18018307 gdt introduction

Training program in Dimensional Tolerancing,

Geometric Dimensioning and Tolerancingfor

HCL Technologies Ltd25th April to 19th May 2005

by

Nettur Technical Training Foundation,Peenya,Bangalore

Ability needed to

REPRESENT

INTERPRET

MANUFACTURE

MEASURE

Dimensional Tolerancing

Main applications of Dimensioning and tolerances are for

Holes & Shafts,

Tapers,

Threads,

Gears, Splines, etc.

R0,5(TYP)

4,15 1,5

0,45

30°

0.6(MAX) x 45°R4

0-1.0

C0.5(BOTH SIDES)

M

Ø38

.0 0 -0

.2

Ø29

.2+0

.016

35,95± 0.125

59,45 ± 0.125

A

0.025 M

0.025 A0.025 M

0.025 M0.015 M

R5

Ø40

Ø73

,5

Ø95

,68

0.0

-0.2

0.05 M

0.02 M

48,3± 0.025

26,58-0.350

0.030 M

Ø25

.25

+0.1

C1.15B

DETAIL AT BSCALE 5:1

REFER FORGING DRAWING NO RD 04066003

FOR MATERIAL, HARDNESS & OTHER DETAILS

NOTE : ALL MACHINED SURFACES TO BE FREE FROM RUST AND DENT MARKS

CAD REF . : DN NGT_GSL_RD040669-04 PN : TRANSMISSION TOOLSDO NOT SCALE : IF IN DOUBT. REFER DESIGN OFFICE

APPD.DGNRBY DATESIGN

SIZE - CTO BE USED ON

TOOL NO : XXXX/Y

SHEET 1 OF 1

SCALE 1 :1TOOL NAME: BLANK DRAWING(TURNED)

PART NAME: FIFTH GEAR - LAYSHAFT

UNSPECIFIED MACHINING DEVIATION

MATERIAL AS NOTED

LINEAR DIMENSION ANGULAR DIMN.

Above Upto Devn.0.5 6 ±0.1

±0.230630 120 ±0.3

±0.5315120315 1000 ±0.8

±1.220001000

Short side of angle ± mm

Deg. of min 1

Above Upto1050

1201205010

0.1 103020100.8

0.50.2

FOR ENGG. REF.

AT ALLOWANCE

0.15 ± 0.075

0.15 ± 0.075

0.2BORE

FRONT FACE

BOSS FACE

FEATURE CONTROL FRAME PLACEMENT

Different types of tolerances are

1. Dimensional Tolerances2. Form Tolerances3. Position Tolerances4. Surface Roughness values5. Combination Tolerances

Other details shown on drawing are

Material specificationSpecial treatments if anyHeat treatmentsAssembly conditionSpecial notes

Tolerance: Tolerance is the total permissible variation from the specified basic size of the part. It is defined as the magnitude of permissible variation of a dimension or measured control criterion from specified value.

Basic size: The basic size is the size on which variation permitted.

Actual size: The size of a feature obtained by measurement

TOL not specified• Follow general engineering tolerance• IS 2102 fine, medium, course & very

course• Unless otherwise specified, it is medium.• Or else it can be IT 14 VALUE, bilateral• All drawings need contain conditions on

general tolerance.

1. Open tolerances or General Engineering tolerancesStandards used are IS 2102 ( Part – 1) – 1993 / ISO 2768 - 1 : 1989

General TolerancesPart – 1: Tolerances for Linear and Angular dimensions without individual tolerance indicationsPart – 2: Geometrical Tolerances for features without individual tolerance indicationsEx: 20.0, 20-f, Ø20-f H

Table 1 – Permissible deviations for linear dimensions except for broken edges(external radii and chamfer heights, see table 2)

Values in millimeters

1) For nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size (s).

± 8± 6± 4± 2,5± 1,5± 1± 0,5-very coarse

v

± 4± 3± 2± 1,2± 0,8± 0,5± 0,3±0,2

coarsec

± 2± 1,2± 0,8± 0,5± 0,3± 0,2± 0,1±0,1

mediumm

-± 0,5± 0,3± 0,2± 0,15± 0,1± 0,05± 0,05finef

Over2000up to4000

Over1000up to2000

Over400

up to400

Over120

up to120

Over30

up to120

Over6

up to30

Over3

up to6

0.5up to

3Descripti

onDesignation

Permissible deviations for basic size rangeTolerance Class

Table 2 – Permissible deviations for broken edges ( external radii and chamfer heights)

Values in millimeters

1) For nominal sizes below 0.5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).

very coarse

v ± 2± 0,1± 0,4coarsecmediumm

± 1± 0,5± 0,2finef

over 6Over 3 up to6

0.5 up to 3Description

Designation

Permissible deviations for basic size rangeTolerance Class

Table 3 – Permissible deviations of angular dimensions

± 00 20± 00 30’± 10± 20± 30very coarse

v± 00 10± 00 15’± 00 30’± 10± 10 30’coarsec

mediumm± 00 5± 00 10’± 00 20’± 00 30± 10fineF

over 400

over 120 up to 400

over 50 up to 120

over 10 up to 50

up to 10Description

Designation

Permissible deviations for ranges of lengths, in millimeters,

of the shorter side of the angle concernedTolerance Class

Table 1 – General tolerances on straightness and flatness

Values in millimeters

Tolerance Class

Straightness and flatness tolerances for ranges of nominal lengths

up to 10 over 10 up to 30

over 30 up to 100

over 100 up to 300

over 300 up to 1000

Over 1000 up to 3000

H 0,02 0,05 0,1 0,2 0,3 0,4

K 0,05 0,1 0,2 0,4 0,6 0,8

L 0,1 0,2 0,4 0,8 1,2 1,6

Table-2 General tolerances on perpendicularityValues in millimeters

Tolerance Class

Perpendicularity tolerances for ranges of nominal lengths of the shorter side

up to 100 over 100 up to 300

over 300up to 1000

over 1000up to 3000

H 0,2 0,3 0,4 0,5

K 0,4 0,6 0,8 1

L 0,6 1 1,5 2

Table-3 – General tolerances on symmetry Values in millimeters

Tolerance Class

Symmetry tolerances for ranges of nominal lengths

up to 100 over 100 up to 300

over 300up to 1000

over 1000up to 3000

H 0,5

K 0,6 0,8 1

L 0,6 1 1,5 2

Table 4 – General tolerances on circular run-outValues in mm

Tolerance class Circular run-out tolerances

H 0,1

K 0,2

L 0,5

IS 2102 – PART – 2• VALUES FOR – Straightness /

perpendicularity / symmetry / Run out specified

• Circularity - limited to diameter tolerance or run out value

• Cylindricity – Limited to combined effect of CIRCULARITY& PARALLELISM.

• Parallelism – Limited to Dimensional Tolerance & flatness tolerance.

• Coaxiality - Limited to run out tolerance.

