1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsWB9423_BSI_StandardColCov_noK_AW:BSI FRONT COVERS 5/9/08 12:55 Page 1Limits and fits for engineeringPart 2: Guide to the selection of fits in BS 1916-1BS 1916-2:2009BS 1916-2:2009 BR
2、ITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when the document was last issued. BSI 2009ISBN 978 0 580 65215 8ICS 17.040.10The following BSI references relate to the work on this standard: Committee reference TDW/4 Draft for comment
3、09/30192611 DCPublication historyFirst published December 1953Second (present) edition, September 2009Amendments issued since publicationDate Text affected BRITISH STANDARD BSI 2009 iBS 1916-2:2009ContentsForeword ii1 Scope 12 Normative references 13 Terms and definitions 14 Terminology 35 Hole tole
4、rances 36 Classification of fits 37 Choice of fit 88 Choice of tolerance 99 Preferred sizes 910 Recommended tolerances for standard fits 14Bibliography 40List of figuresFigure 1 Diagram showing disposition of limits and tolerances (unilateral hole basis) 2Figure 2 The disposition of standard shaft f
5、its with H7 and H8 holes for diameter range 1.19 in to 1.97 in 5Figure 3 The degree of accuracy which can reasonably be expected from various manufacturing processes under average conditions 10Figure 4 Typical data sheet 16Figure 5 Belt drive unit 17Figure 6 Belt driven gear pump 17Figure 7 Link mec
6、hanism: shaft and lever 18Figure 8 Dashpot for oil circuit breaker 19Figure 9 Dashpot for switchgear time lag device 20Figure 10 High pressure hydraulic hand pump 21List of tablesTable 1 Classification of types of fits 4Table 2 Equivalent fits on the hole basis and shaft basis 8Table 3 Preferred siz
7、es: fractional inch series 11Table 4 Preferred sizes: decimal inch series 12Table 5 Complete series of preferred inch sizes 13Table 6 Tolerances for clearance fits, shaft c 22Table 7 Tolerances for clearance fits, shaft d 23Table 8 Tolerances for clearance fits, shaft e 24Table 9 Tolerances for clea
8、rance fits, shaft f 25Table 10 Tolerances for clearance fits, shaft g 26Table 11 Tolerances for clearance fits, shaft h 27Table 12 Tolerances for transition fits, shaft j 28Table 13 Tolerances for transition fits, shaft k 29Table 14 Tolerances for transition fits, shaft m 30Table 15 Tolerances for t
9、ransition fits, shaft n 31Table 16 Tolerances for interference fits, shaft p 32Table 17 Tolerances for interference fits, shaft r 33Table 18 Tolerances for interference fits, shaft s 34Table 19 Tolerances for interference fits, shaft t 36Table 20 Tolerances for interference fits, shaft u 38Summary o
10、f pagesThis document comprises a front cover, an inside front cover, pages i to ii, pages 1 to 40, an inside back cover and a back cover.BS 1916-2:2009ii BSI 2009BRITISH STANDARDForewordPublishing informationThis British Standard is published by BSI and came into effect on 30 September 2009. It was
11、prepared by Technical Committee TDW/4, Technical product realization. A list of organizations represented on this committee can be obtained on request to its secretary.SupersessionThis British Standard supersedes BS 1916-2:1953, which is withdrawn.Relationship with other publicationsThis British Sta
12、ndard is published in three parts:Part 1 Guide to limits and tolerances;Part 2 Guide to the selection of fits in BS 1916-1;Part 3 Guide to tolerances, limits and fits for large diameters;The ISO 286 (BS EN 20286) series establishes the ISO code-system for tolerances of linear sizes and is published
13、in the following parts: ISO 286-1 (BS EN 20286-1), ISO system of limits and fits Part 1: Bases of tolerances, deviations and fits;ISO 286-2 (BS EN 20286-2), ISO system of limits and fits Part 2: Tables of standard tolerance grades and limit deviations for holes and shafts.The ISO 286 series covers t
14、he metric system of limits and fits; the BS 1916 series provides guidance and recommendations on the equivalent inch system (imperial).Information about this documentIn view of the time elapsed since its original publication in 1953, this British Standard was reviewed in detail in 2009. It was decid
15、ed that the technical provisions of the previous edition were still generally applicable, but the figures have been redrawn for ease of use, the wording of some guidance updated for clarity, and the opportunity was taken to update references to other standards.Use of this documentAs a guide, this pa
16、rt of BS 1916 takes the form of guidance and recommendations. It should not be quoted as if it were a specification or a code of practice and claims of compliance cannot be made to it.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a c
17、ontract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.BRITISH STANDARD BSI 2009 1BS 1916-2:20091 ScopeThis British Standard gives guidance on the selection of fits given in BS 1916-1.The recommendations apply, in p
18、articular, to fits between cylindrical parts, designated as “holes” and “shafts”, in which case the term “size” refers to the diameter of the mating parts. The recommendations are also applicable to parts other than cylindrical, in which case the term “size” refers to a length, width or other dimens
19、ion.Tables of preferred sizes are included to avoid the indiscriminate selection of dimensions, and their use is strongly recommended.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies.
