The GD&T Hierarchy Y14.5-2018 Textbook

ISBN 978-0-9983395-3-5

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The GD&T Hierarchy textbook is intended to aid in the instruction of Geometric Dimensioning and Tolerancing (GD&T) in accordance with the ASME Y14.5-2018 Standard as well as the ASME Y14.5M-1994 and ASME Y14.5-2009.  Where a concept is new to the 2018 revision of the Standard it has a shaded background.  Coverage also includes selected topics from ASME Y14.41.

This full color text is in landscape format which made it possible to include more complex drawings than are usually found in a GD&T text. There are over 200 pages with many illustrations of drawings and solid models of actual parts drawn from industry.  In addition to containing the rules, terms and definitions of GD&T, this text makes exclusive use of the GD&T Hierarchy to explain the relationship between tolerances and to guide the reader to the most appropriate applications.

Highlights of the text include:

• Numerous Rules of Thumb
• Overlays to illustrate concepts
• Flowcharts
• Dynamic tolerancing diagrams
• Former practices
   
  Table of Contents:
  

Chapter 1 – Introduction to The GD&T Hierarchy – 2018
Why GD&T Hierarchy 1-7
History of Tolerancing 1-8
Standards You Should Know 1-9
Why Make a revision to the Y14.5 Standard? 1-11
Principal Changes 1-11
Addition of Section 1-4 1-11
Section 1: Scope 1-11
Words [1.4.1] 1-12
Section 2: references 1-13
GD&T Assures Interchangeability 1-14
Evolution of Engineering Drawings 1-15
Fundamental Rules [4.1] 1-16
Linear Units Identifiation [4.2.3] 1-18
Types of Dimensioning and Tolerancing [4.3] & [5.3] 1-18
Millimeter Dimensioning Rules [4.3.1] 1-19
Inch Dimensioning Rules [4.3.2] 1-19
Millimeter Tolerancing Rules [4.3.1] 1-20
Inch Tolerancing Rules [4.3.2] 1-20
Drawing Block Tolerances 1-21
Angular Units and Tolerances [4.2.5] & [5.3.3] 1-21
Types of Tolerances
Directly Toleranced Dimensions 1-22
Basic Dimensions [1.3.23] 1-23
Size Dimensions 1-23
Geometric Tolerances [1.3.62] 1-23
Plated or Coated Parts [5.4.1] 1-23
Repetitive Features and Dimensions [4.6.5] 1-23
Tolerance Accumulation Between Surfaces [5.6] 1-24
Quality and the ASME Y14.5 Standard 1-26
Questions to Ask Prior to Drawing Release 1-27
Defiing the Ideal Geometry 1-27
What is GD&T? 1-28
Introduction – Geometric Shapes 1-29
GD&T Symbols 1-30
Symbols Found on Drawings 1-31
Part Geometry 1-33
The GD&T Hierarchy 1-36

Chapter 2 – Features
GD&T really can be as easy as 1-2-3 2-1
The “Feature of Size” Side of the Pyramid 2-2
Actual Envelopes 2-2
Centers and Surfaces 2-3
Features of Size [3.35] 2-4
Finding an Axis or Center Plane 2-4
Irregular Features of Size [3.35.1] 2-5
Axis of a Feature [3.32] 2-6
Derived Median Line and Point [3.22] 2-6
Center Plane of a Feature [3.33] 2-7
Derived median Plane [3.23] 2-7
Material Condition Modifirs 2-7
Maximum Material Condition [3.41] 2-7
Least Material Condition [3.40] 2-8
The Feature Control Frame [6.4.1] 2-8
Material Condition Modifirs Applied GD&T 2-9
Dynamic Tolerancing Diagrams 2-10
Boundaries [3.2] & [3.5] 2-11
Inner Boundary 2-11
Outer Boundary 2-11
Least Material of Feature Size (LMC) [3.40] 2-12
Regardless of Feature Size (RFS) [3.50] 2-12
What is Meant by the Size of a RFS? 2-13
Individual Feature of Size, Rule #1 [5.8.1] 2-14
Size Controls Form [5.8.1(b)] 2-16
Examples of Verifying Size 2-16
Rule #1, Perfect From at LMC [5.8.1(d)] 2-17
Interruption [3.39] 2-18
Introduction to The GD&T Hierarchy 1-3
Continuous Feature [3.10] 2-19
Continuous Feature of Size [3.11] 2-20
Exception to Rule #1 [5.8.2] 2-20
Free State Modifir [5.8.2(b)] 2-20
Straightness or Flatness for Feature of Size [5.8.2(b)] 2-20
Principle of Independency [2.8] 2-21
Independency Symbol [5.8.2(d)] 2-21
Average Diameter [5.8.2(e)] 2-21
Relationship Between Individual features [5.8.3] 2-22
Rule #2: RFS and RMB Default [5.9] 2-22
Radius [5.16] 2-23
Directly Toleranced Radius [5.16.1] 2-23
Controlled Radius Tolerance [5.16.2] 2-23
Output Shaft Case Study 2-24
Roller Bearing Case Study 2-24
Virtual Condition [3.70] 2-26
Boundaries 2-26
Least Material Boundary (LMB) 2-26
Maximum Material Boundary (MMB) 2-26
Boundary Calculation Example 2-26
Regardless of Material Boundary (RMB) 2-28
Applicability of Modifirs [5.9] 2-28
Actual Mating envelope (AME) [3.29] 2-30
Unrelated Actual Mating Envelope (UAME) [3.29(b)] 2-30
Related Actual Mating Envelope (RAME) [3.29(a)] 2-30
Actual minimum Material envelope (AMME) [3.30] 2-32
Screw Thread rule [5.10] 2-33
Gears and Spines [5.11] 2-33
Inspection Terms 2-34

