e25 lec 18-22 gd&t

ENGR 25 Graphics Powerpoints: Geometric Dimensioning & Tolerancing

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GD&T

Geometric Dimensioning & Tolerancing (GD&T)

Rule #1

Size limits envelope

Section10

GD&T

Rule #1:“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.”

ASME Y14.5

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Ø11.8

(B)

(C)

Ø12.2

Ø11.8

Ø12.2

Ø11.8

Ø12.2

Ø11.8

Ø12.2

Ø11.8 for entire length Ø11.8 for entire length

External dowel plug Internal hole

(A)

at Ø12.2 MMC must be perfect form

at Ø11.8 MMC must be perfect form

Ø12.211.8

Ø12.211.8

When only size tolerance is specified,the object’s form can vary within the stated size limits.

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(A) (B) (C)

Min Min Min

Max Max Max

A cylinder can have a variety of shapes yet stay within the limits of size.

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1614

119

97

2220

7

8(A) (B)

1816

The rectangular prism can vary in shape as long as it stays inside the volume of the limits of size.

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16.015.8

Ø8.0 MMC

Ø7.8 LMC alongentire lengthof dowel

Ø6.8MMC

Ø7.0LMC

Ø7.06.8

Ø8.07.8

Ring gage

Plug gage

(A) Checking geometric form with ring gage

(B) Checking geometric form with plug gage

A ring gage and plug gage are used to check the geometric form of a pin and hole.


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Section10 Datums

Datum axis

Order of Datums

Checking compliance

Compound & coplanar datums

Chain lines & partial datum surfaces

Datum target points

Datum target line

Datum target areas

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Datumfeature

Simulateddatum(surface plate)

Measuredheight

Dial face

ProbeUp

Down

A height gage measures the height of an object from the simulated datum surface of a surface plate.

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+Y

-X+Z

-Y

+X

-Z

Degrees of freedom allow movement in two directions along each axis and rotation about each axis.

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A datum reference frame consists of three intersecting planes at 90° to each other.

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2H for single lettering4H for double lettering

A2H H

H

60°

16

G

H

E

F

Filled orunfilled

(A) H = height of lettering

(B) Applications

Varies

(A) Illustrates the method for drawing the datum symbol while (B) illustrates some applications.

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KJ

J

Ø14Ø8

Ø14

J

-or-

The datum symbol is applied to solid cylinders.


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F G HØ0.1

Ø12

N

P

RM

Ø6

Ø12

Ø6

M

The datum symbol is applied to holes.

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(A)This drawingsymbology

(B) Means this

SU

T

3 pts of contact1 pt of contact

2 pts of contact

S T UØ0.1

TS12

2X Ø6 ± 0.2

6

M

8

U

10

Primary datum S has 3 pts of contact, T 2 pts and U 1pt of contact.

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(1 pt)

(2 pts)

(3 pts)

V W XØ0.1

2X Ø6 ± 0.08M

X

W

V

(1 pt) (3pts)

(2 pts)

Trueheight

VX

W

Correct inspection procedure

True width(1 pt)

(3 pts)(2pts)

VX

W

Falseheight

Incorrect inspection procedure

Falsewidth

The order of the datums is critical!

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GH

(A) This drawing

8

8

8 8

Ø24

0.5 G H4X Ø4±0.5 Intersecting planes

perpendicular to G

Primarydatum G

Datum axis

(B) Means this

The datum axis is formed by two intersecting planes.

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(A) This drawing

(B) Means this

C

Ø10.8±0.1

Simulated datumcylinder C - largest Ø that fits into hole

Datum axis

Datum feature C

Plug gage

The plug gage establishes the datum axis.

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(A) This drawing

(B) Means this

D

Datum feature DSimulated datum D

Datum axis

19±0.5

The smallest circumscribed cylinder establishes the simulated datum and the datum axis.


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B) Means this

A) This drawing 24.223.8

12.211.8

0.4 Y Z

Z

Y

Central datum plane

Simulateddatums atmaximumseparation

Datum features

The simulated central datum plane is established by the center plane of the largest block that fits into the groove.

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B) Means this

A) This drawing

18.2

Simulated datumplanes at minimumseparation

Central datum plane

0.6 A B

B

A

17.8

The simulated central datum plane is established by the center plane located by the two blocks at minimum separation.

