Training program in Dimensional Tolerancing, Geometric Dimensioning and Tolerancing for
HCL Technologies Ltd 25th April to 19th May 2005 by Netturr Techni Nettu Technical cal Training Training Foundatio Foundation, n, Peenya,Bangalore
Dimensional Tolerancing Ability needed to REPRESENT INTERPRET MANUFACTURE MEASURE
Main applications of Dimensioning and tolerances are for Holes & Shafts, Tapers, Threads, Gears, Splines, etc.
59,45
0.02 0.025 5 M
35,95
± 0.125 0.02 0.025 5 M 0.015 M
± 0.125
5 4 , 0
A C0.5(BOTH SIDES)
0.025 A 0.025 M
0.05 M ° 0 3
R0,5(TYP) R4
0.6(MAX) x 45°
0 -1.0
1,5
4,15 R5
DETAIL AT B 1 . 0 +
2 . 0 0 -
0 . 8 3 Ø
B C1.15
6 1 0 . 0 +
0 . . 2 0 0 -
5 2 . 0 5 4 2 Ø Ø
5 , 3 7 Ø
SCALE 5:1
8 6 , 5 9 Ø
REFER FORGING DRAWING NO RD 040660 03 FOR MATERIAL, HARDNESS & OTHER DETAILS
NOTE : ALL MACHINED SURFACES TO BE M
0. 02 02 M
FREE FROM RUST AND DENT MARKS
2 . 9 2 Ø -0.350
26,58
CAD REF . : DN NGT_GSL_RD040669-04
± 0.025 48,3
FOR ENGG. REF.
0.030 M
LINEAR DIMENSION ANGULAR DIMN.
AT
ALLOWANCE
BOSS FACE
0.15 ± 0.075
FRONT FACE
0.15 ± 0.075
BORE
0.2
PN : TRANSMISSION TOOLS
DO NOT SCALE : IF IN DOUBT. REFER DESIGN OFFICE MATERIAL UNSPECIFIED APPD. MACHINING DEVIATION AS NOTED DGNR Abov Abovee Upto Upto Devn. Shortside of ±mm Deg.of min 1 0.5 6 ±0.1 angle 6 30 ±0.2 AboveUpto 30 120 ±0.3 10 0.1 10 120 315 ±0.5 10 50 0.2 30 315 1000 ±0.8 50 120 0.5 20 1000 2000 ±1.2 120 0.8 10
SCALE 1 :1
PART NAME: FIFTH GEAR - LAYSHAFT TOOL NAME: BLANK DRAWING(TURNED)
BY
SIGN DATE
SIZE - C TO BE USED ON TOOL NO : XXXX/Y
SHEET 1 OF 1
FEATURE CONTROL FRAME PLACEMENT
Different types of tolerances are 1. 2. 3. 4. 5.
Dimensio Dimen siona nall Tol Tolera erance ncess Form Fo rm Tol Toler eran ance cess Posi Po siti tion on To Tole lera ranc nces es Surfa Su rface ce Rou Roughn ghness ess val values ues Combi Com binat nation ion Tol Tolera erance ncess
Other details shown on drawing are Material specification Special treatments if any Heat treatments Assembly condition Special notes
Tolerance: Tolerance is the total permissibl permissiblee variation variation from the specified basic size of the part. It is defined as the magnitude magnitude of permissible permissible variation of a dimension or 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 tolerances Standards used are IS 210 2102 2 ( Par Partt – 1) – 199 1993 3 / ISO ISO 276 2768 8 - 1 : 198 1989 9 General Tolerances Partt – 1: Tol Par Tolera erance ncess for for Linea Linearr and and Ang Angula ularr dimensions without individual tolerance indications Partt – 2: Geo Par Geomet metric rical al Tol Tolera erance ncess for for fea featur tures es without individual tolerance indications Ex: 20.0, 20-f, Ø20-f H
Table 1 – Permissible deviations deviations for linear dimensions except except for broken edges (external radii and chamfer heights, see table 2) Values in millimeters Permissible deviations for basic basic size range range Tolerance Class
Desig Descripti nation on
0.5 up to 3
Over 3 up to 6
Over 6 up to 30
Over 30 up to 120
Over 120 up to 120
Over 400 up to 400
Over 1000 up to 2000
Over 2000 up to 4000
± 0, 0,05 05
± 0,1
± 0, 0,15 15
± 0,2
± 0,3
± 0,5
-
f
fine
± 0, 0,05 05
m
medium
± 0,1
± 0,1
± 0,2
± 0,3
± 0,5
± 0,8
± 1,2
±2
c
coarse
± 0,2
± 0,3
± 0,5
± 0,8
± 1,2
±2
±3
±4
v
very coarse
-
± 0,5
±1
± 1,5
± 2,5
±4
±6
±8
1) For nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size (s).
