1、BRITISH STANDARD BS 4929-2: 1973 Specification for Steel hexagon prevailing-torque type nuts Part 2: Unified (inch) seriesBS4929-2:1973 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee, was published under the authorityof the Executive Boardon 15 J
2、une1973 BSI 04-1999 The following BSI references relate to the work on this standard: Committee referenceMEE/60 MEE/60/12 Draft for comment69/4811 ISBN 0 580 07651 2 Co-operating organizations The Mechanical Engineering Industry Standards Committee under whose supervision this British Standard was p
3、repared, consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Technical Committee Engineering Equipment Users Association Association of Consulting Engineers Gas Council* Association of Hydraulic Equipment Institution o
4、f Civil Engineers Manufacturers Ltd.* Institution of Gas Engineers Association of Mining Electrical and Institution of Heating and Ventilating Engineers Mechanical Engineers Institution of Mechanical Engineers British Compressed Air Society Institution of Mechanical Engineers British Electrical and
5、Allied Manufacturers (Automobile Division) Association Institution of Plant Engineers British Gear Manufacturers Association Institution of Production Engineers* British Internal Combustion Engine London Transport Executive Manufacturers Association Machine Tool Trades Association* British Mechanica
6、l Engineering Confederation Ministry of Defence British Pump Manufacturers Association Ministry of Defence, Army Department British Steel Industry* National Coal Board* Crown Agents for Overseas Governments and National Physical Laboratory (Department of Administrations Trade and Industry) Departmen
7、t of Employment Process Plant Association Department of the Environment* Railway Industry Association of Great Britain Department of Trade and Industry Royal Institute of British Architects Department of Trade and Industry National Telecommunications Engineering Engineering Laboratory* Manufacturing
8、 Association Electricity Council the Central Electricity Generating Board and the Area Boards in England and Wales The Government departments and scientific and industrial organizations marked with an asterisk in the above list together with the following, were directly represented on the committee
9、entrusted with the preparation of this British Standard: Black Bolt and Nut Association of Post Office Great Britain Power Generation Association British Bolt. Nut. Screw and Rivet Federation Precision Bolt and Nut Institute British Constructional Steelwork Association Rolled Thread Screw Associatio
10、n British Railways Board Scientific Instrument Manufacturers Constructional Steel Research and Association of Great Britain Development Organisation Society of Motor Manufacturers and Traders Ltd. Fasteners and Turned Parts Institute Washer Manufacturers Association of Institute of iron and Steel Wi
11、re Manufacturers GreatBritain Ministry of Defence, Navy Department Individual Manufacturers Amendments issued since publication Amd. No. Date of issue CommentsBS4929-2:1973 BSI 04-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Definition 1 3 Property class
12、 designation system 1 4 Material and manufacture of steel nuts 1 5 Dimensional requirements 1 6 Mechanical requirements 1 7 Performance requirements 2 8 Test methods 2 9 Marking and identification 3 10 Inspection 4 11 Complete designation for the purpose of an enquiry or order 4 Appendix A BSI polic
13、y statement on screw threads and the metric system 8 Figure 1 Marking for strength class designation 4 Table 1 Mechanical properties of steel nuts 2 Table 2 Dimensions of inch series prevailing-torque type nuts 5 Table 3 Proof load, clamp load and prevailing-torques for property class1 UNC threads 6
14、 Table 4 Proof load, clamp load and prevailing-torques for property class1 UNF threads 6 Table 5 Test washer, inch series 7 Publications referred to Inside back coverBS4929-2:1973 ii BSI 04-1999 Foreword This part of this British Standard has been prepared under the authority of the Mechanical Engin
15、eering Industry Standards Committee as a result of requests received from industry for the provision of a new standard covering steel hexagon prevailing-torque type nuts. This type of product has been standardized in the USA over a period of many years and the USA has submitted a draft ISO proposal,
16、 covering both metric and inch series products which has been adopted by ISO/TC2, “Bolts, nuts and accessories”, as the basis for an ISO Recommendation. Where possible the provisions of the following ISO Recommendations and ISO Standard have also been incorporated in the text of this standard: ISO R
17、ecommendation R 898/I, “Mechanical properties of fasteners. Part I. Bolts, screws and studs”. ISO Recommendation R 898/II, “Mechanical properties of fasteners. Part II. Nuts with specified proof load valves”. ISO Standard R 2359, “Prevailing-torque type steel hexagon, locknuts. Dimensions. Inch unit
