FUNDAMENTALS OF GEOMETRIC DIMENSIONING AND TOLERANCING 3E is a unique book that meets the needs of readers studying industrial technology, CAD, engineering technology, or manufacturing technology. This book clearly organizes geometric dimensioning and tolerancing fundamentals into small, logical units for step-by-step understanding. Measurable performance objectives help readers assess their progress.

It defines and fully encompasses the revised ANSI/ASME Y14.5M-2009 to keep readers current on these important industry standards. This book is cited by top industry professionals as meeting the highest GD&T "standards"!

TABLE OF CONTENTS

TABLE OF CONTENTS

There are six major parts to the fundamentals of GD&T:

Advice This textbook is designed to introduce you to the fundamentals of GD&T; however, only you can ensure a successful understanding of GD&T through proper goal setting and self-discipline. I can lead you into the world of GD&T, but you must make a conscious effort to do the work required tosuccessfully master this subject.

Because of my firm belief that success is achieved through proper goal setting and discipline, I have provided you with goals and performance objectives at the beginning of each chapter. Acquire an understanding of the goals and objectives. Work through the chapter, step by step, and you willsoon have mastered the fundamentals GD&T.

Advice However, to be successful, you should also set some goals, set aside a specific time each day to read, study and complete the questions and problems at the end of each chapter. The results of your work and discipline will be apparent as you successfully grasp each concept and master the performance objectives. Best of all, you will soon realize the larger goal: an understanding of thepreciseness, the flexibility, and the power of GD&T.

Studies about how we learn have identified that several levels of thinking skills are involved in the learning process. Many students try to learn by simply memorizing facts, without a thorough understanding of the topic; however, these studies indicate that memorization alone will not properly prepare the student for tests or using the topic on the job.

Advice Remember, major geometric tolerancing topics are interrelated and build upon one another, so after studying a chapter, review the performance objectives from the beginning of the chapter to be sure you understand the major points and terminology involved. Could you explain these terms and concepts to someone else? Try it! A person who understands a topic can use the correct vocabulary needed toexplain that topic.

I hope you are encouraged enough to begin the hard work needed to master the fundamentals of GD&T, if so, you will be well rewarded. Geometric dimensioning and tolerancing is a comprehensive and useful topic; understanding its six major components is rewarding. In writing this text, I tried to do everything possible to assist you in your journey to learning GD&T. The rest of the work is up to you!

There are six major parts to the fundamentals of GD&T:

GD&T is an international language that is used on engineering drawings to accurately describe a part.

GD&T 是用来在图纸上精确描述零件的国际语言。

GD&T is a precise mathematical language that can be used to describe the size, form, orientation and location of part features.

GD&T 是精确的数学语言，用来描述零件形体的尺寸、形状、方向和位置。

GD&T is a design philosophy (functional dimensioning) on how to design and dimension parts.

GD&T 是关于设计和标注零件的一种设计原理。（基于功能的尺寸标注）

GD&T is a method for precisely defining the geometry of mechanical parts. It introduces tools which allow mechanical designers, fabricators, and inspectors to effectively communicate complex geometrical descriptions which are not otherwise able to be described in a defined language.

GD&T 是精确定义机械部件几何特性的方法。其为机械设计人员、生产人员、检验人员提供了有效沟通复杂几何特性的途径，这是现有的其他语言不能做到的。

dimension: a numerical value(s) or mathematical expression in appropriate units of measure used to define the form, size, orientation or location, of a part or feature. 尺寸：用适当的测量单位来描述零件或形体形状、尺寸、方向或位置的数值或数学表达。 tolerance: the total amount that features of the part are permitted to vary from the specified dimension. The tolerances is the difference between the maximum and the minimum limits. 公差：零件的形体允许超出规定尺寸的量。公差处于最大和最小值之间。

When part features are critical to function or interchangeability.当零部件的形体对功能或者互换性有重要影响时。

When functional gauging techniques are desirable.当需要对功能进行测量时。

When datum references are desirable.当需要有参考基准时。

When computerization techniques are desirable.当需要用到计算机技术时。

When standard interpretation or tolerance is not already implied.当标准和公差没有明确时。

When Should GD&T be Used 什么时候用 GD&T

It saves money.节约金钱。

Provides for maximum producibility of parts.最大化零件的可制造性。

Insures that design tolerance requirements are specifically stated and carried out.确保设计的公差要求得到规定和落实。

Adapts to, and assists, computerization techniques.适合并协助计算机技术。

Ensure interchangeability of mating parts at assembly.确保组装时的配件的互换性。

Provides uniformity and convenience in drawing.确保图纸标准化，容易读懂。

Why Should GD&T be Used为什么用 GD&T

What This Chapter Is About

Chapter 1 introduces the topics of engineering drawings, dimensioning and tolerancing, and the importance of standards.

