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1、BRITISH STANDARD BS 869:1978 Specification for Toolmakers flats and high precision surface plates UDC 621.753:531.717.82:531.745 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 869:1978 This British Standard
2、, having been prepared under the direction of the Mechanical Engineering Standards Committee, was published under the authority of the Executive Board on 31 January 1978 BSI 03-1999 First published September 1939 First revision January 1978 The following BSI references relate to the work on this sta
3、ndard: Committee reference MEE/59 Draft for comment 72/33731 DC ISBN 0 580 09728 5 Cooperating organizations The Mechanical Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific
4、and industrial organizations: Associated Offices Technical Committee Association of Consulting Engineers Association of Hydraulic Equipment Manufacturers Association of Mining Electrical and Mechanical Engineers British Compressed Air Society British Electrical and Allied Manufacturers Association (
5、BEAMA) British Gas Corporation British Gear Manufacturers Association British Internal Combustion Engine Manufacturers Association British Pump Manufacturers Association British Steel Corporation Chartered Institution of Building Services Crown Agents for Oversea Governments and Administrations Depa
6、rtment of Industry, Mechanical Engineering Department of Industry, National Engineering Laboratory Department of the Environment Department of Trade (Marine Division, Department of Transport Electricity Supply Industry in England and Wales Engineering Equipment Users Association Federation of Manufa
7、cturers of Construction Equipment and Cranes Health and Safety Executive Institution of Gas Engineers Institution of Mechanical Engineers Institution of Plant Engineers Institution of Production Engineers* London Transport Executive Machine Tool Trades Association Ministry of Defence* National Coal
8、Board Process Plant Association Railway Industry Association of Great Britain Telecommunication Engineering and Manufacturing Association (TEMA) The Society of Motor Manufacturers and Traders Limited Water-tube Boilermakers Association The organizations marked with an asterisk in the above list, tog
9、ether with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Department of Industry, National Physical Laboratory Department of Prices and Consumer Protection, British Calibration Service Gauge and Tool Makers Association Individual ex
10、pert Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 869:1978 BSI 03-1999i Contents Page Cooperating organizations Inside front cover Forewor
11、d ii 1Scope1 2References1 3Material1 4Features of design and recommended sizes1 5Finish2 6Accuracy2 7Cases for flats2 8Covers for plates2 9Preservation and packing2 10Marking2 Appendix A Compositions of some typical steels and cast irons and notes on the appropriate methods of heat treatment3 Figure
12、 1 Toolmakers flat showing recess in base and groove round periphery1 Table 1 Dimensions of flats and plates1 Table 2 Tolerances2 Publications referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:36 GMT+00:00 2006, Uncontrolled Copy
13、, (c) BSI BS 869:1978 ii BSI 03-1999 Foreword This British Standard, prepared under the direction of the Mechanical Engineering Standards Committee, was first published in 1939 when it specified toolmakers flats and high precision surface plates in inch units. It has now been revised in accordance w
14、ith the policy of producing fully metricated standards. This standard prescribes standards of accuracy for steel toolmakers flats and for small high precision cast iron or granite surface plates. The standard includes only such requirements as are essential to ensure that the flats and plates will b
15、e suitable for high precision work and be sufficiently robust to retain their original accuracy. Inspection and certification of items in this standard may be undertaken by certain laboratories approved for this purpose by the British Calibration Service; addresses can be obtained on application to
16、the Director, British Calibration Service, 26 Chapter Street, London SW1P 4NS. A British Standard 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 co
17、nfer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, 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 indicat
18、ed in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 869:1978 BSI 03-19991 1 Scope This British Standard is applicable to circular hardened steel toolmakers fl
19、ats having a maximum diameter of 200 mm, and to cast iron or granite high precision surface plates having a maximum diameter of 400 mm. 2 References The titles of the publications referred to in this standard are listed on the inside back cover. 3 Material 3.1 Steel toolmakers flats. Toolmakers flat