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(A) This drawing

(B) Means this

E F

Ø8±0.2 Ø9±0.2

0.5 E-F

Three jawed coaxial chucks

Datum axis E-F

Datum feature ESimulated datum E

Datum feature FSimulated datum F

This compound datum holds the object at both its ends in order to check runout.

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X Y

Simulatedcoplanardatum X-Y

Datum feature X

Datumfeature Y

A) This drawing

B) Means this

.08 X-Y

Datum features X and Y establish a coplanar datum.

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(A) This drawing

(B) Means this

G

9

9

22Chain line

Simulateddatum

Datum feature

The 22 chain line determines the area of the datum feature.

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A1

B1 C1Ø8

Ø.750

Datum point orLine ID letter

Datum point or line number

(A) Datum point or point view of line symbol

Ø of targetarea

(C) Datum target area callout

2H

90°

(B) Datum point orline callout

Ø3.5H

Thick lines

Symbology used for the datum target point and datum target line.


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K8

28

18

12

6

K1 K2 K3

This drawing establishes datum plane K using three datum points.

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Dowel pins with

spherical radial tops

Inspection

fixture

Part

This inspection fixture uses three dowels with SR tops to establish three datum points.

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S

S1

2012

S1

When a datum point does not show in an elevation view, two adjacent dimensions locate it.

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Datum line

L

N1

148

24

M

N

M2

M1

M2

M1

Point view ofdatum line (phantom line)

N

Datum lines M1 & M2 establish the secondary datum and N1 the tertiary datum.

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3 locatordowel pinsPart

Inspectionfixture

Dowel pins establish datum lines M1 & M2 and datum line N1.

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B1 C1Ø8

Ø.750

Ø of targetarea

A datum target area callout has the area’s diameter on top and the area’s unique number on the bottom.


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20

12

T

T3

T2

T1Ø6

Ø6

Ø6

A) This drawing B) Means this

3 X Ø6 dowel pins

Inspectionfixture

Part

Three datum target areas are used to check the part’s conformance.

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(A) This drawing showing target areas

U

U3 10

U1 U218

6

12

8

22

Ø4

Ø4 Ø4

Part

Inspectionfixture

2 short dowel pins

1 longerdowel pin

(B) Means this

The three datum targets U1, U2, & U3 (which is at a different elevation) establish datum U.

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P1

10

R1P

R12

22

(Near side)(Far side)Ø6 Ø6

Datum target area P1 is located on the near side while target area R1 is on the far side of the object.

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The top half of the datum target callout is left blank since there is no circular target area.

8

12

V

6

Y1R16R8

V1

W

W1

X1

12

8

12

(A) (B)

(C) (D)

6

12

16X

16

A datum target can take on any shape.

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Section10

Dimensioning symbology

Feature control frame

Geometric characteristic symbols

Modifiers in a feature control frame

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1.5h

12Varies

Basic Dimension

ØDiameter

1.5h

.3h

1.6

2h

( )(

ST

R SR SØ CR

X

2h

h h

90°h

h

0.6h60°

h 2h

0.5h0.5h

30°

hh

h15°

2.5h

1.5h0.8h

60°

Counterbore Countersink Depth (or deep)

Dimension Origin Conical Taper Square

Arc Length Reference Slope

Radius

Places or By

Statistical Tolerance(dimensional)

SphericalRadius

SphericalDiameter

ControlledRadius

These symbols are used when dimensioning.


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2h

h h

90°

h

h

0.6h 60°

h 2h

0.5h0.5h

30°

h

h

Counterbore Countersink Depth (or deep)

Dimension Origin Conical Taper Square

h = height of lettering

These symbols are used when dimensioning.

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1.5h

12

Varies

Basic Dimension

ØDiameter

1.5h

.3h

1.6

2h

( )(

ST

R SR SØ CR

X

h15°

2.5h

1.5h0.8h

60°

Arc Length Reference Slope

Radius

Places or By

Statistical Tolerance(dimensional)

SphericalRadius

SphericalDiameter

ControlledRadius

These symbols are used when dimensioning

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0.2 A B C

Modifier

Numeric tolerance(feature tolerance)

Geometric tolerancesymbol (position)

Tertiary datumSecondary datum with modifier

Primary datum

2h

Diameter symbol

A feature control frame modifies a part’s geometry.

