Geometrical tolerances

Geometrical Tolerances

By Hassan Habib

Objectives

• Introduction to Dimensions

• Terminologies

• Important Fundamental Rules

• Basics about Dimensioning

• Dimensioning Features

• Introduction to Tolerances

• Applications

• Direct Tolerancing Methods

• Tolerance Expressions

• Tolerancing on various Features

Introduction to Dimensions

• About The Standard ASME Y14.5

• The need of Dimensions

• Historical Perspective


• Terminologies

• Dimension (Basic, Reference)

• Geometric Tolerance

• Datum

• Feature

• Feature Control Frame

• MMC & LMC


• Important Fundamental Rules

• Each dimension should have a tolerance

• It should fully define the geometry with no room left for assumptions or over definition

• The dimensions define the finished part, any processing required should be specified

• There should be only one interpretation of every dimension

• Dimensions are valid only where they are specified


•Types of dimensioning

• Millimeter dimensioning

• Zero precedes when the dimension is less than 1 mm.

• In case of whole number neither the decimal point nor the 0 is shown

• Last digit of fractional dimension is not followed by a zero



• Millimeter dimensioning



• Inch dimensioning

• Zero does not precede when the dimension is less than 1 in.

• A dimension is expressed in the same number of zeroes as the tolerances



• Inch dimensioning


• Basics of Dimensions

• Dimension Lines

• Alignment

• Spacing



• Extension Lines

• Crossing of extension lines



• Chain Lines

• Leader Lines



• Reference Dimensions


• Dimensioning various features

• Radii



• Foreshortened Radii



• Irregular Outlines



• Counter bore Holes



• Counter sunk Holes



• Spotfaced Holes



• Chamfers



• Location



• Repetitive features

Introduction to Tolerances

• Application of Tolerances

• As direct limits

• As a geometric tolerance

• In a note or table referring to specific dimensions

• In a general tolerance block referring to all dimensions on a drawing for which tolerances are not otherwise specified


•Direct Tolerancing Methods

• Limit Dimensioning


•Direct Tolerancing Methods

• Plus and Minus Tolerancing


•Tolerance Expression

• Millimeter Tolerance

• Inch Tolerance


•Tolerance Accumulation

• Chain Dimensioning



• Base Line Dimensioning



• Direct Dimensioning



• Dimensional Limits related to an origin


•Tolerancing on different features

• Screw Threads

• Gears and Splines



• Angular Surfaces



• Conical Tapers



• Radii



• Statistical Tolerancing

Thank You for Your Patience

Geometrical tolerances

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