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Shalini Jayaraman

This document provides information about geometric dimensioning and tolerancing (GD&T). It discusses the three categories of dimensioning, including general, geometric, and surface texture. GD&T considers the function of a part and how it interacts with related parts to more precisely define features. GD&T uses standard symbols to indicate tolerances based on a feature's geometry. The document outlines key GD&T concepts like datums, feature control frames, and how they are used to specify tolerances in relation to the part's geometry. It provides examples of how GD&T is applied to drawings to communicate tolerancing requirements.

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PART PRODUCTION COMMUNICATION MODEL MANAGEMENT DESIGN TOOLING PRODUCTION INSPECTION ASSEMBLY ROUTING PLANNING PRICING SERVICE PURCHASING SALES CUSTOMERSVENDORS Geometric Dimensioning and Tolerancing (GD&T) Geometric Dimensioning and Tolerancing (GD&T)
Dimensioning can be divided into three categories: •general dimensioning, •geometric dimensioning, and •surface texture. The following provides information necessary to begin to understand geometric dimensioning and tolerancing (GD&T) Three Categories of Dimensioning Three Categories of Dimensioning
Gdt tutorial
Limit Tolerancing Applied To An Angle Block Limit Tolerancing Applied To An Angle Block
Geometric Tolerancing Applied To An Angle Block Geometric Tolerancing Applied To An Angle Block
Geometric Dimensioning & Tolerancing (GD&T) Geometric Dimensioning & Tolerancing (GD&T) GD&T is a means of dimensioning & tolerancing a drawing which considers the function of the part and how this part functions with related parts. – This allows a drawing to contain a more defined feature more accurately, without increasing tolerances.
GD&T cont’dGD&T cont’d GD&T has increased in practice in last 15 years because of ISO 9000. – ISO 9000 requires not only that something be required, but how it is to be controlled. For example, how round does a round feature have to be? GD&T is a system that uses standard symbols to indicate tolerances that are based on the feature’s geometry. – Sometimes called feature based dimensioning & tolerancing or true position dimensioning & tolerancing GD&T practices are specified in ANSI Y14.5M-1994.
For ExampleFor Example Given Table Height However, all surfaces have a degree of waviness, or smoothness. For example, the surface of a 2 x 4 is much wavier (rough) than the surface of a piece of glass. – As the table height is dimensioned, the following table would pass inspection. If top must be flatter, you could tighten the tolerance to ± 1/32. – However, now the height is restricted to 26.97 to 27.03 meaning good tables would be rejected. Assume all 4 legs will be cut to length at the same time. or
Example cont’d.Example cont’d. You can have both, by using GD&T. – The table height may any height between 26 and 28 inches. – The table top must be flat within 1/16. (±1/32) 27 .06 26 .06 28 .06
WHY IS GD&T IMPORTANTWHY IS GD&T IMPORTANT Saves money – For example, if large number of parts are being made – GD&T can reduce or eliminate inspection of some features. – Provides “bonus” tolerance Ensures design, dimension, and tolerance requirements as they relate to the actual function Ensures interchangeability of mating parts at the assembly Provides uniformity It is a universal understanding of the symbols instead of words
WHEN TO USE GD&TWHEN TO USE GD&T When part features are critical to a function or interchangeability When functional gaging is desirable When datum references are desirable to ensure consistency between design When standard interpretation or tolerance is not already implied When it allows a better choice of machining processes to be made for production of a part
TERMINOLOGY REVIEWTERMINOLOGY REVIEW Maximum Material Condition (MMC): The condition where a size feature contains the maximum amount of material within the stated limits of size. I.e., largest shaft and smallest hole. Least Material Condition (LMC): The condition where a size feature contains the least amount of material within the stated limits of size. I.e., smallest shaft and largest hole. Tolerance: Difference between MMC and LMC limits of a single dimension. Allowance: Difference between the MMC of two mating parts. (Minimum clearance and maximum interference) Basic Dimension: Nominal dimension from which tolerances are derived.
THIS MEAN? WHAT DOES SIZE DIMENSION 2.007 2.003 LIMITS OF SIZELIMITS OF SIZE
SIZE DIMENSION MMC LMC ENVELOPE OF SIZE (2.003) (2.007) ENVELOPE PRINCIPLE LIMITS OF SIZELIMITS OF SIZE A variation in form is allowed between the least material condition (LMC) and the maximum material condition (MMC). Envelop Principle defines the size and form relationships between mating parts.