ISO 2768 - m• General Engg. Tole Tolerance class medium

IS 2102 – f• General Engg. Tole – class fine

ISO 2768 – mK

• General Engg. Tole for dimensions -Tolerance class. m

• General Engg. Tole for form / position –tolerance class. K

IS 2102 – mK - E

• General Engg. Tole for Dimension as per m

• General Engg Tole for Form / position as per K

• Enveloping dia limits -E

ISO 2768 - K

• General tol. as dim not considered. • Form/position as per tol. Class K.

SPECIFIED TOLERANCE

• VALUE GIVEN• VALUE AND POSISTIONAL STATUS

GIVEN• STD.SYMBOLS USED.

2. Specificied tolerancesStandards usedIS 919 (Part – 1) – 1993 / ISO 286 – 1 : 1988ISO System of Limits and Fits

Part – 1: Bases of tolerances, Deviations and FitsPart – 2: Tables of standard tolerance Grades and limit Deviations for Holes and shaft.

Example : 20H7, 20g6, 30 + 0.02

Specific tolerance should be less than open tolerance

STANDARD SPECIFICATIONNeed contain

• HOW MUCH IS THE VALUE OF TOL.• WHERE IT IS DISPOSED.

HOW MUCH IS THE VALUE• IS 919 / SP46 OR STD CHARTS SPECIFY.• 18 GRADES ARE SPECIFIED. VALUE IS

ATTACHED TO A GRADE• IT=INTERNATIONALTOLERANCE

GRADE.• AND 18 REPRESENT THE ROUGHFEST

Mfg process• EVERY MANUFACTURING PROCESS IS

ATTRIBUTED WITH A RANGE OF ACCURACY GRADE

HOW MUCH IS THE VALUE

FOR EX;• TURNING IT7, 8 OR 9 • GRINDING IT 5, OR 7• MILLING IT 6, 7, OR 8• LAPPING IT 1, 2, 3, OR 4• SAND CASTING IT 16, 17, 18• PRESS WORKING IT 10, 11 OR 12• INJ. MOULDING IT 12. 123 OR 14

Grades of tolerances obtainable by various manufacturing processes

According to IS 18 grades of tolerances or accuracy grades of manufacturing IT1, IT2, IT3….IT18

IT GRADE is generally indicated by numbers from 1 to 18

Manufacturing Processes IT grades

Lapping 1, 2, 3, 4

Honing 3 – 5

Laser beam machining 5, 6, 7

Super finishing 4 – 6

Grinding 4 – 8

Electric Discharge machining 6 – 7

Boring 5 – 9

Reaming 5 – 8

Broaching 5 – 9

Turning (Diamond tools) 4 – 7

Turning 7 – 12

Milling 8 – 10

Shaping 10 – 14

Drilling 11 – 14

Extrusion 9 – 12

Blanking 12 – 18

Drawing 10 – 14

Die Casting 12 – 15

Sand casting 14 – 16

HOW MUCH IS THE VALUE.

• EVERY DIM. ALONG WITH A GRADE RECEIVE A TOL. VALUE.

• FOR EX. DIM 40 & GRADE 8, TOL= ?• STD. FORMULA APPLIES TO THIS VALUE• FOR CONVENIENCE, DIMES. ARE

GROUPED. 0 TO 3; 3 TO 6; 6 TO 10 etc.• SAME VALUE OF TOL. VALID FOR A DIA

GROUP WITH ONE GRADE.

Table 1 – Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm

Standard tolerance grades Basic size mm IT12) IT22) IT32) IT42) IT52) IT6 IT7 IT8 IT9 IT10 IT11 IT12 IT13 IT143) IT153) IT163) IT173) IT183)

Above Up to and in- cluding

Tolerances µm mm

- 33 0,8 1,2 2 3 4 6 10 14 25 40 60 0,1 0,14 0,25 0,4 0,6 1 1,4

3 6 1 1,5 2,5 4 5 8 12 18 30 48 75 0,12 0,18 0,3 0,48 0,75 1,2 1,8 6 10 1 1,5 2,5 4 6 9 15 22 36 58 90 0,15 0,22 0,36 0,58 0,9 1,5 2,2

10 18 1,2 2 3 5 8 11 18 27 43 70 110 0,18 0,27 0,43 0,7 1,1 1,8 2,7 18 30 1,5 2,5 4 6 9 13 21 33 52 84 130 0,21 0,33 0,52 0,84 1,3 2,1 3,3 30 50 1,5 2,5 4 7 11 16 25 39 62 100 160 0,25 0,39 0,62 1 1,6 2,5 3,9 50 80 2 3 5 8 13 19 30 46 74 120 190 0,3 0,46 0,74 1,2 1,9 3 4,6 80 120 2,5 4 6 10 15 22 35 54 87 140 220 0,35 0,54 0,87 1,4 2,2 3,5 5,4 120 180 3,5 5 8 12 18 25 40 63 100 160 250 0,4 0,63 1 1,6 2,5 4 6,3 180 250 4,5 7 10 14 20 29 46 72 115 185 290 0,46 0,72 1,15 1,85 2,9 4,6 7,2 250 315 6 8 12 16 23 32 52 81 130 210 320 0,52 0,81 1,3 2,1 3,2 5,2 8,1 315 400 7 9 13 18 25 36 57 89 140 230 360 0,57 0,89 1,4 2,3 3,6 5,7 8,9 400 500 8 10 15 20 27 40 63 97 155 250 400 0,63 0,97 1,55 2,5 4 6,3 9,7 500 6302 9 11 16 22 32 44 70 110 175 180 440 0,7 1,1 1,75 2,8 4,4 7 11 630 8002 10 13 18 25 36 50 80 125 200 320 500 0,8 1,25 2 3,2 5 8 12,5 800 10002 11 15 21 28 40 56 90 140 230 360 560 0,9 1,4 2,3 3,6 5,6 9 14

1000 12502 13 18 24 33 47 66 105 165 260 420 660 1,05 1,65 2,6 4,2 6,6 10,5 16,5 1250 16002 15 21 29 39 55 78 125 195 310 500 780 1,25 1,95 3,1 5 7,8 12,5 19,5 1600 20002 18 25 35 46 65 92 150 230 370 600 920 1,5 2,3 3,7 6 9,2 15 23 2000 25002 22 30 41 55 78 110 175 280 440 700 1100 1,75 2,8 4,4 7 11 17,5 28 2500 31502 26 36 50 68 96 135 210 330 540 860 1350 2,1 3,3 5,4 8,6 13,5 21 33 1) Values for standard tolerance grades IT01 and IT0 for basic sizes less than or equal to 500 mm are given in ISO 286 – 1, annex A, table 5. 2) Values for standard tolerance grades IT1 to IT5 (incl.) for basic sizes over 500 mm are included for experimental use. 3) Standard tolerance grades IT14 to IT18 (incl.) shall not be used for basic sizes less than or equal to 1 mm.

