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Geometric Dimensioning and Tolerance

Geometric Dimensioning and Tolerance. GD&T stands for Geometric Dimensioning & Tolerancing. DIMENSION is a geometric characteristic the size of which is specified such as length,angle,location,or center distance

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Geometric Dimensioning and Tolerance

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  1. Geometric Dimensioning and Tolerance

  2. GD&T stands for Geometric Dimensioning & Tolerancing • DIMENSION is a geometric characteristic the size of which is specified such as length,angle,location,or center distance • TOLERANCE on a dimension is the total permissible variation in its size, which is equal to the difference between the limits of size.

  3. GEOMETRIC DIMENSIONING AND TOLERANCING DIMENSIONS OF A PART

  4. GEOMETRIC DIMENSIONING AND TOLERANCING TOLERANCE SIZES

  5. GEOMETRIC DIMENSIONING AND TOLERANCING TYPE OF TOLERANCE

  6. GEOMETRIC DIMENSIONING AND TOLERANCING SIZES OF MATING PARTS

  7. Deviations • The difference between the basic size and the maximum and minimum sizes are called the UPPER & LOWER deviations. • The BASIC DIMENSION represents the theoretical exact size or location of a feature.

  8. GEOMETRIC DIMENSIONING AND TOLERANCING DEVIATIONS

  9. GEOMETRIC DIMENSIONING AND TOLERANCING BASIC (EXACT) DIMENSIONS Are shown in a rectangle to indicate that the tolerances in the general tolerance note do not apply

  10. Datum • A DATUM is a theoretical exact feature from which dimensions may be taken. • A DATUM is generally chosen as an edge or feature which has the greatest influence in a specific measurement.

  11. GEOMETRIC DIMENSIONING AND TOLERANCING EXAMPLES OF DEVIATION OF FORM WHEN PERFECT FORM AT THE MAXIMUM MATERIAL CONDITION IS REQUIRED

  12. GEOMETRIC DIMENSIONING AND TOLERANCING EXAMPLES OF DEVIATION OF FORM WHEN PERFECT FORM AT THE MAXIMUM MATERIAL CONDITION IS REQUIRED

  13. Geometric Tolerance • A geometric tolerance is the maximum permissible variation of form, profile, orientation, location, and runout from that indicated or specified on a drawing. • Feature control frame for an individual feature is divided into compartments containing, at the least, the geometric tolerance symbol and the geometric tolerance value

  14. Feature control frame (fig.16-16) • Geometric characteristic symbol • Geometric tolerance • Datums (if used) • Modifiers as required (*MMC for example)

  15. TYPE OF TOLERANCE SEE UNIT SYMBOL CHARACTERISTIC FEATURE INDIVIDUAL FEATURES 16-2 16-5 FORM STRAIGHTNESS GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  16. TYPE OF TOLERANCE SEE UNIT FEATURE CHARACTERISTIC SYMBOL SUPPLEMENTARY SYMBOLS MAXIMUM MATERIAL CONDITION 16-4 GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  17. SYMBOL FEATURE TYPE OF TOLERANCE CHARACTERISTIC SEE UNIT SUPPLEMENTARY SYMBOLS LEAST MATERIAL CONDITION 16-4 GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  18. TYPE OF TOLERANCE CHARACTERISTIC SYMBOL FEATURE SEE UNIT SUPPLEMENTARY SYMBOLS PROJECTED TOLERANCE ZONE 16-9 GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  19. SYMBOL SEE UNIT FEATURE TYPE OF TOLERANCE CHARACTERISTIC SUPPLEMENTARY SYMBOLS 16-9 16-11 BASIC DIMENSION GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  20. FEATURE TYPE OF TOLERANCE CHARACTERISTIC SEE UNIT SYMBOL 16-6 SUPPLEMENTARY SYMBOLS DATUM FEATURE GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  21. FEATURE TYPE OF TOLERANCE CHARACTERISTIC SEE UNIT SYMBOL SUPPLEMENTARY SYMBOLS DATUM TARGET 16-11 GEOMETRIC DIMENSIONING AND TOLERANCING GEOMETRIC CHARACTERISTIC SYMBOLS

  22. Form Tolerances • FORM TOLERANCES control the straightness, flatness, circularity and cylindricity • Form tolerances apply to individual features and as such do not require locating dimensions. • ORIENTATION TOLERANCES control angularity, parallelism, and perpendicularity

  23. More on FORM TOLERANCES • Straightness-a condition in which the element of a surface or a median line is a straight line • Flatness of a surface is a condition in which all surface elements are in one plane

  24. GEOMETRIC DIMENSIONING AND TOLERANCING FEATURE CONTROL FRAME

  25. GEOMETRIC DIMENSIONING AND TOLERANCING ATTACHED USING A LEADER APPLICATION OF FEATURE CONTROL FRAME

  26. MMC, RFS, LMC applies to features subject to variations in size • MMC (Maximum Material Condition) is when a feature or part is at the limit of size, which results in its containing the maximum amount of material. • LMC (Least Material Conditon) refers to the size of a feature that results in the part containing the minimum amount of material. Thus it is the minimum limit of size for an external feature. • RFS (Regardless of feature size) indicates that a geometric tolerance applies to any size of a feature that lies within its size tolerance.

  27. Datums and the 3-plane concept (16-5) • Datum is a theoretical point, line, plane, or other geometric surface fromwhich dimensions are measured when so specified or to which geometric tolerances are referenced • Datum feature is a feature of a part, such as a surface, that forms the basis for a datum or is used to establish its location

  28. 3-plane system • The three planes constitue a datum system from which measurements can be taken. They will appear on the drawing. • Datum feature symbol is used on the drawing to identify these surfaces

  29. GEOMETRIC DIMENSIONING AND TOLERANCING THE DATUM PLANES

  30. GEOMETRIC DIMENSIONING AND TOLERANCING THE DATUM PLANES

  31. GEOMETRIC DIMENSIONING AND TOLERANCING THE DATUM PLANES

  32. Orientation tolerancing (16-6) • Angularity, parallelism and perpendicularity are orientation tolerances applicable to related features • Angularity is the condition of a surface or axis at a specified angle (other than 90⁰or 0⁰) from a datum plane or axis • Perpendicularity is the condition of a surface at 90⁰ to a datum plane or axis. *A perpendicularity tolerance for a flat surface specifies a tolerance zone defined by two parallel planes perpendicular to a datum plane or axis • Parallelism is the condition of a surface equidistant at all points from a datum plane. Parallelism for a flat surface specifies a tolerance zone defined by two planes or lines parallel to a datum plane or axis.

  33. Datum Targets (16-11) • Datum target symbols are used to locate specific reference positions to be used on large datum surfaces* • the surface of a feature may be so large that a gage designed to make contact with the full surface may be too expensive or cumbersome to use • Functional requirements of the part may necessitate the use of only a portion of a surface as a datum feature

  34. CAD APPLICATIONS TOLERANCE DIALOG BOX

  35. CAD APPLICATIONS TOLERANCE SYMBOL DIALOG BOX

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