1、BRITISH STANDARD BS4185-10: 1977 Specification for Machine tool components Part10: Trapezoidal threads for lead and feed screw assemblies UDC621.9:621.81 + 621.882.4:621.9589BS4185-10:1977 This British Standard, having been prepared under the directionof the Mechanical Engineering Standards Committe
2、e, was published underthe authority of the Executive Board on 31 March 1977 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference MEE/6 Draft for comment75/75869DC ISBN0 580 09961X Cooperating organizations The Mechanical Engineering Standards Committee, u
3、nder whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The organizations marked with an asterisk in the above list, together with the following, were directly represented on the com
4、mittee entrusted with the preparation of this British Standard: Associated Offices Technical Committee Engineering Equipment Users Association Association of Consulting Engineers Federation of Manufacturers of Construction Association of Hydraulic Equipment Equipment and Cranes Manufacturers Ltd. He
5、alth and Safety Executive Association of Mining Electrical and Institution of Gas Engineers Mechanical Engineers Institution of Mechanical Engineers* British Compressed Air Society Institution of Plant Engineers British Electrical and Allied Manufacturers Institution of Production Engineers* Associa
6、tion London Transport Executive British Gas Corporation Machine Tool Trades Association* British Gear Manufacturers Association Ministry of Defence* British Internal Combustion Engine National Coal Board Manufacturers Association National Engineering Laboratory British Mechanical Engineering Confede
7、ration Department of Industry British Pump Manufacturers Association Process Plant Association British Steel Corporation Railway Industry Association of GreatBritain British Steel Industry Royal Institute of British Architects Chartered Institution of Building Services Society of Motor Manufacturers
8、 and Crown Agents for Oversea Governments and Traders Ltd. Administrations Telecommunication Engineering and Department of the Environment Manufacturing Association Department of Industry* Water-tube Boilermakers Association Department of Trade Electricity Supply Industry in England and Wales Ball a
9、nd Roller Bearing Manufacturers University of Aston in Birmingham Association University of Manchester Institute of Science Machine Tool Industry Research Association and Technology National Federation of Engineers Tool Manufacturers Individual experts Amendments issued since publication Amd. No. Da
10、te of issue CommentsBS4185-10:1977 BSI 08-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Definitions 1 4 Maximum material profile 1 5 Nominal values of pitch, lead and thread diameter 1 6 Accuracy class designations and requirements for assem
11、bled screws andnuts 1 7 Designation 2 Appendix A General guidance 7 Figure 1 Basic profile 2 Figure 2 Maximum material profile 3 Table 1 Dimensions for maximum material profile 3 Table 2 Nominal values of lead, pitch and thread diameter 4 Table 3 Accuracy requirements for assembled screws and nuts 4
12、 Table 4 Dimensions of pitch diameter, major and minor diameter foraccuracyclasses25,40,60,100 and160 5 Table 5 Factors for tolerances for the pitch diameters of multi-start threads 7 Publications referred to Inside back coverBS4185-10:1977 ii BSI 08-1999 Foreword This British Standard has been prep
13、ared under the authority of the Mechanical Engineering Standards Committee. It is based on a draft submitted by the Machine Tool Trades Association. The objective of this standard is to specify criteria for metric trapezoidal thread screw and nut assemblies that will meet the requirements of the vas
14、t majority of machine tools. Therefore, in the final assessment of a screw and nut assembly made to this standard, the criteria by which the assembly is judged shall only be those that relate to assemblies. This standard was derived fromBS5346 “ISO metric trapezoidal screw threads”, which is based o
15、nISO/DIS2901 “ISO metric trapezoidal screw threads Basic profile and maximum material profile” andISO/DIS2902 “ISO metric trapezoidal screw threads General plan”, but certain dimensions and ranges have been altered in order to fulfil the specific requirements of machine tool lead and feed screws. Co
16、mplementary toISO/DIS2901 andISO/DIS2902 is ISO/DIS2903 “ISO metric trapezoidal screw threads Tolerances”, which specifically excludes high accuracy applications such as those required by machine tools, hence the necessity for this standard which also includes a12mm pitch that is not inBS5346. Becau
17、se of the need to attain the requirements of this standard for an assembled screw and nut, it is difficult to completely standardize the screw and nut as individual components. This is due to the high accuracies required in machine tool applications and also to the fact that different manufacturing