20、s shall be of high quality steel, free from inclusions, and shall preferably be made from hammered and upset blanks. The flats shall be hardened and stabilized and shall then give a Vickers hardness of not less than 850 HV1), when tested in accordance with the requirements of BS 427-1. 3.2 Cast iron
21、 surface plates. Surface plates shall be of good quality close grained stabilized cast iron or alloy cast iron, sound and free from blow holes and porous patches. NOTECompositions for suitable steels and cast iron including methods of heat treatment are given in Appendix A. 3.3 Granite toolmakers fl
22、ats and surface plates. Granite may be used as a material for toolmakers flats and surface plates. The rock shall be close grained and of uniform texture, sound and free from flaws and fissures and from inclusions of softer minerals. The colour of the granite, which is dependent on the mineral compo
23、sition, is of no importance, but the colour of any individual plate shall be uniform. 3.4 Defects. The repair of defects in the working surfaces of plates is not permitted. 4 Features of design and recommended sizes 4.1 Toolmakers flats. Toolmakers flats shall be circular and of solid steel or grani
24、te and of an overall thickness not less than that given in Table 1, column 3. Flats may have one or both surfaces finished as working surfaces. Any non-working surface may be recessed, as shown in Figure 1, to approximately the dimensions given in Table 1, columns 4 and 5. The base and the working f
25、ace, or the two working faces, shall be parallel to within 0.0025 mm. All sharp edges shall be removed. It is recommended that a shallow groove be provided around the periphery of the larger flats to facilitate handling. Table 1 Dimensions of flats and plates 4.2 High precision cast iron surface pla
26、tes. Cast iron plates shall be circular and of robust design, with adequate framing and ribbing underneath, so that distortion when in use is reduced to a minimum. Each plate shall be supported on three feet which shall be smoothly machined. The plane of the feet shall be parallel to the working fac
27、e to within 0.012 mm unless means of adjustment of the feet is incorporated. The top of each plate shall project slightly, to at least 20 mm depth, beyond the framing and shall be machined round the outside. The thickness of the top of each plate after machining and finishing shall be not less than
28、the appropriate amount given in Table 1, column 6. 1) The approximate equivalent hardness on the Rockwell C scale is 66 HRC. See BS 860. Figure 1 Toolmakers flat showing recess in base and groove round periphery Dimensions in millimetres 1234567 Recommended size and diameter of flat or plate D Minim
29、um overall thickness of flat T RecessMinimum thickness of top of plate Minimum total depth of plate Dia. A Depth B Flats 63 100 160 200 16 20 32 40 40 80 120 160 2 3 6 6 Plates 250 400 20 30 70 100 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:36 GMT+00:
30、00 2006, Uncontrolled Copy, (c) BSI BS 869:1978 2 BSI 03-1999 The total depth of the top and framing of each plate shall be not less than the appropriate amount given in Table 1, column 7. 4.3 High precision granite surface plates. These plates shall be solid and machined all over. The top of each p
31、late shall project slightly for convenience in lifting. The total depth of each plate shall be not less than the appropriate amount given in Table 1, column 7. 4.4 Recommended sizes. The recommended sizes of flats and plates are listed in columns 1 and 2 of Table 1. 5 Finish The working surface (or
32、surfaces) of the flats and plates shall be finished by high grade lapping2)free from noticeable scratches. Working surfaces shall be free from embedded abrasives. All unmachined parts of cast iron plates shall be painted. 6 Accuracy Each working surface (exclusive of the margin specified in Table 2)
33、 shall everywhere lie between two parallel planes whose distance apart does not exceed the amount given in column 3 of Table 2. Table 2 Tolerances 7 Cases for flats Each flat shall be supplied in a case which shall provide adequate protection for the faces and edges of the flat. 8 Covers for plates
34、Each plate shall be supplied with a protective cover of a suitable material which shall be so constructed as to protect both the surface and the edges of the plate. 9 Preservation and packing During storage and transit all finished surfaces and edges of flats and plates shall be protected against cl
