gd&t 1

• Engineering Drawings - General Review

Seminar Agenda

• Objectives

• Dimensional Engineering Concept

• ASME Y14.5M-1994 and GM Global Addendum

• Why Use GD&T ?

• Basic Rules and Definitions

• Datum Function & Datum Reference Frames

• Datum Planes, Features and Simulators

• Datum Target Areas, Lines, Points and Partial Datum Surfaces

• Video - Introduction to GD&T

• Feature Control Frame Elements

• Variation Simulation Modeling (VSM)

• Tolerances of Form

• Tolerances of Orientation

• Tolerances of Runout

• Tolerances of Profile

• Tolerances of Location

• The Language of GD&T

Course Objectives

Develop an awareness of Dimensional Engineeringconcepts and explain how the techniques are used tounderstand, control, and help reduce variation in theoverall vehicle build process.

Introduction to the Build Tolerance Procedure.

Provide an overview of the Variation SimulationModeling (VSM) process and how it is used topredict variation in the vehicle.

Provide an introduction to Geometric Dimensioningand Tolerancing (GD&T), the ASME Y14.5M-1994Standard including the GM Global Addendum andhow the concepts, symbols and terms of GD&T areused in the engineering process.

Dimensional Engineering Concept

Dimensional Engineering is a sub-process within theoverall vehicle development cycle, key to achievingrobust designs and controlling product definition.

The concept starts with “bubble-up” and continuesthrough the entire Four Phase Vehicle DevelopmentProcess. The “Team Concept” is an integral part ofthe GMTG Dimensional Engineering approach.

What is GD&T?Geometric Dimensioning & Tolerancing is an international graphic engineering language designed to allow designers and engineers to “say exactly what they mean” on engineering drawings. The concepts, symbols and mathematical structure of GD&T provide a precise and logical way to describe the manufacturing tolerance zones that are applied to individual features or groups of features on parts or assemblies.

What is ASME Y14.5M-1994?The ASME Y14.5M-1994 is the latest revised issue of the common Industrial Standard on dimensioning and tolerancing. The Standardestablishes uniform practices for the dimensioning and tolerancingof engineering drawings and related documents. All GD&T rules,concepts, and practices are contained within the current Y14.5MStandard and the GM Global Addendum.

Why a GM Global Addendum?The GM Global Addendum was written to address and/or clarifyconcepts and practices described within the ASME Y14.5M-1994 Standard. Sections 1-6 of the addendum represent the consensusof the US Car GD&T Team and have been adopted by GM, Ford, and Chrysler. Sections 7&8 apply specifically to General Motors.The addendum replaces section A91 of the current GM Drafting Standard.

The goal of GD&T is to improve communication !!

Geometric Characteristic SymbolsSYMBOLCHARACTERISTIC TYPE OF

TOLERANCEFEATURES

Straightness

Flatness

Circularity (roundness)

Cylindricity

Profile of a Line

Profile of a Surface

Angularity

Perpendicularity

Parallelism

Position

Concentricity

Symmetry

Circular Runout

Total Runout

Form

Profile

Orientation

Location

Runout

ForIndividualFeatures

ForIndividualor RelatedFeatures

ForRelated

Features

*

*

* Runout symbols may be filled or not filled

The Language of GeometricDimensioning & Tolerancing

** The RFS symbol is no longer used per ASME Y14.5M-1994. It is applicable only on drawings using earlier standards.

L

F

M

T

P

Maximum Material Condition

Least Material Condition

Free State Datum Modifier

Tangent Plane Modifier

Projected Tolerance Zone

Diameter Symbol

All Around Symbol

Between Symbol

Radius

Controlled Radius

Datum Feature Symbol

Basic Dimension (or Angle)

Regardless of Feature Size s

R

CR

234.5

A

TERM SYMBOL

****

Statistical Tolerance Symbol ST

*

*

*

* Symbols may be filled or not filled


Additional Symbols and Modifiers

CBA1

Secondary Datum

Geometric Characteristic

Symbol

Tolerance Value

Primary Datum

Tertiary Datum

Basic Feature Control Frame

Datum Reference Frame


Each feature control frame contains information identifying a specific featurecharacteristic to be controlled (geometric characteristic symbol),the limits oferror or variation allowed for that characteristic (tolerance value), the point(s)or surfaces from which the characteristic is to be measured (datum referenceframe), and the theoretical shape of the tolerance zone that applies (diametersymbol and material condition modifiers). Feature control frame are the basicbuilding blocks of the GD&T language. The ability to accurately interpret thefeature control frame is fundamental to understanding other GD&T concepts.