Table 1 – Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm

Standard tolerance grades Basic size mm IT12) IT22) IT32) IT42) IT52) IT6 IT7 IT8 IT9 IT10 IT11

Above Up to and

including

Tolerances µm

- 33 0,8 1,2 2 3 4 6 10 14 25 40 60

3 6 1 1,5 2,5 4 5 8 12 18 30 48 75 6 10 1 1,5 2,5 4 6 9 15 22 36 58 90 10 18 1,2 2 3 5 8 11 18 27 43 70 110 18 30 1,5 2,5 4 6 9 13 21 33 52 84 130 30 50 1,5 2,5 4 7 11 16 25 39 62 100 160 50 80 2 3 5 8 13 19 30 46 74 120 190 80 120 2,5 4 6 10 15 22 35 54 87 140 220

120 180 3,5 5 8 12 18 25 40 63 100 160 250 180 250 4,5 7 10 14 20 29 46 72 115 185 290 250 315 6 8 12 16 23 32 52 81 130 210 320 315 400 7 9 13 18 25 36 57 89 140 230 360 400 500 8 10 15 20 27 40 63 97 155 250 400 500 6302 9 11 16 22 32 44 70 110 175 180 440 630 8002 10 13 18 25 36 50 80 125 200 320 500 800 10002 11 15 21 28 40 56 90 140 230 360 560 1000 12502 13 18 24 33 47 66 105 165 260 420 660 1250 16002 15 21 29 39 55 78 125 195 310 500 780 1600 20002 18 25 35 46 65 92 150 230 370 600 920 2000 25002 22 30 41 55 78 110 175 280 440 700 1100 2500 31502 26 36 50 68 96 135 210 330 540 860 1350

1) Values for standard tolerance grades IT01 and IT0 for basic sizes less than or equal to 500 mm are given in ISO 286 – 1, annex A, table 5. 2) Values for standard tolerance grades IT1 to IT5 (incl.) for basic sizes over 500 mm are included for experimental use. 3) Standard tolerance grades IT14 to IT18 (incl.) shall not be used for basic sizes less than or equal to 1 mm.

Table 1 – Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm

Standard tolerance grades Basic size mm IT12 IT13 IT143) IT153) IT163) IT173) IT183)

Above Up to and including

Tolerances mm

- 33 0,1 0,14 0,25 0,4 0,6 1 1,4

3 6 0,12 0,18 0,3 0,48 0,75 1,2 1,8 6 10 0,15 0,22 0,36 0,58 0,9 1,5 2,2 10 18 0,18 0,27 0,43 0,7 1,1 1,8 2,7 18 30 0,21 0,33 0,52 0,84 1,3 2,1 3,3 30 50 0,25 0,39 0,62 1 1,6 2,5 3,9 50 80 0,3 0,46 0,74 1,2 1,9 3 4,6 80 120 0,35 0,54 0,87 1,4 2,2 3,5 5,4

120 180 0,4 0,63 1 1,6 2,5 4 6,3 180 250 0,46 0,72 1,15 1,85 2,9 4,6 7,2 250 315 0,52 0,81 1,3 2,1 3,2 5,2 8,1 315 400 0,57 0,89 1,4 2,3 3,6 5,7 8,9 400 500 0,63 0,97 1,55 2,5 4 6,3 9,7 500 6302 0,7 1,1 1,75 2,8 4,4 7 11 630 8002 0,8 1,25 2 3,2 5 8 12,5 800 10002 0,9 1,4 2,3 3,6 5,6 9 14 1000 12502 1,05 1,65 2,6 4,2 6,6 10,5 16,5 1250 16002 1,25 1,95 3,1 5 7,8 12,5 19,5 1600 20002 1,5 2,3 3,7 6 9,2 15 23 2000 25002 1,75 2,8 4,4 7 11 17,5 28 2500 31502 2,1 3,3 5,4 8,6 13,5 21 33

1) Values for standard tolerance grades IT01 and IT0 for basic sizes less than or equal to 500 mm are given in ISO 286 – 1, annex A, table 5. 2) Values for standard tolerance grades IT1 to IT5 (incl.) for basic sizes over 500 mm are included for experimental use. 3) Standard tolerance grades IT14 to IT18 (incl.) shall not be used for basic sizes less than or equal to 1 mm.

HOW MUCH IS THE VALUE

• 60% INCREASE IN TOL. VALUE FOR EVERY GRADE UP FOR A DIA GROUP

• EVERY 6TH GRADE GETS 100% MORE TOL VALUE

WHERE TO DISPOSE TOLE.

• TOL. CAN BE DISPOSED• ABOVE BASIC DIM.• BELOW BASIC DIM• DISTRIBUTED ON EITHER SIDE

WHERE TO POSITION• POSITIONING IS REPRESENTED BY

CAPITAL LETTERS FOR HOLES A,B,H• BY SMALL LETTERS FOR SHAFTS a,b,h• STD DISTANCES ARE KEPT EACH

LETTER & FOR EACH DIA GROUP FROM BASIC DIM.

• THE DISTANCE TO THE BASIC DIM WITH LEAST VALUE IS TERMED AS FUNDEMENTAL DEVIASION;

• FD IS FIXED FOR A DIA-DIM COMBINATION.

Schematic representation of the positions of fundamental deviations

FITS

When two parts to be assembled, the relation resulting from the difference between the size before assembly is called a fit.

A fit is represented by φ 30 H 7 / g6, φ 30 H 7 / p6, φ 40 H7/h6,φ 40 H7k6, φ 40 H7p6,

Example of general tolerances on a drawing

INTERPRETATION

INTRODUCTION TO GEOMETRIC TOLERANCES

• Geometric characteristic symbols are a set of fourteen Symbols used in the language of geometric tolerancing.

• The symbols are divided into five categories:

1. Form2. Profile3. Orientation4. Location 5. Runout

Feature Control Frame• Geometric tolerances are specified

on a drawing through the use of a feature control frame.

Symbol of Geometric Tol.

Zone of Tolerance P.D S.D T.D

W or w/o zone Modifier

Feature Control Frame

Tolerance frame5.1 The tolerance requirements are shown in a rectangular frame which is divided into two or more compartments. These compartments contain, from left to right ,in the following order (see figures 3,4 and 5) :_ The symbol for the characteristic to be toleranced:_ The tolerance value in the unit used for linear dimensions. This value is preceded by the sign Φ if the tolerance zone is circular or cylindrical:_ if appropriate, the letter or letters identifying the datum feature (see figures 4 and 5)

Figures 5

Figures 4

Figures 3

Tolerance frame(contd)• 5.2 Remarks related to the

tolerance, for example “6 holes”, “4 surfaces” or “6x” shall be written above the frame (see figures 6 and 7)

• 5.3 Indications qualifying the form of the feature within the tolerance zone shall be within near the tolerance frame and may be connected by a leader line (see figures 8 and 9)

Figure 6 Figure 7

Figure 8 Figure 9

Tolerance frame(contd)

5.4 If it is necessary to specify more than one tolerance characteristic for a feature, the tolerance specifications are given in tolerance frames one under the other (see figure 10)

Figure 10

Toleranced features

• The tolerance frame is connected to the toleranced feature by a leader line terminating with an arrow in the following way:

• _ on the outline of the feature or an extention of the outline ( but clearly separated from the dimension line) when the tolerance refers to the line surface itself (see figures 11 and 12)

Figure11

Figure12

Toleranced features (contd)

• _ as an extension of a dimension line when the tolerance refers to the axis or median plane defined by the feature so dimensioned (see figures 13 to 15)

Figure15

Figure14

Figure13

Toleranced features (contd)• _ on the axis when the tolerance

refers to the axis or median plane of all features common to that axis or median plane(see figures 16,17 and 18)

Figure18Figure17

Figure16

Tolerance zones7.1 The width of the tolerance zone is in the direction of the arrow of the leader line joining the tolerance frame to the feature which is tolerance, unless the tolerance value is preceded by the sign Ø (see figures 19&20).

