## Interpretations of limits of size in relation to form

There are two ways of interpreting the limits of size of an individual feature, which are known by;

1 The Principle of Independency, where the limits of size apply to local two point measurements of a feature regardless of form.

2 The Envelope Requirement, also known as The Taylor Principle, where the limits of size of an individual feature are intended to have a mutual dependency of size and form.

Extracted from BS 4500 : 1969

BRITISH STANDARD

SELECTED ISO FITS—HOLE BASIS

Data Sheet

4500A

Issue 1. February 1970 confirmed August 1985

Diagram to scale for 25 mm diameter f

Clearance fits

Nominal sizes

Tolerance

Tolerance

Tolerance

Tolerance

Tolerance

Tolerance

Tolerance

Tolerance

Tolerance

Tolerance

Nominal sizes

Over

To

H11

c11

H9

d10

H9

e9

H8

f7

H7

g6

H7

h6

H7

k6

H7

n6

H7

p6

H7

s6

Over

To

mm

mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

mm

mm

_

3

+ 60 0

0

+ 20 + 14

_

3

- 145

- 78

+ 30 0

0

+ 27 + 19

3

6

6

10

+ 90 0

- 80 - 170

0

+ 32 + 23

6

10

10

- 205

- 120

0

+ 39 + 28

10

18

18

- 92

+ 33 0

0

+ 48 + 35

18

30

30

- 280

+ 62

- 80

+ 62

- 50

+ 39

- 25

+ 25

- 9

+ 25

- 16

+ 25

+ 18

+ 25

+ 33

+ 25

+ 42

+ 25

+ 59

30

40

40

- 290

0

- 180

0

- 112

0

- 50

0

- 25

0

0

0

+ 2

0

+ 17

0

+ 26

0

+ 43

40

50

50

- 330

+ 74

- 100

- 74

- 60

+ 46

- 30

+ 30

- 10

+ 30

- 19

+ 30

+ 21

+ 30

+ 39

+ 30

+ 51

+ 30 0

+ 72 + 53

50

65

- 340

0

- 220

0

- 134

0

- 60

0

- 29

0

0

0

+ 2

0

+ 20

0

+ 32

+ 30 0

+ 78 + 59

65

80

80

100

- 390

+ 87

- 120

- 87

- 72

+ 54

- 36

+ 35

- 12

+ 35

- 22

+ 35

+ 25

+ 35

+ 45

0

+ 93 + 71

80

100

100

120

+ 220 0

- 180 - 400

+ 0

- 260

- 0

- 159

0

- 71

0

- 34

0

0

0

+ 3

0

+ 23

0

+ 37

+ 35 + 0

+ 101 + 79

100

120

120

140

+ 250 0

- 200 - 450

+ 40 0

+ 117 + 92

120

140

140

160

+ 250 0

0

145 305

- 185

- 39

+ 40 0

- 25 0

+ 40 0

+ 28 + 3

+ 40 0

+ 52 + 27

- 40 0

+ 68 + 43

+ 40 0

+ 125 + 100

140

160

160

180

+ 250 0

00

+ 40 0

+ 133 + 108

160

180

180

200

+ 290 0

- 240 530

0

+ 151 + 122

180

200

200

225

0

0

+ 159 + 130

200

225

225

250

+ 290 0

00

0

+ 169 + 140

225

250

250

280

+ 320 0

300 620

+ 130

- 190

+ 130

- 110

+ 81

- 56

+ 52

- 17

+ 52

+ 32

+ 52

- 36

+ 52

+ 66

0

+ 190 + 158

250

280

280

315

+ 320 0

00

0

- 400

0

- 240

0

- 108

0

- 49

0

0

0

+ 4

0

+ 34

0

+ 202 + 170

280

315

315

355

+ 360 0

360 - 720

+ 140

- 210

+ 140

- 125

+ 89

- 62

+ 57

- 18

+ 57

- 36

+ 57

+ 40

+ 57

+ 73

0

+ 226 + 190

315

355

355

400

+ 360 0

400 760