CBA1 MM

Diameter Symbol

Tolerance Material Condition Symbol

Datum Material Condition Symbol

Feature Control Frame with Material Condition Modifiers and Diameter Symbol


As required, additional symbols are used along with the basic feature controlframe to identify specific geometric or dimensional requirements. The aboveexample shows a diameter symbol and two maximum material condition (MMC)symbols that have been added to precisely describe the feature requirements.The diameter symbol describes the cylindrical shape of the feature tolerancezone while the maximum material condition symbols indicate both the featureand secondary datum material condition in which the stated tolerance applies.

Why Use GD&T ?

Parts designed using GD&T methods have maximized producibility because all available manufacturing tolerance has been included.

To Maximize Producibility

Properly applied GD&T assures assembly, interchangeability, and functional performance of all mating details.

Functional Performance

Effective GD&T identifies important dimensional relationships and offers clear communication of functional design requirements.

Clear Communication

Uniform, consistent interpretation of design requirements saves time and money by avoiding errors and controversies resulting from misconceptions and misunderstandings.

Uniform Interpretation

GD&T provides a method of maintaining coordination between functional design features, manufacturing processes & inspection practices (coordinated datum locations).

Coordinated Datum Locations

Using functional tolerancing techniques improves productivity by reducing the potential for the rejection of functional parts.

To Improve Productivity

Manufacturing tolerances acknowledge the fact that dimensional perfection is impossible to achieve. More importantly, from an economic perspective, perfection may be an expensive and inappropriate goal. Unnecessarily small tolerances do not improve quality or performance, they do increase costs. As manufacturing tolerances shrink, production and inspection costs increase rapidly. Properly specified tolerances minimize manufacturing and assembly costs, ensure product performance, and provide a means of assessing and maintaining process controls.

BasicRules andDefinitions

Limits of Size

Unless otherwise specified, the limits of size of a feature prescribe the extent within which variations of geometric form as well as size are allowed. This control applies solely to individual features of size. (ASME Y14.5M-1994, 2.7)

FEATURES OF SIZE: MUST BE WITHIN THE SPECIFIED LIMITS OF SIZE

Individual Feature of Size

Rule #1Where only a tolerance of size is specified, the limits of size of an individual feature prescribe the extent to which variations in its geometric form as well as size are allowed. (ASME Y14.5M-1994, 2.7.1)

In other words, features of size require:

PERFECT FORM AT MAXIMUM MATERIAL CONDITION (MMC)

All Applicable

Rule #2Geometric Tolerances

Regardless of Feature Size (RFS) applies, with respect to the individual tolerance, datum reference or both, where no modifying symbol is specified. Maximum Material Condition (MMC) or Least Material Condition (LMC) must be specified on the drawing where it is required

(ASME Y14.5-1994, 2.8a)

Circular runout, total runout, concentricity, and symmetry can only be applied on an RFS basis and cannot be modified to MMC or LMC.

Notes:The default condition described by Rule #2 applies only to drawings using the ASME Y14.5M-1994 standard. Any drawing using an earlier standard will have a different default condition.

MWHEN THE PART WEIGHS THE MOST!

DefinitionMaximum Material Condition

The condition in which a feature of size contains the maximum amount of material within the stated limits of size -- for example, minimum hole diameter or maximum shaft diameter

(ASME Y14.5M-1994, 1.3.20)

The Maximum Material Condition symbol can be used as a tolerance modifier and/or a datum modifier for internal or external features of size. When the MMC symbol is applied as a tolerance modifier, the specified tolerance value applies when the feature is at its extreme limit of size (min hole, max shaft). When the MMC symbol is applied as a datum modifier, the datum is the axis or center plane of the datum feature at its virtual size.