ENVELOPE PRINCIPLE LMC CLEARANCE MMC ALLOWANCE LIMITS OF SIZELIMITS OF SIZE
LIMITS OF SIZELIMITS OF SIZE The actual size of the feature at any cross section must be within the size boundary. ØMMC ØLMC
No portion of the feature may be outside a perfect form barrier at maximum material condition (MMC). LIMITS OF SIZELIMITS OF SIZE
PARALLEL PLANES PARALLEL PLANES PARALLEL PLANES CYLINDER ZONE GEOMETRIC DIMENSIONING TOLERANCE ZONES PARALLEL LINES PARALLEL LINES PARALLEL LINES PARALLEL PLANES PARALLEL PLANES Other Factors I.e., Parallel Line Tolerance Zones Other Factors I.e., Parallel Line Tolerance Zones
INDIVIDUAL (No Datum Reference) INDIVIDUAL or RELATED FEATURES RELATED FEATURES (Datum Reference Required) GEOMETRIC CHARACTERISTIC CONTROLS TYPE OF FEATURE TYPE OF TOLERANCE CHARACTERISTIC SYMBOL SYMMETRY FLATNESS STRAIGHTNESS CIRCULARITY CYLINDRICITY LINE PROFILE SURFACE PROFILE PERPENDICULARITY ANGULARITY PARALLELISM CIRCULAR RUNOUT TOTAL RUNOUT CONCENTRICITY POSITION FORM PROFILE ORIENTATION RUNOUT LOCATION 14 characteristics that may be controlled
Characteristics & Symbols cont’d. Characteristics & Symbols cont’d. – Maximum Material Condition MMC – Regardless of Feature Size RFS – Least Material Condition LMC – Projected Tolerance Zone – Diametrical (Cylindrical) Tolerance Zone or Feature – Basic, or Exact, Dimension – Datum Feature Symbol – Feature Control Frame
THE GEOMETRIC SYMBOL TOLERANCE INFORMATION DATUM REFERENCES FEATURE CONTROL FRAME COMPARTMENT VARIABLES CONNECTING WORDS MUST BE WITHIN OF THE FEATURE RELATIVE TO Feature Control FrameFeature Control Frame
Feature Control FrameFeature Control Frame Uses feature control frames to indicate tolerance Reads as: The position of the feature must be within a .003 diametrical tolerance zone at maximum material condition relative to datums A, B, and C.
Feature Control Frame Feature Control Frame Uses feature control frames to indicate tolerance Reads as: The position of the feature must be within a .003 diametrical tolerance zone at maximum material condition relative to datums A at maximum material condition and B.
The of the feature must be within a tolerance zone. The of the feature must be within a tolerance zone at relative to Datum . The of the feature must be within a tolerance zone relative to Datum . The of the feature must be within a zone at relative to Datum . The of the feature must be within a tolerance zone relative to datums . Reading Feature Control FramesReading Feature Control Frames
Placement of Feature Control Frames Placement of Feature Control Frames May be attached to a side, end or corner of the symbol box to an extension line. Applied to surface. Applied to axis
Placement of Feature Control FramesCont’d. Placement of Feature Control FramesCont’d. May be below or closely adjacent to the dimension or note pertaining to that feature. Ø .500±.005
Basic DimensionBasic Dimension A theoretically exact size, profile, orientation, or location of a feature or datum target, therefore, a basic dimension is untoleranced. Most often used with position, angularity, and profile) Basic dimensions have a rectangle surrounding it. 1.000
Basic Dimension cont’d. Basic Dimension cont’d.
Form FeaturesForm Features Individual Features No Datum Reference Flatness Straightness CylindricityCircularity
Form FeaturesExamplesForm FeaturesExamples Flatness as stated on drawing: The flatness of the feature must be within .06 tolerance zone. .003 0.500 ±.005 .003 0.500 ±.005 Straightness applied to a flat surface: The straightness of the feature must be within .003 tolerance zone.
Form FeaturesExamplesForm FeaturesExamples Straightness applied to the surface of a diameter: The straightness of the feature must be within .003 tolerance zone. .003 0.500 0.505∅ Straightness of an Axis at MMC: The derived median line straightness of the feature must be within a diametric zone of .030 at MMC. .030 0.500 0.505∅ M∅ 1.010 0.990
BEZEL CASE CLAMP PROBE DIAL INDICATOR 6 8 10 12 10 8 6 4 22 4 Dial IndicatorDial Indicator
Verification of FlatnessVerification of Flatness
Activity 13Activity 13 Work on worksheets GD&T 1, GD&T 2 #1 only, and GD&T 3 – (for GD&T 3 completely dimension. ¼” grid.)
Features that Require Datum Reference Features that Require Datum Reference Orientation – Perpendicularity – Angularity – Parallelism Runout – Circular Runout – Total Runout Location – Position – Concentricity – Symmetry
DatumDatum Datums are features (points, axis, and planes) on the object that are used as reference surfaces from which other measurements are made. Used in designing, tooling, manufacturing, inspecting, and assembling components and sub- assemblies. – As you know, not every GD&T feature requires a datum, i.e., Flat 1.000
Datums cont’d.Datums cont’d. Features are identified with respect to a datum. Always start with the letter A Do not use letters I, O, or Q May use double letters AA, BB, etc. This information is located in the feature control frame. Datums on a drawing of a part are represented using the symbol shown below.