Table 2 – Permi Permissible ssible deviations deviations for broken broken edges ( external radii and chamfer heights) Values in millimeters Permissible deviations for basic size range
Tolerance Class Designation Descriptio n f
fine
m
medium
c
coarse
v
very coarse
0.5 up to 3
Over 3 up over 6 to6
± 0,2
± 0,5
±1
± 0,4
± 0,1
±2
1) For nominal sizes below 0.5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 3 – Permis Permissible sible deviations deviations of angular dimensions dimensions
Tolerance Class
Permissible deviations for ranges of lengths, in millimeters, of the shorter side of the angle concerned
Desig Descript up to 10 nation ion ± 10
over 10 up to 50
over 50 up to 120
over 120 up to 400
over 400
± 00 30
± 00 20’
± 00 10’
± 00 5
± 00 30’
± 00 15’
± 00 10
± 00 30’
± 00 20
F
fine
m
medium
c
coarse
± 10 30’
± 10
v
very coarse
± 30
± 20
± 10
Table 1 – General tolerances tolerances on straightness and and flatness Values in millimeters
Straightness and flatness tolerances for ranges of nominal lengths lengths
Tolerance Class 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 perpendicularity Values in millimeters
Perpendicularity tolerances for ranges of nominal Perpendicularity lengths of the shorter side Tolerance Class up to 100
over 100 up to 300
over 300 up to 1000
over 1000 up 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 tolerances on symmetry symmetry Values in millimeters
Symmetry tolerances for ranges of nominal lengths Tolerance Class over 100 up to 300
up to 100
H
over 300 up to 1000
over 1000 up to 3000
0,5
K
0,6
L
0,6
1
0,8
1
1,5
2
Table 4 – General tolerances tolerances on circular circular run-out Values in mm
Tolerance class
Circular run-out tolerances
H
0,1
K
0,2
L
0,5
IS 21 2102 – PART – 2 • VALUES FOR – Straightness / perpendicularity perpendicu larity / symmetry / Run out specified • Circularity - li lim mited to to di diameter tolerance or run out value • Cylind Cylindricit ricity y – Limit Limited ed to combine combined d effect effect of CIRCULARITY& PARALLELISM. • Pa Para rall llel elis ism m – Li Limi mite ted d to to Dim Dimen ensi sion onal al Tolerance & flatness tolerance. • Coaxi Coaxiality ality - Limit Limited ed to run out toler tolerance ance..
ISO IS O 276 2768 8-m • General Engg. Tole Tolerance class medium
IS 21 2102 02 – f General ral Engg. Engg. Tole – clas classs fine • Gene
ISO IS O 276 2768 8 – 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 • Envel Envelopin oping g dia dia limit limitss -E
ISO IS O 27 2768 68 - 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. USED.
2. Specific Specificied ied toler tolerance ancess Standards used IS 919 (Pa (Part rt – 1) – 199 1993 3 / ISO 286 – 1 : 198 1988 8 ISO System of Limits and Fits Part – 1: Bases of tolerances, tolerances, Deviations Deviations and Fits Part Pa rt – 2: Tabl Ta bles es of st stan anda dard rd to tole lera ranc ncee Gra Grade dess and and limit Deviations for Holes and shaft. 0.02 02 Example : 20H7, 20g6, 30 + 0.