12 0-0.25

External Features of Size (Largest Size)

11.75 +/-0.25

14.9514.90

Internal Features of Size (Smallest Size)

15+0.1 0

Maximum Material Condition

12MMC Size =

14.95MMC Size =

11.75MMC Size =

MMC Size = 15


Definition

The condition in which a feature of size contains the least amount of material within the stated limits of size -- for example, maximum hole diameter or minimum shaft diameter

(ASME Y14.5M-1994, 1.3.19)

LWHEN THE PART WEIGHS THE LEAST!

The Least Material Condition symbol can also be used as a tolerance modifier and/or a datum modifier for internal or external features of size. When the LMC symbol is applied as a tolerance modifier, the specified tolerance value applies when the feature is at its extreme limit of size (max hole, min shaft). When the LMC symbol is applied as a datum modifier, the datum is the axis or center plane of the datum feature at its LMC size.

12 0-0.25

External Features of Size (Smallest Size)

11.75 +/-0.25

14.9514.90

Internal Features of Size (Largest Size)

15+0.1 0


11.5LMC Size =

14.9LMC Size =

12LMC Size =

LMC Size = 15.1

DefinitionRegardless of Feature Size

The term used to indicate that a geometric tolerance or datum reference applies at any increment of size of the feature within its size tolerance. (ASME Y14.5M-1994, 1.3.22)

*

* The RFS symbol is no longer required to indicate “regardless of feature size” conditions for features subject to variations in size (See rule #2 ASME Y14.5M-1994). It is applicable only on drawings using earlier standards.

S

DefinitionFree State Condition

The term used to indicate that a geometric tolerance or datum reference applies in its “FREE STATE” or unrestrained condition.

FWhen applied to geometric tolerances, the free state symbolindicates that individual or related feature tolerance(s) mustbe verified with the part in an unrestrained or unclampedcondition.When used as a datum modifier, only those datum feature(s)specifically identified as “free state” (including “rests” and “assists”) shall be unrestrained or unclamped when verifyingindividual or related feature tolerance(s).

(The use of the free state symbol as a datum condition modifier is valid only when the datum default condition is restrained.)

DefinitionDimensions, Features

and TolerancesDimension

A numeric value expressed in appropriate units of measure and used to define the size, location, geometric characteristic, or surface texture of a part or part feature. (ASME Y14.5-1994, 1.3.8)

FeatureThe general term applied to a physical portion of a part, such as a surface, pin, tab, hole or slot. (ASME Y14.5M-1994, 1.3.12)

ToleranceThe total amount a specific dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits. (ASME Y14.5M-1994, 1.3.31)

Tolerance-BilateralA tolerance in which variation is permitted in both directions from the specified dimension. (ASME Y14.5M-1994, 1.3.32)

Tolerance-UnilateralA tolerance in which variation is permitted in one direction from the specified dimension. (ASME Y14.5M-1994, 1.3.34)

Feature of sizeOne cylindrical or spherical surface, or set of two opposed elements or opposed parallel surfaces associated with a size dimension. (ASME Y14.5M-1994, 1.3.17)

DefinitionBasic Dimension

A numerical value used to describe the theoretically exact size, profile, orientation or location of a feature or datum target. It is the basis from which permissible variations are established by tolerances on other dimensions, in notes or in feature control frames. (ASME Y14.5M-1994, 1.3.9)

234.5 Basic Dimension

30 Basic Angle

24 Basic Diameter

DefinitionDatums, Datum Targets,

Datum Features and Simulators

A theoretically exact point, axis, or plane derived from the true geometric counterpart of a specified datum feature. A datum is the origin from which the location or geometric

characteristics of features of a part are established.

(ASME Y14.5M-1994, 1.3.3)

Datum

An actual feature of a part that is used to establish a datum. (ASME Y14.5M-1994, 1.3.4)

Datum Feature

Datum TargetA specified point, line, or area on a part used to establish a datum. (ASME Y14.5M-1994, 1.3.7)

Datum Feature SimulatorA surface of adequately precise form contacting the datum feature(s) and used to establish the simulated datum(s). (ASME Y14.5M-1994, 1.3.5)

DefinitionVirtual Condition

A constant boundary generated by the collective effects of a size feature’s specified MMC or LMC material condition and the geometric tolerance for that material condition. (ASME Y14.5M-1994, 1.3.37)

The calculated virtual condition boundary for a feature is used to determine the worst case inner or outer boundary for that feature. The virtual condition values are used to evaluate assembly requirements for mating parts and to establish sizes for functional gaging elements.

