This document discusses geometric symbols used in geometric dimensioning and tolerancing (GD&T). It defines common geometric characteristics such as form, profile, orientation, runout, and location that are specified using symbols in a geometric feature control frame. Specific geometric tolerances like flatness, straightness, roundness, cylindricity, profile, perpendicularity, angularity, and parallelism are defined. Each tolerance specifies a zone or area that a geometric feature must fall within to be considered dimensionally compliant according to the drawing.

1. Geometric Symbols
Geometric Dimensions and Tolerances

2. Geometric
Symbols

3. How is GTD information Conveyed on a Drawing?
• Geometric Characteristics are Specified Through
Symbols in a geometric feature control frame
• Modifiers and Tolerances Expand and Clarify
the Symbols to Ensure Drawings are
Unambiguous

4. Geometric Characteristics and Symbols
1. FORM

5. Geometric Characteristics and Symbols
2. Profile , 3. Orientation

6. Geometric Characteristics and Symbols
4. Runout , 5. Location

7. Using Notes

8. Using Symbols

9. GEOMETRIC FEATURE CONTROL FRAME

10. FLATNESS

11. FLATNESS
• The condition of a surface having all points in
one plane.
• A flatness tolerance specifies a zone defined by 2
parallel planes.

12. Flatness

13. Flatness

14. STRAIGHTNESS
• Straightness is the
condition where all the
points on a surface or
an axis are in a straight
line
• A straightness
tolerance specifies a
zone within which the
surface or axis must lie

15. STRAIGHTNESS

16. ROUNDNESS OF A CYLINDER
• Roundness or circularity is the condition of a
cylindrical surface in which all points on the surface
intersected by any plane perpendicular to a common
axis equidistant from the axis.

18. • CIRCULARITY
• Or Roundness tolerance specifies a zone
bounded by two concentric circles within which
the measured surface must lie

19. CIRCULARITY of A SPHERE

20. • The Periphery at any cross section passing
through a common center must be within
the specified tolerance of size and must be
between two concentric circles

21. CYLINDRICITY
 Cylindricity is the condition where
all points of a surface of revolution
are equidistant from a common axis
 cylindricity tolerance specifies a
zone bounded by 2 concentric
cylinders within which the
measured surface must lie.

22. CYLINDRICITY

23. CYLINDRICITY

24. PROFILE TOLERANCE
• PROFILE OF A LINE:
• The tolerance zone established by the profile
of a line tolerance is two dimensional
extending along the length of the considered
feature

25. PROFILE TOLERANCE
• PROFILE OF A SURFACE:
• The established tolerance zone is three
dimensional extending along the length and width
of the considered feature

26. ORIENTATION TOLERANCE
• PERPENDICULARITY
• Is a condition of a line,
center line, axis or surface
at a right angle to a datum
plan or axis.
• Perpendicularity tolerance
specifies one of the
following:

27. PERPENDICULARITY
• 1. A zone defined by 2 parallel planes perpendicular
to a datum plane or axis. In the example shown,
• The surface of the feature must lie within this zone
which is 0.15mm wide and at right angles to datum A.

28. • 2. A zone defined by 2 parallel planes perpendicular to
the datum axis.
• In this example, the axis of the hole must lie within the
zone which is 0.3mm wide and at right angles to
datum axis A. The feature axis must also be within the
tolerance of location.

29. ORIENTATION TOLERANCE

30. ANGULARITY
• Angularity is the condition of a surface or axis at a
specified angle (other than 9O) from a datum plane or
axis.

31. • The tolerance zone is defined by 2 parallel
planes at the specified basic angle from a
datum plane or axis. The surface or axis of
the considered feature must lie within this
zone.

32. • In the example all points of the surface must
lie within the 0.5mm wide tolerance zone.

33. • Parallelism is the condition of a surface or
axis equidistant at all points from a datum
plane or axis.
• Parallelism tolerance specifies one of the
following:
Parallelism

34. • 1. A zone defined by 2 planes or lines
parallel to a datum plane or axis.

35. • In this example, the surface of the feature
must lie within 2 planes 0.25mm y apart
which are parallel to datum A.

36. • 2. A cylindrical tolerance zone whose
axis is parallel to a datum axis.

37. • In this example the axis of the hole must lie
within a cylindrical zone of 0.3mm diameter
parallel to datum A.