Figure 19 Figure 20

Tolerance zones (contd)• 7.2 In general, the direction of the width of the tolerance zone is

normal to the specified geometry of the part (see figures 21&22)

Figure 21Figure 22

Tolerance zones (contd)• 7.3 The direction of the tolerance zone shall be indicated when

desired not normal to the specified geometry of the part (see figures 23&24)

α

α

Figure 23 Figure 24

Tolerance zones (contd)7.4 Individual tolerance zones of the same value applied to several separate features can be specified as shown in figures 25&26.

Figure 25 Figure 26

7.5 Where a common tolerance zone is applied to several separate features, the requirement is indicated by the words “common zone” above the tolerance frame (see figures 27&28).

Figure 27 Figure 28

A

COMMON ZONE

AA

COMMON ZONE3XA

Tolerance zones (contd)

Datums8.1 When a tolerance feature is related to a datum, this is generally shown by datum latter which defines the datum is repeated in the tolerance frame.To identify the datum, a capital letter enclosed in a frame is connected to a solid or blank datum triangle (see figures 29&30).

Figure 29 Figure 30

8.2 The Datum triangle with the datum letter is placed:-On the outline of the feature or an extension of the out line (but

clearly separated from the dimension line), when the datum feature is the line or surface itself (see figures 31)

Figure 31

- as an extension of the dimension line when the datum feature is the axis or median plane (see figures 32 to 34). NOTE - If there is insufficient space for two arrows, one of them may be

replaced by the datum triangle (see figures 33 and 34). on the axis or median plane when the datum is :

a) the axis or median plane of a single feature (for example a cylinder);

b) the common axis or plane formed by two features (see figure 35).

8.3 If the tolerance frame can be directly connected with the datum feature by a leader line, the datum letter may be omitted (see figures 36 and 37).

8.4 A single datum is identified by a capital letter (see figure 38).A common datum formed by two features is identified by two datum letter separated by a hyphen (see figure 39).

If the sequence of two or more datum features is important the datum letters are placed in different compartments (see figure 40), where the sequence from left to right shows the order of priority.

If the sequence of two or more datum features is not important the datum letters are indicated in the same compartment (see figure 41).

9 Restrictive specifications

9.1 If the tolerance is applied to a restricted length, lying anywhere, the value of this length shall be added after the tolerance value and separated from it by an oblique stroke.

In the case of a surface, the same indication is used. This means that the tolerance applies to all lines of the restricted length in any position and any direction (see figure 42).

9.2 If a smaller tolerance of the same type is added to the tolerance on the whole feature, but restricted over a limited length, the restrictive tolerance shall be indicated in the lower compartment (see figure 43).

9.3 If the tolerance is applied to a restricted part of the feature only, this shall be dimensioned as shown in figure 44.

9.4 If the datum is applied to a restricted part of the datum feature only, this shall be dimensioned as shown in figure 45.•9.5 Restrictions to the form of the feature within

the tolerance zone are shown in 5.3.

.

Figure 46Figure 47

Theoretically exact dimensions

If tolerances of position or of profile or of angularity are prescribed for a feature, the dimensions determining the theoretically exact position, profile or angle respectively, shall not be toleranced.

These dimensions are enclosed, for example The corresponding actual dimensions of the part are subject only to the position tolerance, profile tolerance or angularity tolerance specified within the tolerance frame (see figures 46 and 47).

• Projected tolerance zone In some causes the tolerances of orientation and location shall apply not to the feature itself but to the external projection of it. Such projected tolerance zones are to be indicated by the symbol (see figure 48).

Maximum material condition

The indication that the tolerance value applies at the maximum material condition is shown by the symbol placed after:

The tolerance value (see figure 49);

The datum letter (see figure 50);

Or both (see figure 51);According to whether the maximum material principle is to be applied respectively to the toleranced feature. the datum feature or both.

Figure 48

Figure 51

Figure 49

Figure 50

Introduction to Geometric Dimensioning and Tolerancing GD & T standards

ANSI Y 14.5M 1982

ISO 1101 – 1983

ASME 14.5M -1994

ISO 1101 -1983 (Technical Drawings-Geometrical Tolerancing-Tolerancing of Form, Orientation, Location and Run-out)

ANSI Y14.51982-American National Standards Institute (ANSI) published ANSI Y14.5

ASME Y14.5M-1994

ASME Y14.5M-1994 Revised.

ASME Y 14.5M-1994 stand for

• ASME American Society of Mechanical Engineers

• Y 14.5 Standard number.

• M Standard is Metric.

• 1994 Year the standard was officially approved.

DIMENSION AND TOLERANCES• Dimension is a numerical value expressed in

appropriate units of measure and used to define size, location and orientation, form and other geometrical characteristics.

• Tolerance is a total amount the feature of part are permitted to vary from specified dimension. The tolerance is a difference between maximum and minimum limits.

• Types of tolerance Limit tolerance.Plus-minus tolerance.

• Plus –Minus ToleranceEqual bilateral tolerance.Unequal bilateral tolerance.Unilateral tolerance.

DIMENSION AND TOLERANCEScond..

+0.5

0

+0.3

- 0.2

COORDINATE TOLERACING SYSTEM

• Part feature is located (or defined) by means of rectangular dimensions with given tolerances.

GEOMENTRIC DIMENSIONING AND TOLERANCING.

COMPARISION BETWEEN GD&T AND COORDINATE TOLERANCING.

Key terms used in Geometric dimensioning and tolerancing

Modifiers and symbols used in geometric tolerancing

• Understand key terms and how they affect the interpretation of a drawing.

• Understand the modifiers and symbols used in geometric tolerancing.

FEATURES

• A feature is a general term applied to a physical portion of part, such as a surface, hole or slots,tabs.

• An easy way to remember this term is to think of a feature as a part surface.

FEATURES

Features

Feature Of Size Non-Feature Of Size

External

Feature Of Size

Internal

Feature Of Size

FEATURE OF SIZE• This is one cylindrical or spherical

surface, or set of two opposed elements or parallel surfaces associated with size dimension which has an axis, center line or center plane contained within it.