Virtual Condition BoundaryInternal Feature (MMC Concept)

13.5 Virtual Condition Boundary

14.5 MMC Size of Feature (Minimum Size)1 Applicable Geometric Tolerance

Calculating Virtual Condition

1 X Y ZM

15 +/- 0.5

Z

YXX

XX

X

As Shown on Drawing

Axis Location of MMC Hole Shown at Extreme Limit

Boundary of MMC HoleShown at Extreme Limit

1 Positional Tolerance Zone at

MMC

True (Basic)Position of Hole

True (Basic)Position of Hole

Other PossibleExtreme Locations

Virtual ConditionInner Boundary

Maximum InscribedDiameter( )

THE VIRTUAL CONDITION BOUNDARY OF AN INTERNAL FEATURE, SUCH AS A HOLE, REPRESENTS THE LARGEST PERFECTLY LOCATED PIN THAT WILL FIT INTO THE SMALLEST DIAMETER HOLE (MMC) AT THE EXTREME GEOMETRIC TOLERANCE LIMIT.

Virtual Condition BoundaryExternal Feature (MMC Concept)

13.5 Virtual Condition Boundary

12.5 MMC Size of Feature (Maximum Size)1 Applicable Geometric Tolerance

Calculating Virtual Condition

1 L M NM

12 +/- 0.5

N

MXX

XX

L

Axis Location of MMC Feature Shown at Extreme Limit

Boundary of MMC FeatureShown at Extreme Limit

1 Positional Tolerance Zone at

MMC

True (Basic)Position of Feature

True (Basic)Position of Feature

Other PossibleExtreme Locations

Virtual ConditionOuter Boundary

Minimum CircumscribedDiameter( )

As Shown on Drawing

THE VIRTUAL CONDITION BOUNDARY OF AN EXTERNAL FEATURE, SUCH AS A PIN, REPRESENTS THE SMALLEST PERFECTLY LOCATED HOLE THAT WILL ACCEPT THE LARGEST DIAMETER PIN (MMC) AT THE EXTREME GEOMETRIC TOLERANCE LIMIT.

Rules and Definitions Quiz

1. Tight tolerances ensure high quality and performance.

2. The use of GD&T improves productivity.

3. Size tolerances control both orientation and position.

4. Unless otherwise specified size tolerances control form.

5. A material modifier symbol is not required for RFS.

6. A material modifier symbol is not required for MMC.

7. Title block default tolerances apply to basic dimensions.

8. A surface on a part is considered a feature.

9. Bilateral tolerances allow variation in two directions.

10. A free state modifier can only be applied to a tolerance .

11. A free state datum modifier applies to “assists” & “rests”.

12. Virtual condition applies regardless of feature size.

Questions #1-12 True or False

Material Condition Quiz`

Internal Features MMC LMC

External Features MMC LMC

.890

.885

.895

.890

23.45 +0.05/- 0.25

123. 50 +/- 0.1

23.45 +0.05/- 0.25

10.75 +0/- 0.25

123. 50 +/- 0.1

Calculate appropriate values

Fill in blanks

10.75 +0.25/- 0

Blank Page

DatumFunction

andDatum

ReferenceFrames

Datum Requirements

FunctionalDatums Should Be Consistent with Part Assembly Interfaces

Datum Features Should Minimize Assembly Variation

Datums Should Represent Actual Part Feature Relationships

RepeatableDatum Features Must Be Dimensionally Stable

Datum Features Must Provide Secure, Repeatable Orientation and Immobilization of a Part or Assembly as Required

Datums Planes Should Be Independent to Avoid Sensitivity

CoordinatedDatum Reference Frame Establishes a Common Basis forControl and Measurement During All Process Phases of:

ManufactureInspectionAssembly

Datum Features Must Be Common and Coordinated With:StampingDetail GagesAssembly ToolingAssembly Gages

Datum Feature Selection and Coordination

Part features selected to establish datum reference planes onsheet metal panels should be coordinated with tooling locators(CD’s) used during the assembly process and datum featuresused to locate the panel during detail inspection.

