1、BRITISH STANDARD BS 869:1978 Specification for Toolmakers flats and high precision surface plates UDC 621.753:531.717.82:531.745BS869:1978 This British Standard, having been prepared under the directionof the Mechanical Engineering Standards Committee, was published underthe authority of the Executi
2、ve Board on 31January1978 BSI 03-1999 First published September 1939 First revision January 1978 The following BSI references relate to the work on this standard: Committee reference MEE/59 Draft for comment 72/33731 DC ISBN 0 580 097285 Cooperating organizations The Mechanical Engineering Standards
3、 Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Technical Committee Association of Consulting Engineers Association of Hydraulic Equipment Manuf
4、acturers Association of Mining Electrical and Mechanical Engineers British Compressed Air Society British Electrical and Allied Manufacturers Association (BEAMA) British Gas Corporation British Gear Manufacturers Association British Internal Combustion Engine Manufacturers Association British Pump M
5、anufacturers Association British Steel Corporation Chartered Institution of Building Services Crown Agents for Oversea Governments and Administrations Department of Industry, Mechanical Engineering Department of Industry, National Engineering Laboratory Department of the Environment Department of Tr
6、ade (Marine Division, Department of Transport Electricity Supply Industry in England and Wales Engineering Equipment Users Association Federation of Manufacturers of Construction Equipment and Cranes Health and Safety Executive Institution of Gas Engineers Institution of Mechanical Engineers Institu
7、tion of Plant Engineers Institution of Production Engineers* London Transport Executive Machine Tool Trades Association Ministry of Defence* National Coal Board Process Plant Association Railway Industry Association of Great Britain Telecommunication Engineering and Manufacturing Association (TEMA)
8、The Society of Motor Manufacturers and Traders Limited Water-tube Boilermakers Association The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Department of Indus
9、try, National Physical Laboratory Department of Prices and Consumer Protection, British Calibration Service Gauge and Tool Makers Association Individual expert Amendments issued since publication Amd. No. Date of issue CommentsBS869:1978 BSI 03-1999 i Contents Page Cooperating organizations Inside f
10、ront cover Foreword ii 1 Scope 1 2 References 1 3 Material 1 4 Features of design and recommended sizes 1 5 Finish 2 6 Accuracy 2 7 Cases for flats 2 8 Covers for plates 2 9 Preservation and packing 2 10 Marking 2 Appendix A Compositions of some typical steels and cast irons and notes on the appropr
11、iate methods of heat treatment 3 Figure 1 Toolmakers flat showing recess in base and groove round periphery 1 Table 1 Dimensions of flats and plates 1 Table 2 Tolerances 2 Publications referred to Inside back coverBS869:1978 ii BSI 03-1999 Foreword This British Standard, prepared under the direction
12、 of the Mechanical Engineering Standards Committee, was first published in1939when it specified toolmakers flats and high precision surface plates in inch units. It has now been revised in accordance with the policy of producing fully metricated standards. This standard prescribes standards of accur
13、acy 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 be suitable for high precision work and be sufficiently robust to retain their original accuracy. In
14、spection 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 the Director, British Calibration Service, 26Chapter Street, London SW1P4NS. A British Standard doe
15、s 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 cover, an insi
16、de front cover, pages i and ii, pages1 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 indicated in the amendment table on theinside front cover.BS869:1978 BSI 03-1999 1 1 Scope This British Stand
17、ard is applicable to circular hardened steel toolmakers flats having a maximum diameter of200mm, and to cast iron or granite high precision surface plates having a maximum diameter of400mm. 2 References The titles of the publications referred to in this standard are listed on the inside back cover.