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0.08 0.05 A

Geometric tolerance(flatness)

Numeric tolerance

Geometric tolerance(perpendicularity)

Diameter symbolNumeric tolerance

ModifierDatum

(A) (B)

Two additional examples of feature control frames modifying a part’s geometry.

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**

Perpendicularity

Angularity

Runout Circular

Runout Total

Profile surface

Profile line

Symmetry

Cylindricity

Position

Concentricity

Circularity

Straightness

Parallelism

Flatness

Either filled or unfilled

Symbol Description

Fo

rmP

rofi

leO

rien

tati

on

Lo

cati

on

Ru

no

ut

Type oftolerance

Individualfeatures

Individual orrelated features

Relatedfeatures

Geometric Characteristic Symbols

*

Geometric characteristic symbols are categorized in two ways.

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1.5h M1.5h h 0.8h

2h1.5h

0.6h

h

1.5h

Concentricity Circularity Modifier

Straightness Parallelism Flatness

1.5h

GD&T geometric characteristic symbols illustrated.


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1.5hh

2h

h h

60°

1.5h

h

h2h

2h1.2h

0.5hCylindricity Position

All round Profilesurface

Profileline

Symmetry


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h0.8h

0.8h3h

0.6h

1.5h

2h 1.5h

30°

45°

0.6h

1.5h

1.1h

**

Perpendicularity Angularity

Runout Circular Runout Total

Between

*

Filled or unfilled*


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M

L

P

F

T

Maximum Material Condition

Least Material Condition

Projected Tolerance Zone

Free State Variation

Tangent Plane

Modifiers

ST Statistical Tolerance (geometric)

Between





Tangent Plane

Modifiers

Between





Tangent Plane

Modifiers

* Between

*Filled or unfilled

Table lists GD&T geometric characteristic symbol modifiers.

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Section10

Straightness

Flatness

Circularity

Cylindricity

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Ø12.412.00.03

0.03 tolzone

Ø12.4MMC

0.03 longitudinal tol zones

(A) This drawing

(B) Means this

0.03

-or-

Straightness is checked using sufficient individual line element checks to ensure its proper function.

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Adjustable jacks

LevelbarV-block

Cylindricalpart

Part

End view of V-block

Straightness can be checked using adjustable jacks and a V block.


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0.04

0.04- or -

Each line element has a 0.04 tol zonechecked with adial indicator

(B) Means this

(A) This drawing

Straightness checks individual line elements of the “treasure” chest top.

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Ø12.412.0

0.05

Ø12.4 to 12.0over entire length

Ø 0.05cylindrical

tol zone

(A) This drawing

(B) Means this

24.0

Ø12.45

Virtualcondition

Straightness applied to the diameter of the cylinder has a cylindrical tolerance zone the length of the part.

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Straightness of a central axis can be checked by taking surface error readings using opposing dial indicators.

Chuckjaws orcollet

Part

Opposingdial indicator

Straightness axial error is checked with a functional gauge whose length is equal to the pin’s length and the diameter is equal to the hole’s VC.

Ø6.05.6

0.4

PinØ

6.05.95.85.75.6

BonusTol

None0.10.20.30.4

GeomTol

0.40.50.60.70.8

Part

Ø6.4 VC

Length ofpart

VC = Virtual Condition (VC) VC = Part's MMC + Geom TolVC = Ø6.0 + Ø0.4 = Ø6.4

Straightness of a central axis is modified by either a M or L modifier.

Cylindrical tol zone Ø12.4

12.0

0.5 Ø tol zonevaries

0.05Feature

Ø

12.4 MMC12.312.212.112.0 LMC

Ø cyltol zone

0.50.60.70.80.9

0.05Feature

Ø

12.4 MMC12.312.212.112.0 LMC

Ø cyltol zone

0.50.60.70.80.9

(B) (C)

0.5-or-

(A)

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Parallel planes 0.3 apart

14.614.0

0.3

(A) This drawing

(B) Means this

14.614.0

Flatness of a surface has a tolerance zone formed by two parallel planes separated by the tolerance value.


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Part being inspectedslides on table

Dial indicatorInspection

table insection

The entire area of the part slides over the dial indicator which is poking through the inspection table.

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0.2

(A) flatness callout

A surface is called out to be flat within 0.2.

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Adjustablejacks

Dial indicator

Inspected surface

Flatness is checked by leveling the surface with adjustable jacks and inspecting with a dial indicator.