When selecting datum features, careful consideration should begiven to the total number of datum target locations required tophysically stabilize part geometry. Assembly tooling fixtures areoften required to form and hold the nominal contours of flexiblesheet metal parts during welding operations. As a result, theassembly process will frequently make use of more part locatorsthan would be appropriate for a detail inspection tool.

Although the coordination of datum features is recommended to ensure quality vehicle assembly, it is important to recognize thatall tooling locators (CD’s) should not necessarily be considereddatums. The quantity and location of datum targets appropriatefor each application is based heavily on engineering common sense and experience.

Too many datum target areas can over constrain and distorta panel. This could mask actual error and compromise theintegrity of inspection data. Too few and the part may not besupported adequately, which can lead to poor or marginalgage repeatability.

Z Axis Linear

Z Axis Rotational

X Axis Linear

Y Axis Linear

X Axis Rotational

Y Axis Rotational

Six Degrees of Freedom


PRIMARY DATUM PLANE

TERTIARY DATUM PLANE

SECONDARY DATUM PLANE

90 o

90 o

90 o

Basic Datum Sequence

SECONDARY DATUM

PRIMARY DATUM

TERTIARY DATUM

FIRST DATUM PLANE

PART

Fixed

PART

THIRD DATUM PLANE

PART

Fixed

PART

SECOND DATUM PLANE

PART

Fixed

PART


PRIMARY DATUM

FIRST DATUM PLANEFixed

PART

Free

Free

Fixed

Free

PART

Free

Fixed

Fixed

Free


PART

In this example, the first, or primary datum plane provides partialconstraint to the part and prevents free movement in one (1) linearand two (2) rotational degrees of freedom. Primary planar datums requires a minimum of three points of contact on a feature surfaceto constrain part movement. However, the part surface mayactually contact the datum plane or the simulated datum surface inan infinite number of places.

Fixed

SECONDARY DATUMFixed

PART

FixedFixed

Fixed

Free

PART

Fixed

Fixed

Free


PART

SECOND DATUM PLANE

Fixed

Fixed

The second, or secondary datum plane provides additional part constraint and prevents free movement in one (1) additional linearand one (1) rotational degree of freedom. Secondary planar datumsrequire a minimum of two points of contact on a feature surface toconstrain part movement. However, the part surface may actuallycontact the datum plane or the simulated datum surface in an infinitenumber of places.

TERTIARY DATUMFixed

PART

FixedFixed

Fixed

Fixed

PART

Fixed

Fixed

FixedFixed


PART

The third, or tertiary datum plane provides full part constraint andprevents free movement along the one (1) remaining linear degreeof freedom. Tertiary planar datums require a minimum of one pointof contact on a feature surface to restrict the last degree of freedom.However, the part surface may actually contact the datum plane orthe simulated datum surface in an infinite number of places.

THIRD DATUM PLANE

Fixed

Part(Workpiece)

Datum Planes, Features, and Simulated Datums

Simulated Datum(Surface on Gage or Fixture Locator)

Datum Plane(True Geometric Counterpart of

Datum Feature)

Datum Feature(Actual Surface on Part)

Datum Feature Symbol -- Former Practice

Datum Feature Symbol -- Current Standard

Datum Feature Symbols

(ANSI Y14.5M-1982 and earlier standards)

(ASME Y14.5M-1994 standard)

A AB

Base (triangle) may be filled or not filled

A AB

Circular Datum Target Area Symbol

SquareDatum Target Area Symbol

Rectangular Datum Target Area Symbol

GeneralDatum Target

Symbol

A1

10 X 20May be filled or not filled

A112

Target area size (where applicable)Shape of gaging element

(where applicable)

A1

Datum TargetLabel

Datum TargetNumber

Datum Target Symbols

A125

A1

25

Optional methods of specifying shape and size of gaging element

(Datum Target Area)

