ISO GPSGEOMETRICAL PRODUCT SPECIFICATIONS

Ultimate Pocket GuideA Companion to the ISO 1101:2012and Related Geometrical Tolerancing Standards

Alex Krulikowski

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ISO GPS (Geometrical Product Specifications)

Ultimate Pocket GuideA companion to

ISO 1101:2012 and relatedGeometrical Tolerancing Standards

By Alex Krulikowski

Copyright ©2015 Effective Training Inc. an SAE INTERNATIONAL company

www.etinews.com1-800-886-09091-734-744-5940

CONTENTS

Introduction .............................................................. ivAcronyms, abbreviations, and letter symbols ...........vConventions used in this book ................................. viAcknowledgements ................................................ viii

1 - GPS Basics ..................................................................................1

2 - View Projection Options ...............................................................5

3 - Linear Size ...................................................................................9

4 - Non-Size Dimensions .................................................................27

5 - Datum Systems ..........................................................................39

6 - Geometrical Tolerances ..............................................................69

7 - General Tolerances ..................................................................115

8 - Non-Rigid Workpieces ..............................................................121

9 - Workpiece Edges .....................................................................125

10 - Appendices:A - ASME / ISO Comparison .................................................133B - ISO Geometrical Tolerancing Chart .................................139C - Ambiguous Non-Size Dimensions ...................................141

Front cover:Symbol Index ............................................................... inside foldTab Index ...................................................................outside fold

Back cover:List of ISO Standards Referred to in This Guide ......... inside foldAbout the Author ........................................................outside fold

Credit is gratefully given and acknowledgement made for the use of symbols, definitions, and concepts from ISO GPS standards. Definitions used are reproduced or paraphrased from the list of ISO standards listed on the back cover inside fold. This pocket guide covers topics from many ISO standards; however, it is not a replacement for the standards. In numerous places throughout this guide, the relevant ISO standards are listed. The reader should consult the actual ISO standards for definitive drawing interpretation.

ISO, International Organization for Standardization website:http:www.iso.org

About This Pocket GuideAll of the information in this pocket guide is based on ISO GPS standards published as of January 1, 2015. A list of these ISO standards and their current release dates are shown in a chart on the inside of the back cover. Where a standard is referenced in this guide, only the standard number is shown; the date is the current release date shown in the chart.

The purpose of this pocket guide is to simplify the interpretation of engineering drawings. This book will guide you on which ISO standards apply to a drawing and what the notations on the drawing mean. It allows you to easily look up information on a topic without having to navigate through numerous ISO standards.

Each topic covered is followed by a reference to the appropriate ISO GPS standard (and sometimes clause) in italics so you can find additional information.

The ISO GPS (Geometrical Product Specifications) Ultimate Pocket Guide is not intended for standalone use. You should consult the ISO standards referenced for a complete and authoritative explana-tion of the concepts shown.

The pocket guide contains the most common rules, symbols, and concepts in the ISO GPS System. The information in the pocket guide is meant to be a quick reference for drawing interpretation of the most common dimensioning and tolerancing applications. Refer to the standards referenced for less common GPS tools.

This guide also includes several features to help the reader quickly find information:

• The pages are thumb indexed.

• There is a symbol index on the inside front cover of the book.

• Author’s comments are intended to help engineers apply or interpret tolerancing in a cost-effective manner. Each com-ment appears in a highlighted box with a caution symbol.

Every effort has been made to ensure the accuracy of the material in the pocket guide. However, I know from experience that a few errors may have slipped through the final stages of production. I apologize in advance, for any inconvenience this may cause. If you find an error, please send me an email at alexk@etinews.com, and I will correct it in the next printing for the benefit of all readers.

INTRODUCTION

iv

• Author’scommentsaretheauthor’stips,opin-ions,andinsights,andarenotpartoftheISOGPSstandards.

v

ACS Any cross section 64

ASME American Society of Mechanical Engineers 21

CT Common tolerance 18

CZ Common zone 56

GD&T Geometric dimensioning and tolerancing 133

GPS Geometrical product specifications 1

ISO International Organization for Standardization 1

IT International tolerance grade 68

LD Minor diameter 68

LE Line element 71

LMC Least material condition 39

LMR Least material requirement 54

LMS Least material size 55

LMVC Least material virtual condition 55

MD Major diameter 68

MMC Maximum material condition 39

MMR Maximum material requirement 54

MMS Maximum material size 54

MMVC Maximum material virtual condition 54

NC Not convex 71

RPR Reciprocity requirement 69

TED Theoretically exact dimension 25

ACRONYMS, ABBREVIATIONS, AND LETTER SYMBOLS

vi

Terms and DefinitionsThe definitions for the terms in this guide are paraphrased from ISO standard definitions. For the exact definition of a term, please see the appropriate ISO standard.

Practical InterpretationsThe drawing interpretations in this guide are “practical interpreta-tions” that show the requirement (tolerance zone shape, size, and location) and the real surface of the part within the tolerance zone.

CONVENTIONS USED IN THIS BOOK

Line ConventionsThe chart below lists the line conventions used in this book.