Datum Reference SymbolsDatum Reference Symbols The datum feature symbol identifies a surface or feature of size as a datum. A ISO A ANSI 1982 ASME A 1994
Placement of DatumsPlacement of Datums Datums are generally placed on a feature, a centerline, or a plane depending on how dimensions need to be referenced. A AOR ASME 1994 A ANSI 1982 Line up with arrow only when the feature is a feature of size and is being defined as the datum
Placement of DatumsPlacement of Datums Feature sizes, such as holes Sometimes a feature has a GD&T and is also a datum Ø .500±.005 A Ø .500±.005 A Ø .500±.005
6 ROTATIONAL 6 LINEAR AND FREEDOM DEGREES OF UP DOWN RIGHT LEFT BACK FRONT UNRESTRICTED FREE MOVEMENT IN SPACE TWELVE DEGREES OF FREEDOMTWELVE DEGREES OF FREEDOM
Example DatumsExample Datums Datums must be perpendicular to each other – Primary – Secondary – Tertiary Datum
Primary DatumPrimary Datum A primary datum is selected to provide functional relationships, accessibility, and repeatability. – Functional Relationships » A standardization of size is desired in the manufacturing of a part. » Consideration of how parts are orientated to each other is very important. – For example, legos are made in a standard size in order to lock into place. A primary datum is chosen to reference the location of the mating features. – Accessibility » Does anything, such as, shafts, get in the way?
Primary Datum cont’d.Primary Datum cont’d. – Repeatability For example, castings, sheet metal, etc. » The primary datum chosen must insure precise measurements. The surface established must produce consistent » Measurements when producing many identical parts to meet requirements specified.
FIRST DATUM ESTABLISHED BY THREE POINTS (MIN) CONTACT WITH SIMULATED DATUM A Primary DatumPrimary Datum  Restricts 6 degrees of freedom
Secondary & Tertiary Datums Secondary & Tertiary Datums All dimension may not be capable to reference from the primary datum to ensure functional relationships, accessibility, and repeatability. – Secondary Datum » Secondary datums are produced perpendicular to the primary datum so measurements can be referenced from them. – Tertiary Datum » This datum is always perpendicular to both the primary and secondary datums ensuring a fixed position from three related parts.
SECOND DATUM PLANE ESTABLISHED BY TWO POINTS (MIN) CONTACT WITH SIMULATED DATUM B Secondary DatumSecondary Datum  Restricts 10 degrees of freedom.
Tertiary DatumTertiary Datum  Restricts 12 degrees of freedom. 90° THIRD DATUM PLANE ESTABLISHED BY ONE POINT (MIN) CONTACT WITH SIMULATED DATUM C MEASURING DIRECTIONS FOR RELATED DIMENSIONS
Z DATUM REFERENCE FRAME SURFACE PLATE GRANITE PROBE COORDINATE MEASURING MACHINE BRIDGE DESIGN Coordinate Measuring Machine Coordinate Measuring Machine
SIMULATED DATUM- SMALLEST CIRCUMSCRIBED CYLINDER THIS ON THE DRAWING MEANS THIS PART DATUM AXIS A Size Datum (CIRCULAR) Size Datum (CIRCULAR)
Size Datum (CIRCULAR) Size Datum (CIRCULAR) SIMULATED DATUM- LARGEST INSCRIBED CYLINDER THIS ON THE DRAWING MEANS THIS DATUM AXIS A PART A
Orientation TolerancesOrientation Tolerances –Perpendicularity –Angularity –Parallelism Controls the orientation of individual features Datums are required Shape of tolerance zone: 2 parallel lines, 2 parallel planes, and cylindrical
PERPENDICULARITY:PERPENDICULARITY: is the condition of a surface, center plane, or axis at a right angle (90°) to a datum plane or axis. Ex: The tolerance zone is the space between the 2 parallel lines. They are perpendicular to the datum plane and spaced . 005 apart. The perpendicularity of this surface must be within a .005 tolerance zone relative to datum A.
Practice ProblemPractice Problem Plane 1 must be perpendicular within .005 tolerance zone to plane 2. BOTTOM SURFACE
Practice ProblemPractice Problem Plane 1 must be perpendicular within .005 tolerance zone to plane 2 BOTTOM PLANE
2.00±.01 .02 Tolerance Practice ProblemPractice Problem Without GD & T this would be acceptable 2.00±.01 .02 Tolerance .005 Tolerance Zone With GD & T the overall height may end anywhere between the two blue planes. But the bottom plane is restricted to the red tolerance zone.
PERPENDICULARITY Cont’d. PERPENDICULARITY Cont’d. Location of hole (axis) This means ‘the hole (axis) must be perpendicular within a diametrical tolerance zone of .010 relative to datum A’
ANGULARITY:ANGULARITY: is the condition of a surface, axis, or median plane which is at a specific angle (other than 90°) from a datum plane or axis. Can be applied to an axis at MMC. Typically must have a basic dimension. The surface is at a 45º angle with a . 005 tolerance zone relative to datum A.
±0.01 PARALLELISM:PARALLELISM: The condition of a surface or center plane equidistant at all points from a datum plane, or an axis. The distance between the parallel lines, or surfaces, is specified by the geometric tolerance.
