geometric dimensioning and tolerancing gdt

1. GEOMETRIC DIMENSIONING AND TOLERANCING (GDT) Dr. Jack Zhou Department of Mechanical Engineering and Mechanics Drexel University, Philadelphia, PA GEOMETRIC DIMENSIONING AND TOLERANCING (GDT) A COURSE MODULE IN CONCURRENT ENGINEERING FOR GATEWAY EEC PROJECT Dr. Jack Zhou Department of Mechanical Engineering and Mechanics Drexel University, Philadelphia, PA Course Description: The geometric dimensioning and tolerancing are mainly used in engineering design, mechanical drawing & assembly and product inspection. In this course module a fundamental introduction of the concepts, standards, principles and rules for geometric dimensioning and tolerancing in engineering drawings are discussed and various examples of how to symbol and assign geometric tolerance to different forms are also illustrated in details. Course length: This is a three hours lecture, three hours reading assignment and two hours home work course-module. Reading Materials: a) Modern Geometric Dimensioning and Tolerancing by Lowell Foster, NTMA, 1996. b) ASME Standard in Geometric Dimensioning and Tolerancing� Home Work: �Modern Geometric Dimensioning and Tolerancing� Workbook Section, problems 1 to 29. GEOMETRIC DIMENSIONING AND TOLERANCING (GDT) A COURSE MODULE IN CONCURRENT ENGINEERING FOR GATEWAY EEC PROJECT Dr. Jack Zhou Department of Mechanical Engineering and Mechanics Drexel University, Philadelphia, PA Course Description: The geometric dimensioning and tolerancing are mainly used in engineering design, mechanical drawing & assembly and product inspection. In this course module a fundamental introduction of the concepts, standards, principles and rules for geometric dimensioning and tolerancing in engineering drawings are discussed and various examples of how to symbol and assign geometric tolerance to different forms are also illustrated in details. Course length: This is a three hours lecture, three hours reading assignment and two hours home work course-module. Reading Materials: a) Modern Geometric Dimensioning and Tolerancing by Lowell Foster, NTMA, 1996. b) ASME Standard in Geometric Dimensioning and Tolerancing� Home Work: �Modern Geometric Dimensioning and Tolerancing� Workbook Section, problems 1 to 29.

2. SYMBOLS & ABBREVIATIONS General G.D.T. is an international language of symbols that generally eliminates the need for drawing notes. Information related to the construction, form, and proportion of individual symbols described in next figure. SYMBOLS & ABBREVIATIONS General G.D.T. is an international language of symbols that generally eliminates the need for drawing notes. Information related to the construction, form, and proportion of individual symbols described in next figure.

3. DATUM REFERENCING Datum is theoretically exact points, axes, and planes. These elements exist within a framework of three mutually perpendicular intersecting planes known as the datum referencing frame.DATUM REFERENCING Datum is theoretically exact points, axes, and planes. These elements exist within a framework of three mutually perpendicular intersecting planes known as the datum referencing frame.

4. DATUM FEATURE SYMBOL A symbolic means of indicating a datum feature consists of a capital letter enclosed in a square frame and a leader line extending from the frame to concerned feature, terminating with a triangle. The triangle is filled or not fillet. DATUM FEATURE SYMBOL A symbolic means of indicating a datum feature consists of a capital letter enclosed in a square frame and a leader line extending from the frame to concerned feature, terminating with a triangle. The triangle is filled or not fillet.

5. The datum feature symbol is applied to concerned feature surface outline, extension line, dimension line, or feature control frame as follows:a) Placed on the outline of a feature surface, or an extension line of thefeature outline, clearly separated from the dimension line, when the datum feature is the surface itself.The datum feature symbol is applied to concerned feature surface outline, extension line, dimension line, or feature control frame as follows:a) Placed on the outline of a feature surface, or an extension line of thefeature outline, clearly separated from the dimension line, when the datum feature is the surface itself.

6. b) Placed on an extension of the dimension line of a feature of size when the datum is the axis or center plane if there is no sufficient space.b) Placed on an extension of the dimension line of a feature of size when the datum is the axis or center plane if there is no sufficient space.

7. c) Placed on the outline of a cylindrical feature surface or an extension line of the feature outline, separated from the size dimension, when the datum is the axis. c) Placed on the outline of a cylindrical feature surface or an extension line of the feature outline, separated from the size dimension, when the datum is the axis.

