1、BRITISH STANDARD BS EN 27721:1992 ISO 7721:1983 Countersunk head screws Headconfiguration and gaugingBSEN27721:1992 This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Policy Committee, waspublished under the authorityof the Standards Boarda
2、nd comes into effect on 1 May 1992 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference GME/9 Announced in BSI News December1991 ISBN 0 580 20814 1 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision this Eu
3、ropean Standard was prepared, comprises the national standards organizations of the following countries: Austria Oesterreichisches Normungsinstitut Belgium Institut belge de normalisation Denmark Dansk Standardiseringsraad Finland Suomen Standardisoimisliito, r.y. France Association franaise de norm
4、alisation Germany Deutsches Institut fr Normung e.V. Greece Hellenic Organization for Standardization Iceland Technological Institute of Iceland Ireland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherlands Ned
5、erlands Normalisatie-instituut Norway Norges Standardiseringsforbund Portugal Instituto Portugus da Qualidade Spain Asociacin Espaola de Normalizacin y Certificacin Sweden Standardiseringskommissionen i Sverige Switzerland Association suisse de normalisation United Kingdom British Standards Institut
6、ion Amendments issued since publication Amd. No. Date CommentsBSEN27721:1992 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 Text of EN 27721 3 National annex NA (informative) Committees responsible Inside back coverBSEN27721:1992 ii BSI 11-19
7、99 National foreword This British Standard has been prepared under the direction of the General Mechanical Engineering Standards Policy Committee and is the English language version of EN27721:1991, “Countersunk head screws Head configuration and gauging”, published by the European Committee for Sta
8、ndardization (CEN). It is identical with ISO7721:1983, published by the International Organization for Standardization (ISO). EN27721:1991 was produced as a result of international discussion in which the UK took an active part. A British Standard does not purport to include all the necessary provis
9、ions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theEN title page,
10、 pages 2 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 27721 October 1991 UDC 621.
11、882.215.091.6:620.1 Descriptors: Fasteners, screws, countersunk head screws, dimensions, dimensional measurements, standard gauges English version Countersunk head screws Head configuration and gauging (ISO 7721:1983) Vis tte fraise Configuration de la tte et vrification par calibre (ISO 7721:1983)
12、Senkschrauben Gestaltung und Prfung von Senkkpfen (ISO 7721:1983) This European Standard was approved by CEN on 1991-10-10. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard wit
13、hout any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language
14、made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Ita
15、ly, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels CEN 1991 Copyright reserved to all CEN membe
16、rs Ref. No. EN 27721:1991 EEN27721:1991 BSI 11-1999 2 Foreword In 1990, ISO7721:1983 was submitted to the CENP.Q.-procedure. Following the positive result of the P.Q., CEN/BT agreed to submit ISO7721:1983 without modifications to Formal Vote. In accordance with the Common CEN/CENELEC Rules, the foll
17、owing countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Contents Page Foreword 2 1 Scope and field of application 3 2
18、 Head configuration 3 3 Gauging method 4 Annex Calculation basis for the maximum head diameter of countersunk heads for screws 5 Table 1 3 Table 2 4EN27721:1991 BSI 11-1999 3 1 Scope and field of application This International Standard specifies the characteristics of head configurations of slotted
19、and recessed countersunk head screws, and recommends a gauging method for the head dimensions laid down in the respective product standards. 2 Head configuration Table 1 Dimensions in millimetres Thread size, d metric M 1,6 M 2 M 2,5 M 3 M 3,5 M 4 M 5 M 6 M 8 M 10 M 12 M 14 M 16 M 18 M 20 tapping ST
20、 2,2 ST 2,9 ST 3,5 ST 4,2 ST 4,8 ST 5,5 ST 6,3 ST 8 ST 9,5 d k theoretical max. 3,6 4,4 5,5 6,3 8,2 9,4 10,4 11,5 12,6 17,3 20 24 28 32 36 40 min. 3,3 4,1 5,1 5,9 7,7 8,9 9,8 10,9 11,9 16,5 19,2 23,1 27 30,8 34,7 38,5 actual max. 3 3,8 4,7 5,5 7,3 8,4 9,3 10,3 11,3 15,8 18,3 22 25,5 29 32,5 36 min.
