1、BRITISH STANDARD BS 4827:1972 Incorporating Amendment No. 1 Specification for ISO miniature screw threads Metric seriesBS4827:1972 This British Standard, having been approved by the MechanicalIndustry StandardsCommittee, was published under the authorityofthe Executive Boardon 31July1972 BSI 12-1999
2、 The following BSI references relate to the work on this standard: Committee reference MEE/1 andMEE/1/25 Draft for comment 70/37505 ISBN 0 580 07105 7 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consi
3、sts of representatives from the following Government departments and scientific and industrial organizations: The Government department and industrial organization marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the pr
4、eparation of this British Standard. Associated Offices Technical Committee Engineering Equipment Users Association Association of Consulting Engineers Gas Council Association of Hydraulic Equipment Institution of Civil Engineers Manufacturers Ltd. Institution of Gas Engineers Association of Mining E
5、lectrical and Institution of Heating and Ventilating Mechanical Engineers Engineers British Chemical Plant Manufacturers Institution of Mechanical Engineers Association (Automobile Division) British Compressed Air Society Institution of Plant Engineers British Electrical and Allied Manufacturers Ins
6、titution of Production Engineers Association Locomotive and Allied Manufacturers British Gear Manufacturers Association Association of GreatBritain British Internal Combustion Engine London Transport Executive Manufacturers Association Machine Tool Trades Association* British Mechanical Engineering
7、Confederation Ministry of Defence British Pump Manufacturers Association Ministry of Defence, Army Department* British Steel Industry National Coal Board Crown Agents for Oversea Governments and National Physical Laboratory (Department of Administrations Trade and Industry) Department of Employment
8、and Productivity Royal Institute of British Architects (HM Factory Inspectorate) Telecommunications Engineering Department of the Environment Manufacturing Association Department of Trade and Industry Water-tube Boilermakers Association Department of Trade and Industry National Engineering Laborator
9、y Electricity Council, the Central Electricity Generating Board and the Area Boards in England and Wales British Bolt, Nut, Screw and Rivet Federation Smiths Industries Ltd. Fasteners and Turned Parts Institute Timex Ltd. Scientific Instrument Manufacturers Association Amendments issued since public
10、ation Amd. No. Date of issue Comments 2032 June 1976 Indicated by a sideline in the marginBS4827:1972 BSI 12-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Thread form and diameter-pitch combinations 1 3 Limits and tolerances 1 4 Designation 2 5 Inspection
11、 3 6 Coated threads 3 Figure 1 Basic profile 4 Figure 2 Nut threads. Tolerances 4H5 and 4H6 5 Figure 3 Nut threads. Tolerances 3G5 and 3G6 6 Figure 4 Bolt threads. Tolerance 5h3 7 Figure 5 Thread overlap 15 Table 1 Thread data 8 Table 2 Basic dimensions of standard diameter/pitch combinations 9 Tabl
12、e 3 Limits and tolerances. Internal threads (nuts) tolerance class 4H5 10 Table 4 Limits and tolerances. Internal threads (nuts) tolerance class 4H6 11 Table 5 Limits and tolerances. Internal threads (nuts) tolerance class 3G5 12 Table 6 Limits and tolerances. Internal threads (nuts) tolerance class
13、 3G6 13 Table 7 Limits and tolerances. External threads (bolts) tolerance class 5h3 14 Table 8 Thread overlap 16BS4827:1972 ii BSI 12-1999 Foreword This standard makes reference to the following British Standards and ISORecommendation: BS 919, Screw gauge limits and tolerances. BS 919-3, Gauges for
14、ISO metric screw threads. BS 3643, ISO metric screw threads. BS 4183, Machine screws and machine screw nuts metric series. ISO/R 1501, Miniature screw threads. This British Standard, which specifies requirements for ISO miniature screw threads from0.30mm to1.4mm in diameter, has been prepared under
15、the authority of the Mechanical Engineering Industry Standards Committee and is based on ISO/R 1501, “Miniature screw threads”, prepared by Technical Committee ISO/TC1. These threads are distinguished from ISO general purpose metric screw threads by a reduced basic depth of 0.48P compared with appro
16、ximately 0.54P. They have been formulated as a result of lengthy consideration of the practical problems involved in the production and use of small screw threads. Tests by the horological industry showed that small internal threads made nominally to the general purpose profile almost invariably req
17、uired minor diameters considerably larger than basic size if severe difficulties in tapping were to be avoided, and that these larger minor diameters corresponded to a thread depth in the region of0.48P. This enables the minor diameters of the taps and external threads to be increased to the benefit