Activity 13 Cont’d.Activity 13 Cont’d. Complete worksheets GD&T- 2, GD&T-4, and GD&T-5 – Completely dimension. – ¼” grid
Material ConditionsMaterial Conditions Maximum Material Condition (MMC) Least Material Condition (LMC) Regardless of Feature Size(RFS)
Maximum Material ConditionMaximum Material Condition MMC This is when part will weigh the most. – MMC for a shaft is the largest allowable size. » MMC of Ø0.240±.005? – MMC for a hole is the smallest allowable size. » MMC of Ø0.250±.005? Permits greater possible tolerance as the part feature sizes vary from their calculated MMC Ensures interchangeability Used – With interrelated features with respect to location – Size, such as, hole, slot, pin, etc.
Least Material ConditionLeast Material Condition LMC This is when part will weigh the least. – LMC for a shaft is the smallest allowable size. » LMC of Ø0.240±.005? – LMC for a hole is the largest allowable size. » LMC of Ø0.250±.005?
Regardless of Feature SizeRegardless of Feature Size RFS Requires that the condition of the material NOT be considered. This is used when the size feature does not affect the specified tolerance. Valid only when applied to features of size, such as holes, slots, pins, etc., with an axis or center plane.
Location TolerancesLocation Tolerances –Position –Concentricity –Symmetry
Position TolerancePosition Tolerance A position tolerance is the total permissible variation in the location of a feature about its exact true position. For cylindrical features, the position tolerance zone is typically a cylinder within which the axis of the feature must lie. For other features, the center plane of the feature must fit in the space between two parallel planes. The exact position of the feature is located with basic dimensions. The position tolerance is typically associated with the size tolerance of the feature. Datums are required.
Coordinate System PositionCoordinate System Position Consider the following hole dimensioned with coordinate dimensions: The tolerance zone for the location of the hole is as follows: Several Problems: – Two points, equidistant from true position may not be accepted. – Total tolerance diagonally is .014, which may be more than was intended. 2.000 .750
Coordinate System PositionCoordinate System Position Consider the following hole dimensioned with coordinate dimensions: The tolerance zone for the location (axis) of the hole is as follows: Several Problems: – Two points, equidistant from true position may not be accepted. – Total tolerance diagonally is .014, which may be more than was intended. (1.4 Xs >, 1.4*.010=.014) 2.000 .750 Center can be anywhere along the diagonal line.
Position TolerancingPosition Tolerancing Consider the same hole, but add GD&T: Now, overall tolerance zone is: The actual center of the hole (axis) must lie in the round tolerance zone. The same tolerance is applied, regardless of the direction. MMC = .500 - .003 = .497
Bonus ToleranceBonus Tolerance Here is the beauty of the system! The specified tolerance was: This means that the tolerance is .010 if the hole size is the MMC size, or .497. If the hole is bigger, we get a bonus tolerance equal to the difference between the MMC size and the actual size.
Bonus Tolerance ExampleBonus Tolerance Example This system makes sense… the larger the hole is, the more it can deviate from true position and still fit in the mating condition! Actual Hole Size Bonus Tol. Φ of Tol. Zone Ø .497 (MMC) 0 .010 Ø .499 (.499 - .497 = .002) .002 (.010 + .002 = .012) .012 Ø .500 (.500 - .497 = .003) .003 (.010 + .003 = .013) .013 Ø .502 .005 .015 Ø .503 (LMC) .006 .016 Ø .504 ? ? This means that the tolerance is . 010 if the hole size is the MMC size, or .497. If the hole is bigger, we get a bonus tolerance equal to the difference between the MMC size and the actual size. .503
.497 = BONUS 0 TOL ZONE .010 .499 - .497 = BONUS .002 BONUS + TOL. ZONE = .012 Shaft Hole
.501 - .497 = BONUS .004 BONUS + TOL. ZONE = .014 .503 - .497 = BONUS .006 BONUS + TOL. ZONE = .016
What if the tolerance had been specified as: Since there is NO material modifier, the tolerance is RFS, which stands for regardless of feature size. This means that the position tolerance is .010 at all times. There is no bonus tolerance associated with this specification. VIRTUAL CONDITION: The worst case boundary generated by the collective effects of a size feature’s specified MMC or LMC material condition and the specified geometric tolerance. GT = GEOMETRIC TOLERANCE
PERPENDICULARITY Cont’d. PERPENDICULARITY Cont’d. Means “the hole (AXIS) must be perpendicular within a diametrical tolerance zone of . 010 at MMC relative to datum A.” Actual Hole Size Bonus Tol. Ø of Tol. Zone 1.997 (MMC) 1.998 1.999 2.000 2.001 2.002 2.003 Vc =
Activity 13 Cont’d.Activity 13 Cont’d. Worksheet GD&T 6

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Gdt tutorial

  • 1. PART PRODUCTION COMMUNICATION MODEL MANAGEMENT DESIGN TOOLING PRODUCTION INSPECTION ASSEMBLY ROUTING PLANNING PRICING SERVICE PURCHASING SALES CUSTOMERSVENDORS Geometric Dimensioning and Tolerancing (GD&T) Geometric Dimensioning and Tolerancing (GD&T)
  • 2. Dimensioning can be divided into three categories: •general dimensioning, •geometric dimensioning, and •surface texture. The following provides information necessary to begin to understand geometric dimensioning and tolerancing (GD&T) Three Categories of Dimensioning Three Categories of Dimensioning
  • 4. Limit Tolerancing Applied To An Angle Block Limit Tolerancing Applied To An Angle Block
  • 5. Geometric Tolerancing Applied To An Angle Block Geometric Tolerancing Applied To An Angle Block
  • 6. Geometric Dimensioning & Tolerancing (GD&T) Geometric Dimensioning & Tolerancing (GD&T) GD&T is a means of dimensioning & tolerancing a drawing which considers the function of the part and how this part functions with related parts. – This allows a drawing to contain a more defined feature more accurately, without increasing tolerances.
