Geometric Dimensioning and Tolerancing

Chapter 2, Symbols and Abbreviations

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Introduction

• GDT is a language of symbols

• We will see an overview of the symbols associated with:– Dimensioning Symbols– Geometric Characteristics– Modifying Symbols

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Dimensioning Symbols

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Dimensioning Symbols

Diameter Radius R

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Dimensioning Symbols

Spherical Diameter S Spherical Radius SR

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Dimensioning Symbols

Controlled Radius Tolerance CR Number of Places

A controlled radius has no ‘reversals’, but is a smooth curve within the tolerance zone.

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Dimensioning Symbols

Counterbore/Spotface Countersink

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Dimensioning Symbols

Depth/Deep Dimensions Not to Scale

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Dimensioning Symbols

Conical taper Slope

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Dimensioning Symbols

Square Reference Dimension

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Dimensioning Symbols

Dimension Origin Arc Length

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Dimensioning Symbols

All Around All Over

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Dimensioning Symbols

Chain Line

Used to identify a limited region to be treated differently from the rest of the part.

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Geometric Characteristics

Explained in detail in Chapters 6 and 8.

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Modifying Symbols

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Modifying Symbols

Maximum Material ConditionMMC

MMC

Refers to the size of the feature associated with the most material.

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Modifying Symbols

Least Material ConditionLMC

LMC

Refers to the size of the feature associated with the least material.

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Modifying Symbols

Continuous Feature Basic Dimension

Used to describe a theoretically exact size.

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Modifying Symbols

Between

Evaluation