GD&T is a International Language to define the geometry in the drawing.

1. INTRODUCTION
TO
GEOMETRIC DIMENSIONING AND
TOLERANCING (GD&T)
BY KAPIL MURUGESAN

2. TABLE OF CONTENT
• WHAT IS GD&T
• HISTORY OF GD&T
• WHY & ADVANTAGES OF GD&T
• STANDARDS (ASME VS ISO)
• TOLERANCS AND TYPES
• GD&T SYMBOLS

3. WHAT IS GD&T?
• GD&T stands for Geometric Dimensioning and Tolerancing,
as define by ASME Y14.5-2009 and ISO 1101.
• GD&T is a International language has symbols and standards
to used in drawings to accurately describe a part or
assembly in three dimensions.
• The language of GD&T consists of dimensions, tolerances,
symbols, rules, mathematical formulas and definition to
precisely describe the size, form, orientation and location
tolerance of part features of the design model.
• Defined design in depth and functionality of the part be
clearly communicate between the designer, quality and
manufacturer’s. (To avoid language barrier)
• GD&T developed and started by AMSE and ISO
organizations.

4. • GD&T was used in Automobile, Heavy equipment and Aviation.
• Now GD&T is more popular worldwide and using several other
industries.
DESIGNERDESIGNER MANUFACTUREMANUFACTURE INSPECTORINSPECTORGD&TGD&T

5. HISTORY OF GD&T
• GD&T was origin by man called Stephen Stanley
Parker.
• He was working in munition under Britain.
• Torpedoes parts were rejected when inspected
using traditional tolerance.
• On 1938 he was developed the concept of
position or true position (Tolerance).
• Mr. Parker later 1956 published a book in title of
Drawing and Dimensions.
• Since then others grown to include other
concepts like profile, runout, and much more.
• After world war II, GD&T was adopted by military
in 1950 and now us in multiple industries.

6. WHY DO WE USE GD&T?
• It reduces the amount of notes, dimensions and tolerances.
• Ensures interchangeability of mating parts.
• It’s save time during manufacturing and assembly process.
• It is important to reduce cost and improve quality.
• It is important to reduce rework and scraps.
• It is important to increase productivity.

7. ADVANTAGES OF GD&T
• Easy to understood by anyone who knows symbols.
• Eliminates the need for numerous notes.
• Provide accurate communication with one other to reduce
guess work and save time.
• Offer good design clarity, improved fit and better inspection
methods and more realistic tolerance.
• Ensure functional parts pass inspection & non-functional don’t

8. STANDARDS
ASME Y14.5 2009
• ASME means American
Society of Mechanical
Engineers.
• It founded in 1880
• Head in New York, US
• Non-profit & non-government
organization, but government
funding.
• Creating standards & codes.
• Languages : English
ISO 1101
• ISO means International
Standardization for
Organization.
• It founded in1947
• Head in Geneva, Swiss
• Non-profit & non-government
organization, but government
funding.
• Creating International
standards & codes
• Languages : English, French
and Russian

9. • ASME started because of
numerous steam boiler failed
in US.
• ASME is largest and oldest
standards developing
organizations.
• Produces approximately 600
codes & standards in different
technical areas such as
Fasteners, Elevators, pipelines
and Powerplant systems.
ASME Y14.5 2009
• ISA (Today ISO) began
in1926, but It was
suspended in 1942 during
Second World War.
• ISO TC213 technical
committee produced series
of standards for GD&T.
Version Year

10. LIMITS OR PLUS/MINUS TOLERANCE
• Tolerance : Total permissible variations in its sizes. Which is
different between upper and lower limits of an objects.
• There are three types of tolerance:
- Limit Tolerance: Two dimensional values on top of each
other. Both largest and smallest values are allowed. Anything
between these values can acceptable. E.g.: 10.05-9.95
- Unilateral Tolerance : when a target dimension is given along
with a tolerance that allows variation to occur in only one
direction. E.g.: 10.00 (+0.05, -0.00)
- Bilateral Tolerance : Tolerance exist if the variation from a
target dimension is shown occurring in both the positive
and negative directions. E.g.: 10.00 (±0.05)

11. GEOMETRIC TOLERANCES AND SYMBOLS
• Geometric characteristic symbols are a set of fourteen
Symbols used in the language of geometric tolerancing.
• The symbols are divided into five categories:
1. Form
2. Profile
3. Orientation
4. Location
5. Runout

13. FORM-STRAIGHTNESS
• Straightness is a two dimensional tolerance.
• The edge must remain within two imaginary parallel line in
order to control a straightness tolerance.

