1、BRITISH STANDARDBS 7751-2: 1994Incorporating Amendment No. 1Prevailing torque type wire thread inserts Part 2: Specification for ISO metric fine pitch threadsg49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g5
2、5g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58ICS 21.040.10BS7751-2:1994This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15 Septe
3、mber 1994The following BSI references relate to the work on this standard:Committee reference GME/9Draft for comment 92/84543 DCISBN 0 580 23312 XCommittees responsible for this British StandardThe preparation of this British Standard was entrusted by the General Mechanical Engineering Standards Pol
4、icy Committee (GME/-) to Technical Committee GME/9, upon which the following bodies were represented:BEAMA Ltd.British Constructional Steelwork Association Ltd.British Industrial Fasteners FederationBritish Steel IndustryBritish Steel Industry (Wire Section)Gauge and Tool Makers AssociationSociety o
5、f Motor Manufacturers and Traders Ltd.Washer Manufacturers Association of Great BritainThe following bodies were also represented in the drafting of the standard, through subcommittees and panels:Defence Manufacturers AssociationGeneral Municipal Boilermaker and Allied Trades UnionScrew Thread Tool
6、Manufacturers AssociationSociety of British Aerospace Companies LimitedAmendments issued since publicationAmd. No. Date Comments16654 31 October 2006 Changed values in Tables 2 and 3 BSI 2006BS7751-2:1994iContentsPageCommittees responsible Inside front coverForeword ii1 Scope 12 References 13 Defini
7、tions 14 Dimensions 15 Material 56 Finish 57 Insert selection 58 Installation 59 Marking 6Annex A (informative) Insert selection 8Figure 1 Insert wire profile in finished coiled state 2Figure 2 Dimensions of insert in free (unfitted) state 4Figure 3 Position of locking element in fitted insert 5Figu
8、re 4 Insert in fitted state 7Table 1 Dimensions of insert wire profile in finished coiled state 2Table 2 Dimensions of insert in free (unfitted) state 3Table 3 Position of locking element in fitted insert 4Table 4 Insert fitted length 5Table A.1 Recommended nominal lengths of insert to be inserted i
9、nto a material of a given shear strength that can be used with a bolt of a certain property class 8List of references Inside back cover BSI 2006BS7751-2:1994iiForewordThis Part of BS7751 has been prepared under the direction of the General Mechanical Engineering Standards Policy Committee.It is a Pa
10、rt of a series for prevailing torque wire thread inserts.Summary of pagesThis document comprises a front cover, an inside front cover, pages i and ii, This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the in
11、side front cover.Compliance with a British Standard cannot confer immunity from legal obligations. BSI 2006This document does not purport to include all the necessary provisions of a BS7751-1 provides a specification for ISO metric coarse pitch threads.pages1 to 8, an inside back cover and a back co
12、ver.contract. Users are responsible for its correct application.BS7751-2:199411 ScopeThis Part of BS7751 specifies requirements for prevailing torque wire thread inserts which, when fitted into an appropriately prepared hole, will:a) provide ISO metric fine pitch female threads of tolerance class 5H
13、 or 6H in the free running coils with sizes from M8 1to M24 2 inclusive;b) accept ISO metric male threads conforming to BS3643-1:1981 and BS3643-2:1981;c) give a frictional resistance to rotation of a male threaded component assembled with it, of such a value that the insert assembly is considered s
14、elf locking;d) operate successfully in the temperature range50C to +300C.NOTEISO metric MJ threads conforming to BS6293-1 and BS6293-2 may be used with these inserts.2 References2.1 Normative referencesThis Part of BS7751 incorporates, by dated or undated reference, provisions from other publication
15、s. These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this Part of BS7751 only when
16、 incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments.2.2 Informative referencesThis Part of BS7751 refers to other publications that provide information or guidance. Editions of these public
17、ations current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions.3 DefinitionsFor the purposes of this Part of BS7751, the following definitions apply.3.1 prevailing torque type wire thread inserta wire thread insert which,
