? Must specify a tolerance on your drawing regarding the machine part dimension For example, 2.50 cm +/- 0.01 cm © 2011 Cengage Learning Engineering. All Rights Reserved. 16-20

Isometric View Isometric drawing shows the 3-dimensions of an object in a single view Use to visualize objects that are difficult to visualize in their orthographic views Also called technical illustrations Used to show parts or products in parts manuals, repair manuals, and product catalogs © 2011 Cengage Learning Engineering. All Rights Reserved. 16-21

Isometric Drawings – Procedures We will use the object shown to illustrate the steps of isometric drawings Step 1 Draw width, height, and depth axes Step 2 Measure and draw total width, height, and depth of object © 2011 Cengage Learning Engineering. All Rights Reserved. 16-22

Isometric Drawings – Procedures Step 3 Create the front, top, and side work faces Step 4 Complete the drawing as marked by the remaining line numbers Original © 2011 Cengage Learning Engineering. All Rights Reserved. 16-23

Isometric Drawings – Procedures Step 5 Erase unnecessary lines to yield final drawing Original Step 5 © 2011 Cengage Learning Engineering. All Rights Reserved. 16-24

Example 16.3 – Isometric Drawings Given: object as shown Find: draw isometric view of object Solution: Step 1 Draw width, height, and depth axes © 2011 Cengage Learning Engineering. All Rights Reserved. 16-25

Example 16.3 – Isometric Drawings Step 2 Measure and draw total width, height, and depth of object Original Step 3 Create the front, top, and side work faces © 2011 Cengage Learning Engineering. All Rights Reserved. 16-26

Example 16.3 – Isometric Drawings Step 4 Complete the drawing Original Step 5 Erase unnecessary lines © 2011 Cengage Learning Engineering. All Rights Reserved. 16-27

Sectional Views Sectional views are used when objects have complex interiors Reveal the inside of the object Created by making an imaginary cut through the object The direction of the sight is marked using directional arrows © 2011 Cengage Learning Engineering. All Rights Reserved. 16-28

Sectional Views A sectional view of an object Identifying letter on solid section © 2011 Cengage Learning Engineering. All Rights Reserved. 16-29

Sectional Views Based on how complex the inside of an object is, different methods are used to show sectional views Common section types Full section views Created when the cutting plane passes through the object completely © 2011 Cengage Learning Engineering. All Rights Reserved. 16-30

Sectional Views Half-sectional views Rotated section views Used for symmetrical objects Draw half of the object in sectional view Draw the other half of the object as exterior view Can show interior and exterior views of an object using one view Rotated section views Used when the object has a uniform cross section with a shape that is difficult to visualize Section is rotated 90o and is shown in the plane of view © 2011 Cengage Learning Engineering. All Rights Reserved. 16-31

Sectional Views Removed sections Similar to rotated section Rotated section views are removed from the view itself and shown adjacent to the view Used for objects with a variable cross section Generally many cuts through the section are shown © 2011 Cengage Learning Engineering. All Rights Reserved. 16-32

Sectional Views – Illustrations Rotated sectional view Full sectional view Removed sectional view Half-sectional view © 2011 Cengage Learning Engineering. All Rights Reserved. 16-33

Example 16.4 – Sectional Views Given: object as shown on the right Find: draw sectional view of object as marked by the cutting plane Solution: Original Solid material Sectional view © 2011 Cengage Learning Engineering. All Rights Reserved. 16-34

Engineering symbols Why do we need engineering symbols? Symbols are “language” used by engineers to convey Their ideas Their solutions to problems Their analyses of certain situations Conventional engineering symbols Convey information Effectively communicate to other engineers © 2011 Cengage Learning Engineering. All Rights Reserved. 16-35

Examples of Engineering Symbols © 2011 Cengage Learning Engineering. All Rights Reserved. 16-36

Examples of Engineering Symbols © 2011 Cengage Learning Engineering. All Rights Reserved. 16-37

Summary You should have a good understanding of the importance of engineering drawings in conveying information to other engineers, machinists, and assembly personnel You should understand what is meant by orthographic views, isometric drawing, and sectional views. © 2011 Cengage Learning Engineering. All Rights Reserved. 16-38

Summary You should understand basic rules for an engineering drawing Showing dimension Specifying material size Indicating finished surfaces You should know when to use isometric views and finished surfaces You should be familiar with the different types of sectional views © 2011 Cengage Learning Engineering. All Rights Reserved. 16-39

Summary You should know why we need and use engineering symbols to communicate among ourselves You should be familiar with some of the common civil, electrical, and mechanical engineering symbols © 2011 Cengage Learning Engineering. All Rights Reserved. 16-40

Engineering Drawing and Symbols Questions?