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- 7-1 Introduction
- 7-2 Terminology and Conventions-ANSI
- 7-3 Adding Dimensions to a Drawing
- 7-4 Drawing Scale
- 7-5 Units
- 7-6 Dimensioning Holes and Fillets
- 7-7 Dimensioning Counterbored and Countersunk Holes
- 7-8 Angular Dimensions
- 7-9 Ordinate Dimensions
- 7-10 Baseline Dimensions
- 7-11 Locating Dimensions
- 7-12 Fillets and Rounds
- 7-13 Rounded Shapes-Internal
- 7-14 Rounded Shapes-External
- 7-15 Irregular Surfaces
- 7-16 Polar Dimensions
- 7-17 Chamfers
- 7-18 Symbols and Abbreviations
- 7-19 Symmetrical and Centerline Symbols
- 7-20 Dimensioning to a Point
- 7-21 Dimensioning Section Views
- 7-22 Dimensioning Orthographic Views
- Chapter Projects
This chapter is from the book
This chapter is from the book
This chapter is from the book
This chapter is from the book
7-19 Symmetrical and Centerline Symbols
An object is symmetrical about an axis when one side is the exact mirror image of the other. Figure 7-67 shows a symmetrical object. The symbol of two short parallel lines or the note OBJECT IS SYMMETRICAL ABOUT THIS AXIS (centerline) may be used to designate symmetry.
If an object is symmetrical, only half the object needs to be dimensioned. The other dimensions are implied by the symmetry note or symbol.
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The centerline is slightly different from the axis of symmetry. An object may or may not be symmetrical about its centerline. See Figure 7-67. Centerlines are used to define the center of both individual features and entire objects. Use the centerline symbol when a line is a centerline, but do not use it in place of the symmetry symbol.