• Features of size are features, which do have diameter or thickness.

• These may be cylinders, such as shafts and holes. They may also be slots, rectangular or flat parts, where two parallel flat surfaces are considered to form a single feature.

How many feature of size are there?

FEATURE OF SIZE NON FEATURE OF SIZE

EXTERNAL AND INTERNAL FOS

• External FOS are comprised of part surfaces that are external surfaces.– Like shaft diameter or width and

height of a planner surfaces.

• Internal FOS is comprised of part surfaces (or elements) that are internal part surfaces.– like hole diameter or the width of a

slot.

Example:

FEATURE OF SIZE DIMENSIONS

• A feature of size dimension is a dimension that is associated with a feature of size.

ACTUAL MATING ENVELOPE= PERFECT FEATURE COUNTERPART.

• The Actual Mating Envelope (AME) of an external feature of size is a similar perfect feature counterpart of the smallest size that can be circumscribed about the feature so it just contacts the surfaces at the highest points with in the tolerance zone.

Actual Mating Envelope (AME) of an external FOS

ACTUAL MATING ENVELOPE= PERFECT FEATURE COUNTERPART

• The actual mating envelope (AME) of an internal feature of size is a similar perfect feature counterpart of the largest size that can be inscribedwithin the feature so that it just contacts the surfaces at their highest points with in the tolerance zone.

Actual Mating Envelope (AME) of an internal FOS

Actual Mating Envelope (AME) of an internal FOS

MATERIAL CONDITIONS• A geometric tolerance can be specified to

apply at the largest size, smallest size or actual size of a feature of size.

• Maximum Material Condition (MMC)Maximum material condition is the condition in which a feature of size contains the maximum amount of material everywhere within the stated limits of size.

MMCMMC of external Feature Of Size

MMC

MMC of internal Feature Of Size

LEAST MATERIAL CONDITION (LMC)

• Least material condition is the condition in which a feature of size contains the least amount of material everywhere within the stated limits of size .

LEAST MATERIAL CONDITION

Regardless of feature size (RFS)

• Regardless of feature size is the term that indicates a geometric tolerance applies at any increment of size of the feature within its size tolerance.

• RFS applied only to size features, such as hole, shafts, pins, etc.; feature which have an axis, centerplane or centerline.

• Symbol : S

Material Condition Usage• Each material condition is used for

different functional reasons.

• Geometric tolerances are often specified to apply at MMC when the function of a FOS is assembly.

• Geometric tolerances are often specified to apply at LMC to insure a minimum distance on a part.

• Geometric tolerances are often specified to apply at RFS to insure symmetrical relationships.

MODIFIERS

• Modifiers communicate additional information about the drawing or Tolerancing of a part.

• There are nine common modifiers used in geometric tolerancing.

Nine modifiers

PROJECTED TOLERANCE ZONE• Symbol: P• The projected tolerance zone modifier changes the

location of the tolerance zone on the part.

• It projects the tolerance zone above the part surface.

• Height of the projected tolerance zone should be equal to the max. thickness of the mating part.

FEATURE CONTROL FRAME WITH A PROJECTED TOLERENCE ZONE SYMBOL

Using a Projected Tolerance Zone•A projected tolerance zone is a tolerance zone that is projected above the part surface. •A projected tolerance zone modifier is specified as P

•A projected tolerance zone is used to limit theperpendicularity of a hole to ensure assembly with mating part.

Using a Projected Tolerance Zone (Contd..)

Using a Projected Tolerance Zone (contd.)

TANGENT PLANE MODIFIER• The tangent plane modifier denotes that only the

tangent plane of the toleranced surface needs to be within this tolerance zone.

DIAMETER MODIFIER

• The diameter symbol is used twoways: inside a feature control frame as a modifier to denote the shape of the tolerance zone, or outside the feature control frame to simply replace the word "diameter“.

Ø Inside the feature control frame

Ø Outside the feature control frame

Reference modifier• The modifier for reference is simply

the method of denoting that information is for reference only.

• The information is not to be used for manufacturing or inspection.

• To designate a dimension or other information as reference, the reference information is enclosed in parentheses.

Reference Example:

RADIUS MODIFIER• Arcs are dimensioned with radius symbol

on drawings.• A radius is a straight line extending from

the center of an arc or a circle to its surface.

• The Symbol for a radius is "R“.• When the "R" symbol is used, it creates a

zone defined by two arcs.• The part surface must lie within this zone.• The part surface may have flats or

reversals within the tolerance zone.

Radius modifier

Controlled Radius

• The symbol for a controlled radius is "CR“.

• it creates a tolerance zone defined by two arcs.

• The part surface must be within the crescent-shaped tolerance zone and be an arc without flats or reversals.

CONTROL RADIUS

DATUM FEATURE SYMBOL

DATUM IDENTIFYING LETTER

DATUM FEATURE SYMBOLS ON A FEATURE SURFACE AND AN EXTENSION LINE

PLACEMENT OF DATUM FEATURE SYMBOLS ON FEATURES OF SIZE

PLACEMENT OF DATUM FEATURE SYMBOL IN CONJUNCTION WITH A FEATURE CONTROL FRAME

DATUM TARGET SYMBOL

BASIC DIMESNSION SYMBOL

SYMBOL INDICATING THE SPECIFIED TOLERANCE IS A STATISTICAL GEOMETRIC

TOLERANCE

BETWEEN SYMBOL

COUNTERBORE OR SPOTFACE SYMBOL

COUNTERSINK SYMBOL

DIMENSION ORIGIN SYMBOL

DEPTH SYMBOL

SQUARE SYMBOL

SYMBOL FOR ALL AROUND

FEATURE CONTROL FRAME WITH FREE STATE SYMBOL

FEATURE CONTROL FRAME

FEATURE CONTROL FRAME INCORPORATING A DATUM REFERENCE

SYMBOL

ORDER OF PRECEDENCE OF DATUM REFERENCE

MULTIPLE FEATURE CONTROL FRAMES

COMBINED FEATURE CONTROL FRAME AND DATUM FEATURE SYMBOL

FEATURE CONTROL FRAME PLACEMENT

1.Understand Rule #1 and Rule #2.

2. Understand the concepts of basic dimensions, virtual condition, inner and outer boundary, worst-case boundary and bonus tolerance.

RULES & CONCEPTS OF GD & TRULES & CONCEPTS OF GD & T

Rule #1Rule #1 is referred to as the "Individual Feature of Size Rule."

In industry the Rule #1 is paraphrased as “perfect form at MMC” or the “envelope rule”.

“Where only a tolerance of size is specified, the limits of size of an individual feature prescribe the extent to which variations in its form as well as in its size are allowed”.

An example of effects of Rule #1 on a planar FOS.

In Rule #1, the words perfect form mean perfect flatness, straightness, circularity and cylindricity. In other words if the feature of size is produced at MMC, it is required to have perfect form.