0

- 440

0

- 265

0

- 119

0

- 54

0

0

0

+ 4

0

+ 37

0

+ 62

0

+ 244 + 208

355

400

400

450

+ 400 0

00

+ 155

- 230

+ 155

- 135

+ 97

- 68

+ 63

- 20

+ 63

- 40

+ 63

+ 45

+ 63

+ 80

+ 63

+ 108

+ 63 0

+ 272 + 232

400

450

450

500

+ 400 0

00

0

- 480

0

- 290

0

- 131

0

- 60

0

0

0

+ 5

0

+ 40

0

+ 68

+ 63 0

+ 292 + 252

450

Interference fits

V777A

H 11

Holes h 6

d 10

c 11

Shafts

BRITISH STANDARDS INSTITUTION, 2 Park Street, London, W1A 2BS SBN: 580 05766 6

Extracted from BS 4500 : 1969

BRITISH STANDARD

SELECTED ISO FITS—SHAFT BASIS

Data Sheet

4500B

Issue 1. February 1970

Diagram to + scale for 25 mm. diameter

Clearance fits h 7

Transition fits

Interference fits

Nominal sizes

Nominal sizes

Over

To

h11

C11

h9

D10

h9

E9

h7

F8

h6

G7

h6

H7

h6

K7

h6

N7

h6

P7

h6

S7

Over

To

mm

mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

0.001 mm

mm

mm

3

0 - 60

+ 120 + 60

0 - 25

+ 60 + 20

0 - 25

+ 39 + 14

0 - 10

+ 20 + 6

0 - 6

+ 12 + 2

0

0 - 6

0 - 10

0 - 6

- 14

0 - 6

- 6 - 16

- 24

3

.3

6

0 - 75

+ 145 + 70

0 - 30

+ 78 + 30

0 - 30

+ 50 + 20

0 - 12

+ 28 + 10

0

0

0

+ 3 - 9

0 - 8

- 16

0 - 8

- 27

3

6

6

10

0 - 90

+ 170 + 80

0 - 36

+ 98 + 40

0 - 36

+ 61 + 25

0 - 15

+ 35 + 13

- 9

+ 20 + 5

0

- 9

+ 5 - 10

- 9

- 19

- 9

- 32

6

10

10

18

- 110

+ 205 + 95

0 - 43

+ 120 + 50

0 - 43

+ 75 + 32

0 - 18

+ 43 + 16

0 - 11

+ 24 + 6

0

0 - 11

+ 6 - 12

0 - 11

- 23

0 - 11

- 11 - 29

0 - 11

- 21 - 39

10

18

18

30

- 1030

+ 240 + 110

0 - 52

+ 149 + 65

0 - 52

+ 92 + 40

0 - 21

+ 53 + 20

0 - 13

+ 28 + 7

0

0 - 13

+ 6 - 15

0 - 13

- 48

18

30

30

40

- 1060

+ 280 + 120

0

+ 180

0

+ 112

0

+ 64

0

+ 34

0

+ 25

0

+ 7

0

- 8

0

- 17

0

- 34

30

40

40

50

- 1060

+ 290 + 130

- 62

+ 80

- 62

+ 50

- 25

+ 25

- 16

+ 9

- 16

0

- 16

- 18

- 16

- 33

- 16

- 42

- 16

- 59

40

50

50

65

- 1090

+ 330 + 140

0

+ 220

0

+ 134

0

+ 76

0

+ 40

0

+ 30

0

+ 9

0

- 9

0

- 72

50

65

6.5

80

- 1090

+ 340 + 150

- 74

+ 100

- 74

+ 60

- 30

+ 30

- 19

+ 10

- 19

0

- 19

- 21

- 19

- 39

- 19

- 78

65

80

80

100

- 220

+ 390 + 170

0

+ 260

0

+ 159

0

+ 90

0

+ 47

0

+ 35

0

+ 10

0

- 10

0

- 93

80

100

100

120

- 220

+ 400 + 800

- 87

+ 120

- 87

+ 72

- 35

+ 36

- 22

+ 12

- 22

0

- 22

- 25

- 22

- 45

- 22

- 59

0 - 22

- 66 - 101

100

120

120

140

- 250

+ 450 + 200

- 117

120

140

140

160

- 250

+ 460 + 210

- 100

+ 305 + 145

- 100

+ 185 + 85

0 - 40

+ 106 + 43

0 - 25

+ 54 + 14

0 - 25

+ 40 0

- 28

0 - 25

- 12 - 52

0 - 25

- 28 - 68

- 125

140

160

160

180

- 250