20、 For undated references, the latest edition of the referenced document (including any amendments) applies.BS 1916-1:2009, Limits and fits for engineering Part 1: Guide to limits and tolerancesBS 8888, Technical product specification Specification 3 Terms and definitionsFor the purposes of this part
21、of BS 1916, the following terms and definitions apply.NOTE Figure 1 illustrates the basic definitions used in the textBS 1916-2:20092 BSI 2009BRITISH STANDARDFigure 1 Diagram showing disposition of limits and tolerances (unilateral hole basis)13 426111029548712 13 14LHKey1 Fundamental deviation2 Max
22、imum interference (allowance)3 Tolerance4 Maximum clearance5 Minimum clearance (allowance)6 Minimum interference7 Nominal size8 Undersize hole9 Limits for size of shaft10 Limits for size of hole11 Oversize hole12 Clearance13 Transition14 InterferenceBRITISH STANDARD BSI 2009 3BS 1916-2:20094 Termino
23、logyThe disposition of the tolerance zone for a hole relative to the nominal size is denoted by a capital letter and the magnitude, or grade, of the tolerance by a suffix number, e.g. H7.The disposition of the tolerance zone for a shaft relative to the nominal size is denoted by a small letter and t
24、he magnitude, or grade, of the tolerance by a suffix number, e.g. p6.A fit is described by a combination of symbols, e.g. H7p6 or H7/p6.NOTE See BS 1916-1:2009, Clauses 6 and 7.On production drawings, the actual limits for both hole and shaft should be stated by one of the methods recommended in BS
25、8888, so that the actual size of the part can be ascertained without reference to this standard. There are, however, certain circumstances, for example in general specifications, or on preliminary design drawings, in which it is convenient to state the particular type of fit by symbols only.5 Hole t
26、olerancesThe following is a summary of the uses of the various grades of the unilateral hole H from H5 to H11. H5. This grade can normally only be produced by precision boring, fine internal grinding, or honing. H6. This grade can be produced by fine grinding or honing, and possibly hand reaming. H7
27、. This grade is produced by grinding, broaching or careful reaming. H8. This grade is produced by boring or machine reaming. H9. This grade is used on high quality products for milled or slotted widths. H10. This grade is not normally used for diameter fits, although it can be used for drilled holes
28、. It is used for milled widths on unimportant parts. H11. This grade is used for coarse drilled, punched or pressed holes on non-fitting parts.6 Classification of fits6.1 GeneralThe whole range of fits is divided into three main classes: clearance; transition; interference.Each main class, using the
29、 unilateral (H) hole, is further sub-divided into several types of fit; for example, clearance fits are divided into six types, from very fine to very coarse clearance. Each type of fit is classified by the letter symbol of the shaft which produces that type, for example: clearance fit, shaft “e”; o
30、r clearance fit, shaft “f”.BS 1916-2:20094 BSI 2009BRITISH STANDARDIt is more convenient to refer to a type of fit by the shaft symbol only, e.g. an “e” shaft fit or an “f” shaft fit. The classification is given in Table 1 and those fits using the H7 and H8 holes are illustrated in Figure 2. Table 1
31、 Classification of types of fitsClassification With holes RemarksH6 H7 H8 H11ClearanceShaft a No general recommendation can be madeShaft bShaft c c8 c9 c11 Extra loose runningShaft d d8 d8/d10 d11 Loose runningShaft e e7 e8 e8/e9 Easy runningShaft f f6 f7 f8 RunningShaft g g5 g6 (g7 A) Close running
32、Shaft h h5 h6 h7/h8 h11 SlideTransitionShaft j j5 j6 j7 PushShaft k k5 k6 k7 Easy keyingShaft m m5 m6 m7 Tight keyingShaft n n6 n7 Drive p7 r7 Interferencen5 Shaft p p5 p6 Light pressShaft r r5 r6 Shaft s s5 s6 s7 PressShaft t t5 t6 t7 Shaft u u5 u6 u7 Heavy press or shrinkShaft v No general recomme
33、ndations can be madeShaft xShaft yShaft zA)This is a non-standard shaft. If required, the limits for it can be derived by reference to BS 1916-1.The interference fits are classified on the basis of the hole H7 mated with the various shafts. The combination of these shafts with holes of coarser grade
34、s might in some cases result in a different type of fit. For example, in the case of the transition fit using shaft “n”, the fine grade, namely H6n5, will in fact result in a true interference fit, whereas the combinations H8p7 and H7 r7 will produce transition fits, not interference fits.Using the
