1. CHAPTER 16 Engineering Drawings and Symbols
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2. Material to be Covered
Chapter 16: Sections 1 – 5

3. 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
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4. 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
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5. Objectives The objectives of this chapter are to
Introduce engineering graphical communication principles
To discuss why engineering drawings are important
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6. Importance of Engineering Drawing
“a picture is worth a thousand words”
In engineering, a good drawing is worth even more than a thousand words
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7. 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
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8. Orthographic Views
Orthographic views show what an object’s projection looks like when seen from the top, the front, or the side
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9. Orthographic Views
Relative locations of the top, bottom, front, back, right-side, and left-side view
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10. Orthographic Views Views needed to fully describe an object Top view
Front view
Right-side view
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11. 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
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12. Orthographic Views Centerlines represent Line of symmetry
Center of holes
Center of cylinders
visual edge
hidden cylindrical hole
centerline of cylinder
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13. 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
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14. Example 16.1 – Orthographic Views
Given: object as shown
Find: draw the orthographic views
Solution:
Front view
Top view
Side view
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15. 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
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16. 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
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17. 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
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18. Basics of dimensioning practice
leader
centerline
dimension line
extension line
Basics of dimensioning practice
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19. 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
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20. 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 +/ cm
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21. 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
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22. 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
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23. 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
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24. Isometric Drawings – Procedures
Step 5
Erase unnecessary lines to yield final drawing
Original
Step 5
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25. Example 16.3 – Isometric Drawings
Given: object as shown
Find: draw isometric view of object
Solution:
Step 1
Draw width, height, and depth axes
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26. 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
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27. Example 16.3 – Isometric Drawings
Step 4
Complete the drawing
Original
Step 5
Erase unnecessary lines
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28. 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
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29. Sectional Views A sectional view of an object Identifying letter
on solid section
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30. 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
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31. 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
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32. 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
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33. Sectional Views – Illustrations
Rotated sectional view
Full sectional view
Removed sectional view
Half-sectional view
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34. 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
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35. 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
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36. Examples of Engineering Symbols
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37. Examples of Engineering Symbols
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38. 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.
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39. 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
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40. 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
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41. Engineering Drawing and Symbols
Questions?