+ 480 + 230

- 133

160

180

180

200

- 290

+ 530 + 240

- 151

180

200

200

225

- 290

+ 550 - 260

- 115

+ 355 + 170

- 115

+ 215 + 100

0 - 46

+ 122 + 50

0 - 29

+ 61 + 15

- 79

- 159

200

225

225

250

- 290

+ 570 + 280

- 169

225

250

250

280

- 320

+ 620 + 300

0

+ 400

0

+ 240

0

+ 137

0

+ 62

0

+ 52

0

+ 16

0

- 14

0

- 36

- 190

250

280

280

315

- 320

+ 650 + 330

- 130

+ 190

- 130

+ 110

- 52

+ 56

- 32

+ 17

- 32

0

- 32

- 36

- 32

- 66

- 32

- 88

- 202

280

315

315

355

- 360

+ 720 + 360

0

+ 440

0

+ 265

0

+ 151

0

+ 75

0

+ 57

0

+ 17

0

- 16

0

- 41

- 226

315

355

355

400

- 360

+ 760 + 400

- 140

+ 210

- 140

+ 125

- 57

+ 62

- 36

+ 18

- 36

0

- 36

- 40

- 36

- 73

- 36

- 98

- 244

355

400

400

450

- 400

+ 840 + 440

0

+ 480

0

+ 290

0

+ 165

0

+ 83

0

+ 63

0

+ 18

0

- 17

0

- 45

- 272

400

450

450

500

- 400

+ 880 + 480

- 155

+ 230

- 155

+ 135

- 63

+ 68

- 40

+ 20

- 40

0

- 40

- 45

- 40

- 80

- 40

- 108

- 292

450

C 11

D 10

Holes

h 11

Shafts

BRITISH STANDARDS INSTITUTION, 2 Park Street, London, WIY 4AA SBN: 580 05567 1

Figure 19.14 a, b and c illustrate the Principle of Independency.

Figure 19.15 a, b, c, d and e illustrate the Envelope requirement.

The drawing indication in Fig. 19.15a shows a linear tolerance followed by the symbol ©. Two functional requirements are implied by the use of the symbol:

1 That the surface of the cylindrical feature is contained within an envelope of perfect form at maximum material size of 0120.

2 That no actual local size shall be less than 0 119,96. An exaggerated view of the feature in Fig. 19.15b, shows that each actual local diameter of the shaft

 — 0,06 o 0,02

0,02 Max

Any cross section showing max. circularity deviation due to lobed form

must remain within the size tolerance of 0,04 and may vary between 0120 and 0119,96

In the examples which follow, the entire shaft must remain within the boundary of the 0120 envelope cylinder of perfect form.

It follows therefore that the shaft will be perfectly cylindrical when all actual local diameters are at the maximum material size of 0120

Maximum material condition. For further reading see ISO 2692 which states that: If for functional and economic reasons there is a requirement for the mutual dependency of the size and orientation or location of the feature(s), then the maximum material principle M may be applied.

Max straightness deviation

0,02 Max

Any cross section showing max. circularity deviation due to lobed form

Max straightness deviation

Fig. 19.14

Envelope

Actual local diameters

 Envelope 'T r- ■ ' "7l 0,04 diameters 0 119,96 Envelope Actual local diameter