  • 7. GD&T cont’dGD&T cont’d GD&T has increased in practice in last 15 years because of ISO 9000. – ISO 9000 requires not only that something be required, but how it is to be controlled. For example, how round does a round feature have to be? GD&T is a system that uses standard symbols to indicate tolerances that are based on the feature’s geometry. – Sometimes called feature based dimensioning & tolerancing or true position dimensioning & tolerancing GD&T practices are specified in ANSI Y14.5M-1994.
  • 8. For ExampleFor Example Given Table Height However, all surfaces have a degree of waviness, or smoothness. For example, the surface of a 2 x 4 is much wavier (rough) than the surface of a piece of glass. – As the table height is dimensioned, the following table would pass inspection. If top must be flatter, you could tighten the tolerance to ± 1/32. – However, now the height is restricted to 26.97 to 27.03 meaning good tables would be rejected. Assume all 4 legs will be cut to length at the same time. or
  • 9. Example cont’d.Example cont’d. You can have both, by using GD&T. – The table height may any height between 26 and 28 inches. – The table top must be flat within 1/16. (±1/32) 27 .06 26 .06 28 .06
  • 10. WHY IS GD&T IMPORTANTWHY IS GD&T IMPORTANT Saves money – For example, if large number of parts are being made – GD&T can reduce or eliminate inspection of some features. – Provides “bonus” tolerance Ensures design, dimension, and tolerance requirements as they relate to the actual function Ensures interchangeability of mating parts at the assembly Provides uniformity It is a universal understanding of the symbols instead of words
  • 11. WHEN TO USE GD&TWHEN TO USE GD&T When part features are critical to a function or interchangeability When functional gaging is desirable When datum references are desirable to ensure consistency between design When standard interpretation or tolerance is not already implied When it allows a better choice of machining processes to be made for production of a part
  • 12. TERMINOLOGY REVIEWTERMINOLOGY REVIEW Maximum Material Condition (MMC): The condition where a size feature contains the maximum amount of material within the stated limits of size. I.e., largest shaft and smallest hole. Least Material Condition (LMC): The condition where a size feature contains the least amount of material within the stated limits of size. I.e., smallest shaft and largest hole. Tolerance: Difference between MMC and LMC limits of a single dimension. Allowance: Difference between the MMC of two mating parts. (Minimum clearance and maximum interference) Basic Dimension: Nominal dimension from which tolerances are derived.
  • 13. THIS MEAN? WHAT DOES SIZE DIMENSION 2.007 2.003 LIMITS OF SIZELIMITS OF SIZE
  • 14. SIZE DIMENSION MMC LMC ENVELOPE OF SIZE (2.003) (2.007) ENVELOPE PRINCIPLE LIMITS OF SIZELIMITS OF SIZE A variation in form is allowed between the least material condition (LMC) and the maximum material condition (MMC). Envelop Principle defines the size and form relationships between mating parts.
  • 16. LIMITS OF SIZELIMITS OF SIZE The actual size of the feature at any cross section must be within the size boundary. ØMMC ØLMC
  • 17. No portion of the feature may be outside a perfect form barrier at maximum material condition (MMC). LIMITS OF SIZELIMITS OF SIZE
  • 18. PARALLEL PLANES PARALLEL PLANES PARALLEL PLANES CYLINDER ZONE GEOMETRIC DIMENSIONING TOLERANCE ZONES PARALLEL LINES PARALLEL LINES PARALLEL LINES PARALLEL PLANES PARALLEL PLANES Other Factors I.e., Parallel Line Tolerance Zones Other Factors I.e., Parallel Line Tolerance Zones
  • 19. INDIVIDUAL (No Datum Reference) INDIVIDUAL or RELATED FEATURES RELATED FEATURES (Datum Reference Required) GEOMETRIC CHARACTERISTIC CONTROLS TYPE OF FEATURE TYPE OF TOLERANCE CHARACTERISTIC SYMBOL SYMMETRY FLATNESS STRAIGHTNESS CIRCULARITY CYLINDRICITY LINE PROFILE SURFACE PROFILE PERPENDICULARITY ANGULARITY PARALLELISM CIRCULAR RUNOUT TOTAL RUNOUT CONCENTRICITY POSITION FORM PROFILE ORIENTATION RUNOUT LOCATION 14 characteristics that may be controlled
  • 20. Characteristics & Symbols cont’d. Characteristics & Symbols cont’d. – Maximum Material Condition MMC – Regardless of Feature Size RFS – Least Material Condition LMC – Projected Tolerance Zone – Diametrical (Cylindrical) Tolerance Zone or Feature – Basic, or Exact, Dimension – Datum Feature Symbol – Feature Control Frame
  • 21. THE GEOMETRIC SYMBOL TOLERANCE INFORMATION DATUM REFERENCES FEATURE CONTROL FRAME COMPARTMENT VARIABLES CONNECTING WORDS MUST BE WITHIN OF THE FEATURE RELATIVE TO Feature Control FrameFeature Control Frame
  • 22. Feature Control FrameFeature Control Frame Uses feature control frames to indicate tolerance Reads as: The position of the feature must be within a .003 diametrical tolerance zone at maximum material condition relative to datums A, B, and C.
