1、BRITISH STANDARD BS 426:1969 Incorporating Amendment No. 1 Specification for Fixed centres for use on machine tools and in other applications CONFIRMED DECEMBER 2007BS426:1969 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee, was published under th
2、e authorityof the Executive Boardon 15 December 1969 BSI 11-1999 First published November 1931 First revision December 1969 The following BSI references relate to the work on this standard: Committee reference MEE/6/5 Draft for comment 67/23591 ISBN 580 05534 5 Co-operating organizations The Mechani
3、cal Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The Government departments and scientific and industrial organizations marked w
4、ith an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Associated Offices Technical Committee Institute of Marine Engineers Association of Consulting Engineers Institution of Civil Engineers
5、Association of Mining Electrical and Institution of Gas Engineers Mechanical Engineers Institution of Heating and Ventilating Board of Trade Engineers British Chemical Plant Manufacturers Institution of Mechanical Engineers* Association Institution of Mechanical Engineers British Compressed Air Soci
6、ety (Automobile Division) British Electrical and Allied Manufacturers Institution of Production Engineers* Association* Locomotive and Allied Manufacturers British Gear Manufacturers Association Association of Great Britain British Internal Combustion Engine London Transport Board Manufacturers Asso
7、ciation Machine Tool Trades Association* British Mechanical Engineering Federation Ministry of Defence British Pump Manufacturers Association Ministry of Defence, Army Department* British Steel Industry* Ministry of Power Crown Agents for Oversea Governments and Ministry of Public Building and Works
8、* Administrations Ministry of Technology* Department of Employment and Productivity Ministry of Technology National (H.M. Factory Inspectorate) Engineering Laboratory Electricity Council, the Central Electricity Ministry of Transport Generating Board and the Area Boards in National Coal Board Englan
9、d and Wales National Physical laboratory (Ministry of Engineering Equipment Users Association Technology) Gas Council Royal Institute of British Architects Association of Supervisory Staffs, Executives North East Coast Institution of Engineers and and Technicians Shipbuilders Gauge and Toolmakers As
10、sociation Production Engineering Research Association Machine Tool Industry Research Association Society of Motor Manufacturers and Traders Ministry of Defence, Air Force Department Ltd. Ministry of Defence, Navy Department Trades Union Congress Ministry of Technology National Federation of Engineer
11、s Tool Manufacturers Amendments issued since publication Amd. No. Date of issue Comments 1591 October 1974 Indicated by a sideline in the marginBS426:1969 BSI 11-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Materials 1 3 Constructional requirements 2 4 F
12、inish 2 5 Designation 2 6 Marking 2 Figure 1 Fixed centre, long series, standard Morse taper shank 3 Figure 2 Fixed centre, short series, standard Morse taper shank 5 Figure 3 Half centre, long series, standard Morse taper shank 6 Figure 4 Tungsten carbide tip 7 Figure 5 Type 1 fixed centre with car
13、bide tip insert 8 Table 1 Dimensions for fixed centre, long series, standard Morse taper shank 4 Table 2 Dimensions for fixed centre, short series, standard Morse taper shank 5 Table 3 Dimensions for half centre, long series, standard Morse taper shank 6 Table 4 Dimensions of tungsten carbide tip 7
14、Table 5 Dimensions relating to the regrinding of the 60 nose cone of a fixed centre with a tungsten carbide tip insert 8BS426:1969 ii BSI 11-1999 Foreword This standard makes reference to the following British Standards: BS 891, Method for Rockwell hardness test Part 1: Testing of metals. BS 970, Wr
15、ought steels in the form of blooms, billets, bars and forgings Part 1: Carbon and carbon manganese steels including free cutting steels Part2: Direct hardening alloy steels including alloy steels capable of surface hardening by nitriding. BS 1134, Centre-line-average height method for the assessment
16、 of surface texture. BS 1660, Machine tapers Part 1: Self-holding tapers and gauges for self-holding tapers. BS 3730, Methods for the assessment of departures from roundness. BS 4276, Hard metal for wire, bar and tube drawing dies. BS 4659, Tool steels. This British Standard has been prepared under
17、the authority of the Mechanical Engineering Industry Standards Committee. It is based on proposals submitted by the Machine Tool Trades Association and is a revision of BS426:1931, “Lathe centres”. The present title reflects the wider applications to which the centres which are the subject of this s
