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# Eas 3711 dimensioning and tolerancing

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### Eas 3711 dimensioning and tolerancing

1. 1. Dimensioning & Tolerancing<br />Dr. Fairuz I. Romli<br />Semester 2 2009/2010<br />
2. 2. Introduction: Dimensioning<br />Working drawings must show dimensions and contain notes conveying sizes, specifications and other information<br />Techniques of dimensioning presented are based primarily on the standards of the American National Standards Institute (ANSI)<br />Two commonly used units of measurement<br />Metric units – in millimeter – round the millimeters to the nearest whole number<br />English units – in inches – <br /> always show up to two decimal <br /> places, even for whole numbers<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
3. 3. Dual Dimensioning<br />On some drawings, both metric and English units might be required<br />Place the millimeter equivalent either under or over the inch units<br />Place the converted dimension in brackets to the right of the original dimension<br />Be consistent in the arrangement throughout the whole drawing<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
4. 4. Metric Designation<br />In metric system (SI)<br />First-angle projection positions the front view over the top view and the right-side view to the left of the front view<br />American system – use third-angle projection – places top view over the front view<br />Label metric drawings with one of the symbols<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
5. 5. Numeric & Symbolic Dimensioning<br />Vertical dimensions – aligned or uni-directional<br />Uni-directional – all dimensions appear in the standard horizontal position<br />Aligned – numerals are parallel with vertical and angular dimension lines and read from the right-hand side of the drawing, never from the left-hand side<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
6. 6. Numeric & Symbolic Dimensioning<br />Placement<br />Dimensions should be placed on the most descriptive views of the part being dimensioned<br />First row of dimensions should be at least 3 times the letter height (3H) from the object<br />Successive rows of dimensions should be spaced equally at least 2 times the letter height (2H)<br />Regardless of space limitations – numerals have to be the same size throughout the entire drawing<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
7. 7. Numeric & Symbolic Dimensioning<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
8. 8. Numeric & Symbolic Dimensioning<br />Symbols<br />To save some drawing times – use these symbols instead of words<br />Size usually based on the letter height – often 1/8 inch<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
9. 9. Dimensioning Rules<br />To place dimensions and notes on drawings most effectively<br />However, from time to time, rules of dimensioning must be violated due to the complexity of the part or shortage of space<br />Rules for prisms<br />Place the first row of dimensions at least 3H from the object<br />Successive rows at least 2H from each other<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
10. 10. Dimensioning Rules<br />Rules for prisms<br />Place the dimensions between the views sharing these dimensions<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
11. 11. Dimensioning Rules<br />Rules for prisms<br />Place the dimensions on the most descriptive views of an object<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
12. 12. Dimensioning Rules<br />Rules for prisms<br />Dimension visible features, not hidden features<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
13. 13. Dimensioning Rules<br />Rules for prisms<br />Leave the last dimension blank in a chain of dimensions when you also give an overall dimension<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
14. 14. Dimensioning Rules<br />Rules for prisms<br />Place dimensions in well-organized lines for uncluttered drawings<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
15. 15. Dimensioning Rules<br />Rules for prisms<br />Do not duplicate dimensions on a drawing to avoid errors or confusion<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
16. 16. Dimensioning Rules<br />Rules for prisms<br />Dimension lines should cross any other lines unless absolutely necessary<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
17. 17. Dimensioning Rules<br />Rules for prisms<br />Extension lines may cross other extension lines or object if necessary<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
18. 18. Dimensioning Rules<br />Rules for prisms<br />Leave a small gap from the edges of an object to extension lines that extend from them. Do not leave gaps where extension lines cross object lines or other extension lines<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
19. 19. Dimensioning Rules<br />Rules for prisms<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
20. 20. Dimensioning Rules<br />Rules for angles<br />Place angular dimensions outside angular notches by using extension lines<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
21. 21. Dimensioning Rules<br />Rules for angles<br />Dimension a bent surface rounded corner by locating its theoretical point of intersection with extension lines<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
22. 22. Dimensioning Rules<br />Rules for cylindrical parts and Holes<br />Dimension the diameter (not the radius) of a cylinder in the rectangular view<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
23. 23. Dimensioning Rules<br />Rules for cylindrical parts and Holes<br />Dimensions on concentric cylinders are easier to read if they are staggered within their dimension lines<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
24. 24. Dimensioning Rules<br />Rules for cylindrical parts and Holes<br />Dimension holes in their circular view with leaders whenever possible, but dimension them in their rectangular views if necessary<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
25. 25. Dimensioning Rules<br />Rules for cylindrical parts and Holes<br />Draw leaders pointing toward the centers of holes<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
26. 26. Dimensioning Rules<br />Rule for leaders<br />Extend leaders from the first or the last word of a note with a horizontal elbow<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
27. 27. Dimensioning Rules<br />Rule for arcs and radii<br />When space permits, place dimensions and arrows between the center and the arc<br />When space is not available for the numbers, place the arrow between the center and the arc number outside<br />If there is no space for the arrow inside, place both the dimension and arrow outside the arc with a leader<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
28. 28. Dimensioning Rules<br />Rule for location dimensions<br />Locate cylindrical holes in their circular views by coordinates to their centers<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
29. 29. Introduction: Tolerancing<br />Technique of dimensioning parts within a required range of variation <br />Each dimension is allowed a certain degree of variation within a specified zone<br />A tolerance should be as large as possible without interfering with the function of the part to minimize production costs<br />Manufacturing costs increase as tolerances become smaller<br />Positioning of tolerances<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
30. 30. Rules of Tolerancing<br />Order of numbers<br />Place upper limits either above or to the right of lower limits<br />In plus minus tolerancing, place the plus limits above the minus limits<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
31. 31. Rules of Tolerancing<br />Positioning of numbers<br />Spacing and ratios of numerals used to specify tolerances on dimensions<br />Earle, J. H. “Graphics for Engineers”, Addison-Wesley Publishing, 1996<br />
32. 32. Q1<br />
33. 33. Q1<br />
34. 34. Q1<br />
35. 35. Q2<br />
36. 36. Q2<br />
37. 37. Q2<br />