View ProjectionsUnless otherwise specified, the view projection method in the fig-ures is first angle projection.

vii

Separators for Non-Whole Number DimensionsIn this pocket guide, a decimal point is used as a separator for non-whole number dimensions. In industry, a comma can also be used as a separator.

Projection LinesIn accordance with ISO 129:1988, projection lines are shown on drawings with no visible gap between the part outline and the pro-jection line.

ACKNOWLEDGEMENTSFirst, I want to thank a very special person who has brought im-mense happiness into my life. Pat is my best friend and wife. Pat’s support, help, and encouragement are unwavering. Our love grows deeper every day.

I would also like to recognize the employees at Effective Training. As always, they put forth a superb effort in turning my notes and rough sketches into a book that is going to help many engineers around the world. Matthew Pride created the graphics and cover de-sign, and Katherine Palmer formatted the guide and edited the text.

Last, but not least, I would like to give credit to the book’s proofread-ers. They made numerous improvements to the technical contents and readability of the book.

Todd Barnett

Sadiq Ali Basha G

Jim Beary

Elizabeth Burkett

William Caldwell

Roy Cross

Joe Dalton

Don Holder

Evan Janeshewski

Doug Keller

Dan Meyers

Mary E. O’Donnell

Gili Omri

Curtis A. Pawloski

Jim Pearson

Beata Schoenberg

Ganesan Somasundaram

Glen Voglesong

Bart Vos

Datum Systems 39

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Call 1.800.886.0909 for geometrical tolerancing assistance

DATUM SYSTEMSIntroductionIn the ISO GPS standards system, datums and datum systems are used on technical drawings. The ISO standards that cover datums and datum systems are 5459 for datum indications and 2692 for MMC & LMC datum indications.

To obtain repeatable measurements (for orientation or location) of workpiece features, the workpiece must be positioned in a specific relationship to a coordinate system. The use of a datum system al-lows the positioning of a workpiece to a coordinate system in a spe-cific relationship.

Since workpiece features are imperfect, the relating of the work-piece to a coordinate system must include the sequence in which the workpiece features are to be related to the planes (or other ele-ments) of a datum systems. This sequence is indicated in the datum references of tolerance frames.

This section shows the drawing indications for datum applications and the workpiece with the resulting datums indicated. It does not include the processes or methods of extraction, filtering, or asso-ciation.

Datum SystemA datum system is a set of two or more datums (situation features - see page 42) established in a specific order so that they orient and locate tolerance zones and virtual condition boundaries relative to a coordinate system. See Figure 5.1 for the symbols used in the datum system.

Degrees of FreedomA workpiece has six degrees of freedom in space: three translation-al and three rotational. The three translational degrees of freedom are X, Y, and Z.

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Figure 5.1 Symbols and modifiers used in the datum system

Symbols Used in the Datum System

Datum Systems 41

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Figure 5.2 Datum feature indicator

Datum Feature Indicator SymbolThe datum feature indicator symbol is used to indicate a datum fea-ture on a drawing. See Figure 5.2

Figure 5.3 Indications of datum features in a tolerance frame

Referencing Datum Features in a Tolerance FrameWhen tolerance frames reference datum features, they indicate the sequence for relating the workpiece features to the datums. The tol-erance frame is read from left to right. See Figure 5.3.

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When a plane that is perpendicular to a cylinder and the cylinder are both used as datum features, they can be referenced as a da-tum system or as a common datum. When referenced as a datum system, the primary datum reference determines the orientation of the workpiece to the datum reference frame. When referenced as a common datum, the workpiece is balanced between the associated features. See Figure 5.30.

Figure 5.30 Examples of a plane and a perpendicular cylinder as datum features

Examples of Planes and Cylinders as Datum Features

Datum Systems 67

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When a single datum or common datum is established, it constrains one or more degrees of freedom. The resulting datum is a plane, point, line, or combination thereof. The datum is a reference for lo-cating or orienting a tolerance zone.

The default condition is that a single datum or common datum locks all possible degrees of freedom that it can. If it is not required for a datum feature to lock all possible degrees of freedom of a da-tum feature reference; modifying symbols (PL, SL, PT, ><) may be added to indicate which degrees of freedom are locked by the datum feature.

When a datum is established from a complex surface, the datum consists of a plane, a line, and a point.

Several examples of indicating modifiers for locking or releasing degrees of freedom are shown in Figure 5.31.

Locking and releasing degrees of freedom are only intro-duced here. See ISO 5459 for additional rules.

Figure 5.31 Examples of locked or released degrees of freedom

Locked or Released Degrees of Freedom in a Datum System

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Threads, Splines and Gears as Datum Features

Figure 5.32 Indicating major or minor diameter of a datum feature

Where a single datum feature is a screw thread, spline, or gear, and no modifier indicates otherwise, the default for establishing the da-tum is the pitch diameter. Where it is desired to use the major diam-eter [MD] or minor diameter [LD] to establish the datum, a modifying symbol must be indicated near the datum indicator. See Figure 5.32.

PD027104

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