21、2,7 3,5 4,4 5,2 6,9 8 8,9 9,9 10,9 15,4 17,8 21,5 25 28,5 31,9 35,4 F max. 0,15 0,15 0,2 0,2 0,25 0,25 0,3 0,3 0,35 0,4 0,4 0,45 0,5 0,6 0,65 0,75 k max. (ref.) metric 1 1,2 1,5 1,65 2,35 2,7 2,7 3,3 4,65 5 6 7 8 9 10 tapping 1,1 1,7 2,35 2,6 2,8 3 3,15 4,65 5,25 EN27721:1991 4 BSI 11-1999 3 Gauging
22、 method Table 2 Dimensions in millimetres Thread size, d metric M 1,6 M 2 M 2,5 M 3 M 3,5 M 4 M 5 M 6 M 8 M 10 tapping ST 2,2 ST 2,9 ST 3,5 ST 4,2 ST 4,8 ST 5,5 ST 6,3 ST 8 ST 9,5 D max. 3,6 4,4 5,5 6,3 8,2 9,4 10,4 11,5 12,6 17,3 20 min. 3,55 4,35 5,45 6,25 8,15 9,35 10,35 11,45 12,55 17,25 19,95 d
23、 a max. 1,84 2,36 2,74 3,3 3,9 4,4 5,5 5,68 6,6 8,54 10,62 min. 1,74 2,26 2,64 3,2 3,8 4,3 5,4 5,58 6,5 8,44 10,52 F max. 0,15 0,15 0,2 0,2 0,25 0,25 0,3 0,3 0,35 0,4 0,4 min. 0,14 0,14 0,19 0,19 0,24 0,24 0,29 0,29 0,34 0,39 0,39 d h min. 2,68 3,48 4,38 5,18 6,88 7,98 8,88 9,88 10,88 15,38 17,78 ma
24、x. 2,7 3,5 4,4 5,2 6,9 8 8,9 9,9 10,9 15,4 17,8 NOTEDiameters d amin. are based on fillet radius r = 0,25 d for metric screws and0,4d for tapping screws.EN27721:1991 BSI 11-1999 5 Annex Calculation basis for the maximum head diameter of countersunk heads for screws Basic assumptions 1. When heads ar
25、e being formed with minimum heights, the clearance between punch and die will have minimum values C as follows: 2. When heads are being formed with maximum heights and maximum actual diameters, the peripheral contour of the head and the clearance between punch and die will be as shown in the above d
26、iagram. From the diagram: d kactual max. = d ktheoretical max. 2s = d ktheoretical max. 1,66 (F + C) It is also assumed that the relationship between theoretical and actual diameters is roughly constant: d kactual min. d ktheoretical min. (d ktheoretical max. d kactual max.) where d ktheoretical min
27、. = d ktheoretical max. 2 F. Thread size, d metric M 1,6 M 2 M 2,5 M 3 M 3,5 M 4 M 5 M 6 M 8 M 10 tapping ST 2,2 ST 2,9 ST 3,5 ST 4,2 ST 4,8 ST 5,5 ST 6,3 ST 8 C min. 0,2 0,22 0,28 0,3 0,32 0,35 0,38 0,4 0,42 0,5 0,63 s = p r but p and r = LM = (F + C) sec 45 = LM tan 22 30 = (F + C) sec 45 tan 22 3
28、0 s = (F + C) sec 45 (F + C) sec 45 tan 22 30 = (F + C) (sec 45 ) (1 tan 22 30) . 0,83 (F + C)6 blankBSEN27721:1992 BSI 11-1999 National annex NA (informative) Committees responsible The United Kingdom participation in the preparation of this European Standard was entrusted by the General Mechanical
29、 Engineering Standards Policy Committee (GME/-) to Technical Committee GME/9 upon which the following bodies were represented: BEAMA Ltd. British Constructional Steelwork Association Ltd. British Industrial Fasteners Federation British Railways Board British Steel Industry British Steel Industry (Wi
30、re Section) Gauge and Tool Makers Association Ministry of Defence Society of Motor Manufacturers and Traders Ltd. Washer Manufacturers Association of Great Britain The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Furniture Manufact
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