18、tandard are put. This standard specifies three quite distinct but interchangeable series of fixed centres: Type 1. Fixed centre, long series, standard Morse taper shank. Type 2. Fixed centre, short series, standard Morse taper shank. Type 3. Half centre, long series, standard Morse taper shank. In c
19、ompiling this standard, due consideration has been given to the need for regrinding of the nose cone to take account of breakage, wear, etc. NOTEFor certain applications, a short series centre is required with a Morse taper shank shorter than the Type2. This is often referred to as a “stub” centre,
20、the only difference being in the length of the Morse taper shank rearward of the gauge plane, the diameter at gauge plane and rate of taper being identical to the standard Morse taper as used for all standard centres. Details of stub centres are not quoted in this standard. A British Standard does n
21、ot 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 cover, an inside
22、front cover, pages i and ii, pages1 to8 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.BS426:1969 BSI 11-1999 1 1 Scope 1.1 This British Standard relates to fixed
23、centres for use on machine tools and their auxiliary equipment, and in any other suitable circumstances such as on inspection or gauging equipment, etc. 1.2 The fixed centres specified in this standard fall into the following three series: Type 1. Fixed centre, long series, standard Morse taper shan
24、k. This type utilizes the Morse taper shank details, and conforms to relevant dimensions contained in ISO/R296 1) , ISO/R298 2)and BS1660-1 3) . The section forward of the gauge plane includes a parallel cylindrical portion (seeFigure 1). When this type is fitted with a tungsten carbide tipped nose
25、cone the amount of regrinding of the tip is strictly limited. Details showing the extent of regrinding are given inFigure 5. Type 2. Fixed centre, short series, standard Morse taper shank. This type conforms to Type1 in respect of the dimensions rearward of the gauge plane. The section forward of th
26、e gauge plane conforms in part to Type1, but it is arbitrary whether a parallel cylindrical portion is included forward of the gauge plane or whether the Morse taper is extended (seeFigure 2). Type 3. Half centre, long series, standard Morse taper shank. This type utilizes the same basic dimensions
27、as Type1 with the exception that a portion of the centre forward of the gauge plane is cut away parallel to the axis of the centre (seeFigure 3). NOTEThe dimensions of the cutaway area align with those of DIN806, “Lathe centres (60 )”. 2 Materials 2.1 The fixed centre shall be manufactured from stee
28、l 535A99 conforming to BS970-2 or from steel having equivalent mechanical properties. 2.2 It shall be heat treated in accordance with standard practice in order to obtain a hardness value of60 to63HRC 4) . 2.3 Alternatively the fixed centre shall, according to the Morse taper shank size, be manufact
29、ured from the following materials: 0 and 1 Morse taper shank. High speed steel, Grade BTI, BS 4659 5) , or high speed steel having equivalent mechanical properties. 2, 3, 4, 5 and6 Morse taper shank. High speed steel cone, Grade BTI, BS 4659 5) , suitably affixed to a shank manufactured from steel08
30、0 M40 6)BS970-1 7)or from materials having equivalent mechanical properties. The shank shall be heat treated in accordance with standard practice in order to obtain a hardness value of50 to55HRC 4) . 2.4 Hard metal tipped centres 2.4.1 When the fixed centre incorporates a tungsten carbide tipped nos
31、e cone, it shall be suitably affixed to a shank manufactured from steel 080M40 6)BS970-1 steel or from steel having equivalent or superior mechanical properties, and all finished dimensions shall conform to those shown inTable 1 andTable 2. 2.4.2 When a Type 1 fixed centre incorporates a tungsten ca
32、rbide tipped nose cone, regrinding of the cone is limited. Details of the limiting dimensions are given inTable 5. Dimension A inTable 5 relates to the depth to which the tungsten carbide tips are embedded and the manufacturer shall ensure that the values quoted are maintained. Maximum regrinding al
33、lows the depth of tungsten carbide tip insert remaining embedded to be approximately0.5times the diameter of the insert. Regrinding of the60 nose cone shall be discontinued once the groove shown inFigure 5 has been reached. 2.5 Hard metal material. The composition and hardness of a hard metal grade
34、shall be suitable for the duty it has to perform. 2.5.1 Impurities. These shall not exceed the values stated in Clause8 of BS4276:1968 8) . 2.5.2 Porosity. The-hard metal inserts shall be free from inherent porosity which would affect performance during their useful life. 1) ISO/R 296, “Self-holding
