BS A 55_AND_56-1951__A3-2012

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BS A 55 AND 56:1951+A3:2012

BRITISH STANDARDS INSTITUTION

BRITISH STANDARD SPECIFICATIONS FOR

GRUB SCREWS

FOR AERONAUTICAL PURPOSES

SCOPE

1. These British Standards specify the material, dimen-

sions and finish of grub screws for aeronautical

purposes.

CAUTION. BS A 55 grub screws have cadmium as a

plating material which has been restricted and/or banned

for use in many countries owing to environmental and

health concerns; they should not be used in new product

designs. Local officials should be consulted about any

concerns on using cadmium-plated parts.

MATERIAL

2. The grub screws shall be machined from the

appropriate material specified in Table 1.

FREEDOM FROM DEFECTS

2A. a. The grub screws shall be free from harmful

defects

b. Grub screws may be rejected at any time for faults

in, or revealed by, manufacture although they have been

made from material passed previously for chemical

composition and mechanical tests.

PROTECTIVE FINISH

3. Finished grub screws in En. 1A material shall be

uniformly coated with cadmium in accordance with the

latest issue of Def Stan 03-19 or BS EN 2133.

DIMENSIONS

4. The grub screws, after coating, where an anti-corrosion

coating is applied, shall conform to the dimensions

specified in Table 2.

SCREW THREADS

5. The grub screws shall, for their full screwed length,

have their screw threads in accordance with the sizes

and tolerances laid down in the appropriate British

Standard specification as follows:—

a. B.S.F. grub screws. The screw threads on all B.S.F.

grub screws shall be in accordance with BS 84:2007,

and shall conform to the “medium class” limits and

tolerances specified in Table 10 of that standard.

b. B.A. grub screws. (i) The screw threads on all B.A.

grub screws shall conform (after coating, if required) to

the limits and tolerances specified for close class bolts in

BS 93:2008, ‘British Association (B.A.) screw

threads’.

(ii) The minimum major, effective, and minor diameters

of threads of grub screws required to be coated may,

before coating, be 0.001 in smaller than the minimum

dimensions specified in BS 93:2008, Table 2, in

order to avoid any undue restriction of the tolerance

allowed for screwing.

(iii) In view of the tendency for closely fitting threads

in stainless steel to seize when tightened together, the

maximum major, effective, and minor diameters of

stainless steel grub screws shall be 0.001 in below the

maximum specified in BS 93:2008, Table 2. The

full close class tolerance specified in Table 2 that

standard shall, however, be allowed.

IDENTIFICATION

6. The grub screws shall be identified for ordering

purposes by the number of the relevant British Standard

as shown in Table 1, together with the appropriate part

number shown in Table 2, e.g. a cadmium plated

freecutting steel 2 B.A. grub screw of length ⅝ in., is

A. 55 C. 10.

TABLE 1

BRITISH STANDARD NUMBERS AND

MATERIALS

British Standard

Number

Material

Description Specification

A. 55 Free-cutting

steel

BS EN 10087-2 †

11SMn30 (1.0715)

A. 56 Stainless

steel

BS EN 10088-3 †

X5CrNi18-10(1.4301) or

X5CrNiMo17-12-2(1.4401) or

X8CrNiS18-9(1.4305) or

X2CrNi18-9(1.4307) or

X3CrNiMo17-13-3(1.4436) or

X2CrNiMo17-12-2(1.4404) or

X6CrNiMoTi17-12-2(1.4571)

or X17CrNi16-2(1.4057) or

X6CrNiTi18-10(1.4541)

† Latest issue.

Footnote deleted.

ICS: 49.030.20

TABLE 2. DIMENSIONS AND PART NUMBERS

Nominal

size

Diameter

Width of slot

Depth of slot

Standard Length L in inches –0.000

and part numbers

min. max. min. max. 3⁄16 ¼5⁄16 ⅜½⅝¾⅞

6 B.A.

0.110

0.025

0.031

0.030

0.050 A3 A4 A5 A6 A8 — — —

4 B.A. 0.142 0.029 0.035 0.040 0.065 — B4 B5 B6 B8 B10 — —

2 B.A. 0.185 0.037 0.043 0.050 0.080 — — C5 C6 C8 C10 C12 —

¼ in B.S.F. 0.250 0.054 0.060 0.070 0.100 — — — E6 E8 E10 E12 E14

This British Standard is published by BSI Standards Limited, under licence from The British Standards

Institution.

THIS BRITISH STANDARD, having been approved by the Aircraft Industry Standards Committee and

endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of

the General Council of the Institution on 30th March, 1951.

BS A 55 and 56:1951+A3:2012 supersedes BS A 55 and 56:1951 (incorporating Amendment No. 2:1958),

which is withdrawn.

The start and finish of text introduced or altered by Amendment No.3:2012 is indicated in the text by

tags and. Minor editorial changes are not tagged. Changes from Amendments No.1 and No.2 are

not shown.

This publication does not purport to include all the necessary provisions of a contract. Users are

responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

BS A 55 AND 56:1951+A3:2012

+0.030

BS A 55 AND 56:1951+A3:2012

ISBN: 978 0 580 76859 0

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摘要：

This document covers the British Standards BS A 55, BS A 56, and the associated amendment A3 issued in 2012, providing essential technical specifications for aerospace components. The standard defines critical dimensions, material requirements, and t

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