  • 23. Feature Control Frame Feature Control Frame Uses feature control frames to indicate tolerance Reads as: The position of the feature must be within a .003 diametrical tolerance zone at maximum material condition relative to datums A at maximum material condition and B.
  • 24. The of the feature must be within a tolerance zone. The of the feature must be within a tolerance zone at relative to Datum . The of the feature must be within a tolerance zone relative to Datum . The of the feature must be within a zone at relative to Datum . The of the feature must be within a tolerance zone relative to datums . Reading Feature Control FramesReading Feature Control Frames
  • 25. Placement of Feature Control Frames Placement of Feature Control Frames May be attached to a side, end or corner of the symbol box to an extension line. Applied to surface. Applied to axis
  • 26. Placement of Feature Control FramesCont’d. Placement of Feature Control FramesCont’d. May be below or closely adjacent to the dimension or note pertaining to that feature. Ø .500±.005
  • 27. Basic DimensionBasic Dimension A theoretically exact size, profile, orientation, or location of a feature or datum target, therefore, a basic dimension is untoleranced. Most often used with position, angularity, and profile) Basic dimensions have a rectangle surrounding it. 1.000
  • 29. Form FeaturesForm Features Individual Features No Datum Reference Flatness Straightness CylindricityCircularity
  • 30. Form FeaturesExamplesForm FeaturesExamples Flatness as stated on drawing: The flatness of the feature must be within .06 tolerance zone. .003 0.500 ±.005 .003 0.500 ±.005 Straightness applied to a flat surface: The straightness of the feature must be within .003 tolerance zone.
  • 31. Form FeaturesExamplesForm FeaturesExamples Straightness applied to the surface of a diameter: The straightness of the feature must be within .003 tolerance zone. .003 0.500 0.505∅ Straightness of an Axis at MMC: The derived median line straightness of the feature must be within a diametric zone of .030 at MMC. .030 0.500 0.505∅ M∅ 1.010 0.990
  • 34. Activity 13Activity 13 Work on worksheets GD&T 1, GD&T 2 #1 only, and GD&T 3 – (for GD&T 3 completely dimension. ¼” grid.)
  • 35. Features that Require Datum Reference Features that Require Datum Reference Orientation – Perpendicularity – Angularity – Parallelism Runout – Circular Runout – Total Runout Location – Position – Concentricity – Symmetry
  • 36. DatumDatum Datums are features (points, axis, and planes) on the object that are used as reference surfaces from which other measurements are made. Used in designing, tooling, manufacturing, inspecting, and assembling components and sub- assemblies. – As you know, not every GD&T feature requires a datum, i.e., Flat 1.000
  • 37. Datums cont’d.Datums cont’d. Features are identified with respect to a datum. Always start with the letter A Do not use letters I, O, or Q May use double letters AA, BB, etc. This information is located in the feature control frame. Datums on a drawing of a part are represented using the symbol shown below.
  • 38. Datum Reference SymbolsDatum Reference Symbols The datum feature symbol identifies a surface or feature of size as a datum. A ISO A ANSI 1982 ASME A 1994
  • 39. Placement of DatumsPlacement of Datums Datums are generally placed on a feature, a centerline, or a plane depending on how dimensions need to be referenced. A AOR ASME 1994 A ANSI 1982 Line up with arrow only when the feature is a feature of size and is being defined as the datum
  • 40. Placement of DatumsPlacement of Datums Feature sizes, such as holes Sometimes a feature has a GD&T and is also a datum Ø .500±.005 A Ø .500±.005 A Ø .500±.005
  • 41. 6 ROTATIONAL 6 LINEAR AND FREEDOM DEGREES OF UP DOWN RIGHT LEFT BACK FRONT UNRESTRICTED FREE MOVEMENT IN SPACE TWELVE DEGREES OF FREEDOMTWELVE DEGREES OF FREEDOM
  • 42. Example DatumsExample Datums Datums must be perpendicular to each other – Primary – Secondary – Tertiary Datum
  • 43. Primary DatumPrimary Datum A primary datum is selected to provide functional relationships, accessibility, and repeatability. – Functional Relationships » A standardization of size is desired in the manufacturing of a part. » Consideration of how parts are orientated to each other is very important. – For example, legos are made in a standard size in order to lock into place. A primary datum is chosen to reference the location of the mating features. – Accessibility » Does anything, such as, shafts, get in the way?