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820

1218

0.08

A specific area is checked for flatness using basic dimensions, callout, and phantom lined hatched area.

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Ø11.010.6

0.02

A

A

(A) This Drawing

Ø11.0 (Largest diameter atSection A-A)

Ø10.96(Ø11.0 - 0.04)

Ø0.02Circular

Tolerance Section A-A(B) Checked at any given cross section

-or-

Circularity requires the surface of any cross section to meet size requirements and also be within the circularity tolerance zone.

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(A) Between centers

(B) In chuck or collet

Rotate

Independentmeasurements

Rotate

Independentmeasurements

Circularity can be checked by taking independent measurements while between centers or using a chuck.


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Circularity error

Inscribedcircle

Polar graphpaper

Circularprofile

Circumscribedcircle

Circularity can be checked by plotting a circular profile on polar graph paper.

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0.4

(A) circularity callout on the cone of a nail set

(B) circularity callout on the curves of a garden tool handle

0.6

Circularity can control shapes other than cylinders.

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(A) This drawing Ø18.217.8

0.06

(B) Means this

0.06 tolerance zone

zone

2 concentric cylinders

Cylindricity requires that the entire face of the cylinder be contained between two concentric cylinders.

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Part

Dial indicator

Front Right

Ro

tate

Check cylindricity by rotating the cylinder between centers while transversing a dial indicator along top dead center.

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Rotate

Part

Spindle

Probe

Check cylindricity by rotating the cylinder in a chuck while transversing a dial indicator vertically along top dead center.

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Section10

Profile of a line

Profile of a surface


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without a datum only form is controlled

with datums, form and orientation are controlled

with datums and a basic dimension, form, orientation and location are controlled

15

B

A

0.2 A B

(C) Form, orientation, & set location of tol zone

B

A

0.2 A B

(B) Form & orientation only & floating tol zone

(A) Form only

0.2

15.114.9

Profile of a Line controls form, orientation, and location.

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(A) Simple callout (B) Tol zone 0.1 each side of perfect form

0.2

0.2

2R10

6

17

15

R9 Perfectform

The profile of a line tolerance zone is two parallel lines 0.2 apart following perfect form.

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Each line element checked separately

1

2

3

23

1

Each profile is checked separately.

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Ø3.02.8

C0.16 A B C A

B

The guitar bridge and string template’s top curve is called out with a profile of a line control.

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Hold down knob

Followertemplate

Followertip

A

B

C

Path of dial indicator

Profile of a line is checked using a follower template machined to follow perfect form.

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0.2

(A) Bilateral tolerance

(B) Unilateral tolerance out

(C) Unilateral tolerance in

0.2

0.2

0.2

0.2

0.2

Profile of a line and surface can have one of three profile zones: bilateral, unilateral in, and unilateral out.


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20 18

2 size tolerance

1.0 floatinggeometrictolerance zone

2018

2X R11

1.0

(A) This drawing

(B) Creates a floating tolerance zone with in the size tolerance

The 1.0 profile of a line tolerance zone floats within the 2 size tolerance zone.

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R10 6

17

15

R9

(A) This callout

0.4

Tol zone is twoparallel planes0.2 each side ofperfect surface

(B) Has this tolerance zone

2

Profile of a line is checked using a follower template machined to perfect form.

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7 13

R13

Ø1211

60°

A

B

0.1 A B

0.2 A B

3

Profile of a surface can be used to control spherical radius surfaces and planar surfaces.

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0.1 tol zone

0.2 tolzone

Path followingfixture template

Dial indicators follow the path of perfect form to perform inspection.

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(A) This drawing

(B) Means this Two concentric cones 0.08 apart

30°

4

26.025.8

0.08

Profile of a surface on a conical shaped router bit collet has a tolerance zone of two concentric cones.

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A

B

C

Ø3

20

6

2X R20.5 A B C

3°

Adding a circle to the elbow of the profile of a line leader means the entire surface of the slot must be checked. X


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X0.1

X Y

Y

The between symbol and labeled points designate the exact limits of the profile of a line tolerance.

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Section10

Angularity

Parallelism

Perpendicularity

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45°

0.2 A

A

(A) This drawing

0.2 widetolerancezone

(B) Means this

45°

The tolerance zone is two parallel planes 0.2 apart and on a basic 45° angle.