18、3 Material 3.1 Steel toolmakers flats. Toolmakers flats 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 than850HV 1) , when tested in accor
19、dance with the requirements of BS427-1. 3.2 Cast iron 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 treatme
20、nt are given in Appendix A. 3.3 Granite toolmakers flats 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
21、 the granite, which is dependent on the mineral composition, 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. Toolmaker
22、s flats shall be circular and of solid steel or granite and of an overall thickness not less than that given in Table 1, column3. 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
23、Table 1, columns4 and5. The base and the working face, or the two working faces, shall be parallel to within0.0025mm. 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
24、 plates 4.2 High precision cast iron surface plates. 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
25、of the feet shall be parallel to the working face to within0.012mm unless means of adjustment of the feet is incorporated. The top of each plate shall project slightly, to at least20mm depth, beyond the framing and shall be machined round the outside. The thickness of the top of each plate after mac
26、hining and finishing shall be not less than the appropriate amount given in Table 1, column6. 1) The approximate equivalent hardness on the Rockwell C scale is66HRC. See BS860. Figure 1 Toolmakers flat showing recess inbase and groove round periphery Dimensions in millimetres 1 2 3 4 5 6 7 Recommend
27、ed size and diameter of flat or plate D Minimum overall thickness of flat T Recess Minimum 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 100BS869:1978 2 BSI 03-1999 The total depth of the top and f
28、raming of each plate shall be not less than the appropriate amount given in Table 1, column7. 4.3 High precision granite surface plates. These plates shall be solid and machined all over. The top of each plate shall project slightly for convenience in lifting. The total depth of each plate shall be
29、not less than the appropriate amount given in Table 1, column7. 4.4 Recommended sizes. The recommended sizes of flats and plates are listed in columns1and2of Table 1. 5 Finish The working surface (or surfaces) of the flats and plates shall be finished by high grade lapping 2) free from noticeable sc
30、ratches. 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) shall everywhere lie between two parallel planes whose distance apart does not exceed the amount
31、given in column3of 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 Each plate shall be supplied with a protective cover of a suitable material which shall be so constr
32、ucted 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 climatic conditions by being covered with a suitable corrosion preventative preparation 3) . 10 Markin
33、g Each flat and plate shall have legibly and permanently marked on the side in characters not less than3mm high, the manufacturers name or trademark and serial number. Marking shall not be of such a nature as to impair the surface of the plate, e.g.stamping. NOTE As an alternative to the marking of
34、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 by the purchaser. 1 2 3 Diameter of flat or plate Marginal width which may be disregarded Separation
35、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.BS869:1978 BSI 03-1999 3 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 composi
36、tion for carbon steel is as follows. The flat is heated slowly and uniformly to a temperature between770C and780C, and is maintained sufficiently long at this temperature to ensure an even temperature through the flat. The flat is then quenched in a5% to10% solution of brine and is immediately tempe
37、red in a furnace or oil bath at a temperature of150C. The flat is maintained at this temperature for a period between4h and5h 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 s
38、teel no.1is as follows. The flat is heated slowly and uniformly to a temperature between950C and960C, and is maintained at this temperature for a period between30min and45min. The flat is then quenched in oil, and is immediately tempered by the process described above for straight carbon steel. A.3
39、Carbon-chromium alloy steel no.2. (Produced by the crucible or electric process.) The recommended chemical composition for carbon-chromium alloy steel no.2is as follows. The flat is heated slowly and uniformly to a temperature between830C and840C, and is maintained at this temperature for a period b
40、etween30min and45min. The flat is then quenched in water at about20C 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 stabilizat
41、ion by stress relieving of plates 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 between510C and560C maximum, and be maintained at this temperature fo
42、r a long period(25h for 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 st
43、and in service. For small 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 exceeding5C/h down to100C before opening the furnace and allowing it t
44、o cool naturally. 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 t
45、emperature between560C and590C maximum. Carbon 1.00% to 1.10% Manganese 0.30% max. Silicon 0.25% max. Carbon 1.90% to 2.00% Chromium 11.00% to 13.50% Manganese 0.25% max. Silicon 0.30% max. Nickel 0.50% max. Carbon 0.95% to 1.10% Chromium 1.00% to 1.50% Manganese 0.25% to 0.40% Silicon 0.30% max. To
46、tal carbon 3.0% to 3.5% Combined carbon 0.4 % to 0.7 % Manganese 0.5 % to 1.2 % Silicon 1.0 % to 1.6 % a Sulphur 0.15 % max. Phosphorus 1.2 % max. a The higher silicon limits are intended for the lighter sectional castings. Total carbon 2.8 % to 3.2 % Silicon 0.8 % to 1.5 % a Manganese 0.6 % to 1.0
47、% Sulphur 0.12 % max. Phosphorus 0.3 % max. Nickel 1.4 % to 1.6 % Chromium 0.4 % to 0.6 % a The higher silicon limits are intended for the lighter sectional castings.4 blankBS869:1978 BSI 03-1999 Publications referred to BS 427, Method for Vickers hardness test. BS 427-1, Testing of metals. BS 860,
48、Tables for comparison of hardness scales. BS 1133, Packaging code. BS 1133-6, Temporary protection of metal surfaces against corrosion (during transport and storage). BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
49、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that
