This document discusses Geometric Dimensioning and Tolerance (GD&T) standards. It introduces ASME Y14.5-2009, the authoritative guideline for GD&T design language published by the American Society of Mechanical Engineers. GD&T can control 14 geometric characteristics including form, profile, orientation, runout, and location through standards like straightness, flatness, circularity, position, and concentricity. Form and profile tolerances apply to individual or related features, while orientation, runout, and location tolerances require reference to a datum and relate multiple features.

1. Geometric Dimensioning and
Tolerance
- Harshada Gurav.

2. Introduction to ASME Y14.5 – 2009
• It is a standard published by American Society of
Mechanical Engineers (ASME) and is considered
the authoritative guideline for the design language
of geometric dimensioning and tolerance (GD&T).
• The International System of Units (SI) is featured
in this Standard

3. ANSI/ASME Y14.5
 Responsibility for Maintenance of the Standard
Shifted ANSI → ASME after the 1994 Version

4. Example

5. Tolerances of Form
• Form tolerances control straightness,
flatness, circularity, and cylindricity.
• Form tolerances are applicable to single
(individual) features, elements of single
features, or features of size.

6. Straightness
• Straightness is a condition where an
element of a surface, or derived median line,
is a straight line. It is applied in the view
where the elements to be controlled are
represented by a straight line.

7. Flatness
• Flatness is the condition of a surface or
derived median plane having all elements in
one plane.

8. Circularity or Roundness
• Circularity is a condition of a surface where
– for a feature other than a sphere, all points of the
surface intersected by any plane perpendicular to an
axis or spine (curved line) are equidistant from that
axis or spine
– for a sphere, all points of the surface intersected by
any plane passing through a common center are
equidistant from that center.

9. Cylindricity
• Cylindricity is a condition of a surface of
revolution in which all points of the surface
are equidistant from a common axis.

10. Tolerances of Orientation
• An orientation tolerance controls parallel,
perpendicular, and all other angular
relationships.
• There are three orientation relationships
and three symbols to define those
relationships.
– Angularity
– Parallelism
– Perpendicularity

11. Angularity
• Angularity is the condition of a surface,
feature’s center plane, or feature’s axis at
any specified angle from a datum plane or
datum axis.

12. Parallelism
• Parallelism is the condition of a surface or
feature’s center plane, equidistant at all
points from a datum plane; or a feature’s
axis, equidistant along its length from one
or more datum planes or datum axis.

13. Perpendicularity
• Perpendicularity is the condition of a
surface, feature’s center plane, or feature’s
axis at a right angle to a datum plane or
datum axis.

14. Tolerances of Location
• It Includes position, concentricity, and
symmetry
Symmetry
• Symmetrical relationships may be
controlled using either positional, profile, or
symmetry tolerances.

15. Position
• Position is the location of one or more features of
size relative to one another or to one or more
datums.

16. Concentricity
• Concentricity is a tolerance that controls the
central axis of the referenced feature, to a
datum axis.

17. Tolerances of Profile
• A profile tolerance may be applied to an
entire part, multiple features, individual
surfaces, or to individual profiles taken at
various cross sections through a part.
• There are two types
– Line profile
– surface profile

18. Line profile
• Each line element tolerance zone established by
the profile of a line tolerance requirement is two-
dimensional (an area) and the tolerance zone is
normal to the true profile of the feature at each
line element.

19. surface profile
• The surface profile tolerance is three
dimensional (a volume), extending along the
length and width (or circumference) of the
considered feature or features.

20. Tolerances of Runout
• Runout is a tolerance used to control the
functional relationship of one or more
features to a datum axis established from a
datum feature specified at RMB (Regardless
of Material Boundary).
• TYPES OF RUNOUT TOLERANCES
– Circular Runout
– Total Runout

21. Circular Runout
• Circular runout provides control of circular
elements of a surface. The tolerance is
applied independently at each circular
measuring position as the part is rotated the
full angular extent of the surface about the
simulated datum axis.

22. Total Runout
• Total runout provides control of all surface
elements. The tolerance is applied simultaneously
to all circular and profile measuring positions as
the part is rotated 360⁰ about the datum axis.

23. GD&T – Form & Profile
INDIVIDUAL
(No Datum
Reference)
INDIVIDUAL
or RELATED
FEATURES
GEOMETRIC CHARACTERISTIC CONTROLS
TYPE OF
FEATURE
TYPE OF
TOLERANCE
CHARACTERISTIC SYMBOL
FLATNESS
STRAIGHTNESS
CIRCULARITY
CYLINDRICITY
LINE PROFILE
SURFACE PROFILE
FORM
PROFILE
14 characteristics that may be controlled

24. GD&T – Orient, RunOut, Location
RELATED
FEATURES
(Datum
Reference
Required)
GEOMETRIC CHARACTERISTIC CONTROLS
TYPE OF
FEATURE
TYPE OF
TOLERANCE
CHARACTERISTIC SYMBOL
SYMMETRY
PERPENDICULARITY
ANGULARITY
PARALLELISM
CIRCULAR RUNOUT
TOTAL RUNOUT
CONCENTRICITY
POSITION
ORIENTATION
RUNOUT
LOCATION
14 characteristics that may be controlled