Datum Targets

Datum Target Area

15

15

A1

12

DATUM BLOCK

Method Showing Target Zone and Location

PART

PARTIAL SURFACE CONTACT

15

15

A1

12

DATUM BLOCK

Method Showing Target Location Only

PART

PARTIAL SURFACE CONTACT

Datum Targets

Datum Target Line

120

A1

A1

As Shown on Drawing

Means This:PART

LOCATING PIN

LINE CONTACT

Datum Target Line

Datum Targets

Datum Target Point

A1

A1

120

25

POINT CONTACT

LOCATING PIN

PART

As Shown on Drawing

Means This:

Datum Target Point

Datum Targets

Partial Datum Surface

As Shown on Drawing

Means This:

50

A

50

LENGTH OF DATUM CONTACT

TRUE GEOMETRIC COUNTERPART OF PARTIAL SURFACE

1. Datum target areas are theoretically exact.

2. Datum features are imaginary.

3. Primary datums have only three points of contact.

4. The 6 Degrees of Freedom are U/D, F/A, & C/C.

5. Datum simulators are part of the gage or tool.

6. Datum simulators are used to represent datums.

8. All datum features must be dimensionally stable.

9. Datum planes constrain degrees of freedom.

10. Tertiary datums are not always required.

12. Datums should represent functional features.

Datum Quiz

11. All tooling locators (CD’s) are used as datums.


7. Datums are actual part features.

Datum Quiz

The three planes that make up a basic datum reference

frame are called _______, _________, and ________.

An unrestrained part will exhibit _________and __________ degrees of freedom.

A planar primary datum plane will restrain _________ and __________ degrees of freedom.

The primary and secondary datum planes together will restrain ___ degrees of freedom.

The primary, secondary and tertiary datum planes together will

restrain all ___ degrees of freedom.

The purpose of a datum reference frame is to ________________ of a part in a gage or tool.

A datum must be __________, __________, and ___________.

A ______ _______ is an actual feature on a part.

A ______ is a theoretically exact point, axis or plane.

A _____ ________ is a precise surface used to establish a simulated datum.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Questions #1-10 Fill in blanks (choose from below)

primary

secondary

tertiary 3-rotational

3-linear

2-rotational

datumthree

twoone

sixfunctional

restrain movement coordinated

datum simulatordatum feature

repeatablefive

1-linear

FeatureControlFrame

Elements

Feature Control Frame Elements

Feature Control Frame with Multiple Datum Features (Shown as Primary)

CA-B2.5 M D M

Multiple Datum Features (Primary)

C

D

CA-B2.5 M D M

A B


B

A

C

BA0.5 MM

C Datum Feature Symbol

Feature Control Frame

BA0.5 MM

Combined Feature Control Frame with Datum Feature Symbol


Feature Control Frame with Projected Tolerance Zone Symbol

Minimum Projected Height of Tolerance Zone

Projected Tolerance Zone Symbol

B

A5X M14X1-6H

20 minimum projected height of tolerance zone *

BA0.5 P 20M M

BA0.5 P 20M M

0.5 diametertolerance zone *

* Projected tolerance zones lie entirelyoutside the boundary of the part feature


Feature Control Frame w/ All Around Symbol

All Around Symbol

BA

C

BA1 C

BA1 C


Feature Control Frame w/ Between Symbol

B C

X Y

X YBA1 C

A

X YBetween Symbol

BA1 C


Feature Control Frame with Free State Symbol (Used as a Tolerance Zone Modifier)

1 F

14.9514.80

AVG

Free State Symbol

1 F


Feature Control Frame with Free State Symbol (Used as a Datum Condition Modifier)

BA-D0.5 M F C MM

Free State Symbol

A3A4 D1

A2A1

BC

Note: In this example Datum target D1 is unrestrained

The freestate datum condition modifier can only be appliedwhen the specified drawing default condition is restrained

BA-D0.5 M F C MM


A3A4

A2A1

BC

BA2.5 M C MSTM

Statistical Tolerance Symbol

BA2.5 M C MSTM

Feature Control Frame w/ Symbol Indicating the Tolerance was Statistically Determined