Chapter 3 – Form
Flatness [8.4.2] 3-1
Flatness Feature Control Frame Placement 3-2
Surface Flatness 3-2
Inspecting Flatness 3-3
Flatness Applied to a Size Dimension [8.4.2.1] 3-4
Flatness at MMC Example 3-4
Form Controls on Continuous Features (CF) [8.4] 3-5
Unit Basis [8.4.2.2] 3-6
Flatness Summary 3-7
Straightness [8.4.1] 3-8
Represented Line Element [3.52] 3-10
Surface Straightness Summary 3-10
Straightness Applied to a Size Dimension 3-11
Straightness at MMC [8.4.1.3] 3-11
Remember, Size Controls Form 3-12
LMC and Straightness 3-12
Keep those Shafts Straight with Runout 3-13
Straightness Summary 3-13
Circularity [8.4.3] 3-14
Circularity Summary 3-15
Cylindricity [8.4.4] 3-15
Cylindricity Summary 3-16

Chapter 4 – Datum Reference Frame
Datum [3.14] 4-1
Datum Feature [3.17] 4-1
Degrees of Freedom [7.2] 4-2
Datum Feature Symbol [6.3.2] 4-3
Datum Feature Symbol Placement [6.3.2] 4-4
Datum Feature Simulators [3.18 and 7.6] 4-7
Part Immobilization 4-7
Datum Reference Frame [3.19] 4-7
True Geometric Counterpart [7.5] 4-8
Planar Feature [7.3 (a)] 4-10
Hole Feature 4-11
Width [7.3(b)] 4-11
Spherical [7.3(c)] 4-12
Cylindrical [7.3(d)] 4-15
Conical [7.3(e)] 4-15
1-4 © Tec-Ease, Inc., 2021 The GD&T Hierarchy-2018
Linear Extruded Shape [7.3(f)] 4-16
Complex Feature [7.3(g)] 4-16
Datum Precedence [7.4] 4-17
Datum Features Must Be Referenced to Be Used 4-20
Common Datum [7.12] 4-21
Datum Feature Selection [7.18] 4-23
Pump Cover Case Study 4-25
Datums Must Be of Suffient Size [7.8] 4-27
Deleted Defiitions 4-28

Chapter 5: Orientation
Orientation 5-1
Perpendicularity [3.46] 5-2
Each Radial Element [9.3.3] 5-7
Perpendicularity Summary 5-8
Parallelism [3.43] 5-9
Parallelism of an Axis of Center Plane 5-10
Parallelism Summary 5-11
Angularity [3.1] 5-12
Angularity of an Axis or Center Plane 5-13
Angularity Does Not Locate Features 5-13
Angularity Summary 5-15
When to Use Orientation Controls 5-16
One Orientation Symbol [9.6] 5-17
Tangent Plane [3.47 and 9.4] 5-19

Chapter 6: Datum Feature Controls
Datum Feature Controls [7-9] 6-1
Datum Features Applicable RMB [7.11.4] 6-7
MMB Calculation Examples [7.11.6] 6-8
Effcts of Straightness on Datum Simulation [7.11.6] 6-9
Worst-Case material Boundary [7.11.9.1] 6-11
Effct of Modifirs 6-13
No Modifirs for TGC Boundaries [7.11.10] 6-15
Unit Vectors [7.11.12] and [7.24.2(b)] 6-15
Translation Modifir [7.11.12] 6-16
Rotational Constraint [7.16] 6-16
Regardless of Material Boundary Application 6-21
Maximum Material Boundary Application 6-22
MMB Examples 6-23
RMB Example 6-25
Irregular Features of Size as Datum Features [7-17] 6-27