Specific tolerance should be less than open tolerance
STANDARD SPECIFICATION Need 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
PRES ESS S WO WORKIN ING G • PR
IT 10 10, 11 11 OR OR 12 12
• INJ. MOULDING
IT 12. 123 OR 14
Grades of tolerances obtainable manufacturing manufacturin g processes
by
various
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 CONVENIENCE, DIMES. ARE • FOR 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
IT14 3)
IT153)
IT16 3)
IT173)
IT183)
Above
Up to and including
-
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
Tolerances µm
mm
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
1000
2
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
1600
2
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
2000
2
18
25
35
46
65
92
150
230
370
600
920
1,5
2,3
3,7
6
9,2
15
23
2000
2500
2
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)
Up to and including
Above
IT42)
IT52)
IT6
IT7
IT8
IT9
IT10
IT11
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
100 100
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
110 110
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 t han 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
IT14 3)
IT153)
IT163)
IT173)
IT183)
Above
Up to and including
-
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
Tolerances mm
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 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
630
2
0,7
1,1
1,75
2,8
4,4
7
11
630
800
2
0,8
1,25
2
3,2
5
8
12,5
2
0,9
1,4
2,3
3,6
5,6
9
14
2
1,05
1,65
2,6
4,2
6,6
10,5
16,5
2
1,25
1,95
3,1
5
7,8
12,5
19,5
2
1,5
2,3
3,7
6
9,2
15
23
1,75
2,8
4,4
7
11
17,5
28
2,1
3,3
5,4
8,6
13,5
21
33
800
1000
1000
1250
1250
1600
1600
2000
2000
25002
2500
3150
2
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 MORE TOL VALUE
GETS
100%
WHERE TO DISPOSE TOLE. 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; IS FIXED FOR A DIA-DIM • FD 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 represente represented d by 30 H 7 / g6, 30 H 7 / p6, 40 H7k6, 40 H7p6,
40 H7/h6,
Example of general tolerances on a drawing
INTERPRETATION
INTRODUCTION TO GEOMETRIC TOLERANCES •
• 1. 2. 3. 4. 5.
Geometric characteristic symbols are a set of fourteen of fourteen Symbols used in the language of geometric tolerancing. The The sym symbo bols ls are are div divid ided ed into into five five categories: Form Profile Orientation Location Runout
Feature Control Frame • Geometric Geometric toler tolerances ances are are specifie specified d on a drawing through the use of a feature control frame.
Symbol of Geometric Tol.
Zone of Tolerance
P.D
W or w/o zone Modifier
S.D
T.D
Feature Control Frame
Tolerance frame 5.1 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 3
Figures 4
Figures 5
Tolerance frame(contd) •
5.2 Rem 5.2 Remar arks ks re rela late ted d to to the the tolerance, for example “6 holes”, “4 surfaces” or “6x” shall be written above the frame (see figures 6 and 7) • 5. 5.3 3 Indi Indica cati tion onss qua quali lify fyin ing g the form of the feature within the tolerance zone shall be within near the tolerance frame and may be connected by a leader
Figure 6
Figure 7
Figure 9
Figure 8
line (see figures 8 and 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
Tolera Tolerance nced d featu features res •
•
The The toler tol eraanc ncee fram fra me is is connected to the toleranced feature by a leader line terminating with an arrow in the following way:
Figure11
_ on on the the out outli line ne of th thee fea featu ture re or an extention 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) Figure12
Tolera Tolerance nced d featur features es (contd) (contd) •
_ as as an ex exte tens nsio ion n 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)
Figure13
Figure14
Figure15
Tolera Tolerance nced d featu features res (contd) (contd) •
_ on th thee axi axiss whe when n the the tole tolera ranc ncee refers to the axis or median plane of all features common to that axis or median plane(see figures 16,17 and 18)
Figure16
Figure17
Figure18
Tolerance zones 7.1 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 In genera general, l, the the direc direction tion of the the width width of of the the tolera tolerance nce zone is normal to the specified geometry of the part (see figures 21&22)
Figure 22 Figure 21
Tolerance zones (contd) •
7.3 The The direct direction ion of of the tole toleranc rancee zone zone shall shall be indi indicat cated ed when 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 26
Figure 25
Tolerance zones (contd) 7.5 Where a common tolerance tolerance zone is applied applied to several separate features, the requirement is indicated by the words “common zone” above the tolerance frame (see figures 27&28).
3XA COMMON ZONE
COMMON ZONE
A
Figure 27
A
Figure 28
A
Datums 8.1 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
8.2
Figure 30
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 there is insufficie insufficient nt space space for two arrows, 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 separate d 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.
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 correspon corresponding ding actual dimensions of the part are subject only to the position tolerance, profile tolerance or angularity angularity tolerance tolerance specified specified within within the tolerance frame (see (see figures 46 and 47). Figure 46
Figure 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 indicat indication ion that the tolerance tolerance value applies at the maximum material condition is shown by the symbol placed after: The tolerance value (see figure 49);
Figure 48
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 50
Figure 51
Introduction to Geometric Dimensioning and Toler To leranc ancing ing GD & T sta stand ndar ards ds ANSI Y 14.5M 1982 ISO I SO 110 1101 1 – 19 1983 83 ASME 14.5M -1994
ISO 1101 -1983 (Technical Drawings-Geometrical TolerancingTolerancing of Form, Form, Orientation, Orientation, Location and Runout) ANSI Y14.5 1982-American 1982-Ame rican 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 14.5 .5 St Stan anda darrd nu numb mber er.. •
M
Standard is Metric.