TECHNOTE – For features of size, where only a tolerance of size is specified, the surfaces shall not extend beyond a boundary (envelope) of perfect form at MMC.

INSPECTING A FEATURE OF SIZE

When inspecting a FOS that is controlled by Rule #1, both its size and form need to be verified. The MMC size and the Rule #1 envelope can be verified with a Go gage. A Go gage is made to the MMC limit of the FOS and has perfect form.Go gage must be at least as long as the FOS it is verifying.

The minimum size (LMC) of a FOS can be measured with a No-Go gage.A No-Go gage is made to the LMC limit of the FOS.

Rule#2

“RFS applies, with respect to the individual tolerance, datum reference, or both, where no modifying symbol is specified. MMC and LMC must be specified on the drawing where required”.

Relationship between Dimensional tolerancing

andGeometric tolerancing

Dimensional tolerancing

Geom. tolerancing

Rule #2a is an alternative practice of Rule #2 according to which RFS may be specified as a symbol in feature control frames if desired and applicable.

INTRODUCTION TO BASIC INTRODUCTION TO BASIC DIMENSIONSDIMENSIONS

Basic Dimension

The basic dimension is the goal, and a geometric tolerance specifies the amount of acceptable variation from the goal.

“A basic dimension is a numerical value used to describe the theoretically exact size, true profile, orientation, or location of a feature or gage information (i.e., datum targets)”.

On engineering drawings there are two uses for basic dimensions:

1. To define the theoretically exact location, size, orientation, or true profile of a part feature.

2. To define gauge information.

Basic dimensions must get their tolerances from a geometric tolerance or from a special note.

The basic dimension only specifies half the requirement. To complete the specification, a geometric tolerance must be added to the feature involved with the basic dimension.

Basic Dimension Symbol

Basic Dimension examples.

No geometric control is used on basic dimensions that specify datum targets. When basic dimensions specify datum targets, they are considered gage dimensions.

Basic Dimensions used to locate Datum Targets.

• Interpret the flatness control.

• Interpret the straightness control.

• Interpret the circularity control.

• Interpret the cylindricity control.

FORM CONTROLS

• Flatness. c

• Straightness.

• Circularity. „

• Cylindricity. g

FLATNESSFLATNESS

ZONE OF TOLERANCE :- TWO PARALLEL PLANES

SYMBOL :-

STRAIGHTNESSSTRAIGHTNESS

ZONE OF TOLERANCE :- CYLINDER

SYMBOL :-

CIRCULARITYCIRCULARITY

ZONE OF TOLERANCE :- TWO COPLANAR CONCENTRIC CIRCLES

SYMBOL :-

CYLINDRICITYCYLINDRICITY

ZONE OF TOLERANCE :- TWO COAXIAL CYLINDERS

SYMBOL :-

FLATNESS

Definition : Flatness is the condition of a surface having all of its elements in one plane. The tolerance zone for a flatness control is three-dimensional.General representation

Interpretation of Flatness tolerance :

It consists of two parallel planes within which all the surface elements must lie. The distance between the parallel planes is equal to the flatness control tolerance value.

Rule #1 Effect on Flatness•Whenever Rule #1 applies to a feature of size that consists of two parallel planes, an automatic indirect flatness control exists for both surfaces.

Rule #1 Effect on Flatness•When the feature of size is at MMC, both surfaces must be perfectly flat. •As the feature departs from MMC, a flatness error equal to the amount of the departure is allowed.

Flatness Control ApplicationSome examples of when a designer uses flatness control on a drawing are to provide a flat surface:• For a gasket or seal.• To attach a mating part.• For better contact with a datum plane.

When these types of applications are involved, the indirect flatness control that results from Rule #1 is often not sufficient to satisfy the functional requirements of the part surface.

This is when a flatness control is specified on a drawing:

Inspecting Flatness•Establish the first plane of the tolerance zone by placing the part surface on a surface plate that has a small hole.

• The surface plate becomes the true counterpart of the controlled feature. A dial indicator is set in the small hole.

• The tip of the dial indicator traces a path across the entire part surface.

• Then the part is moved over the hole at random.

• If the FIM (full indicator movement) is larger than the flatness tolerance value at any point on the path, then the surface flatness is not within its specification.

STRAIGHTNESS :Definition : Straightness of a line element is the condition where each line element (or axis or center plane) is a straight line.The tolerance zone for a straightness control (as a surface line element control) is two-dimensional.General Representation :

General Representation

Interpretation (Straightness applied to the surface element)

Rule#1’s Effects on Surface Straightness• Whenever Rule #1 is in effect, an automatic indirect straightens control exists for the surface line elements.

Rule#1’s Effects on Surface Straightness• When the feature of size is at MMC, the line elements must be perfectly straight. Asthe FOS departs from MMC a straightness error equal to the amount of the departure is allowed.

Interpretation (Straightness applied to the axis)

0.2

0.2mm

Straightness at MMC Application• A common reason for applying a straightness control at MMC to a FOS on a drawing is to insure the function of assembly. • Whenever the MMC modifier is used in a straightness control, it means the stated tolerance applies when the FOS is produced at MMC.

Straightness at MMC Application• An important benefit becomes available when straightness is applied at MMC: extra tolerance is permissible. • As the FOS departs from MMC towards LMC, a bonus tolerance becomes available.

Inspecting a Straightness Control (Applied to a FOS at MMC)

Definition: Circularity is a condition where all points of a surface of revolution, at any Section perpendicular to a common axis, are equidistant from that axis.General representation:

0.2

39.0

38.5

CIRCULARITY

Example :

•A circularity control is a geometric tolerance that limits the amount of circularity on a part surface.

•It specifies that each circular element of a feature’s surface must lie within a tolerance zone of two coaxial circles.

•It also applies independently at each cross section element and at a right angle to the feature axis.

•The radial distance between the circles is equal to the circularity control tolerance value.

Circularity control :

INTERPRETATION

0.294.2 – 94.6

0.279.4 – 79.8

0.2

Two imaginary and concentric circles with their radii 0.2mm apart.

Part surface

Circularity application :

•Is to limit the lobing (out of round) of a shaft diameter.

•In certain cases, lobing of a shaft diameter will cause bearings or bushings to fail prematurely.

Circularity application :

•The diameter must be within its size tolerance.

•The circularity control does not override Rule #1.

•The circularity control tolerance must be less than the size tolerance.

•The circularity control does not affect the outer boundary of the FOS.

INSPECTION OF CIRCULARITY

Cylindricity

Definition :Cylindricity is a condition of a surface of revolution in which all points of the surface are equidistant from a common axis.General Representation :

g

0.2

39.0

38.5

Example & Interpretation:

•A cylindricity control is a geometric tolerance that limits the amount of cylindricity error permitted on a part surface.

•It specifies a tolerance zone of two coaxial cylinders within which all points of the surface must lie. A cylindricity control applies simultaneously to the entire surface.