Engineering drawings are the documents most companies use to communicate product requirements. Dimensioning and tolerancing is typically used on engineering drawings to define the size, shape, feature relationships, and allowable variation of a workpiece. Standards are necessary to create common specifications and promote common interpretation practices.

A good engineering drawing should be able to speak for itself, it should be able to go anywhere, and competent people should have the same interpretation of the drawing without question.

Performance Objectives Upon completing this chapter, you should be able to:1. Describe what an engineering drawing is (p.2)2. Explain the importance of an engineering drawing (p.3)3. List four consequences of engineering drawing errors (p.4)4. List the two primary dimensioning and tolerancing standards used globally (p.4)5. Describe which ASME standards cover dimensioning and tolerancing (p.4)6. Describe the role of dimensioning and tolerancing standards on engineering drawings (p.5)7. Identify which dimensioning and tolerancing standards apply to an engineering drawing (p.5)

See Figure 1-1. An engineering drawing consists of pictures, words, numbers, and symbols that are used to communicate the part requirements. An engineering drawing typically includes: 1. Geometry (shape, size and form of the part) 2. Important functional relationships Tolerance (variation) permitted for proper function Material, heat treat, surface coatings Part documentation information (part number, revisionlevel, etc.) The engineering drawing is where the engineering requirementsof the part are documented.

Mil Std 8 1950’sMil Std 8AMil Std 8B

Mil Std 8C-1963

ASA-Y14.5-1957

USASI Y14.5-1966

ANSI Y14.5-1973

ANSI Y14.5M-1982

ASME Y14.5M-1994

ASME Y14.5-2009

History of Dimensioning and Tolerancing Standards in the USA

ISO 1101-2004

G B/T 1182-2008

History and Background 历史背景

“Never accept anything for true which you do not clearly know to be such.”

Eli Whitney, is the inventor of the cotton gin and a pioneer in the use of mass production methods.

Around 1798, he won a contract to supply muskets to the United States government. The firearms manufacture were based on the concept of interchangeable parts.

He made a presentation to congress by building 10 guns and assembling and disassembling them claiming the same exact parts and mechanisms.

Eli Whitney 1765 - 1825

History and Background 历史背景

两国的有关标准：

中国 GB/T 1182 - 2008 产品几何技术规范- 几何公差 形状、方向、位置、 跳动公差标注 GB/T 4249 - 1996 公差原则 GB/T 13319 - 2003 几何公差 位置度公差注法 GB/T 16671 - 1996 形状和位置公差 最大实体要求、最小实体要求和 可逆要求 GB/T 16892 - 1997 形状和位置公差 非刚性零件注法 ……

美国 ASME Y14.5M-94(旧) Dimensioning and Tolerancing ASME Y14.5M-09(新) Dimensioning and Tolerancing通用 A-91- 89 (旧) Dimensioning and Tolerancing Global Dimensioning and Tolerancing Addendum – 97/01/04注：97/01版本为通用/福特/克莱斯勒一起发布，04版本为通用单独发布。

相应的国际标准有：

ISO 1101-04、ISO 5459-00、 ISO 8015-85、 ISO 2692-06、ISO 10579-10等。

There are two major dimensioning and tolerancing standards used around the world. The ASME standards are published by the American Society of Mechanical Engineers and are predominant in the U.S. Although the ASME standards are created in the U.S., they are used on engineering drawings in many countries around the world, so they are considered global standards.

Global Standards

The other major dimensioning and standards are the ISO standards, published by the International Organization ofStandards.

ASME Standards

ASME Y14.5-2009 is the standard for dimensioning and tolerancing. At a minimum, an engineering drawing should specify this standard. An engineering drawing will often invoke several additional standards.

The ASME standards that cover engineering drawings and dimensioning and tolerancing are listed in Figure 1-5.

If any of these standards are used, they must be specified on the drawing or invoked by a document referenced on the drawing.

FIGURE 1-5 ASME Drawing-Related Standards

Dimensioning and tolerancing standards have a critical rolein industry. Standards ensure:

1. Common rules and conventions for specifying dimensions and tolerances; 2. Common interpretations of dimensions and tolerances.

Without common specifications of dimensions and tolerances, engineering drawings would be more difficult to understand. Without common interpretation of dimensions and tolerances, it would be impossible to determine if parts meet their specifications. Therefore, dimensioning and tolerancing standards are used on most engineering drawings around the world.

1. An engineering drawing is a document (or digital datafile) that communicates a precise description of a part;

2. Common interpretations of dimensions and tolerances.

Key Points：

3. The least costly time to fix a drawing error is while it isstill in the design department.;

4. The two primary dimensioning and tolerancing standardsused globally are the ASME and ISO standards.

5. The role of dimensioning and tolerancing standards is to establish rules and conventions for common specification and common interpretation of dimensions andtolerances.

6 . The primary ASME standard for dimensioning and tolerancing is ASME Y14.5-2009.

7. The applicable dimensioning and tolerancing standard is typically specified in the title block or in the notes area of an engineering drawing.

Key Points：

The end