Geometric dimensioning and tolerancing (GD&T) uses symbols to specify the geometric characteristics and dimensional requirements of parts and assemblies according to the ANSI/ASME Y14.5M-2009 standard. GD&T defines symbols for form, profile, orientation, location and runout tolerances and controls dimensions through features control frames and datum references. The ISO also sets preferred metric limits and fits designations using letters and numbers to define tolerance zones for holes and shafts.

2. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)
•Purpose is to describe the engineering intent of parts
and assemblies
•Uses symbols to specify geometric characteristics and
dimensional requirements
•Current GD&T standard: ANSI/ASME Y14.5M-2009
•Symbols for:
•Form and profile tolerances, orientation tolerances,
location tolerances, runout tolerances

3. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

6. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)
•Feature control frame

7. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

8. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)
Examples of Modifiers
•MMC – Maximum Material Condition
•LMC – Least Material Condition

9. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

10. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

11. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)
•ISO standard of preferred metric limits and fits: In
the dimension 16h11, the tolerance zone is specified
by a letter and a number, I.e. h11. An uppercase
letter indicates that the tolerance applies to the hole;
a lowercase letter indicates the tolerance applies to
the shaft.

12. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

13. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

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TOLERANCING (GD&T)

15. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

16. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

17. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

18. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

19. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

20. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

21. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

22. GD&T

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24. GD&T
•Basic Dimension: Theoretically exact, untoleranced
dimensions that specify the perfect location, size,
shape, or angle of a feature.
•Basic dimensions are identified by enclosing the
dimension in a box.
•Basic dimensions specify theoretically exact value from
which variations are defined through feature control
frames as well as toleranced features and notes.
•General tolerances do not apply to basic dimensions.

25. GD&T

26. GD&T – Datum Surfaces and Features

27. GD&T – Datum Surfaces and Features

28. GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)

29. GD&T – Datum Surfaces and Features

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