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Part beinginspected

Dial indicator

Gageblocks Surface

plate

Sinebar

Angularity can be checked using sine bars and gage blocks.

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(A) This drawing

60°

0.2 C D

Ø8.28.0

C

D

(B) Means this

Ø0.2 cyltol zone

Possibleorientation

The tolerance zone is a cylinder with a Ø0.2 diameter.

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Parallel surface

X0.4 X

2 planes parallel to datum X 0.4 apart

(A) Parallelism called out on a drawing

(B) Means this

(C) Checking parallelism with a dial indicator while on a surface plate

Dial indicatorSurface plate

The parallelism tolerance zone is two parallel planes 0.4 apart and parallel to the surface plate (datum X).


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7±0.1

0.4 T

T

Ø6±0.1

Ø0.4 cylindrical tolerance zone parallel to datum T

Ø12±0.1

Possible orientation

(B) Means this

(A) This drawing

7±0.1

The tolerance zone is a cylinder with a Ø0.4 diameter parallel to cylindrical datum T.

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G

Ø5.05.3

0.2 G

The hole is to be parallel to simulated datum G.

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Zero dial indicator

Check FIM

2 parallel planes 0.2 apart

Simulated datum G surface plate

12

A dial indicator checks to insure the center line is between the two parallel plates 0.2 apart.

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0.4 H

H

(A) This drawing (B) Means this

0.4 tol zone 2 parallel planes

The tolerance zone is two parallel planes 0.4 apart and perpendicular to datum H.

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Angleblock

Simulateddatum H

Datum Hfeature

Dialindicator

0.4 tol zone 2 parallel planes perpendicular to simulated datum H

Spacerblock

Perpendicularity is being checked with the aid of an angle block and dial indicator.

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0.2 G

Ø10.09.8 2 parallel planes

0.2 apart

(A) Perpendicular callout (B) Tolerance zone

This perpendicular tolerance zone is two parallel planes 0.2 part and perpendicular to datum G.X


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Section10

Virtual condition

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30.027.7J

0.3 J

Pin Ø18 MMC17.917.817.7 LMC

Geom ØTol Zone

Ø0.3Ø0.4Ø0.5Ø0.6

18.017.7Ø

(A) (B)

At MMC (Ø18mm) the tolerance is Ø0.3mm while at LMC (Ø17.7mm) the tolerance is Ø0.6mm.

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VC = 18(MMC) + 0.3(geom tol) = Ø18.3

(B) (C)

Ø18.3VCØ18MMC

Ø18MMC

Ø0.3 Cyltol zone

Ø17.7LMC

Ø0.6 Cyltol zone

Ø18 MMCperfectform

Ø18 MMCØ0.3 tolzone

Ø17.7 LMCØ0.6 tolzone

(A)

Pin is shown in three conditions: perfect, MMC, and LMC.This four part assembly has a shaft with a MMC of Ø8, a perpendicular tolerance of Ø0.4 at MMC, and a VC of Ø8.4.

VC = Virtual conditionVC = MMC of 1 Base & Shaft + geometric tolVC = Ø8.0 + Ø0.4VC = Ø8.4 Minimum hole size for 2 Bevel Gear

X

0.4 X

Ø8.07.6

4 Snap Ring

2 Bevel Gear

3 Washer

1 Base & Stud

(A) Bevel gear assembly

(B) 1 Base & Stud (C) 2 Bevel Gear

8.68.4Ø

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Section10

Positional tolerance

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16

12

10

RS

0.2 P R S 0.2 tol zone at true position of hole

P

The true position of the hole is given by basic dimensions and a Ø0.2 positional tolerance.


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8.38.0

11

11

0.4 V W

4X Ø6.05.7

W

Ø

7 7 V

11

11

0.4 V W

4X Ø6.05.7

W

Ø

7 7 V

Positional tolerance is applied to a group of holes located with basic dimensions.

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4X Ø 0.4 tol zones at true position

An array of four tolerance zones is the result of the positional callout.

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The central axes of the holes are: at true position, at extreme position, and at extreme attitude.

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U

Ø8.38.0

0.4 U V W

WV

Hole Ø Pos Tol

7.6 MMC 0.47.7 0.57.8 0.67.9 0.78.0 LMC 0.8

16

10

The table shows the positional tolerance increasing as the hole moves away from MMC.

