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Geometric Dimensioning and Tolerancing

Geometric Dimensioning and Tolerancing. Unit 3 – How the GDT System Works. Geometric Tolerancing Workbook. Everyone should have a workbook to follow along. It contains necessary reference information along with class exercises.

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Geometric Dimensioning and Tolerancing

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  1. Geometric Dimensioning and Tolerancing Unit 3 – How the GDT System Works

  2. Geometric Tolerancing Workbook Everyone should have a workbook to follow along. It contains necessary reference information along with class exercises. Page numbers in yellow on the slides match pages in the workbook.

  3. Plus/Minus Tolerancing Drawing with plus/minus or directly toleranced dimensions All ANGLES ±1º 3.2

  4. Manufactured part with variation How do you verify conformance? 3.2

  5. Plus/Minus Tolerancing for unopposed surfaces is not clear. 24.3 MAX A variety of interpretations are possible. 24.3 MAX 24.3 MAX 2.12

  6. All ANGLES ±1º 3.2

  7. Hole Bar Assembly HOLE BAR Function: Part mounts in corner and large hole must clear the blue pin. 3.2

  8. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  9. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 Hole is .750 Pin is .740 .010 Must clear Ø.740 Pin Clearance 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  10. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole is .750 Pin is .740 .010 Must clear Ø.740 Pin Clearance 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  11. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole is .750 Pin is .740 .010 Must clear Ø.740 Pin Clearance 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  12. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 ±.005 establishes a .010 square tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  13. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves right and clears the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  14. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves left and clears the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  15. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves down and clears the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  16. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves up and clears the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  17. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves diagonal up and over and interferes with the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  18. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves diagonal down and over and interferes with the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  19. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Hole moves diagonal up and over and interferes with the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  20. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 ± . 0 0 5 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 ± . 0 0 5 . 7 5 0 Hole moves diagonal down and over and interferes with the pin Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  21. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  22. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 .010 Must clear Ø.740 Pin .010 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  23. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 ± . 0 0 5 ± . 0 0 5 .010 .014 Across Corners Must clear Ø.740 Pin .010 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  24. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 Problem - Square tolerance zone allows more tolerance across the corners than the flats. ± . 0 0 5 ± . 0 0 5 .010 .014 Across Corners Must clear Ø.740 Pin .010 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  25. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 . 7 5 0 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 To solve this problem some designers cut the tolerance to +.0035. This gives .010 across corners but only .007 across flats 5 ± . 0 0 3 ± . 0 0 5 ± . 0 0 5 5 ± . 0 0 3 .007 .010 Across Corners Must clear Ø.740 Pin .007 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  26. HOLE BAR In the past this is how designers calculated hole locations with Plus/Minus tolerancing 1 . 5 0 0 5 ± . 0 0 3 ± . 0 0 5 2 . 5 0 0 . 7 5 8 ± . 0 0 5 . 7 5 0 5 ± . 0 0 3 In the 1930’s, Stanley Parker from the Royal Torpedo factory in Scotland came up with the idea of using round tolerance zones rather than square zones. Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.3

  27. HOLE BAR First, make all the dimensions locating the holes basic, (without tolerance) by placing a box around the dimensions. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  28. HOLE BAR First, make all the dimensions locating the holes basic, (without tolerance) by placing a box around the dimensions. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  29. HOLE BAR Since Geometric Tolerancing is a feature based system, use the position symbol to locate the feature 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  30. HOLE BAR Next, specify that the tolerance zone should be round with the diameter symbol. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  31. HOLE BAR Next, specify the total tolerance of .010 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  32. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  33. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  34. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  35. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  36. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  37. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  38. HOLE BAR The axis of the hole can move up and down and around anywhere within the round tolerance zone. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M .010 diameter tolerance zone Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  39. HOLE BAR Still a problem. Must establish a Datum Reference Frame. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M Must clear Ø.740 Pin 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  40. HOLE BAR Still a problem. Must establish a Datum Reference Frame. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in assembly 2 . 5 0 0 3.6

  41. HOLE BAR Produced part is imperfect and not square 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M Imperfect part 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  42. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  43. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  44. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  45. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  46. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  47. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  48. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  49. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

  50. HOLE BAR How do you place an imperfect datum reference frame? It rattles around. 1 . 5 0 0 2 . 5 0 0 . 7 5 8 . 7 5 0 . 0 1 0 A B C M 1 . 5 0 0 Part mounted in DRF 2 . 5 0 0 3.6

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