18、s”. This standard purposely relates to inch series products only, since it was felt that confusion might arise if metric series products were included in a composite document having similar performance, functional and material requirements, but differing with regard to dimensional and identification
19、 characteristics. Thus, not withstanding the amount of duplication involved, it was considered advisable to prepare similar but separate documents for the metric and inch series products. The dimensional and identification requirements in this document are based on current ISO inch (Unified) practic
20、e. NOTE 1For BSI policy statement on screw threads see Appendix A. NOTE 2One property class1 (equivalent to Class8 from ISO/R898/II) has been included in this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsib
21、le 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, pagesi andii, pages1 to8, aninside back cover and a back cover. This standard has been update
22、d (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS4929-2:1973 BSI 04-1999 1 1 Scope 1.1 This part of this British Standard specifies the general dimensions and tolerances of prevailing-torque type nuts with ISO i
23、nch (Unified) threads in diameters from No.8 (0.164 in) to1in inclusive. 1.2 Mechanical properties and performance requirements are given only in respect of steel nuts, with or without non-metallic inserts such as nylon, which are not to be used for special applications such as those requiring welda
24、bility, corrosion resistance or the ability to withstand temperatures above300 C (120 C for nuts with non-metallic inserts) or below 50 C. 1.3 Two nut heights are specified, designated “normal” and “high” respectively. The particular design used by the nut manufacturer will determine which of these
25、height categories is applicable. 1.4 Unless otherwise specified by the purchaser either normal or high nuts, with or without non-metallic inserts, may be supplied. NOTEThe titles of the Publicationsreferred to in this standard are listed on the inside back cover. 2 Definition For the purposes of thi
26、s part of this British Standard, the following definition applies: 2.1 prevailing-torque type nut a nut which is frictionally resistant to rotation due to a self-contained prevailing-torque feature, and not because of a compressive load developed at first assembly against the bearing surface of the
27、nut. The term prevailing-torque is not intended to imply an indefinite permanence of fixity 3 Property class designation system 3.1 This standard specifies one property class1 as indicated below: NOTEProperty class designation1, which is equivalent to strength grade8 given in ISO/R898/II, has been u
28、tilized in order to help differentiate between inch series and metric series products. 4 Material and manufacture of steel nuts 4.1 Material. Nuts shall be made of carbon or alloy steel of a grade adequate for the nut to meet the mechanical performance requirements of this standard. The prevailing-t
29、orque element of insert design nuts may be of a material other than steel. 4.2 Heat treatment. Class1 nuts may be heat treated as necessary. 4.3 Finish. Nuts shall be finished plain (bare metal) or with a protective coating (electro-deposited plating or chemical conversion coating) as specified on t
30、he order. Plating shall be in accordance with BS3382. All nuts shall be provided with a supplementary lubricant if necessary to meet the stated performance requirements without galling and shall be clean and dry to touch. 5 Dimensional requirements 5.1 Basic dimensions. Nuts shall be in accordance w
31、ith the dimensions given in Table 2. The portion of the nut containing the prevailing-torque feature may have a special contour within the maximum permitted width across flats and thickness. The minimum width across flats shall not apply at a depressed portion of the nut at the prevailing-torque fea
32、ture. 5.2 Thread form, series and tolerances. The threads of the nuts shall be to the ISO Unified (inch) coarse or fine pitch series in accordance with BS1580. The tolerance class shall be“2B”. The portion of the nut containing the prevailing-torque element need not be in accordance with this requir
33、ement. 5.3 Thread start. The nuts shall assemble a minimum of one full turn by hand on a basic GO thread plug gauge. The plug gauge shall be chamfered at45 to at least the full depth of the thread. 5.4 Defects. The nuts shall be free from burrs, loose scale, sharp edges and all other defects that mi
34、ght adversely affect their service. 6 Mechanical requirements 6.1 Proof load. The nuts shall withstand the proof stresses specified in Table 3 and Table 4 when tested as specified in8.1. 6.2 Hardness. The nuts shall have a hardness not in excess of the hardness specified in Table 1 when tested as sp