•
1994 19 94
Year th Year thee st stan anda dard rd wa wass of offi fici cial ally ly 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.
DIMENSION AND TOLERANCES cond.. • Plus –Minus Tolerance Equal bilateral tolerance. Unequal bilateral tolerance. Unilateral tolerance.
+0.5 0
+0.3 - 0.2
COORDINATE TOLERACING SYSTEM • Part feature is located (or defined) by means of rectangular dimensions dimensions with given given tolerances. tolerances.
GEOMENTRIC DIMENSIONING AND TOLERANCING.
COMPARISION BETWEEN GD&T AND COORDINATE TOLERANCING.
Key terms used in Geometric dimensioning and tolerancing
Modifiers and symbols geometric tolerancing
used
• Un Unde ders rsta tand nd key terms and how they affect the interpretation of a drawing. • Unde Unders rsta tand nd th the e mod modif ifie iers rs an and d symbols used in geometric tolerancing.
in
FEATURES • A feature is a general term applied to a physical portion of part, part, such as a surface, hole or slots,tabs. • An easy easy way to remembe rememberr this term term is to think of a feature as a part surface.
FEATURES
Features
Feature Of Size
Non-Feature Of Size
External
Internal
Feature Of Size
Feature Of Size
FEATURE OF SIZE • This This is one one cylindrical or spherical surface,, or set of two opposed elements or surface parallel surfaces associated with size dimension which has an axis, center line or center plane contained within it. • Features Features of of size size are features, features, which do have diameter or thickness. • These may be cylinde cylinders, rs, such such as as shafts 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 • Ex Exte tern rnal al FOS FOS are comprised of part surfaces that are external surfaces. surfaces. – Like shaft shaft diameter diameter or width height of a planner surfaces.
and
• In Inte tern rnal al FO FOS S is comprised of part surfaces (or elements) that are internal part surfaces. surfaces. – like hole diameter 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 si size is a similar simi lar perfe perfect ct featu feature re coun counterpa terpart rt 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.. 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 inscribed within 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 geometri geometric c toleranc tolerance e can be specifie specified d to apply at the largest size, smallest size or actual size of a feature of size. •
(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. Maximum
Material
Condition
MMC of external Feature Of Size MMC
MMC of internal Feature Of Size
MMC
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) • Regardles Regardless s of feature feature size size is the term term that that indicates a geometric tolerance applies at any increment of size of the feature within its size tolerance. • RFS applied applied only only to size feature features, s, such such as hole, shafts, pins, etc.; feature which have an axis, centerplane or centerline. • Symbol :
S
Material Condition Usage • Each Each materia materiall conditi condition on is used used for different functional reasons. • Geometric Geometric tolerances tolerances are often often specified specified to apply at MMC when the function of a FOS is assembly assembly.. • Geometric Geometric tolerances tolerances are often often specified specified to apply at LMC to insure a minimum distance on a part. part. • Geometric Geometric tolerances tolerances are often often specified specified to apply at RFS to insure symmetrical relationships.
MODIFIERS • Modifiers communicate additional information about the drawing or Tolerancing of a part. • Ther There e are are nine common modifiers used in geometric tolerancing.
Nine modifiers
PROJECTED TOLERANCE ZONE • Symbol:
P
• The proj project ected ed toler toleranc ancee zone zone modif modifier ier changes changes the location of the tolerance zone on the part. • It projec projects ts the tolera tolerance nce zone zone above the part surface. • Height Height of of the the project projected ed tolera tolerance nce zone zone should should be 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
Using a Projected Tolerance Zone (Contd..) •A projected tolerance zone is used to limit the perpendicularity of a hole to ensure assembly with mating part.
Using a Projected Tolerance Zone (contd.)
TANGENT PLANE MODIFIER • The tangen tangentt plane plane modif modifier ier denot denotes es that that only only the tangent plane of the toleranced surface needs to be within this tolerance zone.
DIAMETER MODIFIER
• The diamet diameter er symb symbol ol is is used used two ways: 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 modifie modifierr for referenc reference e is simply simply the method of denoting that information is for reference only. only. • The inform informati ation on is not to be used for manufacturing or inspection. • To designa designate te a dimensi dimension on or other other information as reference, the reference information is enclosed in parentheses.
