Geometrical Dimensioning & Tolerancing

Introduction to GD&T according to ISO 1101.

1. Geometrical Dimensioning & Tolerancing
ISO 1101
By Hassan Habib

2. What are we going to learn
What is Geometrical Dimensioning & Tolerancing
Its :
benefits
Types
Some general principles
Details of tolerances of:
Form
Orientation
Location
Profile

3. What is
Geometrical
Dimensioning
Tolerancing

4. Hmmmm. . . .
What would I
prefer?

5. Slide Title
Benefits of
GD&T

6. Geometrical tolerances vs size tolerances

7. Precision &
Accuracy

8. Reduced
rework cost

9. Reduced
Defects

10. Increased
understanding
Mfg Design Quality

11. Slide Title
Types of
GD&T

12. Types of Geometrical tolerances
Form Tolerances
Orientation Tolerances
Location tolerances
runouttolerances
•Straightness
•Flatness
•Circularity
•Cylindricity
•Parallelism
•Perpendicularity
•Angularity
•Position
•Symmetry
•Concentricity
•Coaxiality
•Circular runout •Total runout

13. Slide Title
Some general
principles

14. Some general priciples
Basic concepts
Geometrical tolerances shall be specified in accordance with functional
requirements. Manufacturing and inspection requirements can also
influence geometrical tolerancing

15. Some general priciples
Basic concepts
Geometrical tolerances which are assigned to features related to a datum
do not limit the form deviations of the datum feature itself. It may be
necessary to specify tolerances of form for the datum feature(s)

16. Some general priciples
Basic concepts
Feature control frame

17. Some general priciples
Three golden rules
1. Location tolerances of a feature control location
deviation, orientation deviation and form deviation of
this feature, and not vice-versa.
2. Orientation tolerances of a feature control
orientation and form deviations of this feature and not
vice-versa.
3. Form tolerances of a feature control only form
deviations of this feature.re control frame

18. Slide Title
Details of
Tolerances

19. Form Tolerances

20. straightness
The tolerance zone, in the considered plane, is limited by two parallel
straight lines a distance apart and in the specified direction only
Straightness tolerance

21. straightness
Any extracted (actual) generating line on the cylindrical surface shall be
contained between two parallel planes T distance apart
Straightness tolerance

22. straightness
The extracted (actual) median line of the cylinder to which the tolerance
applies shall be contained within a cylindrical zone of diameter
Straightness tolerance

23. fLATNESS
The extracted (actual) surface shall be contained between two parallel
planes DISTANCE T apart.
flatness tolerance

24. roundness
The tolerance zone, in the considered cross -section, is limited by two
concentric circles with a difference in radii of t
roundness tolerance

25. CYLINDRICITY
The tolerance zone is limited by two coaxial cylinders with a difference in
radii of T
cylindricitytolerance

26. Slide Title
Details of
Tolerances

27. orientation Tolerances

28. PARALLELISM
The tolerance zone is limited by two parallel planes a distance apart. The
planes are parallel to the datumsand in the direction specified
Direction
specified
Parallelism tolerance of a line related to a datum system

29. PARALLELISM
The tolerance zone is limited by two parallel planes a distance apart. The
planes are parallel to the datumsand in the direction specified
Direction
specified
Parallelism tolerance of a line related to a datum system

30. PARALLELISM
The tolerance zone is limited by a cylinder of diameter t , parallel to the
datum, if the tolerance value is preceded by the symbol Ø
Parallelism tolerance of a line related to a datum line

31. PARALLELISM
Each extracted (actual) line shall be contained between two parallel lines
0,02 apart parallel to datum A and lying in a plane parallel to datum B
Parallelism tolerance of a line related to a datum system

32. prependicularity
The tolerance zone is limited by two parallel planes a distance apart and
perpendicular to the datum
Perpendicularity tolerance of a line related to a datum line

33. prependicularity
The tolerance zone is limited by two parallel planes a distance t apart.
The planes are perpendicular to the datum A and parallel to datum B
Perpendicularitytoleranceofalinerelatedtoadatumsystem

34. prependicularity
The tolerance zone is limited by a cylinder of diameter perpendicularto
the datum if the tolerance value is preceded by the symbol Ø
Perpendicularity tolerance of a line related to a datum surface