18、techniques available (thread turning, whirling, grinding, milling, etc.)can produce slight variations on the profile of the mating component. When thread profile modification occurs as a direct result of the chosen manufacturing process, this is generally acceptable provided that the appropriate spe
19、cifications inTable 2 andTable 3 are adhered to. However, if the customer demands strict compliance with the thread profile, it is the customers responsibility to ensure that a statement to that effect is made when placing the order. Appendix A of this standard gives information that may provide use
20、ful guidance when selecting nominal dimensions and accuracy classes, and it may serve to indicate where extra information could be added to the specification if considered necessary. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards
21、 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, pages1 to 8, an inside back cover and a back cover. This standa
22、rd 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.BS4185-10:1977 BSI 08-1999 1 1 Scope This British Standard specifies a range of nominal diameters(10mm to100mm), nominal pitches(2mm to20mm) and
23、tolerances for machine tool lead and feed screws and nuts. This standard does not make any recommendations concerning features such as material, length or mounting criteria for lead and feed screws. 2 References The titles of the publications referred to in this standard are listed on the inside bac
24、k cover. 3 Definitions For the purposes of this British Standard the following definitions apply. 3.1 basic profile the basic profile is the theoretical profile associated with the basic sizes of the major, pitch and minor diameters of the thread. The deviations are applied to these basic sizes NOTE
25、SeeFigure 1. 3.2 basic size the theoretical size to which the deviations are applied in order to obtain the limits of size 3.3 nominal size the size that is used for general identification. It is generally the basic major diameter of the thread 3.4 feed screw and lead screw a threaded spindle impart
26、ing accurate displacement or motion to a machine tool element with respect to another element 3.5 lead the distance measured parallel to the axis between corresponding points on consecutive contours of the same thread helix in the same axial plane section and on the same side of the helix 3.6 pitch
27、the distance measured parallel to the axis between corresponding points on adjacent profiles lying in the same axial plane and on the same side of the axis NOTEFor a single-start screw, the lead and pitch are the same. For a2-start screw, the lead is twice the pitch. 3.7 accumulated effective pitch
28、deviation the accumulated effective pitch minus the accumulated nominal pitch for the same angle of rotation 4 Maximum material profile Dimensions shall comply with those givenin Table 1. This profile has prescribed clearances on the major, minor and pitch diameters referring to the basic profile(se
29、eFigure 2). 5 Nominal values of pitch, lead and thread diameter The nominal values of pitch, lead and thread diameter and their permissible combinations shall comply with the requirements ofTable 2. All multi-start threads shall use multiples of the pitches specified inTable 2 and the helix angle sh
30、all not exceed25 . 6 Accuracy class designations and requirements for assembled screws and nuts 6.1 General. Accuracy class designations and requirements shall comply withTable 3. Clearances are expressed axially or diametrically in order to enable different measuring methods to be used, neither the
31、 nut nor the screw being permitted to rotate during measurement. Where anti-backlash devices are used, the axial clearance is the criterion and diametral clearances greater than those stated may be used. Where half or split nuts are used, as on lathe lead screws, neither clearance applies. 6.2 Threa
32、d tolerances. In order to achieve the requirements of the various classes of accuracy, different procedures have to be adopted depending on the required accuracy. It is unlikely that nuts and screws for assemblies to classes4 and10 will be made to any recognized thread tolerancing system, since the
33、magnitude of the accumulated effective pitch deviation is the overriding factor. Nut and screw specifications will therefore need to be selected accordingly. Certain tolerance classes derived from the basic system that is described inBS5346 may be used as a basis for specifying the components for as
34、semblies to classes25,40,60,100 and160. 6.3 Nut base system. For this system the nut shall be manufactured to the tolerances given inTable 4 (i.e.tolerance class4H on the pitch diameter); the screw is then made to suit the nut and the class of accuracy chosen.BS4185-10:1977 2 BSI 08-1999 6.4 Screw b
