Interpretation of Geometric Dimensioning and Tolerance

Interpretation of Geometric Dimensioning and Tolerance Presented by Deepak Chandra Sekaran RAssistant ProfessorDepartment of Automobile EngineeringPrerequisitesToleranceLimitsTypes of fitsFundamental Deviation6/12/20142Learning ObjectivesCognitive Domain Understand LevelDescribe GD&T?

Compare Co-ordinate Tolerance method with GD&T

Interpret the GD&T information in an engineering drawing6/12/20143GD&T It is compilation of symbols and rules that efficiently describe and control, dimensioning & tolerancing for all drawings (castings, machined components,etc.). ASME Y14.5-2009

6/12/20144ToleranceDefinition: Allowance for a specific variation in the size andgeometry of part. Why is it needed: No one or thing is perfect ! Hence, engineers have come up with a way to make thingsclose to perfect by specifying Tolerances ! Since variation from the drawing is inevitable theacceptable degree of variation must be specified. Large variation may affect the functionality of the part Small variation will effect the cost of the part requires precise manufacturing. requires inspection and the rejection of parts.6/12/20145When does Tolerances become importantAssemblies: Parts will often not fit together if their dimensions do not fall with in a certain range of values.Interchange ability: If a replacement part is used it must be a duplicate of the original part within certain limits of deviationThe relationship between functionality and size or shape of an object varies from part to part.

6/12/20146Advantage over - Co-ordinate Tolerancing

6/12/20147Form Error

6/12/20148Terminologies to rememberBasic DimensionMaximum Material Condition (MMC)Lower Material Condition (LMC)Datums

6/12/20149Maximum Material ConditionThat condition where a feature of size contains the maximum amount of material within the stated limits of size. Example: minimum hole size, and maximum shaft size.

6/12/201410Least Material ConditionThat condition where a feature of size contains the least amount of material within the stated limits of size. Example: maximum hole size, and minimum shaft size.

6/12/201411DatumsThis symbol is attached to a plane or size feature that must be contacted for machining and inspection.

6/12/201412Types of DatumsPrimary Datum (A)Secondary Datum (B)Tertiary Datum (C)

6/12/201413Types of Datums (Cont.)

6/12/201414Geometric Characteristics

6/12/201415Straightness

6/12/201416Flatness

6/12/201417Circularity

6/12/201418Cylindricity

6/12/201419Cylindricity

6/12/201420OrientationParallelism

6/12/201421Perpendicularity

6/12/201422Angularity

6/12/201423LocationConcentricity

6/12/201424Line Profile

6/12/201425Feature Control Frame

6/12/201426Advantages of GD&TIt forces the designer to totally consider function, manufacturing process, and inspection methods.Provides more bonus tolerance.Reduces rejection of parts.Reduces manufacturing cost.Improves communication between various engineering departments.6/12/201427Measuring Instruments

CMMDial Indicator6/12/201428SummaryWhat is GD&T?Terminologies used in GD&TSymbols used in GD&TAdvantages of GD&T

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6/12/201431Quiz 01

Time Starts Now32Time OverQuiz 02

6/12/201433Time Starts NowTime OverQuiz 02

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