35. Angularity
a) Line and datum line in the same plane:
The tolerance zone is limited by two parallel planes a distance t apart
and inclined at the specified angle to the datum.
Angularity tolerance of a line related to a datum line

36. Angularity
b) The tolerance zone is limited by two parallel planes a distance t apart
and inclined at the specified angle to the datum. The considered line and
the datum line are not in the same plane
Angularity tolerance of a line related to a datum line

37. Angularity
The tolerance zone is limited by two parallel planes a distance t apart and
inclined at the specified angle to the datum
Angularity tolerance of a line related to a datum surface

38. Angularity
The tolerance zone is limited by a cylinder of diameter t if the tolerance
value is preceded by the symbol Ø. The cylindrical tolerance zone is
parallel to a datum plane B and inclined at the specified angle to the datum
plane A
Angularity tolerance of a line related to a datum surface

39. Slide Title
Details of
Tolerances

40. location Tolerances

41. position
The tolerance zone is limited by a sphere of diameter t if the tolerance
value is preceded by the symbol SØ. The center of the spherical tolerance
zone is fixed by theoretically exact dimensions with respect to the datums
A, B and C
Position tolerance of a point

42. position
The tolerance zone is limited by two parallel planes a distance t apart and
symmetrically disposed about the center line. The center line is fixed by
theoretically exact dimensions with respect to datumsA and B. The
tolerance is specified in one direction only.
Position tolerance of a line

43. position
The tolerance zone is limited by two pairs of parallel planes a distance 0,05
and 0,2 apart respectively and symmetrically disposed about the
theoretically exact position. The theoretically exact position is fixed by
theoretically exact dimensions with respect to the datumsC, A and B. The
tolerance is specified in two directions with respect to the datums.
Position tolerance of a line

44. position
Position tolerance of a line

45. position
The tolerance zone is limited by a cylinder of diameter t if the tolerance
value is preceded by the symbol Ø. The axis of the tolerance cylinder is
fixed by theoretically exact dimensions with respect to the datum s C, A
and B
Position tolerance of a line

46. position
The tolerance zone is limited by two parallel planes a distance t apart and
symmetrically disposed about the theoretically exact position fixed by
theoretically exact dimensions with respect to the datumsA and B
Position tolerance of a flat surface or a median p lane

47. Concentricity
The tolerance zone is limited by a circle of diameter t; the tolerance value
shall be preceded by the symbol . The center of the circular tolerance
zone coincides with the datum point
Concentricity tolerance of a point

48. coaxiality
The tolerance zone is limited by a cylinder of diameter t; the tolerance
value shall be preceded by the symbol Ø. The axis of the cylindrical
tolerance zone coincides with the datum
Coaxiality tolerance of an axis

49. symmetry
The tolerance zone is limited by two parallel planes a distance t apart,
symmetrically disposed about the median plane, with respect to the datum.
Symmetry tolerance of a median plane

50. Slide Title
Details of
Tolerances

51. RunoutTolerances

52. Circular runout
The tolerance zone is limited within any cross-section perpendicular to
the datum axis by two concentric circles with a difference in radii of t,
the centers of which coincides with the datum
Circular run-out tolerance —radial

53. Circular runout
Run-out usually applies to complete features, but could be applied to a
restricted part of a feature
Circular run-out tolerance —radial

54. Circular runout
The tolerance zone is limited to any cylindrical section by two circles
with a distance t apart lying in the cylindrical section, the axis of which
coincides with the datum
Circular run-out tolerance —axial

55. Circular runout
Circular The tolerance zone is limited within any conical section b y two
circles a distance t apart, the axes of which coincide with the datum.
Circular run-out tolerance in any direction

56. Circular runout
The tolerance zone is limited within any conical section of the specified
angle by two circles a distance t apart, the axes of which coincide with
the datum
Circular run-out tolerance in a specified direction

57. Total runout
The tolerance zone is limited by two coaxial cylinders with a difference in
radii of t, the axes of which coincide with the datum
Total radial run-out tolerance

58. Total runout
The tolerance zone is limited by two parallel planes a distance t apart and
perpendicular to the datum
Total axial run-out tolerance