1、BRITISH STANDARD BS 5204-1: 1975 Incorporating Amendment No. 1 Specification for Straightedges Part 1: Cast iron straightedges (bow shaped and I-section) UDC 621.753.3:531.717.86:669.13BS5204-1:1975 This British Standard, having been approved by the Mechanical Engineering Industry Standards Committe
2、e, was published under the authority of the Executive Board on 30 April 1975 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference MEE/59 Draft for comment 73/36833 DC ISBN 0 580 08543 0 Co-operating organizations The Mechanical Engineering Industry Standa
3、rds Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and professional and industrial organizations: The Government department and the organization marked with an asterisk in the above list, together with the
4、following, were directly represented on the committee entrusted with the preparation of this British Standard. Associated Offices Technical Committee Department of Trade Association of Consulting Engineers Electricity Supply Industry in England and Association of Hydraulic Equipment Wales Manufactur
5、ers Ltd. Engineering Equipment Users Association Association of Mining Electrical and Mechanical Federation of Manufacturers of Engineers Construction Equipment and Cranes British Compressed Air Society Institution of Gas Engineers British Electrical and Allied Institution of Heating and Ventilating
6、 Manufacturers Association Engineers British Gas Corporation Institution of Mechanical Engineers British Gear Manufacturers Association Institution of Plant Engineers British Internal Combustion Engine Institution of Production Engineers* Manufacturers Association London Transport Executive British
7、Mechanical Engineering Confederation Machine Tool Trades Association British Pump Manufacturers Association Ministry of Defence* British Steel Corporation National Coal Board British Steel Industry Process Plant Association Crown Agents for Oversea Governments and Railway Industry Association of Gre
8、at Administrations Britain Department of Employment (HM Factory Royal Institute of British Architects Inspectorate) Society of Motor Manufacturers and Department of the Environment Traders Ltd. Department of Industry Telecommunication Engineering and Department of Industry National Engineering Manuf
9、acturing Association Laboratory British Calibration Service Gauge and Toolmakers Association Department of Prices and Consumer Joint Equipment Standardization Committee Protection Amendments issued since publication Amd. No. Date of issue Comments 4129 November 1982 Indicated by a sideline in the ma
10、rginBS5204-1:1975 BSI 07-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Nomenclature and definitions 1 4 Material 2 5 Lengths of straightedges 2 6 General features 3 7 Finish 4 8 Flatness of working surfaces 5 9 Equality of depths 5 10 Flatn
11、ess of side faces 6 11 Squareness of working surface and side faces 6 12 Marking 6 13 Protection against climatic conditions 6 14 Case 6 Appendix A Minimum general dimensions for straightedges 7 Appendix B Recommended methods of testing cast iron straightedges 7 Appendix C Recommended chemical compo
12、sitions of plain and alloy cast irons and method of heat treatment 10 Figure 1 Bow shaped straightedge 1 Figure 2 I-section straightedge 1 Figure 3 Exaggerated illustration of squareness deviation 2 Figure 4 Alternative positions 3 Figure 5 Design of supporting feet 3 Figure 6 Alternative methods of
13、 using parallel blocks to support the straightedge in position (b) of Figure 4 4 Figure 7 Test by inclination method 8 Figure 8 Plotting of readings 8 Table 1 Tolerances on flatness of working surfaces 5 Table 2 Tolerances on equality of depth between working surface and faces of support feet (bow s
14、haped): tolerances on uniformity of depth between working surfaces (I-section) 5 Table 3 Minimum general dimensions for bow shaped straightedges 7 Table 4 Minimum general dimensions for I-section straightedges 7 Publications referred to 12BS5204-1:1975 ii BSI 07-1999 Foreword This Part of this Briti
15、sh Standard is one of a series for engineers precision measuring equipment that is now being revised and metricated to replace those in imperial units. This standard replaces BS 818 “Cast iron straightedges (bow shaped and I-section)” which was first published in1938 to cover the bow shaped type and
16、 revised in 1963 to include straightedges of I-section. BS818 is now withdrawn. Part 2 1)of this standard will replace BS 863 “Steel straightedges of rectangular section” and will be in metric units. Certification. Attention is drawn to the certification facilities described on the inside back cover
17、 of this standard. 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 confer immunity from legal obligations. Summary of pages This