18、 when installed in a hole tapped in accordance with BS4377:1991, will provide a female thread containing a prevailing torque element. The frictional resistance of the prevailing torque element is of such a value that the insert is considered screw locking3.2 prevailing torque element (locking device
19、)the coil(s) of the insert designed to impose friction between the insert and the installed male thread3.3 prevailing (locking) torquethe torque to be applied to maintain rotation of the male part relative to the installed insert when the assembly is under no axial load and the thread of the male pa
20、rt is fully engaged with the locking elementNOTEThere is no permanence of prevailing torque for indefinite reusability. The reusability should be determined by the application.4 Dimensions4.1 Insert wire profileThe dimensions of the insert wire profile when it is in the finished coiled state shall b
21、e in accordance with Table 1 and Figure 1.4.2 Unfitted insertThe dimensions of an unfitted insert shall be in accordance with Table 2 and Figure 2.The surface roughness of the insert wire in the finished coiled state shall not exceed 8 m.NOTE 1Minimum contact pressure is to be used when measuring th
22、e insert outside diameter to avoid distortion of the insert.NOTE 2Ignore any reduced leading coil if it is present when measuring the insert outside diameter.NOTE 3Since the relationship between the insert unfitted length and the number of coils is interdependent with coiling tension, the number of
23、coils N is given for identification purposes only.NOTE 4The notch depth is to be sufficient to allow the tang to be broken off cleanly with a sharp blow after installation and then permit the through passage of a male threaded component.4.3 Locking coils (prevailing torque element)The coils which fo
24、rm the locking element shall be contained within the limits specified inTable 3 and Figure 3.NOTEThe number, shape and orientation of the locking coils, the spacing between the locking coils and the number of faces on the locking coils are the sole responsibility of the manufacturer. BSI 20064.BS775
25、1-2:19942Table 1 Dimensions of insert wire profile in finished coiled stateDimensions in millimetresThread size X W T Ediameter pitch min. max. min. max. min. max. min. max.M8 1 0.744 0.757 0.986 1.082 0.716 0.874 0.625 0.650M10 1.25 0.935 0.947 1.242 1.354 0.897 1.095 0.787 0.813M12 1.25 0.935 0.94
26、7 1.242 1.354 0.897 1.095 0.787 0.813M14 1.5 1.123 1.138 1.509 1.623 1.077 1.313 0.947 0.975M16 1.5 1.123 1.138 1.509 1.623 1.077 1.313 0.947 0.975M18 1.5 1.123 1.138 1.509 1.623 1.077 1.313 0.947 0.975M20 1.5 1.123 1.138 1.509 1.623 1.077 1.313 0.947 0.975M22 1.5 1.123 1.138 1.509 1.623 1.077 1.313
27、 0.947 0.975M24 2 1.501 1.516 2.012 2.164 1.435 1.750 1.265 1.298NOTESee Table 1 for dimensions.Figure 1 Insert wire profile in finished coiled state BSI 2006BS7751-2:19943Table 2 Dimensions of insert in free (unfitted) stateDimensions in millimetresThread size Outside diameter D Nominal lengthNo. o
28、f coils N Tang length LSpace for tang Mdiameter, d pitch min. max. min. max. min. max.1d1.5dM8 1 10.25 2d2.5d3d1d 5.61.5dM10 1.25 12.65 2d2.5d3d1d 7.01.5dM12 1.25 15.00 2d2.5d3d1d1.5d 11.6M14 1.5 2d2.5d3d1d1.5d 13.4M16 1.5 2d2.5d3d1d1.5dM18 1.5 2d2.5d3d1d 11.01.5dM20 1.5 2d2.5d3d9.712.1014.316.5518.
29、9021.0523.15 24.22219.917.75.69.112.716.219.99.212.916.220.111.415.620.021.26.911.115.319.723.98.012.917.722.427.49.214.720.125.631.110.516.622.628.634.76.19.613.216.820.46.19.813.417.020.67.511.916.120.524.77.415.920.224.58.518.223.027.99.715.220.626.131.617.123.129.135.24.856.057.158.279.4510.5211
30、.502.202.702.703.273.273.273.27 BSI 2006BS7751-2:19944Table 2 Dimensions of insert in free (unfitted) stateTable 3 Position of locking element in fitted insertDimensions in millimetresThread size Outside diameter D Nominal lengthNo. of coils N Tang length LSpace for tang Mdiameter, d pitch min. max.
31、 min. max. min. max.1d1.5dM22 1.5 25.55 2d2.5d3d1d 9.2 9.81.5dM24 2 29.10 2d2.5d3d1)See note 4 to 4.2.2)See note 3 to 4.2.Figure 2 Dimensions of insert in free (unfitted) stateDimensions in millimetresThread size Nominal thread length1d 1.5d 2d 2.5d 3ddiameter, d pitch Amin.Bmax.Amin.Bmax.Amin.Bmax.
32、Amin.Bmax.Amin.Bmax.M8 1M10 1.25M12 1.25M14 1.5M16 1.5M18 1.5M20 1.5M22 1.5M24 226.828.1011.6 12.118.124.531.43814.820.125.631.018.725.43238.615.220.626.131.512.7714.053.274.332.0 5.2 4.0 7.2 6.0 9.25 6.0 11.25 13.22.5 6.6 5.0 9.0 7.5 11.6 7.5 14.1 7.56.016.63.5 7.6 6.5 10.6 9.5 13.6 9.5 16.6 19.64.
