gd&t book#1
TRANSCRIPT
Geometric Dimensioning and TolerancingVariation Simulation Modeling
DimensionalDimensionalEngineeringEngineering
Seminar Seminar
GM General Motors Truck Group
No part of this publication may be reproduced, stored in a retrieval system,or transmitted in any form or by any means, electronic, mechanical, recordingor otherwise without prior written permission of the author and publisher.
Date of Publication: January 12, 1998
Latest Revision Date: May 1, 1999
Based on the ASME Y14.5M-Based on the ASME Y14.5M-1994 Dimensioning and 1994 Dimensioning and Tolerancing StandardTolerancing Standard
as amended by the GM Global as amended by the GM Global Addendum-1997Addendum-1997
Copyright 1998 by General Motors Corp.c
ALL RIGHTS RESERVED
GM General Motors Truck Group
DIMENSIONAL ENGINEERING
GM General Motors Truck Group
• 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
The Language of GeometricDimensioning & Tolerancing
Additional Symbols and Modifiers
CBA1
Secondary Datum
Geometric Characteristic
Symbol
Tolerance Value
Primary Datum
Tertiary Datum
Basic Feature Control Frame
Datum Reference Frame
The Language of GeometricDimensioning & Tolerancing
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
The Language of GeometricDimensioning & Tolerancing
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
Least Material Condition
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
Least Material Condition
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
Datum Reference Frame
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
Datum Reference Frame
PRIMARY DATUM
FIRST DATUM PLANEFixed
PART
Free
Free
Fixed
Free
PART
Free
Fixed
Fixed
Free
Datum Reference Frame
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
Datum Reference Frame
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
Datum Reference Frame
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.
Questions #1-12 True or False
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
Feature Control Frame Elements
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 Elements
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 Elements
Feature Control Frame w/ All Around Symbol
All Around Symbol
BA
C
BA1 C
BA1 C
Feature Control Frame Elements
Feature Control Frame w/ Between Symbol
B C
X Y
X YBA1 C
A
X YBetween Symbol
BA1 C
Feature Control Frame Elements
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 Elements
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
Feature Control Frame Elements
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
Feature Control Frame Elements
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
Feature Control Frame Elements
One Composite True Position Control Frame
Two Single Segment True Position Control Frames
Feature Control Frame Elements
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 Control Frame Elements
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 Location Only to Datum features A,B & C
Feature Form & Orientation to Datum features A, B & C
(when Datum B is an axis)
BA2.5 CBA0.5 C
Feature Location Only to Datum features A,B & C
Feature Form &
Feature Locating
All feature elements must lie within bothspecified tolerance zones simultaneously
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
Feature Control Frame Elements
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
Feature Location, Orientation & Feature-to-feature relationship to
Datum features A, B & C
BA1.5 CBA0.2
Feature Location, Orientation & Feature-to-feature relationship to
Datum features A & B
Feature Location & Feature-to-feature relationship to Datum feature C only
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 True Position Control Frame
Feature Control Frame Elements
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)
All feature elements must lie within bothspecified tolerance zones simultaneously
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
Notes
END
• 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
Questions #1-12 True or 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.
Questions #1-12 True or False
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