•The radial distance between the two coaxial cylinders is equal to the cylindricity control tolerance value.

•A cylindricity control is a composite control that limits the circularity, straightness, and taper of a diameter simultaneously.

Cylindricity control :

Cylindricity application :

•Is to limit the surface conditions (out of round, taper, and straightness) of a shaft diameter.

•In certain cases, surface conditions of a shaft diameter will cause bearings or bushings to fail prematurely.

Cylindricity application :

•The diameter must also be within its size tolerance.

•The cylindricity control does not override Rule #1.

•The cylindricity control tolerance must be less than the total size tolerance.

•The cylindricity control does not affect the outer boundary of the FOS.

INSPECTION OF CYLINDRICITY

DATUM SYSTEMS (PLANAR DATUM)

• Set of symbols and rules that communicates to the drawing user how dimensional measurements are to be made.

WHY DATUM SYSTEM?

• First, it allows the designer to specify which part surfaces are to contact the inspection equipment for the measurement of a dimension.

• Second, the datum system allows the designer to specify, in which sequence the part is to contact the inspection equipment for the measurement of a dimension.

BENEFITS OF DATUM SYSTEM

-It aids in making repeatable dimensional measurements.

-It aids in communicating part functional relationships.-It aids in making the dimensional measurement as

intended by the designer.

CONSEQUENCES

-Good parts are rejected-Bad parts are accepted

DATUMS(PLANAR)

• DATUM• DATUM FEATURE• DATUM FEATURE SIMULATOR• SIMULATED DATUM• DATUM FEATURE SYMBOL• DATUM SELECTION

DATUM

• A datum is a theoretically exact plane, point or axis from which a dimensional measurement is made.

• A Datum is the true geometric counter part of a datum feature

• A true geometric counter part is the theoretical perfect boundary or best fit tangent plane of a datum feature.

DATUM FEATURE

• A datum feature is a part feature that exists on the part and contacts a datum.

SIMULATED DATUM

• A simulated datum is the plane established by the inspection equipment.

DATUM FEATURE SIMULATOR

•A datum feature simulator is the inspection equipment that includes the gage elements used to establish the simulated datum.

DATUM FEATURE SYMBOL• The symbol used to specify a datum feature on a

drawing is called the datum feature symbol.

FOUR WAYS OF REPRESENTING PLANAR DATUMS

DATUM REFERENCE IN FEATURE CONTROL FRAME

• The drawing must communicate when and how the datums should be used. This is typically done through the use of feature control frames.

DATUM REFERENCE IN FEATURE CONTROL FRAME

DATUM REFRENCE FRAME

• A datum reference frame is a set of three mutually perpendicular datum planes.

• The datum reference frame provides direction as well as an origin of dimensional measurements.

DATUM REFRENCE FRAME

Datum-related versus FOS dimensions

• Only dimensions that are related to a datum reference frame through geometric tolerances should measure in a datum reference frame.

• If a dimension is not associated to a datum reference frame with a geometric tolerance, then there is no specification on how to locate the part in the datum frame.

Datum-related versus FOS dimensions(contd…)

INCLINED DATUM FEATURES

• An inclined datum feature is a datum feature that is at an angle other than 90°, relative to the other datum features.

MULTIPLE DATUM REFERENCE FRAMES

• A part may have as many datum reference frames as needed to define its functional relationships.

COPLANAR DATUM FEATURES

• COPLANAR SURFACES.

• COPLANAR DATUM FEATURES.-In this case, a datum feature symbol is attached to a profile control.-The profile control limits the flatness and

co planarity of the surfaces.

COPLANAR DATUM FEATURES(contd…)

DATUM TARGETS• Datum targets are symbols that describe the shape,

size and location of gauge elements that used to establish datum planes or axes.

• Datum targets are shown on the part surfaces on a drawing, but they actually do not exist on a part.

• Datum targets can be specified to simulate a point, line or area contact on a part.

• The use of datum targets allows a stable and repeatable relationship for a part with its gauge.

• Datum targets should be specified on parts where it is not practical (or possible) to use an entire surface as a datum feature.

DATUM TARGETS SYMBOLS

• A datum target application uses two of symbols:1.A datum target identification symbol2.Symbols that denote which type of

gauge elements are to be used.• The leader line from the symbol specifies whether

the datum target exists on the surface shown or on the hidden surface side of the part.

• Three symbols used to denote the type of gauge element in a datum target application are the symbols for a target point, a target line, and a target area.

DATUM TARGETS SYMBOLS(contd….)

DATUM TARGETS SYMBOLS(contd….)

• A datum target point is specified by an X shaped symbol, consisting of a pair of lines intersecting at 90°.

• Basic dimensions should used be used to locate datum target points relative each other and the other datums on the part.

DATUM TARGETS SYMBOLS(contd….)

• Datum target point

DATUM TARGETS SYMBOLS(contd….)

• Datum target line

DATUM TARGETS SYMBOLS(contd….)

• Datum target areas

DATUM TARGETS SYMBOLS(contd….)

Creating a partial reference frame fromoffset surfaces(contd…)

DATUM AXIS &

DATUM CENTER PLANE

INTRODUCTION

• Here Feature of Size is used as a datum features

• When a diameter is used as a datum feature, It results in a datum axis

• When a planar is used as a datum feature, it results in a datum center plane Describe the datum that results from a FOS datum feature

3 Ways for representing an axis as datum• Datum identification symbol can be touching the surface of a

diameter to specify axis as the datum

Describe the ways to specify an axis as a datum.

3 Ways for representing an axis as datum (Contd….)

• Datum identification symbol can be touching the beginning of a leader line of FOS to specify an datum axis

• Datum identification symbol can be touching the feature control frame to specify an axis or centre plane as datum

3 Ways for representing an axis as datum (Contd….)

• Datum identification symbol can be inline with dimension line to specify on axis or centre plane as datum

2 Ways for representing a centre plane as datum

Describe the ways to specify an centre plane as a datum.

• Datum identification symbol can replace one side of the dimension line and arrow head

2 Ways for representing a centre plane as datum (Contd….)

Datum Terminology• Datum feature A• Datum feature

simulator / Gauge element

• Simulated datum axis A

• Simulated datum Feature A

FOS datum feature referenced at MMC

FOS datum feature referenced at MMC (Contd…)

• The gauging equipment that serves as the datum feature simulator is a fixed size

• The datum axis or center plane is the axis or center plane of the gage element

• The size of the true geometric counterpart of the datum feature is determined by the specified MMClimit of size or, in certain cases, its MMC virtual condition

FOS datum feature referenced at MMC (Contd…)

• Referencing a FOS datum at MMC has two effects on the part gaging :– The gage is fixed in size – The part may be loose (shift) in the gage

List two effects of referencing a FOS datum at MMC

Datum axis MMC primary

Draw the datum feature simulator for an external and internal FOS datum feature (MMC primary).

