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Training on

Geometrical Dimensioning & Tolerancing

( G D & T )

Suresh Mangawati

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DIMENSIONING:

Unnecessary Dimensions

Locating Holes

Section Lines

Staggered Numerals

Arcs

Notes Chamfers

TOLERANCING:

Bilateral

Cumulative

SYMBOLS OF GD&T:

Form

Straightness

Flatness

Circularity

Cylindricity

Profile

Profile of a Line

Profile of a Surface

Orientation

Angularity

Perpendicularity

Parallelism

Location Position

Concentricity

Symmetry

Run out

Circular Run out

Total run Out

Agenda

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Projections

A

C

E

B

D

F

AD C

E

B

FIRST ANGLE

A

E

DC

B

THIRD ANGLE

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DIMENSIONING

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Dimensions of Size S

Dimensions of Position P

Dimensions

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Unnecessary Dimensions

One unnecessary dimension

Unnecessary dimension omitted

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Dimensioning - Cylinders

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Locating Holes

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Locating Holes about a center

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Dimensions & Section Lines

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Staggered Numerals

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Dimensioning Arcs

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Arcs

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Dimensions inside view

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Dimensions for one view only

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Dimensioned distance given in normal view

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Dimensions midway between arrow heads

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Values Staggered for clarity

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Dimensions arranged in continuous form

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Dimensions Staggered

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Dimensioning Notes

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Dimensioning Notes

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Dimensioning Chamfers

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Examples

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TOLERANCING

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Method of giving Limits

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Tolerance Expression

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Bilateral Tolerances

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Cumulative Tolerances

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Geometrical Dimensioning

&

Tolerancing (GD & T)

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Uses symbols to specify geometric characteristics

and dimensional requirements

Current GD&T standard: ANSI/ASME Y14.5M-1994

Symbols for:

Form and profile tolerances

Orientation tolerances

Location tolerances

Runout tolerances

GD & T

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MMC Maximum Material Condition

LMC Least Material Condition

ISO standard of preferred metric limits and fits: In the dimension 16h11, the tolerance zone is

specified by a letter and a number, I.e. h11. An

uppercase letter indicates that the tolerance

applies to the hole; a lowercase letter indicates

the tolerance applies to the shaft.

GD & T

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Basic Dimension: Theoretically exact, untoleranced

dimensions that specify the perfect location, size,

shape, or angle of a feature.

Basic dimensions are identified by enclosing thedimension in a box.

Basic dimensions specify theoretically exact value

from which variations are defined through feature

control frames as well as toleranced features andnotes.

General tolerances do not apply to basic dimensions.

GD & T

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Geometric Characteristics (ANSI Y14.5M-1994)

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Feature Control Frame

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Form - Straightness StraightnessFlatness

CircularityCylindricity

F

O

RM

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Form - Straightness StraightnessFlatness

CircularityCylindricity

F

O

RM

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Form - Flatness StraightnessFlatness

CircularityCylindricity

F

O

RM

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Form - Flatness StraightnessFlatness

CircularityCylindricity

F

O

RM

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Form - Circularity StraightnessFlatness

CircularityCylindricity

F

O

RM

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Form - Cylindricity StraightnessFlatness

CircularityCylindricity

F

O

RM

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Profile Surface all aroundLine

Surface

PROFILE

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Profile Surface between pointsLine

Surface

PROFILE

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Profile Surface of revolutionLine

Surface

PROFILE

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Orientation - Angularity ORIENTATIONAngularity

PerpendicularityParallelism

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Orientation - PerpendicularityORIENTATION

AngularityPerpendicularity

Parallelism

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Orientation - Perpendicularity ORIENTATIONAngularity

PerpendicularityParallelism

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Orientation - Perpendicularity ORIENTATIONAngularity

PerpendicularityParallelism

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Orientation - Parallelism ORIENTATIONAngularity

PerpendicularityParallelism

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Orientation - Parallelism ORIENTATIONAngularity

PerpendicularityParallelism

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Orientation Angularity & Parallelism ORIENTATIONAngularity

PerpendicularityParallelism

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Location - Position LOCATIONPosition

ConcentricitySymmetry

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Location - Position LOCATIONPosition

ConcentricitySymmetry

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Location - Concentricity LOCATIONPosition

ConcentricitySymmetry

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Runout Circular & Total RUNOUTCircular

Total

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Runout Circular & Total RUNOUTCircular

Total

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Example

TOTAL RUNOUT

OF 0.03 w.r.t. C & D

RUNOUT

OF 0.01 w.r.t. C & D

PERPENDICULARITYOF 0.02 w.r.t. C

CONCENTRICITY

OF 0.02 w.r.t. D

PROFILE_SURFACE

OF 0.02 w.r.t. C & D

PARALLELISM

OF 0.02 w.r.t. C