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.04 A B C0.2 A

Pattern location tolerance

Feature relating tolerance

A composite positional tolerance is used when the location of a pattern of features is less restrictive than the hole-to-hole requirements.

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`

20

10

10

24

C

B

0.4 A B C0.2 A

4X Ø14.314.0

Pattern locating tolFeature relating tol

20

24

The red dots show the feature relating and the yellow the pattern location tolerance.


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Position # 1 Alternate position # 2

The center axes of the holes must meet the pattern locating and feature relating tolerances simultaneously.

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Feature relating boundary – axis on edge of pattern locating boundary

Hole

Pattern location boundary at true position

A portion of the feature relating tolerance zone can spill over beyond the pattern location tolerance zone.

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0.4 A B C0.2

Pattern of holesPattern tolerance in true position

Feature tolerance

Datum CDatum B

Datum A

If no datum is specified in the second row, the central axes of the hole pattern has no orientation requirements.

A primary datum in the second row, requires the central axes to be perpendicular to the specified primary datum.

Datum CDatum B

Datum A

0.4 A B C

0.2 A

With two datums specified in the second row, the central axis of the hole pattern must be perpendicular to the primary datum and parallel to the secondary datum.

0.4 A B C

0.2 A B

Datum B

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Section10

Concentricity

Symmetry


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(A) As drawn

(B) Axis has attitudeyet is still within Ø0.4 tol zone

(C) Axis is not concentric yet still within Ø0.4 tol zone

Ø Ø

A 0.4 A

Ø0.4 tol zone

Ø18.017.8 Ø

10.09.8

A 0.4 A

Ø0.4 tol zone

The central axis of the smaller shaft must stay within the cylindrical concentric tolerance zone of Ø0.4

GD&T

Ø18.017.8

A(A) As drawn

Ø0.4 cylindrical tol zone

Ø10.09.8

0.4 A

Ø18.0

Ø10.4

VC =Ø10.0 + 0.4

(B) Functional gage simulates mating part

A coaxial feature can be checked with a positional tol and a functional gage which simulates the mating part.

GD&T

16

24

(A) (B)

0.2 D

D

Central plane of control feature

0.2 tol zone

Central planeof feature

The central plane of the two rails are to be symmetric about a continuous 0.2 wide tolerance zone.

GD&T


Section10

Runout

Total runout

GD&T

(A) This drawing

(B) Means this

0.6 A

Ø12.011.0

0.6 A

0.6 A

-or-

-or-

A

Chuck jaws

0.6 Max FIM each measurement taken separately as part is rotated

Rotation

There are three ways to callout runout which is checked by taking individual FIM readings.

GD&T

0.4 B

0.2 B (Curve)

(Sphere)0.6 B

(Cone)

B

(A) This drawing

(B) Means thisRotate

Chuck jaws

Runout can check a variety of shapes while the dial indicator stays perpendicular to the surface.


8/10/2020

20

GD&T

0.2 JJ

0.2 Max FIM measured separately at each circular reading

Ø12.011.8

(A) This drawing

(B) Means this Rotate

On a flat surface perpendicular to the datum axis several individual circular readings must be taken.

GD&T

90°90°

YX

10 0.4 X-Y

The chain line (phantom line) and dimension designates the limit of the circular runout control.

GD&T

(B) Means this

(A) This drawing 90°90°

0.01 X-Y0.04 X-Y

0.01 X-Y0.02 X-Y

X Y

Four separate total runout readings are required on this part.

GD&T

0.02 G H

H

Ø16.215.8

Ø32.632.4

0.04 G H

Ø 8.17.7

G

(A) This drawing

Datum feature H

3 jawed chuck pressed against datum feature H

(B) Means this

Rotation

A chuck squeezes datum feature G and flat surface datum feature H is pressed tight to the chuck jaw ends.

GD&T


Section10

Projected tolerance zone

GD&T

T12 P 9 T

12 P T

(A)

(B)

M16 X 2

M16 X 2

T

9

There are two methods for specifying a projected tolerance zone.


8/10/2020

21

GD&T

Ø0.08 projected tolerance zone 12 above datum T at true position

12Part with threads

Part with clearance holeCenter line of bolt

T

The center line of the bolt must stay within the cylindrical projected tolerance zone.

e25 lec 18-22 gd&t

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