35、imatic conditions by being covered with a suitable corrosion preventative preparation3). 10 Marking Each flat and plate shall have legibly and permanently marked on the side in characters not less than 3 mm high, the manufacturers name or trademark and serial number. Marking shall not be of such a n
36、ature as to impair the surface of the plate, e.g. stamping. NOTE As an alternative to the marking of the manufacturers name or trademark on the machined edge, the name or mark may, in cases of cast iron plates, be legibly cast on the framing. 2) A non-wringing surface (or surfaces) may be specified
37、by the purchaser. 123 Diameter of flat or plate Marginal width which may be disregarded Separation of limiting planes Flats up to 200 mm 250 mm plates 400 mm plates mm 2 6 10 4m 0.5 0.8 1.0 3) See BS 1133-6. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:
38、36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 869:1978 BSI 03-19993 Appendix A Compositions of some typical steels and cast irons and notes on the appropriate methods of heat treatment A.1 Carbon steel. The recommended chemical composition for carbon steel is as follows. The flat is heated slowly
39、 and uniformly to a temperature between 770 C and 780 C, and is maintained sufficiently long at this temperature to ensure an even temperature through the flat. The flat is then quenched in a 5 % to 10 % solution of brine and is immediately tempered in a furnace or oil bath at a temperature of 150 C
40、. The flat is maintained at this temperature for a period between 4 h and 5 h and is then allowed to cool naturally in the furnace or tempering bath. A.2 Carbon-chromium alloy steel no.1. The recommended chemical composition for carbon-chromium alloy steel no.1 is as follows. The flat is heated slow
41、ly and uniformly to a temperature between 950 C and 960 C, and is maintained at this temperature for a period between 30 min and 45 min. The flat is then quenched in oil, and is immediately tempered by the process described above for straight carbon steel. A.3 Carbon-chromium alloy steel no.2. (Prod
42、uced by the crucible or electric process.) The recommended chemical composition for carbon-chromium alloy steel no.2 is as follows. The flat is heated slowly and uniformly to a temperature between 830 C and 840 C, and is maintained at this temperature for a period between 30 min and 45 min. The flat
43、 is then quenched in water at about 20 C and is immediately tempered by the process described above for straight carbon steel. A.4 Cast iron. The recommended chemical compo- sition for plain cast iron is as follows. The appropriate treatment for the dimensional stabilization by stress relieving of p
44、lates made from cast iron of the above composition is as follows. The plates, after being rough machined and fully fettled, should be placed in an annealing furnace and be heated slowly to a temperature between 510 C and 560 C maximum, and be maintained at this temperature for a long period (25 h fo
45、r best results). The casting has to be protected from the direct heat of the flames by means of suitable baffle plates and the heating should be as uniform as possible throughout. Also the casting should be supported in the furnace on the points on which it will subsequently stand in service. For sm
46、all castings, more uniform heating may be achieved by packing the castings in iron filings in boxes. Rigorous control of the cooling rate has to be exercised. The furnace should be “fired down” at a rate not exceeding 5 C/h down to 100 C before opening the furnace and allowing it to cool naturally.
47、A.5 Alloy cast iron. The recommended chemical composition for alloy cast iron is as follows. The stress relieving of plates made from alloy cast iron of the above composition is similar to that given above for plain cast iron, except that the castings should be slowly heated to a temperature between
48、 560 C and 590 C maximum. Carbon1.00 % to 1.10 % Manganese0.30 % max. Silicon0.25 % max. Carbon1.90 % to 2.00 % Chromium11.00 % to 13.50 % Manganese0.25 % max. Silicon0.30 % max. Nickel0.50 % max. Carbon0.95 % to 1.10 % Chromium1.00 % to 1.50 % Manganese0.25 % to 0.40 % Silicon0.30 % max. Total carb
49、on3.0 % to 3.5 % Combined carbon0.4 % to 0.7 % Manganese0.5 % to 1.2 % Silicon1.0 % to 1.6 %a Sulphur0.15 % max. Phosphorus1.2 % max. a The higher silicon limits are intended for the lighter sectional castings. Total carbon2.8 % to 3.2 % Silicon0.8 % to 1.5 %a Manganese0.6 % to 1.0 % Sulphur0.12 % max. Phosphorus0.3 % max. Nickel1.4 % to 1.6 % Chromium0.4 % to 0.6 % a The higher silicon limits are intended for the lighter sectional castings. Licensed Copy: London South Bank University, London South Bank Univ
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