18、 of core strength, productivity and tool life but at the cost of thread overlap (depth of engagement). In the range below 1.0mm diameter the ISO miniature screw threads specified in this standard form part of the complete series of the metric screw threads recommended by ISO. In the range from 1.0mm
19、 to 1.4mm diameter ISO general purpose metric screw threads to BS 3643 1)are recommended for standard screws and nuts (for example to BS 4183 2) ) but the miniature screw thread form incorporated in this standard is available for use where the reduction of thread overlap is acceptable. This standard
20、 supersedes BS 3369, “Unified miniature screw threads”, which was an attempt to reconcile the ISO/Unified thread form with American Standard B1.10:1958, “Unified machine screw threads” having a basic thread depth of0.52P. The Swiss Horological Industry Standards NIHS 06-02 and 06-05 are in conformit
21、y with the ISO Recommendation and it is understood that the American Standard is being revised to incorporate the new profile, even though it may differ from the ISO Recommendation in some other respects without affecting interchangeability between threads of the same diameter and pitch. A British S
22、tandard does not purport to include all the necessary provisions 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 cov
23、er, an inside front cover, pagesi andii, pages1 to16, 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. 1) BS 3643, “ISO metric screw threads”.
24、2) BS 4183, “Machine screws and machine screw nuts metric series”.BS4827:1972 BSI 12-1999 1 1 Scope This British Standard specifies requirements for ISO miniature screw threads from0.30mm to1.4mm in diameter with 60 ISO miniature screw thread form specified in ISO/R1501 and conforms dimensionally wi
25、th it. 2 Thread form and diameter-pitch combinations 2.1 Basic profile. The basic profile, shown inFigure 1, is the theoretical profile of depth0.48P associated with the basic sizes of the major, pitch and minor diameters of the thread. The fundamental deviations, which in this standard are zero for
26、 external thread (bolt) major and pitch diameters and negative for the bolt minor diameter, and which are zero for the internal thread (nut) minor diameter and either zero or positive for the nut pitch and major diameters, are applied to the basic sizes and establish the maximum material limits. The
27、 application of tolerances to the maximum material limits, negative for bolts, positive for nuts, determines the minimum material limits.Table 1 includes the basic thread data for each standard pitch. 2.2 Diameter-pitch combinations. Table 2 gives the standard series of nominal diameters and their a
28、ssociated pitches with the corresponding basic major, pitch, and minor diameters. The nominal diameters are classified as first or second choice. Sizes1.0mm to1.4mm diameter are all second choice because ISO metric general purpose screw threads to BS3643 are recommended for standard screws and nuts
29、(for example, BS4183). 2.3 Maximum and minimum material profiles. Figure 2 and Figure 3 for nuts andFigure 4 for bolts show the maximum and minimum material profiles derived from the basic profile as described in2.1 above.Table 1 includes data for the maximum material depth of the bolt, 0.56P, and t
30、he root radius of approximately 0.2P associated with it. This root radius is not tangential to the flanks of the thread. Roots of bolts must lie between the maximum material root profile with 0.2P radius and a minimum material root profile having a flat minor diameter. Crests of bolts must lie betwe
31、en maximum and minimum material profiles having flat major diameters. In practice, bolt crests and roots are seldom truly flat or truly radiused, but it is desirable that they are rounded. The maximum material major diameters of nuts are flat but these are in practice cleared by taps having crests o
32、f approximately 0.07P radius. 3 Limits and tolerances 3.1 Fundamental deviations, tolerance grades and positions, tolerances, limits of size. In the case of nuts, tolerance position H indicates zero fundamental deviation for all elements of the thread and thus maximum material limits equal to basic
33、size. No minimum material limit is specified for the major diameter D, one grade of tolerance, i.e. 4, is specified for the pitch diameterD 2 , and two grades of tolerance,5 and 6, are specified for the minor diameter D 1 . These details together with the limits of size are shown inTable 3 andTable
34、4. Also for nuts, tolerance position G indicates positive fundamental deviations DEI and D 2 EI for the maximum material limits of the major diameter D and the pitch diameter D 2 , but with zero fundamental deviation for the minor diameter D 1so that the maximum material limit of D 1is basic size (a