35、ecified in8.2. Property class Proof load stress (Sp) Ibf/in 2 1 120000BS4929-2:1973 2 BSI 04-1999 Table 1 Mechanical properties of steel nuts 7 Performance requirements 7.1 Prevailing-torque. The prevailing-torque developed by the nuts during their first installation, or any subsequent installation
36、or removal, shall not exceed the torque specified in Table 3 and Table 4 when tested as specified in8.3. In addition the maximum and minimum prevailing-torque developed by the nuts during their first and fifth removals shall not be less than the “highest” and “lowest” reading removal torques specifi
37、ed in Table 3 and Table 4 when tested as specified in8.3. 7.2 Definition. The prevailing-torque developed by a nut is the torque necessary to rotate the nut on its mating externally threaded component, with the torque being measured while the nut is in motion, and with no axial load in the mating co
38、mponent. 8 Test methods 8.1 Proof load test. The test sample nut shall be assembled on a test bolt (see8.1.1) or on a hardened mandrel (see8.1.2) with a minimum of three full threads projecting through the nut. For referee test purposes, the hardened mandrel shall be used. The maximum torque occurri
39、ng during the assembly of the nut on the test bolts or mandrel shall be recorded. A tensile load equal to the specified proof load for the nut, as given in Table 3 and Table 4 shall be applied through the test bolt or mandrel against the nut bearing surface in an axial direction. The nut shall resis
40、t this load without thread stripping or rupture. The torque necessary to remove the nut from the test bolt or mandrel shall not exceed the maximum torque occurring during assembly. 8.1.1 Test bolt. The bolt used for proof load testing a nut shall have threads in accordance with class“2A” of BS1580.
41、The test bolt shall have a yield strength in excess of the specified proof load of the nut being tested. 8.1.2 Hardened mandrel. The hardened mandrel used for proof load testing a nut shall have threads in accordance with BS1580, tolerance class“3A” except that the tolerance on the major diameter sh
42、all be the minimum with a tolerance of+0.002 in. The mandrel shall be heat treated to a hardness of Rockwell C4550 or Brinell HB430-486. 8.2 Hardness test. The hardness of a sample nut shall be determined on a suitable surface. The preparation of the test specimen and the method of performing the te
43、st shall be in accordance with the following British Standards: 8.3 Prevailing-torque test. The prevailing-torque test shall be conducted at room temperature using a load measuring device (see8.3.1). A test bolt (see8.3.2) shall be inserted in the load measuring device a hardened washer (see8.3.3) p
44、laced on the bolt and the sample nut then assembled on the bolt. The nut shall be advanced on the bolt until a minimum of two full bolt threads protrude through the nut. At that time, the maximum torque occuring while the nut is being advanced through the next360 of nut rotation shall be recorded. T
45、his torque shall not exceed the first installation prevailing-torque value as specified in Table 3 and Table 4. Property class 1 lbf/in 2 Proof load stress a(S p ), min. 120000 Vickers hardness HV, max. 310 Rockwell hardness bHRC, max. 32.2 Brinell hardness bHB, max. 294.5 a The proof load is calcul
46、ated by multiplying the proof load stress by the tensile stress area of the bolt. b The conversion from Vickers hardness into Rockwell hardness and Brinell hardness has been taken from BS860. Vickers hardness BS427-1 Brinell hardness BS240-1 Rockwell hardness BS891-1BS4929-2:1973 BSI 04-1999 3 Tight
47、ening shall be continued until the nut is seated against the hardened washer. The length of the test bolt should be such that seating of the nut shall occur when a length equivalent to four to seven thread pitches of the test bolt protrude through the top of the nut measured from the end of the bolt
48、. The nut shall then be tightened until a tensile load equal to the clamp load, as specified in Table 3 and Table 4, is developed in the bolt. The hardened washer shall be prevented from turning during nut tightening. The nut shall then be backed off by the application of reverse torque until the te
49、nsile load in the bolt has been reduced to zero. The maximum and minimum torques occurring while the nut is being backed off throughout the next360 of rotation shall be recorded. The maximum torque shall not be less than the first removal “highest reading” prevailing-torque value as specified in Table 3 and Table 4. The minimum torque shall not be less than the first removal “lowest reading” prevailing-torque values as specified in Table 3 and Table 4. The nuts shall then be backed off until the prevailing-torque element is disengaged from the bolt thr