Reference Example:
RADIUS MODIFIER • Arcs are dimensioned dimensioned with radius radius symbol symbol on drawings. • A radius is a straight line extending from the center of an arc or a circle to its surface. • The Symb Symbol ol for for a radiu radius s is "R“. "R“. • When When the the "R" "R" sym symbo boll is use used, d, it it crea create tes sa zone defined by two arcs. • The part part surface surface must must lie lie within within this this zone. zone. • The part part surfac surface e may may have have flats or reversals within the tolerance zone.
Radius modifier
Controlled Radius • The symbol symbol for for a control controlled led radius radius is is "CR“. "CR“. • it creates creates a tolerance tolerance zone defined defined by two two arcs. • The part part surfa surface ce must must be with within in the the crescent-shaped tolerance zone and be an arc without flats or reversals.
CONTROL RADIUS
DATUM IDENTIFYING LETTER
DATUM FEATURE SYMBOL
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
RULES & CONCEPTS OF GD & T 1. Understand Rule Rule #1 and Rule #2. 2. Understand the concepts of basic dimensions, virtual condition, inner and outer boundary, worst-case boundary and bonus tolerance.
Rule #1 Rule #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. form.
TECHNO TECHNOTE TE – For featur features es of size, size, where 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 both its size and and form need to be be verified. verified. The MMC size and the the Rule #1 envelop envelope e 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 minimum size (LMC) of a FOS FOS can be be measured with a No-Go gage. A No-Go gage gage is made made to the LMC 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 and Geometric tolerancing
Dimensional tolerancing 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 DIMENSIONS 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.
Basic Dimension Symbol
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 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. • Straightness. ss. • Circulari arity. • Cylin lindricit city.
FLATNESS
SYMBOL :-
ZONE OF TOLERANCE TOLERANCE :- TWO PARALLEL PARALLEL PLANES PLANES
STRAIGHTNESS
SYMBOL :-
ZONE OF TOLERANCE TOLERANCE :- CYLINDER
CIRCULARITY
SYMBOL :-
ZONE OF OF TOLERANCE TOLERANCE :- TWO COPLANAR CONCENTRIC CIRCLES
CYLINDRICITY
SYMBOL :-
ZONE OF TOLERANCE :- TWO COAXIAL COAXIAL CYLINDERS CYLINDERS
FLATNESS Defini Definitio tion n : Flatn Flatness ess is the the condit condition ion of of a surface having all of its elements in one plane. The tolerance zone for a flatness control is three-dimensional. General representation
Interpre Interpretatio tation n of Flatness Flatness toleranc tolerance e: It consists of two parallel planes within which all the surface elements must lie. 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 Application Some examples of when a designer uses flatness control on a drawing are to provide a flat surface: • For a gasket gasket or seal. seal. • To attac attach h a mating mating part. part. • For better better contact contact with 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 surf surface ace plate plate beco becomes mes the the true true counte counterpa rpart rt of the controlled feature. A dial indicator is set in the small hole. • The tip tip of the the dial dial indic indicato atorr traces traces a path path across across the entire part surface. • Then Then the part part is move moved d over over the the hole hole at random. random.
• If the the FIM (full (full indica indicator tor move movemen ment) t) is large larger r than the flatness tolerance value at any point on the path, then the surface flatness is not within its specification.
STRAIGHTNESS : Defini Definitio tion n : Straig Straightn htness ess of a line line eleme element nt 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 twodimensional. General General Represe Representa ntatio tion n:
General Representation
Interpretation (Straightness applied to the surface element)
Rule#1’s Effects on Surface Straightness • Whenever Whenever Rule #1 is in effect, effect, an automat automatic ic indirect straightens control exists for the surface line elements.
Rule#1’s Effects on Surface Straightness • When the the feature feature of size is at MMC, MMC, the line line elements must be perfectly straight. As the 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 commo common n reason reason for applying a straightness control at MMC to a FOS on a drawing is to insure the function of assembly. • Whenev Whenever er 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 import important ant benef benefit it becomes available when straightness is applied at MMC: extra tolerance is permissible. • As the the FOS FOS depa departs rts from MMC towards LMC, a bonus tolerance becomes available.
Inspecting a Straightness Control (Applied to a FOS at MMC)
CIRCULARITY Definition: Definition: Circularity Circularity is a condition condition where 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
Example :
Circularity control : •A circularity circularity control control is a geometric geometric tolerance 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.
INTERPRETATION 94.2 – 94.6 0.2
79.4 79.4 – 79.8 79.8 0.2
Two imaginary and concentric circles with their radii 0.2mm apart.