  • 44. Primary Datum cont’d.Primary Datum cont’d. – Repeatability For example, castings, sheet metal, etc. » The primary datum chosen must insure precise measurements. The surface established must produce consistent » Measurements when producing many identical parts to meet requirements specified.
  • 45. FIRST DATUM ESTABLISHED BY THREE POINTS (MIN) CONTACT WITH SIMULATED DATUM A Primary DatumPrimary Datum  Restricts 6 degrees of freedom
  • 46. Secondary & Tertiary Datums Secondary & Tertiary Datums All dimension may not be capable to reference from the primary datum to ensure functional relationships, accessibility, and repeatability. – Secondary Datum » Secondary datums are produced perpendicular to the primary datum so measurements can be referenced from them. – Tertiary Datum » This datum is always perpendicular to both the primary and secondary datums ensuring a fixed position from three related parts.
  • 47. SECOND DATUM PLANE ESTABLISHED BY TWO POINTS (MIN) CONTACT WITH SIMULATED DATUM B Secondary DatumSecondary Datum  Restricts 10 degrees of freedom.
  • 48. Tertiary DatumTertiary Datum  Restricts 12 degrees of freedom. 90° THIRD DATUM PLANE ESTABLISHED BY ONE POINT (MIN) CONTACT WITH SIMULATED DATUM C MEASURING DIRECTIONS FOR RELATED DIMENSIONS
  • 49. Z DATUM REFERENCE FRAME SURFACE PLATE GRANITE PROBE COORDINATE MEASURING MACHINE BRIDGE DESIGN Coordinate Measuring Machine Coordinate Measuring Machine
  • 50. SIMULATED DATUM- SMALLEST CIRCUMSCRIBED CYLINDER THIS ON THE DRAWING MEANS THIS PART DATUM AXIS A Size Datum (CIRCULAR) Size Datum (CIRCULAR)
  • 51. Size Datum (CIRCULAR) Size Datum (CIRCULAR) SIMULATED DATUM- LARGEST INSCRIBED CYLINDER THIS ON THE DRAWING MEANS THIS DATUM AXIS A PART A
  • 52. Orientation TolerancesOrientation Tolerances –Perpendicularity –Angularity –Parallelism Controls the orientation of individual features Datums are required Shape of tolerance zone: 2 parallel lines, 2 parallel planes, and cylindrical
  • 53. PERPENDICULARITY:PERPENDICULARITY: is the condition of a surface, center plane, or axis at a right angle (90°) to a datum plane or axis. Ex: The tolerance zone is the space between the 2 parallel lines. They are perpendicular to the datum plane and spaced . 005 apart. The perpendicularity of this surface must be within a .005 tolerance zone relative to datum A.
  • 54. Practice ProblemPractice Problem Plane 1 must be perpendicular within .005 tolerance zone to plane 2. BOTTOM SURFACE
  • 55. Practice ProblemPractice Problem Plane 1 must be perpendicular within .005 tolerance zone to plane 2 BOTTOM PLANE
  • 56. 2.00±.01 .02 Tolerance Practice ProblemPractice Problem Without GD & T this would be acceptable 2.00±.01 .02 Tolerance .005 Tolerance Zone With GD & T the overall height may end anywhere between the two blue planes. But the bottom plane is restricted to the red tolerance zone.
  • 57. PERPENDICULARITY Cont’d. PERPENDICULARITY Cont’d. Location of hole (axis) This means ‘the hole (axis) must be perpendicular within a diametrical tolerance zone of .010 relative to datum A’
  • 58. ANGULARITY:ANGULARITY: is the condition of a surface, axis, or median plane which is at a specific angle (other than 90°) from a datum plane or axis. Can be applied to an axis at MMC. Typically must have a basic dimension. The surface is at a 45º angle with a . 005 tolerance zone relative to datum A.
  • 59. ±0.01 PARALLELISM:PARALLELISM: The condition of a surface or center plane equidistant at all points from a datum plane, or an axis. The distance between the parallel lines, or surfaces, is specified by the geometric tolerance.
  • 60. Activity 13 Cont’d.Activity 13 Cont’d. Complete worksheets GD&T- 2, GD&T-4, and GD&T-5 – Completely dimension. – ¼” grid
  • 61. Material ConditionsMaterial Conditions Maximum Material Condition (MMC) Least Material Condition (LMC) Regardless of Feature Size(RFS)
  • 62. Maximum Material ConditionMaximum Material Condition MMC This is when part will weigh the most. – MMC for a shaft is the largest allowable size. » MMC of Ø0.240±.005? – MMC for a hole is the smallest allowable size. » MMC of Ø0.250±.005? Permits greater possible tolerance as the part feature sizes vary from their calculated MMC Ensures interchangeability Used – With interrelated features with respect to location – Size, such as, hole, slot, pin, etc.