35、unilateral (H) hole, the resulting fits in combination with the various shafts are as given in 6.2, 6.3 and 6.4.BRITISH STANDARD BSI 2009 5BS 1916-2:2009Figure 2 The disposition of standard shaft fits with H7 and H8 holes for diameter range 1.19 in to 1.97 in Unit = 0.001 inu 6t 6s 6r 6p 6n 6m 6k 6j
36、 6h 6g 6f 7e 8d 8c 8u 7t 7s 7r 7p 7n 7m 7k 7j 7h 7h 8g 7f 8e 9e 8d 10d 8c 9-10-505-10-505WITH HOLE H7 WITH HOLE H8SHAFTSCLASSSHAFTSCLASSShaftsHoles 6.2 Clearance fits6.2.1 Shafts a, b and cThese fits give a large clearance and are not widely used.6.2.2 Shaft dThis fit is available in grades 8 to 11
37、and is generally suitable for loose running fits, e.g. plummer block bearings and loose pulleys.6.2.3 Shaft eThis fit is available in grades 7, 8 and 9, and is recommended for general loose clearance fits, and for properly lubricated bearings requiring appreciable clearance. In the finer grades it c
38、an be used for large, high-speed, heavily loaded bearings such as turbo-generator and large electric motor bearings, according to circumstances.BS 1916-2:20096 BSI 2009BRITISH STANDARD6.2.4 Shaft fThis fit is available in grades 6, 7 and 8 and is recommended for use as a normal running fit. It is wi
39、dely used as a normal grease-lubricated or oil-lubricated bearing where no substantial temperature differences are encountered. Typical applications are gearbox shaft bearings and the bearings of small electric motors, pumps, etc.6.2.5 Shaft gThis fit is expensive to manufacture since the clearance
40、is small, and it is not recommended as a running fit except in precision equipment where shaft loadings are very light. Typical applications are the bearings for accurate linkwork, and for piston and slide valves. In addition it is often used for spigot or location fits.6.2.6 Shaft hThe upper shaft
41、limit of this fit is zero, although in practice a slight clearance will usually be found. It exists in grades 5 to 11, and is widely used for non-running parts. It is useful for normal location and spigot fits and in the finer grades can be used as a precision sliding fit.6.3 Transition fits6.3.1 Sh
42、aft jThis is a transition fit averaging a slight clearance, and is available in grades 5 to 11. It is recommended for location fits, requiring slightly less clearance than is given with the “h” shaft, and where a slight interference is permissible. Typical applications are coupling spigots and reces
43、ses, gear rings clamped to steel hubs, etc.6.3.2 Shaft kThis is a true transition fit averaging virtually no clearance. It is available in grades 5 to 11, and is recommended for location fits where a slight interference can be tolerated with the object, for example, of eliminating vibration.6.3.3 Sh
44、aft mThis transition fit averages a slight interference, although appreciable assembly force will be required if the extremes are encountered. It is available in grades 5, 6 and 7.6.3.4 Shaft nThis transition fit averages slightly more interference than the “m” shaft, and gives clearance only on ext
45、reme sizes. It is available in grades 5, 6 and 7, and is recommended for generally “tight” assembly fits. The finest grade (n5) is used as a true interference fit with the hole H6.BRITISH STANDARD BSI 2009 7BS 1916-2:20096.4 Interference fitsNOTE The factors governing the choice of an interference f
46、it are such that only generalized recommendations can be made. Some general guidance is given here and some particular examples are quoted in the fit tables (Table 16 to Table 20), but it is recommended that in every case, careful consideration be given to the factors affecting the fit, i.e. diamete
47、r and length of engagement, materials, surface finish, induced stresses, gripping forces, assembly forces and assembly method, before the final choice is made.6.4.1 Shafts6.4.1.1 Shaft pThis will give a true interference fit with holes of grades 6 or 7, but with holes of grade 8 a transition fit wil
48、l be obtained. The amount of interference is not excessive but is sufficient to give non-ferrous parts a light press fit which can be dismantled when required. It is the standard press fit for steel, cast iron or brass-to-steel assemblies. The amount of interference is too small for satisfactory fit
49、s to be obtained in very elastic materials, such as light alloys.6.4.1.2 Shaft rThis combination will give a medium drive fit on ferrous parts, and on non-ferrous parts a light drive fit which can be easily dismantled when required. With the hole H8 an interference fit is obtained with diameters over 3.94 in; with smaller diameters a transition fit results.6.4.1.3 Shaft sThis is used for the permanent or se
