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Functional Dimensioning and Surfaces

Functional Dimensioning and Surfaces. Lecture 19. Topics For Today. Quick Review of Dimensioning Principles Functional Dimensioning Methods Dimensioning to Finished Surfaces. Each feature dimensioned once and only once Dimensions should suit the function of the object.

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Functional Dimensioning and Surfaces

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  1. Functional Dimensioning and Surfaces Lecture 19 Autumn Quarter

  2. Topics For Today • Quick Review of Dimensioning Principles • Functional Dimensioning Methods • Dimensioning to Finished Surfaces Autumn Quarter

  3. Each feature dimensioned once and only once Dimensions should suit the function of the object Principles of Good Dimensioning Autumn Quarter

  4. Principles of Good Dimensioning • Attach dimensions to most descriptive view Autumn Quarter

  5. Principles of Good Dimensioning • Angles as Right Angles Assumed 90o unless otherwise noted • Dimensions outside of object whenever possible Autumn Quarter

  6. Principles of Good Dimensioning • Dimension lines aligned and grouped to promote uniform appearance Autumn Quarter

  7. Principles of Good Dimensioning • Dimension lines should be unbroken except for the number between the arrowheads • Space (at least) • 3/8 in. from object to 1st line • 1/4 in. from line to next line Autumn Quarter

  8. Gap – object to extension line = 1/16 in. Extension lines 1/8 in. beyond dimension line Extension lines broken for crossing Principles of Good Dimensioning Autumn Quarter

  9. f1.50 f1.50 Incorrect Correct Principles of Good Dimensioning • Leader lines used to dimension circles and arcs should be radial Autumn Quarter

  10. Principles of Good Dimensioning • Positive Cylinder in longitudinal view, Holes in Circular View, f before value Autumn Quarter

  11. Principles of Good Dimensioning • Internal and external radii should be dimensioned with numerical value preceded by the symbol R (Note small cross for center.) Autumn Quarter

  12. Principles of Good Dimensioning • Do a final check! • Every feature has been dimensioned once and only once • Make sure the numerical values are correct Autumn Quarter

  13. Finished surface (machined, laser cut, etc.) are used to get more exact “fits”. Finished surfaces have sharp edges Exception: If a radius is machined Dimensioning to Finished Surfaces Autumn Quarter

  14. Dimensioning to Finished Surfaces • Finished surfaces should always be used to locate features on drawing. Autumn Quarter

  15. Holes need to be located relative to each other or to finished surfaces. Locating Features on an Object Autumn Quarter

  16. Dimensioning to Finished Surfaces – Assembly Drawings • What are the most critical dimensions for the function of the assembly? • How do we dimension to minimize variation in critical relationships? • Examples: Today's drawings Autumn Quarter

  17. Assignments • Dwg 37 – A24 Dimensioning (metric) • Select and place the dimensions required to complete the detail drawing of the Bracket. • Keep in mind which dimensions/features are important • Dwg 38 – A25-A Dimensions (inches) • Note that the scale is half size Autumn Quarter

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