Datum centre plane MMC primary

Datum axis MMC secondary

Draw the datum feature simulator for an FOS datum feature (MMC secondary with virtual condition)

Datum axis secondary (MMC) ,Datum centre plane tertiary (MMC)

Datum axis secondary (MMC) ,Datum centre plane tertiary (MMC)

(Contd…)

• When referencing the datums with the face primary, diameter secondary (MMC), and slot tertiary (MMC), the following conditions apply:• The part will have a minimum of three points of

contact with the primary datum plane • The datum feature simulators will be fixed size gage

elements. • The datum axis is the axis of the datum feature

simulator

Datum axis secondary (MMC) ,Datum centre plane tertiary (MMC)

(Contd…)

• The datum axis is perpendicular to the primary datum plane

• Depending upon the datum feature's actual mating size, a datum shift may be available.

• Second and third datum planes are to be associated with the datum axis

• The tertiary datum center plane is the center plane of the tertiary datum feature simulator

Datum Axis from a Pattern of Holes, MMC Secondary

Draw the datum axis when using a pattern of FOS as a datum feature (MMC secondary)

Datum sequence

Panel-A

Explain how changing the datum reference sequence in a feature control frame affects the part and gauge

Datum sequence (contd…)• Panel A

• An adjustable gauge is required.• No datum shift is permissible on datum feature A• The part is oriented in the gage by datum feature A• Datum feature B will have a minimum of one point

contact with its datum feature simulator• The orientation of the holes will be relative to

datum axis A

Panel B

Datum feature simulator for datum plane B

• Panel B• Datum feature B will have 3- point contact with its

datum plane• The part is oriented in the gauge by datum feature B• The orientation of holes will be relative to datum

plane B• An adjustable gauge is required and no datum shift is

permissible on datum feature A

Panel C

Virtual condition=Ф10.2

Basics of Orientation Control

• Interpret the perpendicularity control.

• Interpret the angularity control.

• Interpret the parallelism control.

PERPENDICULARITYPERPENDICULARITY

ZONE OF TOLERANCE :-TWO PARALLEL PLANES PERPENDICULAR TO DATUM SURFACE

SYMBOL :-

Perpendicularity Control

Define Perpendicularity

• Perpendicularity is the condition that results when a surface, axis, or centerplane is exactly 90 deg to a datum.

• A perpendicularity control is a geometric tolerance that limits the amount a surface, axis, or centerplane is permitted to vary from being perpendicular to the datum.

Perpendicularity Tolerance Zones

1. Two Parallel Planes

2. A cylinder

Perpendicularity Applications

1. Perpendicularity applied to a surface.

2. Perpendicularity applied to a planar FOS.

3. Perpendicularity applied to a cylindrical FOS.

Perpendicularity applied to a surface

Interpretations

• Tolerance zone – two parallel planes that are perpendicular to the datum plane.

• Distance between tolerance plane – specified tolerance value.

• Important criteria – all elements of the surface must be within the tolerance zone.

• Perpendicularity tolerance zone limits the flatness of toleranced feature.

Inspection of perpendicularity

Perpendicularity with multiple datums

Interpretations

• Tolerance zone – two parallel planes that are perpendicular to the datum plane.

• Distance between tolerance plane – specified tolerance value.

• Important criteria – all elements of the surface must be within the tolerance zone.

• Perpendicularity tolerance zone limits the flatness of toleranced feature

Perpendicularity control that contains MMC modifier

Interpretations

• Tolerance zone – two parallel planes that are perpendicular to the datum plane.

• Distance between tolerance plane – specified tolerance value.

• The center plane of the Actual Mating Envelope must be within the tolerance zone.

• A bonus tolerance is permissible.• A fixed gauge may be used to verify the

perpendicularity control.

Perpendicularity control with MMC modifier applied to

cylindrical FOS

Interpretations

• Tolerance zone – a cylinder that is perpendicular to the datum plane.

• Diameter of the tolerance zone – specified tolerance value.

• The axis of the diameter must be within the tolerance zone.

• A bonus tolerance is permissible.• A fixed gauge may be used to verify the

perpendicularity control.

Indirect perpendicularity controls

Perpendicularity can be indirectly controlled by –• Position tolerance.• Runout tolerance.• Profile tolerance.

Angularity Control

• Angularity is the condition of a surface, center plane, or axis being exactly at the specified angle.

• An angularity control is a geometric tolerance that limits the amount a surface, center plane, or axis is permitted to vary from its specified angle.

ANGULARITYANGULARITY

ZONE OF TOLERANCE :- TWO PARALLEL PLANES INCLINED 60 DEGREE TO DATUM SURFACE.

SYMBOL :-

a

Angularity tolerance zones

1. Two parallel planes

2. A cylinder

Angularity applications

1. Angularity applied to a surface.

2. Angularity applied to a cylindrical FOS.

Angularity applied to a surface.

Interpretations

• Tolerance zone – two parallel planes that are perpendicular to the datum plane.

• Distance between tolerance plane – specified tolerance value.

• Important criteria – all elements of the surface must be within the tolerance zone.

• Tolerance zone is oriented relative to the datum plane by a basic angle.

• Angularity tolerance zone limits the flatness of toleranced feature

Inspection of Angularity

Angularity control applied to a diametrical FOS

Interpretations

• Tolerance zone – a cylinder.• Diameter of the tolerance zone – specified

tolerance value.• The axis of the toleranced feature must be within

the tolerance zone.• Tolerance zone is oriented relative to the datum

plane by a basic angle.• An implied 90 deg basic angle exists in other

direction

Indirect angularity control

Angularity can be indirectly controlled by –• Position tolerance.• Runout tolerance.• Profile tolerance.

Parallelism Control

• Parallelism is the condition of a surface, center plane, or axis being exactly parallel to the datum.

• An parallelism control is a geometric tolerance that limits the amount a surface, center plane, or axis is permitted to vary from being parallel to the datum.

Parallelism Tolerance Zones

1. Two parallel planes.

2. A cylinder.

Parallelism Applications

• Parallelism applied to a surface.

• Parallelism applied to a cylindrical FOS.

PARALLELISMPARALLELISM

ZONE OF TOLERANCE :- CYLINDER

SYMBOL :-

Parallelism Applied To a Surface

Interpretations

• Tolerance zone – two parallel planes that are parallel to the datum plane.

• Tolerance zone is located within the limits of size dimension.

• Distance between tolerance plane – specified tolerance value.

• Important criteria – all elements of the surface must be within the tolerance zone.

• Parallelism tolerance zone limits the flatness of toleranced feature.

Inspection

Parallelism Applied to a FOS at MMC

Interpretation

• Tolerance zone – a cylinder that is parallel to the datum plane.

• Diameter of the tolerance zone – specified tolerance value.

• The axis of the diameter must be within the tolerance zone.

• A bonus tolerance is permissible.• A fixed gauge may be used to verify the

parallelism control.• Parallelism tolerance zone limits flatness of the

toleranced feature.