14. FORM-FLATNESS
• Flatness tolerance is a three dimensional version of
straightness.
• The surface must remain within two imaginary perfectly flat
parallel plane.
• Only the surface, not entire thickness is referenced to the
planes

15. FORM-CIRCULARITY
• Circularity (Roundness) is a two dimensional tolerance.
• Any two dimensional cross section of a round feature must
remain within the tolerance zone.
• This tolerance can applied to cylinders, cones and spheres
features.

16. FORM-CYLINDRICITY
• Cylindricity is a three dimensional tolerance specifics the
roundness of the entire cylinder over the surface.
• All cross section of the cylinder must be measure together, so
cylindricity tolerance is only applied to cylinders.

17. PROFILE TOLERANCE
• Profile tolerance can be used to control features such as
cones, curves, flat surfaces, irregular surfaces or cylinders.
• There are two types of profile tolerance:
i) Profile of a line
ii) Profile of surface

18. PROFILE OF A LINE
• Profile of a line is a 2-Dimensional tolerance range that can be
applied to any linear or straight tolerance.
• Profile of a line would specify how much that cross-
section could vary from a true curved radius.
• Profile of a line takes a cross section at any point along the
surface and sets a tolerance zone on either side of the profile.

19. PROFILE OF A SURFACE
• Profile of a surface is a 3-Dimensional tolerance zone around a
surface.
• It is applied to complex and curved surface such as aircraft and
automobile outer parts.
• The entire surface where the radius is has to fall within the
tolerance zone.

20. ORIENTATION
• Orientation tolerance refers to the angular relationship, which
exist between two or more line, surface or other features.

21. ANGULARITY
• Angularity is a three dimensional tolerance.
• Shape of the tolerance depend upon the shape of the features.
• If applied to flat surface, tolerance become two imaginary
planes, parallel to the ideal angle.
• If applied to hole, tolerance become two imaginary cylinders,
around the ideal angle.

22. PARALLELISM AND PERPENDICULARITY
• Three dimensional tolerance that use the same tolerance
zones as angularity.
• Parallelism defines two features remain parallel to other.
• Perpendicularity tolerance specifies a 90 degree angle
between features.

23. LOCATION TOLERANCE
• A location tolerance states how far or near a feature may vary
from the perfect location which related to the datums or
other features.
• There are three symbols presented in this location tolerance
i) Position Tolerance
ii) Concentricity Tolerance
iii)Symmetry Tolerance

24. POSITION TOLERANCE
• Position tolerance is also most common location tolerance.
• Three dimensional tolerance.
• Involve more than one datum to establish position of
features.
• Hole: Tolerance involve the center axis of the hole and must
be within imaginary cylinder around the true position of hole.
• Rectangular: zone involves two imaginary planes to a specific
distance form the true position.

25. CONCENTRICITY TOLERANCE
• Concentricity is also three dimensional tolerance similar like
position.
• It relates a feature to one or more other datum features.
• Shaft is measured in multiple diameters to ensure that they
share a common center-axis.

26. SYMMETRY TOLERANCE
• Symmetry tolerance is much like concentricity.
• Difference is that controls rectangular features and involves
two imaginary flat planes.
• Both symmetry and concentricity are difficult to measure and
increase costs of inspection.

27. RUNOUT TOLERANCE
• Runout tolerance is used to control the location of a circular
part features relatives to its axis.
• Runout is usually applied to parts with cross sections that
must be assembled like drill bits, segmented shaft and so on.
• Runout helps to limits the axis offsets of two parts to ensure
that can spin and wear evenly.
• Types of runout tolerance
- Circular Runout
- Total Runout

28. CIRCULAR RUNOUT
• Circular runout is three dimensional tolerance and can apply
only to cylindrical parts.
• Tolerance refers the cylindrical features to a center-axis and
simultaneously control the location, form and orientation of
the feature.
• Circular runout can only be inspected when a part is rotating.
• Calibrated instrument is placed against the surface of the
rotating parts to detect the highest and lowest pointes.
• Surface must remain two imaginary circles , centers located
on the center-axis.

29. TOTAL RUNOUT
• Total runout is similar to circular runout except that involves
tolerance control along the entire length.
• Two imaginary lines not like cross sections.
• If the parts meet total runout tolerance automatically satisfy
all of the circular runout tolerance.
• Total runout tolerance is very demand and costly barrier to
manufacturing and inspection.

30. REFERENCES
• ASME Y14.5-2004, “Dimensioning and Tolerancing”.
• Alex Krulikowski (1994), “Geometric Dimensioning and
Tolerancing”
• GD&T BASICS, https://www.gdandtbasics.com/straightness/