0.2
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 Defini Definitio tion n :Cylin :Cylindric dricity ity is a condit condition ion of of a surface of revolution in which all points of the surface are equidistant from a common axis. General General Represen Representat tation ion : 0.2
39.0 38.5
Example & Interpretation:
Cylindricity control : •A cylindricity control is 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 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 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 communicates to the drawing user how dimensional measurements are to be made.
WHY DATUM SYSTEM?
• First, First, it allows allows the the designe designerr to specify specify which which part surfaces are to contact the inspection equipment for the measurement of a dimension. • Second, Second, the the datum datum system system allows allows the the desig designer ner 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 measurement as intended by the designer.
CONSEQUENCES -Good parts are rejected -Bad parts are accepted
DATUMS(PLANAR)
• DATUM • DATUM FE FEATURE • DATU DATUM M FEA FEATU TURE RE SIMUL SIMULAT ATOR OR • SIMU SIMULA LATE TED D DA DATUM TUM • DATU DATUM M FEAT FEATUR URE E SYMB SYMBOL OL • DATUM TUM SE SELECT LECTIO ION N
DATUM • A datum is a theoretically exact plane, point or axis from which a dimensional dimensional measurement is made. part of a datum • A Datum is the true geometric counter part of feature • A true true geometric geometric counter counter part part is the the theoret theoretical ical perfec perfectt boundary or best fit tangent plane of a datum feature. feature.
DATUM FEATURE
• A datum feature is a part part feature that exists on on the part and contacts a datum.
SIMULATED DATUM
• A simula simulated ted datum datum is the the plane plane establ establishe ished d by the inspection equipment.
DATUM FEATURE SIMULATOR
•A datum feature simulator is the inspection equipment equipment that includes the gage elements used to establish the simulated datum.
DATUM FEATURE SYMBOL • The symbol symbol used used to speci specify fy a datum datum feat feature ure on a drawing is called the datum feature symbol.
FOUR WAYS OF REPRESENTING PLANAR DATUMS
DATUM REFERENCE IN FEATURE CONTROL FRAME
• The draw drawing ing must must com commu munic nicate ate when when and and how 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 datum referen reference ce frame frame provides provides direction direction as well as an origin of dimensional measurements. measurements.
DATUM REFRENCE FRAME
Datum-related versus FOS dimensions • Only Only dimens dimension ionss that that are relat related ed to a datu datum m reference frame through geometric tolerances should measure in a datum reference frame. • If a dime dimensi nsion on is not asso associa ciated ted to to a datum 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(con dimensions(contd…) td…)
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 part may have as as many many datum datum refere reference nce fram frames es as needed 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 Datum targets targets are shown shown on the the part part surfaces surfaces on a drawing, but they actually do not exist on a part. • Datum Datum target targetss can can be specified specified to simul simulate ate a point, line or area contact on a part. • The use of of datum datum targ targets ets allows allows a stable stable and and repeatable relationship for a part with its gauge. • Datum Datum targets targets should should be be specifie specified d on parts where it is not practical (or possible) to use an entire surface as a datum feature.
DATUM TARGETS SYMBOLS • A datum datum target target applicati application on uses uses two two of symbols symbols:: 1.A datum target identification symbol 2.Symbols that denote which type of gauge elements are to be used. • The leader leader line from the symb symbol ol specifi specifies es whethe whether r the datum target exists on the surface shown or on the hidden surface side of the part. • Three symbols symbols used to denot denotee the the type type of of gauge 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… SYMBOLS(contd….) .)
DATUM TARGETS SYMBOLS(contd… SYMBOLS(contd….) .) • A datum datum target target point point is specified specified by an X shaped shaped symbol, consisting consisting of a pair of lines intersecting at 90°. • Basic dimensi dimensions ons shoul should d used used be used to locat locatee datum target points relative each other and the other datums on the part.
DATUM TARGETS SYMBOLS(contd… SYMBOLS(contd….) .) • Datum atum tar target get poi point nt
DATUM TARGETS SYMBOLS(contd… SYMBOLS(contd….) .) • Datum atum tar target get li line
DATUM TARGETS SYMBOLS(contd… SYMBOLS(contd….) .) • Datum atum targ targeet ar areas
DATUM TARGETS SYMBOLS(contd… SYMBOLS(contd….) .)
