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Dimensioning

Dimensioning. Lecture 16. Dimensioning. Goals Understand the principles of good dimensioning practice Apply the standard dimensioning practices for engineering drawings Reference BTG Chapter 7 – Dimensions and Tolerances. Geometrics .

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Dimensioning

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  1. Dimensioning Lecture 16 Autumn Quarter

  2. Dimensioning • Goals • Understand the principles of good dimensioning practice • Apply the standard dimensioning practices for engineering drawings • Reference • BTG Chapter 7 – Dimensions and Tolerances Autumn Quarter

  3. Geometrics • The science of specifying and tolerancing shapes and locations of features of on objects Autumn Quarter

  4. Geometrics • It is important that all persons reading a drawing interpret it exactly the same way. • Parts are dimensioned based on two criteria: • Basic size and locations of the features • Details of construction for manufacturing • Standards from ANSI (American National Standards Institute) Autumn Quarter

  5. Scaling vs. Dimensioning • Drawings can be a different scales, but dimensions are ALWAYS at full scale. Autumn Quarter

  6. Units of Measure Angle Dimensions • Length • English - Inches, unless otherwise stated • Up to 72 inches – feet and inches over • SI – millimeter, mm • Angle • degrees, minutes, seconds Autumn Quarter

  7. Dimensioning Terminology Autumn Quarter

  8. Dimensioning Standards (.25 in) (.375 in) Autumn Quarter

  9. Dimensioning Basic Shapes -Assumptions • Perpendicularity • Assume lines that appear perpendicular to be 90° unless otherwise noted • Symmetry • If a part appears symmetrical – it is(unless it is dimensioned otherwise) • Holes in the center of a cylindrical object are automatically located Autumn Quarter

  10. Dimensioning Basic Shapes • Rectangular Prism Autumn Quarter

  11. Cylinders Positive Negative Dimensioning Basic Shapes Autumn Quarter

  12. Dimensioning Basic Shapes • Cone Frustum Autumn Quarter

  13. Dimensioning Basic Shapes • Circle Pattern Center Lines Autumn Quarter

  14. Dimensioning Shows: Size Location & Orientation Autumn Quarter

  15. Example Problem • What dimensions (size & location) are needed? • Where should they be placed? Think Individually, then share with the person next to you. - Compare with the other pair at your table Autumn Quarter

  16. Yes No Grouping Dimensions • Dimensions should always be placed outside the part Autumn Quarter

  17. Put the lesser dimensions closer to the part. Try to reference dimensions from one surface This will depend on the part and how the tolerances are based. Staggering Dimensions Autumn Quarter

  18. Extension Line Practices Autumn Quarter

  19. Repetitive Features Use the Symbol ‘x’ to Dimension Repetitive Features Autumn Quarter

  20. Symbols for Drilling Operations Autumn Quarter

  21. Example Problem • What dimensions (size & location) are needed? • Where should they be placed? Think Individually, then share with the person next to you. - Compare with the other pair at your table Autumn Quarter

  22. Assignments • Dwg 31 – DIM-1 • Fully dimension the objects shown using correct dimensioning practices.(part is fully dimensioned if it is possible to machine it from the dimensions provided) • Use Inch Dimensions to the second place (x.xx) • Dwg 32 – DIM-2 • Fully dimension the objects shown using correct dimensioning practices. • Use one-place metric dimensions (x.x) • Bring your AutoCAD 2D Book Tomorrow Autumn Quarter

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