35、s for tolerance position H). No minimum material limit is specified for the major diameter D, one grade of tolerance, i.e.3, is specified for the pitch diameter D 2 , and two grades of tolerance, 5 and 6, are specified for the minor diameter D 1 . These details, together with the limits of size, are
36、 shown inTable 5 and Table 6. The two grades of tolerance, 5 and 6, provided in Table 3 Table 6 for the nut minor diameters D 1are not so much a measure of quality as a recognition of the practical difficulties met with in tapping miniature screw threads in more difficult materials or deep holes. Th
37、e use of the grade 6 tolerances provided for sizes from0.40mm to1.4mm diameter makes it possible to increase tapping hole sizes and so to alleviate the difficulties mentioned.BS4827:1972 2 BSI 12-1999 It will be seen fromTable 3Table 6 that the maximum (i.e. minimum material) pitch diameters D 2are
38、the same throughout, the difference between the Grade 4 tolerances ofTable 3 andTable 4, and the Grade 3 tolerances ofTable 5 andTable 6, lying in the clearance provided inTable 5 andTable 6 at the minimum (i.e. maximum material) pitch diameters by the fundamental deviations D 2 EI. A similar cleara
39、nce is provided at the minimum major diameter D. No such clearance is provided at the minimum minor diameterD 1 . NOTEThe necessity for this clearance has given rise to some controversy. However, the practical result of working toTable 3 andTable 4 will adequately ensure compatibility. The Swiss Hor
40、ological Industry on the other hand prefer working toTable 5 andTable 6. In any event users should not indiscriminately specify all four Table 3Table 6. A choice should be made between(1) usingTable 3 normally, withTable 4 in difficult conditions and (2) usingTable 5 normally, withTable 6 in difficu
41、lt conditions. In the case of bolts, tolerance position h indicates zero fundamental deviation for the major diameter d and pitch diameter d 2 , and thus maximum material limits equal to basic size. The maximum (i.e. maximum material) limit of the minor diameter d 1has a negative fundamental deviati
42、on of 0.16P, i.e. 2 (0.56P 0.48P) as a result of the specified maximum material bolt thread depth of 0.56P. The tolerance on major diameter d is Grade 3, on pitch diameter d 2 , Grade 5, and on minor diameter d 1 , Grade4. These details, together with the limits of size, are shown inTable 7. 3.2 Thr
43、ead overlap. The thread overlap (depth of engagement) between bolts and nuts when assembled concentrically is shown inFigure 5 andTable 8. Designers may find this information useful when deciding, in the range from 1.0mm to 1.4mm diameter, whether to use the thread form of this standard or the threa
44、d form of the ISO general purpose standard. 4 Designation 4.1 A complete designation of a thread gives information on the thread system, the size and pitch of the thread and the tolerances applicable to it. ISO/R1501 omits the pitch from the designation of miniature threads but this British Standard
45、 requires its inclusion in all cases. 4.2 Screw threads to this standard are designated by S followed by the nominal size in millimetres, the pitch, the pitch diameter tolerance grade number, the tolerance position letter (capital for internal threads, lower-case for external threads) and the tolera
46、nce grade number for the nut minor diameter or bolt major diameter. Example for ISO miniature external screw thread S0.6 mm diameter: S0.6 0.155h3. 4.3 A fit between mating threads is designated by a combination of the nut and bolt designations in that order. Example for ISO miniature screw thread S
47、0.6mm diameter:BS4827:1972 BSI 12-1999 3 5 Inspection Differences in methods of gauging and measurement have a considerable bearing on tolerances, especially where, as in this case, uncertainties in gauging and measurement may be quite significant in relation to the size of the product and its toler
48、ances. GO ring screw gauges and GO plug screw gauges for the maximum material limits can be of value provided that they are made to closer tolerances than those in BS919-3, for the same tolerances. Where pitches do not comply with the requirements of BS919-3, the tolerances shall be proportionally c
49、loser. It is in the miniature range of screw threads that the NOT GO gauging of minimum material limits becomes of progressively less value, with correspondingly greater reliance having to be placed on skilful and conscientious workmanship and on the accuracy of threading tools. Whether GO gauges are used or not, it is recommended that external miniature screw threads and the taps for the internal threads be inspected optically by projection or in a toolmakers measuring microscope. The illuminating beam should be parallel an