Creating a partial reference frame from offset surfaces(contd surfaces(contd…) …)
DATUM AXIS & DATUM CENTER PLANE
INTRODUCTION • Here Here Feat Featur uree of of Size Size is used as a datum features • When hen a diam diameeter ter is is used as a datum feature, It results in a datum axis • When hen a plan planar ar is used 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 datumbe touching • Datum identificat identification ion symbol symbol can be touching the the surfac surfacee 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 identifica identification tion symbol symbol can can be touching touching the the beginnin beginning g of a leader line of FOS to specify an datum axis
3 Ways for representing an axis as datum (Contd….) • Datum Datum identif identificati ication on symbol symbol can be touching touching the feature feature control frame to specify an axis or centre plane as datum
2 Ways for representing a centre plane as datum • Datum Datum identi identificat fication ion symbol symbol can be be inline inline with dimension line to specify on axis or centre plane as datum
Describe the ways to specify an centre plane as a datum.
2 Ways for representing a centre plane as datum (Contd….) • Datum identifica identification tion symbol symbol can can replac replacee one one side side of the dimension line and arrow head
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 gaug gauging ing equip equipmen mentt that that serve servess as the the datum feature simulator is simulator is a fixed size • The datum datum axis or center center plane is the the axis axis or center center plane of the gage element • The size of the the true true geometr geometric ic counte counterpart rpart of the the datum feature is determined by the specified MMC limit of size or, in certain cases, its MM MMC C vi virt rtua uall condition
FOS datum feature referenced at MMC (Contd…) • Refere Referenci ncing ng a FOS FOS datum datum at MMC has has two two effec effects ts on the part gaging : – The gage is fixed fixed in in size size – The part part may be loose loose (shift) (shift) in the gage 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 referencin referencing g the the datums datums with the face face prima primary, ry, diameter secondary (MMC), and slot tertiary (MMC), the following conditions apply : • The part part will will have a minim minimum um of three three points points of of contact with the primary datum plane • The datum datum feature feature simula simulators tors will will be fixed fixed size size gage elements. • The datum datum axis axis is is the axis axis of the datum datum feature feature simulator
Datum axis secondary (MMC) , Datum centre plane tertiary (MMC) (Contd…) • The datum datum axis is perpend perpendicul icular ar to the prima primary ry datum datum plane • Dependin Depending g upon upon the the datum datum feature's feature's actual actual mating mating size, a datum shift may be available. • Second Second and third datum datum planes planes are to to be associated associated with the datum axis • The tertia tertiary ry datum datum center center plane plane is the center 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 adjus adjustab table le gauge gauge is requi required red.. No datum datum shift shift is permi permissib ssible le on datum datum featur featuree A The part part is orient oriented ed in the the gage gage by datum datum feature feature A Datum Datum feature feature B will will have have a minimum minimum of of one point point contact with its datum feature simulator • The orient orientatio ation n of the the holes holes will be relative relative to to datum axis A
Panel B
Datum feature simulator for datum plane B
• Panel B • Datum Datum featu feature re B will will have have 3- point point cont contact act with with its its datum plane • The part part is orient oriented ed in the the gauge gauge by datum datum feature feature B • The orient orientatio ation n of holes holes will will be relativ relativee to datum datum plane B • An adjusta adjustable ble gauge gauge is requi required red and no no datum datum shift 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.
PERPENDICULARITY
SYMBOL :-
ZONE OF TOLERANCE :-TWO PARALLEL PLANES PERPENDICULAR TO DATUM SURFACE
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.
Perp Perpen endi dicu cula lari rity ty appl applie ied d to to a surface. surface.
2.
Perp Perpen endi dicu cula lari rity ty appl applie ied d to to a planar FOS. FOS.
3.
Perp Perpen endi dicu cula lari rity ty appl applie ied d to to a cylindrical FOS.
Perpendicularity applied to a surface
Interpretations • Tolerance zone – zone – two two parallel planes that are perpendicular to the datum plane. • Distan Distance ce betw between een toler toleranc ancee plane plane – specified – specified tolerance value. value. • Import Important ant criter criteria ia – all elemen elements ts of of the the surfa surface ce must be within the tolerance zone. zone . • Perpen Perpendic dicula ularit rity y tole toleran rance ce zon zonee limits the flatness of toleranced feature. feature.