35、ase system. In this case the screw shall be manufactured to the tolerances given inTable 4 (i.e.tolerance class3e on the pitch diameter); the nut is then made to fit the screw. In general, the screw accuracy regulates the value of accumulated effective pitch deviation achieved for the assembled nut
36、and screw. NOTETolerance on minor diameter=1.25 tolerance on pitch diameter. 6.5 3e/4H screw/nut assemblies. The axial and diametral clearances of assemblies to classes100 and160 may be achieved in practice by using screws to tolerance class3e and nuts to tolerance class4H. NOTECare is necessary to
37、avoid confusion when using the number/letter tolerance class system described inBS5346 and the letter/number tolerance class system described inBS4500-1. The3e/4H assembly approximates to the class4G fit from BS1104. 7 Designation Single-start trapezoidal threads shall be designated by the letters T
38、r followed by the nominal diameter and the pitch expressed in millimetres, the class of accuracy and the number of this British Standard, e.g. Tr20 4Class10 BS4185-10 Multi-start threads shall be designated by the letters Tr followed by the nominal diameter and the lead with the pitch in brackets (a
39、ll expressed in millimetres), the class of accuracy and the number of this British Standard, e.g. Tr20 4(P2) Class10 BS4185-10 Figure 1 Basic profileBS4185-10:1977 BSI 08-1999 3 Table 1 Dimensions for maximum material profile (seeFigure 2) Figure 2 Maximum material profile All dimensions in millimet
40、res. Pitch H 1 =0.5P H 4 = h 3 a c R 1max. R 2max. P 2.0 2.5 4 5 6 10 12 20 1 1.25 2 2.5 3 5 6 10 1.25 1.5 2.25 2.75 3.5 5.5 6.5 11 0.25 0.25 0.25 0.25 0.5 0.5 0.5 1.0 0.13 0.13 0.13 0.13 0.25 0.25 0.25 0.5 0.25 0.25 0.25 0.25 0.5 0.5 0.5 1.0BS4185-10:1977 4 BSI 08-1999 Table 2 Nominal values of lea
41、d, pitch and thread diameter Table 3 Accuracy requirements for assembled screws andnuts All dimensions in millimetres. Values in parentheses are second choice. Thread diameter Lead 2 (2.5) 4 5 6 10 10 12 12 20 20 Pitch 2 (2.5) 4 5 6 5 10 6 12 5 10 20 10 12 16 2 2 2 (2.5) (2.5) (2.5) (4) (4) 4 (5) (6
42、) 20 (25) 30 2 (2) 2 (2.5) (2.5) (2.5) 4 (4) 4 5 (5) 5 (6) (6) 6 (10) 10 (10) 10 40 50 60 5 5 5 6 6 6 10 10 10 10 10 10 12 12 12 12 12 12 20 (20) 70 80 6 6 6 10 10 10 12 12 12 12 20 20 20 20 20 All dimensions in millimetres. Class of accuracy Accumulated effective pitch deviation Clearances between
43、nut and screw Over a measuring length of Axial Diametral 300 60 4 0.004 0.003 0.01 nom. 0.04 nom. 10 0.010 0.005 25 0.025 0.010 0.01 min. 0.04 max. 0.04 min 0.15 max. 40 0.040 0.015 60 0.060 0.020 100 0.100 0.025 0.01 min. 0.08 max. 0.04 min. 0.30 max. 160 0.160 0.030 0.01 min. 0.10 max. 0.04 min. 0
44、.40 maxBS 4185-10:1977 BSI 08-1999 5 Table 4 Dimensions of pitch diameter, major and minor diameter for accuracy classes25,40,60,100 and160 All dimensions in millimetres This table applies to single-start threads only. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Nominal diameter Pitch Screw b
45、ase Nut base Pitch diameter 3e Major diameter h7 * Minor diameter 3e Pitch diameter 4H Major diameter Minor diameter H7 * min. max. max. min. min. max. min. max. min. min. max. 10 2 8.854 8.929 10.000 9.985 7.335 7.429 9.000 9.125 10.500 8.000 8.015 2.5 8.595 8.675 10.000 9.985 6.825 6.925 8.750 8.8
46、82 10.500 7.500 7.515 4 7.810 7.905 10.000 9.985 5.286 5.405 8.000 8.160 10.500 6.000 6.015 12 2 10.849 10.929 12.000 11.982 9.329 9.429 11.000 11.132 12.500 10.000 10.018 2.5 10.590 10.675 12.000 11.982 8.819 8.925 10.750 10.890 12.500 9.500 9.518 4 9.799 9.905 12.000 11.982 7.273 7.405 10.000 10.1
47、80 12.500 8.000 8.018 16 2 14.849 14.929 16.000 15.982 13.329 13.429 15.000 15.132 16.500 14.000 14.018 2.5 14.590 14.675 16.000 15.982 12.819 12.925 14.750 14.890 16.500 13.500 13.518 4 13.799 13.905 16.000 15.982 11.273 11.405 14.000 14.180 16.500 12.000 12.018 5 13.282 12.394 16.000 15.982 10.254
48、 10.394 13.500 13.690 16.500 11.000 11.018 6 12.764 12.882 16.000 15.982 8.735 8.882 13.000 13.200 17.000 10.000 10.018 20 2 18.849 18.929 20.000 19.979 17.329 17.429 19.000 19.132 20.500 18.000 18.021 2.5 18.590 18.675 20.000 19.979 16.819 16.925 18.750 18.890 20.500 17.500 17.521 4 17.799 17.905 2
49、0.000 19.979 15.273 15.405 18.000 18.180 20.500 16.000 16.021 5 17.282 17.394 20.000 19.979 14.254 14.394 17.500 17.690 20.500 15.000 15.021 6 16.764 16.882 20.000 19.979 12.735 12.882 17.000 17.200 21.000 14.000 14.021 25 2 23.844 23.929 25.000 24.979 22.323 22.429 24.000 24.140 25.500 23.000 23.021 2.5 23.585 23.675 25.000 24.979 21.813 21.925 23.750 23.900 25.500 22.500 22.521 4 22.793 22.905 25.000 24.979 20.265 20.405 23.000 23.190 25.500 21.000 21.021 5 22.276 22.394 25.000 24.979 19.247 19.394 22.500 22.700 25.500 20.000