33、0 8.9 7.5 12.4 11.0 15.9 11.0 19.4 11.0 22.95.0 9.9 9.0 13.9 13.0 17.9 13.0 21.9 13.0 25.96.0 10.9 10.5 15.3 15.0 19.9 15.0 24.4 15.0 25.97.0 11.9 12.0 16.9 17.0 21.9 17.0 26.9 17.0 31.98.0 12.9 13.5 18.4 19.0 23.9 19.0 29.4 19.0 34.98.0 14.5 14.0 20.5 20.0 26.5 20.0 32.5 20.0 38.5 BSI 20069.5(conti
34、nued)BS7751-2:199455 MaterialThe insert wire shall be manufactured from austenitic stainless steel of the type characterized as 18% chromium, 8% nickel.NOTEThe precise composition is at the manufacturers discretion.6 FinishThe finished coiled insert shall be in the natural condition.7 Insert selecti
35、onThe length of insert selected shall be such that no stripping of the tapped hole in the parent metal into which the insert is fitted occurs before tensile failure of the male threaded part that is screwed into the fitted insert.NOTEAnnex A gives guidance on the selection of insert length required
36、for different grades of bolt and tapped parent material strengths.8 InstallationThe insert shall be capable of being installed into threaded holes prepared in accordance with BS4377:1991.NOTE 1The class of fit produced by the installed insert, e.g. 5H or 6H, is dependent upon the class of fit of the
37、 threaded hole into which it is installed as well as the dimensional accuracy of the insert. The users attention is therefore drawn to the importance of maintaining the tolerance requirements of BS4377:1991.The insert fitted length shall be as given inTable 4 and Figure 4.NOTE 2It is recommended tha
38、t the insert is fitted at least a distance equal to half of its thread pitch below the surface (seeFigure 4).Table 4 Insert fitted lengthFigure 3 Position of locking element in fitted insertDimensions in millimetresThread size Nominal lengthFitted lengthdiameter, d pitch min. max.1d 7.0 7.51.5d 11.0
39、 11.5M8 1 2d 15.0 15.52.5d 19.0 19.53d 23.0 23.51d 8.75 9.3751.5d 13.75 14.375M10 1.25 2d 18.75 19.3752.5d 23.75 24.3753d 28.75 29.3751d 10.75 11.3751.5d 16.75 17.375M12 1.25 2d 22.75 23.3752.5d 28.75 29.3753d 34.75 35.3751d 12.50 13.251.5d 19.50 20.25M14 1.5 2d 26.50 27.252.5d 33.50 34.253d 40.50 4
40、1.251d 14.50 15.251.5d 22.50 23.25M16 1.5 2d 30.50 31.252.5d 38.50 39.253d 46.50 47.251d 16.50 17.251.5d 25.50 26.25M18 1.5 2d 34.50 35.252.5d 43.50 44.253d 52.50 53.251d 18.50 19.251.5d 28.50 29.25M20 1.5 2d 38.50 39.252.5d 48.50 49.253d 58.50 59.25 BSI 2006BS7751-2:19946Table 4 Insert fitted lengt
41、h 9 MarkingWhen designating for the purpose of an enquiry or order, the following information shall be given:a) general product description, i.e. wire thread insert;b) the number and date of this British Standardi.e. BS7751-2:19941);c) the letter “M” indicating that the product is ISO metric;d) the
42、female thread diameter of the fitted insert in millimetres;e) the nominal length of the insert,i.e. 2.5d.EXAMPLE. The designation of a M18 wire thread insert of nominal length1.5d is as follows:Wire thread insert BS7751-2:1994 M18 1.5dDimensions in millimetresThread size Nominal lengthFitted lengthd
43、iameter, d pitch min. max.1d 20.50 21.251.5d 31.50 32.25M22 1.5 2d 42.50 43.252.5d 53.50 54.253d 64.50 65.251d 22.00 23.001.5d 34.00 35.00M24 2 2d 46.00 47.002.5d 58.00 59.003d 70.00 71.001) Marking BS7751-2:1994 on or in relation to a product represents a manufacturers declaration of conformity,i.e
44、. a claim by or on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is solely the claimants responsibility. Such a declaration is not to be confused with third party certification of conformity, which may also be desirable. BSI 2006BS 7751
45、-2:19947Figure 4 Insert in fitted state BSI 2006BS7751-2:19948Annex A (informative) Insert selectionThe standard engineering practice of balancing the tensile strength of the bolt material against the shear strength of the material into which it is screwed applies equally to wire thread inserts.Tabl
46、e A.1 gives a recommendation as to what nominal length of insert will need to be inserted into a material having a certain shear strength, so that when it is used with a bolt of a certain property class, tensile failure of the bolt should occur before the insert is pulled from the material in which
47、it is inserted.Table A.1 assumes that full thread engagement of the male fastener in the insert occurs.The following equation was used as a basis for the recommendations given inTable A.1.whereNOTEIf this equation is used to calculate a value for H and it falls outside the limits given inTable 3, th
48、en the next longest nominal length of insert should be used.Table A.1 is given for guidance only and it remains the responsibility of the user to ensure that the insert nominal length chosen is suitable for the particular application concerned.Table A.1 Recommended nominal lengths of insert to be in
49、serted into a material of a given shear strength that can be used with a bolt of a certain property classH is the fitted length of the insert (in mm);Rm is the nominal tensile strength of bolt used (in MPa);S is the stress area of bolt used (in mm2);Rc is the shear strength of material into which the insert is to be inserted (in MPa);D2 is the mean pitch diameter of the tapped hole in the material in which the insert is to be inserted (in mm);0.5 is an arbitrary coefficient based on shearing of the material in which the ins
