Bsi bs a 311 1997 (iso 13921 1996)

BRITISH STANDARD AEROSPACE SERIES BS A 311 1997 ISO 13921 1996 Aerospace — Screws, 100° reduced countersunk head, internal offset cruciform ribbed or unribbed drive, normal shank, short or medium leng[.]

Aerospace —

ICS 4 0 0.2

This Bri sh Stan ard, ha ing

b en pre ared u der the

directon of the Eng ine ring

Sector Bo rd,was published

u der the authoriy of the

Stan ards Bo rd an comes

into efect on

1 Mar h 1 9

© BSI 1 -1 9

The folowing BSI references

relate to the work on this

stan ard:

Commi e reference ACE/12

Draft for comment 9 / 71 7 0 DC

ISBN 0 5 0 2 6 8 1

The prep ration of this British Stand rd was entrusted b Technical

Commit e ACE/12, Aerosp ce fastener and fastening sy stems, upon which

the folowing bodies were represented:

British Industrial Fastener Fed eration

Ministry of Defence

Society of British Aerosp ce Comp nies

Am endm ents is ued sinc publ cation

Pag e

National foreword

This British Stand rd has be n prep red b Technical Commit e ACE/12 It is

id entical with ISO 13 2 :19 6, A er ospa ce — Scr ews, 10 ° r ed uc d cou ter su k

hea d , inter na l o fs t cr ucifr m r ib ed o u r ib ed d r ive, nor ma l sha nk, shor t o

med ium length MJ thr ea d s, meta llc ma ter ia l, coa ted o uncoa ted , str ength

cla ss s le s tha n o equa l to 1 100MPa — Dimensions, publ shed b the

International Org anization for Stand rdization ( ISO)

A British Stand ard d oes not purport to includ e al the neces ary prov isions of a

contract User of British Stand rd s are responsible for their cor ect a plcation

Com pl anc with a British Standard does not ofitself confer im m unity

f om leg al o l g ations

Cros - referenc s

Inte national s and rd Cor esp nding British Stand rd

ISO 3 5 :19 2 BS 2A 231:19 3 R oled thr ea d s fr bols Lea d a nd

r unout r equir ements

( Id entical

ISO 5 5 -2:19 8 BS 629 A er ospa ce MJ thr ea d s

Part 2:19 4 Limi d imensions f r bol s a nd n ts

( Id entical

ISO 7 13:19 4 BS 2A 29 :19 5 B ols a nd s r ews, metr ic Toler a nc s o

f r m a nd posiion

( Id entical

Sum mary of pag es

This document comprises a f ont cov er, an insid e font cov er, p g es i an i ,

p g es1 an 2, an insid e b ck cov er and a b ck cov er

This stand rd has be n up ated ( se copy rig ht d ate) an ma hav e ha

amendments incorporated This wi l be ind icated in the amendment ta le on

theinside f ont cov er

1 Scope

This International Stand rd specifies the

dimensions of 10 ° red uced counter u k hea

s rews with internal ofset c uciform rib ed or

u rib ed d riv e, close or larg e tolerance normal

shank, short or medium leng th MJ threa s, in

metal c material, coated or uncoated, with streng th

clas es les than or equal to 1 10 MPa

This International Stand ard is a plca le to the

compiation of aerosp ce product stand rd s

2 Normative r f r nces

The fol owing stand ard s contain prov isions which,

throug h reference in this text, constitute prov isions

of this International Stand ard At the time of

publcation, the editions ind icated were v ald All

stand ards are subject to rev ision, and p rties to

ag re ments b sed on this International Stand rd

are encourag ed to inv estig ate the pos ibi ty of

a ply ing the most recent editions of the stand rds

indicated below Member of IEC and ISO maintain

reg ister of cur ently v ald International Stand ards

ISO 28 -2:19 8, ISO system o lmis a nd fis —

Pa r t 2: Ta ble o sta nd a r d toler a nc gr a d es a nd

lmi d evia tions fr hole a nd sha fts

ISO 3 5 :19 2, A er ospa ce — R oled thr ea d s fr

bols — Lea d a nd r unout r equir ements

ISO 5 5 -2:19 8, A er ospa ce — MJ thr ea d s —

Pa r t 2: Limi d imensions fr bols a nd n ts

ISO 7 13:19 4, A er ospa ce — B ols a nd s r ews,

metr ic — Toler a nc s o fr m a nd posiion

ISO 1427 :—

1)

A er ospa ce — Dr ive , inter na l, o fs t

cr ucif r m, r ib ed — Metr ic s r ie

ISO 1427 :—

1)

A er ospa ce — Dr ive , inter na l, o fs t

cr ucif r m — Metr ic s r ie

3 Config uration and dimensions

Se Fig ure 1 an Ta le 1 Dimensions and

tolerances are ex res ed in mi imetres They are

a plca le after any sur ace coating , but before the

a plcation of any lubricant

Detai s of form not stated are left to the

man facturer’s dis retion

Tolerances of form and position are specified

in ISO 7 13

1)

To b published

Fig ure 1

Ta le 1

Ta le 1

Diam ete

co e

T r a a

D

1

D

2 D

3 D

4

1

nom

Co ted sc ews Unco ted

sc ews

– 0,010

– 0,0 5

6,25 5,4 4,82 0,9 3 to 4

– 0,0 8

1 ,5 1 ,3 10,28 1,9 6 to 8

10 MJ10 × 1,25 – 4h6h10

h1 d

f7 d

h1 d

15,6 14,4 1 ,8 2,3 8 to 10

14 MJ14 × 1,5 – 4h6h 14

– 0,016

– 0,0 1

2 ,8 20,6 18 3,32 10 to 14

2 0 MJ20 × 1,5 – 4h6h 20

– 0,020

– 0,0 5

31,2 3 25,71 4,7 1 to 20

L

2

L

3

D

5

6 Y

Diam ete

co e

co e

short m edium short m edium nom tol nom tol m in H1

d

1,5

7

R5

1,9

2,4

R8

0,6 R10

R1

a

In ac ordance wih ISO 5 5 -2

b

For co ted or u co ted srews wih a close tolerance on D

1 ,the thre d major diameter, d, shal b

d ma = D

1 min – 0,0 5

c

Inc ements:

1 for L

1

≤ 3

2 for 3 < L

1

≤ 1 0

4 for L

1

> 1 0

If g re ter leng ths are re uired, the shal b chosen using these inc ements

d

Se ISO 2 6-2

e

In acordance wih ISO 1 2 5 or ISO 1 2 6

0

– 0,0

0

– 0,5

0

– 0,2

0

– 0,3

B

3 9Ch isw i ckH i g hR oa

Lon don

W44 AL

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