Chapter 7: Datum Concepts
Datum Concepts MMB and LMB 7-1
Simultaneous requirements [7.19] 7-2
Separate Requirements [10.5.4.2] 7-3
Patterns 7-4
Multiple Features of Size [10.5.3.4] and [10.6.2.3] 7-5
Restrained Clarifid and Freestate [7.20] and [6.3.20] 7-6
Datum Targets [7.24] 7-8
Movable Datum Targets [7.24.6] 7-11
The Coordinate System 7-13
Labeling the Coordinate System [7.21] 7-14
Datum Reference Frame Identifiation [7.21] 7-15
Degrees of Freedom 7-16
Repetitive Patterns of Features 7-17
Customized Datum Reference Frame [7.22] 7-18
Mathematically Defied Surface [7.13] 7-21
Clarifying Applicable Boundaries [7.11.6.3] 7-21

Chapter 8: Profie
Profie [11] 8-1
Between Symbol [6.3.11] 8-2
A Note Defiing Profie Tolerance [11.4.1.1] 8-3
Cutter Ring Case Study 8-3
All Around Symbol [11.3.1.3] 8-4
Profie as a General Requirement [11.2.3] 8-4
All Over Specifiation [11.3.1.5] 8-4
Application Options for Profie Summarized 8-6
Unilateral and Unequally Disposed Profie [11.3.1.2] 8-6
Unilateral Profie Tolerance [11.3.1.2(a) & (b)] 8-7
Introduction to The GD&T Hierarchy 1-5
Composite Profie Tolerancing [11.6.1] 8-9
Composite Profie with Independent Size[11.6.2] 8-13
Combined Controls [11.8] 8-15
Coplanarity [11.4.1.1] 8-16
Offet Surfaces [11.4.1.2] 8-16
Profie and Datum Modifirs 8-17
Electrical Connector Case Study 8-18
Hole Boundary Study 8-19
Nonuniform Tolerance Zone [11.3.2] 8-22
Zone to Smooth the Transitions [11.3.2.2] 8-22
Additional Nonuniform Tolerance Zone [11.3.2] 8-23
Profie on Nonsize Datum Features [11.4.3] 8-24
Profie per Unit Length 8-26
Casting Study 8-27
Casting Study Exercise 8-28
Casting and Machining Study 8-29
Orientation of Line element Using Profie [11.9] 8-32
Dynamic Profie Tolerance Zone [11.10] 8-34
Location Controls 8-36
The Hierarchy Pyramid 8-37
Profie of a Line Summary 8-38
Profie of a Surface Summary 8-38

Chapter 9: Position
Positional Tolerancing Method [5.1.1.1] 9-1
Position [10.2] 9-2
Implied Conditions 9-3
Surface Method [10.3.3.1(a)] 9-5
Pattern Location [10.5] 9-6
Composite Positional Tolerancing [10.5.1] 9-7
Inspecting Position 9-8
Positional Tolerance with No Datum [10.6.2.3] 9-10
Projected Tolerance Zone [10.4.1] 9-11
Position Summary 9-13
Symmetry 9-14
Application: Control of Center Plane 9-14
Application: Control of the Surface Boundary 9-15
Application: Control of Surfaces 9-16
LMC as related to Position [10.3.5] 9-19

Chapter 10: Coaxial Features
Coaxial Features 10-1
Position [10.6.1] 10-3
FIM (Full Indicator Movement) [12.3.2] 10-4
Runout [12.2] 10-4
Designed Interruptions are Ignored [12.4] 10-5
Tolerance Zone [12.4.1.1, 12.4.1.2, 12.4.2.1, 12.4.2.2] 10-6
Circular Runout Ex 1: (Nonplanar [12.4.1.1]) 10-6
Circular Runout Ex 2: [12.4.1.2] 10-7
Circular Runout Ex 3: [12.4.1.1] 10-8
Total Runout Ex 1:Cylindrical Features [12.4.2.1] 10-9
Total Runout Ex 2:Planar Features [12.4.2.2] 10-10
Relationship - Runout and Size Tolerance [12.5] 10-11
Inspecting Runout 10-16
Runout Summary 10-17
Between Symbol - Dimensioning Limited Area [12.4.3] 10-17
Runout on a tangent Plane [12.6.7] 10-18
Runout in an Assembly [12.6.8] 10-19
Profie Controlling Coaxiality 10-20
Runout Summary 10-9
Profie Controlling Coaxiality [Fig. 8-26] 10-10
Molded Parts Supplement S-1
Appendix A, Position Conversion Chart A-1
Appendix B, Surface Texture