Inspection of perpendicularity
Perpendicularity with multiple datums
Interpretations • Tolerance zone – zone – two two parallel planes that are perpendicular to the datum plane. • Distan Distance ce betw between een toler toleranc ancee plane plane – specified – specified tolerance value. value. • Import Important ant criter criteria ia – all elemen elements ts of of the the surfa surface ce must be within the tolerance zone. zone . • Perpen Perpendic dicula ularit rity y tole toleran rance ce zon zonee limits the flatness of toleranced feature
Perpendicularity control that contains MMC modifier
Interpretations • Tolerance zone – zone – two two parallel planes that are perpendicular to the datum plane. • Distan Distance ce betw between een toler toleranc ancee plane plane – specified – specified tolerance value. • The The cen cente terr pla plane ne of the 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 perpendicularity control.
Perpendicularity control with MMC modifier applied to cylindrical FOS
Interpretations • Tolerance zone – zone – aa cylinder that cylinder that is perpendicular to the datum plane. • Diameter of the tolerance zone – specified tolerance value. • The axis of the diameter must diameter must be within the tolerance zone. • A bonus tolerance is permissible. • A fixed gauge may be used to verify the perpendicularity perpendicularity control.
Indirect perpendicularity controls Perpendicularity can be indirectly controlled by – • Po Posi siti tion on tol toler eran ance ce.. • Runout tolerance. • Pr Prof ofil ilee to tole lera ranc ncee.
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.
ANGULARITY
SYMBOL :-
a
ZONE OF TOLERANCE TOLERANCE :- TWO PARALLEL PARALLEL PLANES PLANES INCLINED 60 DEGREE TO DATUM SURFACE.
Angularity tolerance zones 1.
Two pa parallel pl planes
2.
A cylinder
Angularity applications 1.
Angu ngulari laritty appl applie ied d to a surface. surface.
2.
Angu ngulari laritty appl applie ied d to a cylindrical FOS. FOS.
Angularity applied to a surface.
Interpretations • Tolerance zone – zone – two two parallel planes that are perpendicular to the datum plane. • Distan Distance ce betw between een toler toleranc ancee plane plane – specified – specified tolerance value. • Import Important ant criter criteria ia – all elemen elements ts of of the the surfa surface ce must be within the tolerance zone. zone . • Tolerance zone is oriented relative to the datum plane by a basic angle. angle . • Angu Angula lari rity ty tol toler eran ance ce zon zonee limits the flatness of toleranced feature
Inspection of Angularity
Angularity control applied to a diametrical FOS
Interpretations • Tolerance zone – zone – aa cylinder. • Diameter Diameter of of the tolerance zone – specified – specified tolerance value. value. • The axis of the toleranced feature must be within the tolerance zone. • Tolerance Tolerance zone is orien oriented ted relative relative to the the datum datum plane by a basic a basic angle. • An implied 90 deg basic angle exists in other direction
Indirect angularity control Angularity can be indirectly controlled by – • Po Posi siti tion on tol toler eran ance ce.. • Runout tolerance. • Pr Prof ofil ilee tol toler eran ance ce..
Parallelism Control • Parallelism is the condition of a surface, center plane, or axis being exactly parallel to the datum. • An parallelism An parallelism control is a geometric tolerance that limits the amount a surface, center plane, or axis is permitted is permitted to vary from being parallel being parallel to the datum.
Parallelism Tolerance Zones 1.
Two pa parallel pl planes.
2.
A cylinder.
Parallelism Applications • Para Parall llel elis ism m appl applie ied d to a surface. • Para Parall llel elis ism m appl applie ied d to a cylindrical FOS.
PARALLELISM
SYMBOL :-
ZONE OF TOLERANCE TOLERANCE :- CYLINDER
Parallelism Applied To a Surface
Interpretations • Tolerance zone – zone – two two parallel planes that are parallel to the datum plane. • Tole Tolera ranc ncee zone zone is is loc locat ated ed within the limits of size dimension. • Distan Distance ce betw between een toler toleranc ancee plane plane – specified – specified tolerance value. • Import Important ant criter criteria ia – all elemen elements ts of of the the surfa surface ce must be within the tolerance zone. • Para Parall llel elis ism m tole tolera ranc ncee zone zone limits the flatness of toleranced feature.
Inspection
Parallelism Applied to a FOS at MMC
Interpretation • Tolerance zone – zone – aa cylinder that cylinder that is parallel to the datum plane. • Diame Diameter ter of the tolera tolerance nce zone zone – specified – specified tolerance value. • The axis of the diameter must diameter must be within the tolerance zone. • A bonus tolerance is permissible. • A fixed gauge may be used to verify the parallelism control. • Para Parall llel elis ism m tole tolera ranc ncee zone zone limits flatness of the toleranced feature.