  • 63. Least Material ConditionLeast Material Condition LMC This is when part will weigh the least. – LMC for a shaft is the smallest allowable size. » LMC of Ø0.240±.005? – LMC for a hole is the largest allowable size. » LMC of Ø0.250±.005?
  • 64. Regardless of Feature SizeRegardless of Feature Size RFS Requires that the condition of the material NOT be considered. This is used when the size feature does not affect the specified tolerance. Valid only when applied to features of size, such as holes, slots, pins, etc., with an axis or center plane.
  • 66. Position TolerancePosition Tolerance A position tolerance is the total permissible variation in the location of a feature about its exact true position. For cylindrical features, the position tolerance zone is typically a cylinder within which the axis of the feature must lie. For other features, the center plane of the feature must fit in the space between two parallel planes. The exact position of the feature is located with basic dimensions. The position tolerance is typically associated with the size tolerance of the feature. Datums are required.
  • 67. Coordinate System PositionCoordinate System Position Consider the following hole dimensioned with coordinate dimensions: The tolerance zone for the location of the hole is as follows: Several Problems: – Two points, equidistant from true position may not be accepted. – Total tolerance diagonally is .014, which may be more than was intended. 2.000 .750
  • 68. Coordinate System PositionCoordinate System Position Consider the following hole dimensioned with coordinate dimensions: The tolerance zone for the location (axis) of the hole is as follows: Several Problems: – Two points, equidistant from true position may not be accepted. – Total tolerance diagonally is .014, which may be more than was intended. (1.4 Xs >, 1.4*.010=.014) 2.000 .750 Center can be anywhere along the diagonal line.
  • 69. Position TolerancingPosition Tolerancing Consider the same hole, but add GD&T: Now, overall tolerance zone is: The actual center of the hole (axis) must lie in the round tolerance zone. The same tolerance is applied, regardless of the direction. MMC = .500 - .003 = .497
  • 70. Bonus ToleranceBonus Tolerance Here is the beauty of the system! The specified tolerance was: This means that the tolerance is .010 if the hole size is the MMC size, or .497. If the hole is bigger, we get a bonus tolerance equal to the difference between the MMC size and the actual size.
  • 71. Bonus Tolerance ExampleBonus Tolerance Example This system makes sense… the larger the hole is, the more it can deviate from true position and still fit in the mating condition! Actual Hole Size Bonus Tol. Φ of Tol. Zone Ø .497 (MMC) 0 .010 Ø .499 (.499 - .497 = .002) .002 (.010 + .002 = .012) .012 Ø .500 (.500 - .497 = .003) .003 (.010 + .003 = .013) .013 Ø .502 .005 .015 Ø .503 (LMC) .006 .016 Ø .504 ? ? This means that the tolerance is . 010 if the hole size is the MMC size, or .497. If the hole is bigger, we get a bonus tolerance equal to the difference between the MMC size and the actual size. .503
  • 72. .497 = BONUS 0 TOL ZONE .010 .499 - .497 = BONUS .002 BONUS + TOL. ZONE = .012 Shaft Hole
  • 73. .501 - .497 = BONUS .004 BONUS + TOL. ZONE = .014 .503 - .497 = BONUS .006 BONUS + TOL. ZONE = .016
  • 74. What if the tolerance had been specified as: Since there is NO material modifier, the tolerance is RFS, which stands for regardless of feature size. This means that the position tolerance is .010 at all times. There is no bonus tolerance associated with this specification. VIRTUAL CONDITION: The worst case boundary generated by the collective effects of a size feature’s specified MMC or LMC material condition and the specified geometric tolerance. GT = GEOMETRIC TOLERANCE
  • 75. PERPENDICULARITY Cont’d. PERPENDICULARITY Cont’d. Means “the hole (AXIS) must be perpendicular within a diametrical tolerance zone of . 010 at MMC relative to datum A.” Actual Hole Size Bonus Tol. Ø of Tol. Zone 1.997 (MMC) 1.998 1.999 2.000 2.001 2.002 2.003 Vc =
  • 76. Activity 13 Cont’d.Activity 13 Cont’d. Worksheet GD&T 6

Editor's Notes

  • #2: Pat McQuistion
  • #11: Quotes from Geo Metric III Foster
  • #12: Quotes from Geo Metric III Foster
  • #13: Quotes from Geo Metric III Foster Pat McQuistion
  • #14: Pat McQuistion
  • #15: Pat McQuistion
  • #17: Pat McQuistion
  • #18: Pat McQuistion
  • #30: Why symbols? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • #31: Why symbols? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • #32: Why symbols? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • #36: Why symbols? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • #53: Why symbols? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • #63: Foster’s text
  • #65: Foster’s text
  • #66: Why symbols? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.