Two Geometric Characteristic Symbols

One Geometric Characteristic Symbol

BA2.5 CBA0.5

BA2.5 CBA0.5


One Composite Profile Control Frame

Two Single Segment Profile Control Frames

BA1.5 M CBA0.2 M

Two Geometric Characteristic Symbols

One Geometric Characteristic Symbol

BA1.5 M CBA0.2 M


One Composite True Position Control Frame

Two Single Segment True Position Control Frames


Two Single-Segment Profile Control Frames

Feature Location, Form & Orientation to Datum features A, B & C

Feature Location, Form & Orientation to Datum features A, B & C

Feature Form Refinement Only (No Datum Reference)

Feature Location & Orientationto Datum features A, B & C

Feature Location, Form & Orientation to Datum feature A only

Feature Location, Form & Orientation to Datum features B & C

Feature Location, Form & Orientation to Datum features A & B

Feature Location, Form & Orientation to Datum feature C only

BA2.5 CBA0.5 C

BA2.5 C0.5

BA2.5 CA0.5

BA2.5 CBA0.5

All feature elements must lie within bothspecified tolerance zones simultaneously

When two single-segment feature control frames are applied to an individualfeature, the two segments cannot contain identical datum references. In thiscase, the larger of the two tolerances is redundant and does not apply.

Composite Profile Control Frame


Feature Form Refinement Only (No Datum Reference)

Feature Location & Orientationto Datum features A, B & CBA2.5 C

0.5

BA2.5 CA0.5 Feature Form & Orientation

to Datum feature A only

Feature Location Only to Datum features A,B & C

BA2.5 CBA0.5

Feature Form & Orientation to Datum features A, B & C (when Datum B is a surface)


Feature Form & Orientation to Datum features A, B & C

(when Datum B is an axis)

BA2.5 CBA0.5 C


Feature Form &

Feature Locating


When a composite feature control frame is applied to an individual feature,the two segments can contain identical datum references. In this case, eachtolerance is applied to a different component of the composite requirement.

Reference

Orientation Reference


Two Single-Segment True Position Control Frames

BA1.5 C0.2

Coaxial Refinement Only (No Datum Reference)

Feature Location, Orientation & Feature-to-feature relationship to Datum

features A, B & C

BA1.5 CA0.2 Feature-to-feature relationship

& Orientation refinement to Datum feature A

Feature Location & Orientation to Datum features B & C

BA1.5 CBA0.2 C

Feature Location, Orientation & Feature-to-feature relationship to

Datum features A, B & C


Datum features A, B & C

BA1.5 CBA0.2


Datum features A & B

Feature Location & Feature-to-feature relationship to Datum feature C only


When two single-segment feature control frames are applied to an individualfeature, the two segments cannot contain identical datum references. In thiscase, the larger of the two tolerances is redundant and does not apply.

Composite True Position Control Frame


When a composite feature control frame is applied to an individual feature,the two segments can contain identical datum references. In this case, eachtolerance is applied to a different component of the composite requirement.

Coaxial Refinement Only (No Datum Reference)

BA1.5 C0.2

Pattern Location, Orientation & Feature-to-feature relationship to Datum

features A, B & C

Pattern Orientation & Feature-to-feature relationship to Datum feature A

BA1.5 CA0.2

Pattern Location & Orientation to Datum features B & C

Pattern Location Only to Datum features A, B & C

Pattern Orientation and Feature-to-feature relationship to Datum features A,

B & C (when Datum B is an axis)

BA1.5 CBA0.2 C

BA1.5 CBA0.2

Pattern Location Only to Datum features A, B & C

Pattern Orientation & Feature-to-feature relationship to Datum features A, B & C

(when Datum B is a surface)

Feature Relating Tolerance

Pattern Locating Tolerance

Zone Framework (FRTZF)

Zone Framework (PLTZF)


CBA1 M

DiameterSymbol

MaterialModifier

(Tolerance)

DatumReference

Frame

SecondaryDatum

ToleranceGeometric

CharacteristicSymbol

BA0.5 MM P 20

C

ProjectedTolerance

Symbol

MinimumProjected

Zone Height

MaterialModifier(Datum)

DatumFeatureSymbol

Feature Control Frame Review

BA2.5 CBA0.5

Feature ProfileLocating Datum

Reference

Feature ProfileForm/OrientationDatum Reference

Feature ProfileLocating

Tolerance

Feature ProfileForm/Orientation

Tolerance

CompositeProfile Symbol

(Profile of a Surface)