8. d) Placed on a dimension leader line to the feature size dimension where no geometrical tolerance and feature control frame are used. d) Placed on a dimension leader line to the feature size dimension where no geometrical tolerance and feature control frame are used.

9. e) Placed above or below and attached to the feature control frame when the feature (or group of features) controlled is the datum axis or datum center plane. e) Placed above or below and attached to the feature control frame when the feature (or group of features) controlled is the datum axis or datum center plane.

10. MAXIMUM MATERIAL CONDITION The symbol for maximum material condition is a capital �M� in a circle, Maximum material condition may abbreviated MMC. The term maximum material condition is used to describe the maximum condition of a feature of size. For example, a hole is a feature of size that is permitted to vary in size within the limits of a plus/minus tolerance. For holes or any internal feature, MMC is the smallest size for that feature. In other words, the max. material remains in the piece the hole was put in.MAXIMUM MATERIAL CONDITION The symbol for maximum material condition is a capital �M� in a circle, Maximum material condition may abbreviated MMC. The term maximum material condition is used to describe the maximum condition of a feature of size. For example, a hole is a feature of size that is permitted to vary in size within the limits of a plus/minus tolerance. For holes or any internal feature, MMC is the smallest size for that feature. In other words, the max. material remains in the piece the hole was put in.

11. LEAST MATERIAL CONDITION The symbol is a capital �L� in a circle,�. The term least material condition (LMC), is used to describe the opposite condition as maximum material condition. Least material condition also applies to external features of size.LEAST MATERIAL CONDITION The symbol is a capital �L� in a circle,�. The term least material condition (LMC), is used to describe the opposite condition as maximum material condition. Least material condition also applies to external features of size.

12. Straightness TOLERANCES OF FORM Straightness Definition: Straightness is the condition where one line element of a surface or axis is in a straight line.Tolerance: Straightness tolerance provides a zone in which a surface element or axis implied regardless of feature size.TOLERANCES OF FORM Straightness

13. Flatness  Definition: Flatness is the condition of a surface where all elements are in one plane. Tolerance: Flatness tolerance provides a zone of a specified thickness defined by two parallel planes in which the surface must lie. The specified tolerance in the feature control frame is implied as regardless of feature size (RFS).Flatness Definition: Flatness is the condition of a surface where all elements are in one plane. Tolerance: Flatness tolerance provides a zone of a specified thickness defined by two parallel planes in which the surface must lie. The specified tolerance in the feature control frame is implied as regardless of feature size (RFS).

14. Circularity  Definition: Circularity is roundness. Circularity is a condition of a cylindrical surface at any cross-sectional measurement where all points of the surface are perpendicular.  Tolerance: Circularity tolerance provides a circular zone in which all points of a cross section or slice of the surface must lie. Circularity Definition: Circularity is roundness. Circularity is a condition of a cylindrical surface at any cross-sectional measurement where all points of the surface are perpendicular. Tolerance: Circularity tolerance provides a circular zone in which all points of a cross section or slice of the surface must lie.

15. Cylindricity  Definition: Cylindricity is the condition of an entire feature surface during one revolution in which all surface points are an equal distance from a common axis.  Tolerance: Cylindricity tolerance provides a zone bounded by two concentric cylinders in which the controlled surface must lie. Cylindricity tolerance is a radial tolerance. Cylindricity Definition: Cylindricity is the condition of an entire feature surface during one revolution in which all surface points are an equal distance from a common axis. Tolerance: Cylindricity tolerance provides a zone bounded by two concentric cylinders in which the controlled surface must lie. Cylindricity tolerance is a radial tolerance.

16. TOLERANCES OF ORIENTATION Perpendicularity Definition: Perpendicularity is the condition of an entire surface plane or axis at a right angle to a datum plane or axis.  Tolerance: Perpendicularity tolerance provides a zone defined by two parallel planes, two parallel lines, or a cylinder parallel to a datum. TOLERANCES OF ORIENTATION Perpendicularity Definition: Perpendicularity is the condition of an entire surface plane or axis at a right angle to a datum plane or axis. Tolerance: Perpendicularity tolerance provides a zone defined by two parallel planes, two parallel lines, or a cylinder parallel to a datum.