18、document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 12, 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 the inside front cover. 1) In
19、course of preparation.BS5204-1:1975 BSI 07-1999 1 1 Scope This Part of this British Standard specifies requirements for cast iron straightedges of bow shaped design and of I-section in metric sizes. Two grades of accuracy are provided for each type, namely grade A and grade B. Requirements applicabl
20、e to both types are given in clauses3 and 4 and 7 to14 inclusive while clauses 5 and 6 specify particular requirements relating to bow shaped straightedges in lengths up to and including 8 000 mm and I-section straightedges in lengths up to and including 5 000 mm. Recommended general dimensions, met
21、hods of testing and heat treatments are given in appendices. NOTEA straightedge complying fully with the requirements of a superseded standard continues to be operational but it should be brought into full association with this standard when convenient, i.e. when the surfaces are reconditioned and/o
22、r retested. 2 References The titles of the British Standards referred to in this standard are listed on page 12. 3 Nomenclature and definitions For the purposes of this Part of this British Standard the nomenclature indicated in Figure 1 and Figure 2 has been adopted and the following definitions ap
23、ply. 3.1 deviation from flatness of the working surface the minimum distance between two parallel planes which just envelope the working surface NOTEIt may be necessary to control the maximum slope of the surface deviations with respect to the enclosing planes. Figure 1 Bow shaped straightedge Figur
24、e 2 I-section straightedgeBS5204-1:1975 2 BSI 07-1999 3.2 flatness tolerance the maximum permissible value of the deviation from flatness NOTEThe working surfaces of straightedges covered by this standard are not strictly speaking straight edges; they are elongated surfaces for which it is appropria
25、te to specify flatness tolerances. 3.3 deviation from squareness of two surfaces the minimum distance between two parallel planes which just enclose one surface and are perpendicular to a datum plane in contact with the other surface NOTESeeFigure 3. 3.4 squareness tolerance the maximum permissible
26、value of the deviation from squareness 4 Material The straightedges shall be of close-grained, plain or alloy cast iron in accordance with the minimum requirements for grade12 as specified in BS1452:1961. NOTEHigher grades of cast iron are available which would be more resistant to possible mishandl
27、ing than grade12, but grade12 is specified for this equipment because it offers the best combination of wear resistance and rigidity. The material shall be sound and free from blowholes and porosity. Minor defects may, however, be repaired by plugging with material of similar composition to that fro
28、m which the straightedge is made. A suitable heat treatment to relieve internal stresses is given inAppendix C. 5 Lengths of straightedges The recommended lengths of straightedges are as follows: Straightedges of intermediate lengths should be ordered only when it is not practicable to adopt one of
29、the recommended lengths. Such straightedges shall conform to the same tolerances as those given for the next shorter recommended length. Figure 3 Exaggerated illustration of squareness deviation Bow shaped: 300, 500, 1 000, 2 000, 4 000, 6 000 and 8 000 mm, I-section: 300, 500, 1 000, 2 000, 3 000,
30、4 000 and 5 000 mm.BS5204-1:1975 BSI 07-1999 3 6 General features 6.1 Bow shaped. The general design of the straightedge is left to the manufacturer (seeAppendix A for recommended dimensions). Provision shall be made for two feet (seeFigure 1) of the same width as the working surface and so located
31、as to allow the straightedge to be used in the following positions (shown in Figure 4): a) resting upon the feet; b) with the working surface downward; c) lying on either side. In any of these positions the accuracy of the straightedge as specified in clauses 8 to 11 inclusive shall be maintained. T
32、he feet shall be designed in the form shown in Figure 5, one foot having two supporting surfaces comprising not more than the two outer thirds of the foot and the other having one supporting surface comprising not more than the middle third of the foot. For supporting in position (b) of Figure 4, tw
33、o or three equal and parallel blocks providing localized support may be used, disposed as shown inFigure 6. NOTEFailure to support the straightedge in the manner shown in Figure 6 may cause it to wind or distort over its width. Figure 4 Alternative positions Figure 5 Design of supporting feetBS5204-