BA0.5 M CBA0.2 M

CompositeTrue Position

Symbol

Pattern LocatingTolerance Zone

Feature RelatingTolerance Zone

Pattern LocatingTolerance Zone

Framework (PLTZF)

Feature RelatingTolerance Zone

Framework (FRTZF)

Feature Control Frame Review

• Engineering Drawings - General Review

Seminar Agenda

• Objectives

• Dimensional Engineering Concept

• ASME Y14.5M-1994 and GM Global Addendum

• Why Use GD&T ?

• Basic Rules and Definitions

• Datum Function & Datum Reference Frames

• Datum Planes, Features and Simulators

• Datum Target Areas, Lines, Points and Partial Datum Surfaces

• Video - Introduction to GD&T

• Feature Control Frame Elements

• Tolerances of Form

• Tolerances of Orientation

• Tolerances of Runout

• Tolerances of Profile

• Tolerances of Location

• The Language of GD&T

Rules and Definitions Quiz

1. Tight tolerances ensure high quality and performance.

2. The use of GD&T improves productivity.

3. Size tolerances control both orientation and position.

4. Unless otherwise specified size tolerances control form.

5. A material modifier symbol is not required for RFS.

6. A material modifier symbol is not required for MMC.

7. Title block default tolerances apply to basic dimensions.

8. A surface on a part is considered a feature.

9. Bilateral tolerances allow variation in two directions.

10. A free state modifier can only be applied to a tolerance.

11. A free state datum modifier applies to “assists” & “rests”.

12. Virtual condition applies regardless of feature size.

FALSE

TRUE

FALSE

TRUE

TRUE

FALSE

FALSE

TRUE

TRUE

TRUE

FALSE

FALSE


Material Condition Quiz

Internal Features MMC LMC

External Features MMC LMC

0.8900.885

0.8950.890

23.45 +0.05/-0.25

10.75 +0.25/-0

123. 50 +/-0.1

23.45 +0.05/-0.25

10.75 +0/-0.25

123. 50 +/-0.1

Calculate appropriate values

Fill in blanks

10.75 11

23.20 23.50

123.40 123.60

0.890 0.895

10.75 10.50

23.50 23.20

123.60 123.40

0.890 0.885

1. Datum target areas are theoretically exact.

2. Datum features are imaginary.

3. Primary datums have only three points of contact.

4. The 6 Degrees of Freedom are U/D, F/A, & C/C.

5. Datum simulators are part of the gage or tool.

6. Datum simulators are used to represent datums.

8. All datum features must be dimensionally stable.

9. Datum planes constrain degrees of freedom.

10. Tertiary datums are not always required.

12. Datums should represent functional features.

Datum Quiz

11. All tooling locators (CD’s) are used as datums.


7. Datums are actual part features.

FALSE

FALSE

FALSE

FALSE

TRUE

TRUE

FALSE

TRUE

TRUE

TRUE

FALSE

TRUE

Datum Quiz

The three planes that make up a basic datum reference frame are called primary, secondary, and tertiary.

An unrestrained part will exhibit 3-linear and 3-rotational degrees of freedom.

A planar primary datum plane will restrain 1-linear and 2-rotational degrees of freedom.

The primary and secondary datum planes together will restrain five degrees of freedom.

The primary, secondary and tertiary datum planes together will

restrain all six degrees of freedom.

The purpose of a datum reference frame is to restrain movementof a part in a gage or tool.

A datum must be functional, repeatable, and coordinated.

A datum feature is an actual feature on a part.

A datum is a theoretically exact point, axis or plane.

A datum simulator is a precise surface used to establish a simulated datum.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Questions #1-10 Fill in blanks (choose from below)

primary

secondary

tertiary 3-rotational

3-linear

2-rotational

datumthree

twoone

sixfunctional

restrain movement coordinated

datum simulatordatum feature

repeatablefive

1-linear

gd&t 1

Documents

language of gdt

gdt language

gdt concepts

rfs symbol

tolerancing gdt

engineering process

gdt rules

use gdt