17. Angularity  Definition: Angularity is the condition of an axis or plane at an angle other than 90o to another datum plane or axis.  Tolerance: Angularity tolerance provides a zone defined by two parallel planes the stated tolerance apart and at the specified basic angle to the datum reference. The controlled feature surface, plane, or axis must lie within this zone. Angularity Definition: Angularity is the condition of an axis or plane at an angle other than 90o to another datum plane or axis. Tolerance: Angularity tolerance provides a zone defined by two parallel planes the stated tolerance apart and at the specified basic angle to the datum reference. The controlled feature surface, plane, or axis must lie within this zone.

18. Parallelism Definition: Parallelism is the condition of a surface or axis an equal distance at all points from a datum plane or axis.  Tolerance: Parallelism tolerance provides a zone defined by two parallel planes, lines, or a cylinder parallel to a datum plane or axis within which the surface elements or axis of the controlled feature must lie. Parallelism

19. TOLERANCE OF PROFILE Profile  Definition: Profile tolerancing is a method of specifying control of deviation from the desired profile along the surface of a feature.  Tolerance: Profile tolerance may be specified either as a surface or line profile. The tolerance provides a uniform zone along a desired true profile of the part. The surface of controlled feature must lie within this zone. TOLERANCE OF PROFILE Profile Definition: Profile tolerancing is a method of specifying control of deviation from the desired profile along the surface of a feature. Tolerance: Profile tolerance may be specified either as a surface or line profile. The tolerance provides a uniform zone along a desired true profile of the part. The surface of controlled feature must lie within this zone.

21. TOLERANCE OF RUNOUT Definition: Runout is a composite form and location control of permissible error in the desired part surface during a complete revolution of the part around a datum axis.  Tolerance: Runout tolerance may be specified as either total or circular. The specified tolerance is the deviation permitted in relation to the controlled feature�s axis. The surface must lie within the specified tolerance zone.TOLERANCE OF RUNOUT Definition: Runout is a composite form and location control of permissible error in the desired part surface during a complete revolution of the part around a datum axis. Tolerance: Runout tolerance may be specified as either total or circular. The specified tolerance is the deviation permitted in relation to the controlled feature�s axis. The surface must lie within the specified tolerance zone.

23. TOLERANCE OF LOCATION Concentricity Definition: Concentricity is the condition where the axes of all cross-sectional surface elements during one complete revolution are common to a datum feature axis within a specified tolerance.  Tolerance: Concentricity tolerance is always implied and specified as regardless of feature size. The tolerance is a diametrical zone in which the axis of the axis of the controlled feature must lie. TOLERANCE OF LOCATION Concentricity Definition: Concentricity is the condition where the axes of all cross-sectional surface elements during one complete revolution are common to a datum feature axis within a specified tolerance. Tolerance: Concentricity tolerance is always implied and specified as regardless of feature size. The tolerance is a diametrical zone in which the axis of the axis of the controlled feature must lie.

24. Position  Definition: Position is the condition where a feature or group of features is located (positioned) in relation to an other feature or datum feature.  Tolerance: Location tolerance zones are either cylindrical or noncylindrical; this is determined in the feature control frame. The tolerance zone is cylindrical if the diameter symbol precedes the specified tolerance. Position Definition: Position is the condition where a feature or group of features is located (positioned) in relation to an other feature or datum feature. Tolerance: Location tolerance zones are either cylindrical or noncylindrical; this is determined in the feature control frame. The tolerance zone is cylindrical if the diameter symbol precedes the specified tolerance.

25. TOLERANCE OF LOCATION Symmetry  Definition: Symmetry is the condition where a feature or part has the same profile on either side of the center line (median plane) of a datum feature.  Tolerance: The tolerance for symmetry is always implied to be RFS. The tolerance is applied equally on either side of the controlled feature center line. TOLERANCE OF LOCATION Symmetry Definition: Symmetry is the condition where a feature or part has the same profile on either side of the center line (median plane) of a datum feature. Tolerance: The tolerance for symmetry is always implied to be RFS. The tolerance is applied equally on either side of the controlled feature center line.

27. Quiz If a shaft is 10�0.05 inch what is its maximum and minimum material conditions. Please draw circularity and perpendicularity symbol blocks and tolerance zones for a cylinder and a upside down T shape block, respectively.