GD&T - PPT

GD&T is an international way of describing a part accurately. It is used widely in all manufacturing sectors for part dimensioning. This ppt contains basic overview of GD&T. The detailed version will be uploaded soon.

1. GD&T (Geometric Dimensioning & Tolerancing ) - Sreelakshmy (B.E)

2. Context Introduction Revised changes made in ASME Y14.5 2009 Definitions Symbols Modifiers Additional symbols Datum Datum symbols Feature control Frame GD&T in a part design (An example model)

3. Introduction GD&T is an international language used to describe a part accurately. It comprises of symbols, rules and definitions for defining a geometry of mechanical part. It has many benefits like uniformity in drawings, Better designs, No assumptions, large tolerances It is used especially in the manufacturing sector for dimensioning and Tolerancing The standard used was ASME Y14.5M-1994 and now, ASME Y14.5-2009 is used

4. Revised changes made in ASME Y14.5 2009 Important changes that has been made in 2009 version from 1999 are: Concept of FOS Datum References Degree of Freedom Composite Position Tolerances Surface Boundaries Axis Method of Interpretation Profile Tolerances Modifiers Tool Symbology

5. Definitions Dimension It is the numerical value expressed in units of measure to define SIZE, LOCATION, ORIENTATION, FORM or any other CHARACTERISTICS of a part Feature It is a general term applied to a physical portion of part such as surface, hole or slot FOS (Feature of Size) It is a cylindrical/Spherical surface or set of two opposed elements associated with size dimensions Datum It is a co-ordinate system used to locate places Datum Shift It is the allowable movement between the part feature and the gage Nominal Value It is the specified value on a drawing Tolerance It is the total amount that part features are permitted to vary from their specified dimension Types of tolerances Limit Tolerance, Plus-Minus Tolerance, Equal Bilateral Tolerance, Unequal bilateral tolerance, Unilateral Tolerance

6. Definitions Contd.. Actual Local Size It is the value of any individual distance at a cross section of a FOS. It is a point-to-point measurement Actual Mating Envelope Measure of distance between the highest points in a part design MMC (Maximum Material Condition) It is the maximum amount of material within the limits LMC (Least Material Condition) It is the least amount of material within the limits Bonus Tolerance It is the additional tolerance permitted only when MMC or LMC is specified in the feature control Frame Regardless of FOS It is the Geometric tolerance applied to any size the part is produced

7. Symbols & its characteristics There are 14 geometric characteristic symbols. They are categorized with the type of geometric control ( Form, Profile, Orientation, Location Run-Out )

8. Modifiers and its symbols They are symbols which defines conditions for the tolerance zone of a geometric tolerance. There are six modifiers. The symbols of modifiers and their meaning is shown

9. Additional Symbols

10. Datum It is a theoretically exact plane from which a dimensional measurement is made Datum system is a set of symbols which is used to describe the function and dimensions to the user Datum plane, Datum axis and Datum center plane are used to make measurements of a part

11. Datum symbols

12. Feature Control Frame It is a rectangular box which is divided into compartments within which symbols, modifiers, tolerances, etc… are placed. Below is an example for feature control frame

13. GD&T in a part design (An example)

14. Thank you!! (Referred from Wikipedia and concerned websites)