35、 tapers for tool shanks”. 2) ISO/R 298, “Lathe centres. Sizes for interchangeability”. 3) BS 1660, “Machine tapers”, Part1, “Self-holding tapers and gauges for self-holding tapers”. 4) BS 891, “Method for Rockwell hardness test”, Part1, “Testing of metals”. 5) BS 4659, “Tool steels”. 6) Steel EN 8 o
36、f BS 970:1955. 7) BS 970, “Wrought steels in the form of blooms, billets, bars and forgings” Part1, “Carbon and carbon manganese steels including free Cutting steels”. 8) BS 4276, “Hard metal for wire, bar and tube drawing dies”.BS426:1969 2 BSI 11-1999 2.5.3 Defects. The hard metal shall be free fr
37、om eta-phase and from any undue amount of cobalt segregation. 2.5.4 Brazing. The hard metal inserts shall be suitably brazed in position. 3 Constructional requirements 3.1 Dimensions. Fixed centres shall conform to the dimensions given inFigure 1, Figure 2 and Figure 3 andTable 1, Table 2 and Table
38、3. The included angle of the nose cone of fixed centres is60 . NOTEWhen a greater angle is considered necessary for particularly heavy workpieces, ISO/R298, “Lathe centres. Sizes for interchangeability”, recommends that either75 or90 be used. When further studies have been completed only one of thes
39、e alternatives will be chosen. 3.2 Tolerances. The 60 included angle of the nose cone shall be to a tolerance of . The rate of taper of the Morse taper shank shall always be nominal to fast. The tolerance shall bemm per cent on diameter, over the gauge length of the taper. The out of roundness 9)of
40、the cylindrical surface of the Morse taper shall not exceed0.005mm FIM. The eccentricity of the nose cone to the Morse taper shank shall not exceed0.005mm FIM. The combined out of roundness and eccentricity shall not exceed0.008mm. 4 Finish The surfaces of the fixed centre marked with a machining sy
41、mbol inFigure 1, Figure 2 and Figure 3 shall have a surface texture value not exceeding0.44m CLA 10) . The remainder of the fixed centre shall have a surface texture value not exceeding3.24m CLA. The fixed centre shall be free from defects, including cracks, burrs, sharp edges, etc. 5 Designation Fi
42、xed centres complying with this British Standard shall be designated by a code showing the type number, the Morse taper number, the material, whether fitted with a tungsten carbide tipped nose cone, and the number of this British Standard. Examples: 1) For a fixed centre, Type2,3 Morse taper, high s
43、peed steel: Fixed centre23 MTHSBS426 2) For a fixed centre, Type2,3 Morse taper, with tungsten carbide tipped nose cone: Fixed centre23 MTTCBS426 3) For a fixed centre, Type2,3 Morse taper, cast steel: Fixed centre23 MTCSBS426 6 Marking Fixed centres complying with this British Standard shall be mar
44、ked by the manufacturer with the type number, the Morse taper number, material identification, and the number of this BritishStandard. Example: For a fixed centre, Type2,3 Morse taper, high speed steel: 23MTHSBS426 9) BS 3730, “Methods for the assessment of departures from roundness”. 10) BS 1134, “
45、Centre-line-average height method for the assessment of surface texture”.10 +0 0.005 +0 BS 426:1969 BSI 11-1999 3 Figure 1 Fixed centre, long series, standard Morse taper shankBS 426:1969 4 BSI 11-1999 Table 1 Dimensions for fixed centre, long series, standard Morse taper shank All dimensions in mil
46、limetres 1 2 3 4 5 6 7 8 9 10 11 Morse taper number (MT) Nominal taper Included angle of taper Diameter at gauge plane Length of protected end Diameter of protected end Length rear of gauge plane Nose diameter Nominal length forward of gauge plane Overall length of centre (auxiliary) Diameter of con
47、e flat (calculated) A B C D E G H J Nominal Tolerance h14 Nominal Tolerance h12 Nominal Tolerance Nominal Tolerance h9 Max. 0 0.624 6 : 12 = 0.052 05 2 58.75 9.045 4 6 50 9.2 20 70 1 1 0.598 58 : 12 = 0.049 88 2 51.45 12.065 5 9 53.5 12.2 26.5 80 2 0.599 41 : 12 = 0.049 95 2 51.68 17.780 14 64 18 36
48、 100 3 0.602 35 : 12 = 0.050 20 2 52.52 23.825 7 19 81 24.1 44 125 4 0.623 26 : 12 = 0.051 94 2 58.51 31.267 9 25 102.5 31.6 57.5 160 5 0.631 51 : 12 = 0.052 63 3 00.87 44.399 10 35.7 129.5 44.7 70.5 200 2 6 0.625 65 : 12 = 0.052 14 2 59.19 63.348 16 51 182 63.8 88 2700 + 0.120 0 + 1 0 +0.036 0 + 0.
49、300 0 + 0.150 0 + 0.043 0 + 0.180 0 + 0.360 0 +0.210 0 + 0.052 0 +1.5 0 +0.62 0 +0.250 0 + 0.430 0 +0.300 0 +0.074 BS426:1969 BSI 11-1999 5 Table 2 Dimensions for fixed centre, short series, standard Morse taper shank (SeeFigure 2) Figure 2 Fixed centre, short series, standard Morse taper shank All dimensions in millimetres 1 2 3 Morse taper number (MT) Nominal length forward of gauge plane G Overall length of centre (auxiliary) H 0 10 60 1 16.5 70 2 21 85 3 29 110 4 37.5 14