34、1:1975 4 BSI 07-1999 6.2 I-section. The general design of the straightedge is left to the manufacturer (seeAppendix A for recommended dimensions) but the two working surfaces shall have the same width and the rigidity shall be such that when the straightedge is supported on either working surface in
35、 the manner shown in Figure 6 at the points indicated by the engraved arrows, or lying on either of its side faces, the working surfaces shall conform to the tolerances given in clauses8 to11 inclusive. NOTEFailure to support the straightedge in the manner shown in Figure 6 may cause it to wind or d
36、istort over its width. Arrows, together with the word SUPPORT, shall be engraved on the side faces to indicate the points at which the straightedge should be supported to ensure minimum deflection under its own weight. These arrows are placed two-ninths of the length of the straightedge from each en
37、d (seeFigure 2). 7 Finish The working surfaces and supporting feet of grade A straightedges shall be finished by scraping or any other process which produces a similar type of surface to that obtained by scraping. The working surfaces of grade B straightedges and the side faces of all straightedges
38、shall be finished by similar processes or by smooth machining. The proportion of bearing area of the working surface shall be not less than20% for grade A straightedges and not less than 10% for grade B straightedges. High spots shall be uniformly distributed and the percentage of bearing area shoul
39、d not be so high as to cause wringing. NOTERecommended methods of testing applicable to straightedges with scraped surfaces are given in Appendix B. All sharp edges shall be removed. All unmachined parts shall be painted. Figure 6 Alternative methods of using parallel blocks to support the straighte
40、dge in position(b) of Figure 4BS5204-1:1975 BSI 07-1999 5 8 Flatness of working surfaces The bearing area of the working surfaces shall be flat within the tolerances given in Table 1. Table 1 Tolerances on flatness of working surfaces In addition to conforming to the tolerances given in Table 1, the
41、 deviation from flatness over any local length on straightedges 1000 mm and larger shall not exceed the following amounts: grade A: 0.003 mm per 300 mm grade B: 0.006 mm per 300 mm. 9 Equality of depths (working surface to faces of support feet) (seeFigure 1) When a bow shaped straightedge rests on
42、a flat base (see position (a) of Figure 4), the depths from the working surface of the straightedge to this base, measured immediately over each support foot, shall be equal to each other to within the tolerances given in Table 2. Table 2 Tolerances on equality of depth between working surfaceandfac
43、esofsupportfeet(bow shaped):tolerances on uniformityofdepthbetweenworkingsurfaces(I-section) NOTEThese tolerances apply to the straightedge supported in any of the three positions as specified in clause 6. Length of straightedge Flatness tolerance Grade A Grade B mm mm mm 300 500 1 000 2 000 3 000 4
44、 000 5 000 6 000 8 000 0.003 0.005 0.010 0.020 0.030 0.040 0.050 0.060 0.080 0.006 0.010 0.020 0.040 0.060 0.080 0.100 0.120 0.160 NOTETolerances on flatness of working surfaces for straightedges with lengths other than those listed in Table 1 can be calculated at the rate of 0.001 mm per 100 mm for
45、 grade A and0.002 mm per 100 mm for grade B, with minimum of 0.003 mm for grade A and 0.006 mm for grade B. Grade A tolerances are to be rounded up to the nearest 0.001 mm and grade B tolerances expressed to the nearest 0.002 mm. NOTEThese tolerances apply to the straightedge supported in any of the
46、 three positions as specified in clause 6. Length of straightedge Tolerances on equality or uniformity of depth Grade A Grade B mm mm mm 300 500 1 000 2 000 3 000 4 000 5 000 6 000 8 000 0.003 0.005 0.010 0.020 0.030 0.040 0.050 0.060 0.080 0.006 0.010 0.020 0.040 0.060 0.080 0.100 0.120 0.160BS5204
47、-1:1975 6 BSI 07-1999 10 Flatness of side faces Any 300 mm length of each side face of a grade A straightedge shall be flat to within0.025mm and any300mm length, of each side face of a grade B straightedge shall be flat to within0.05mm. The maximum tolerance on flatness over the whole length of stra
48、ightedges up to and including4000mm shall be0.05mm for grade A and0.1mm for grade B; for longer straightedges, these tolerances shall be doubled for both grades. 11 Squareness of working surface and side faces When a straightedge is laid on its side on a grade A surface plate (as specified in BS817:
49、1972) the working surface shall be square to the surface plate to within0.008mm per25mm for grade A straightedges and0.015mm per25mm for grade B straightedges. (See alsoFigure 4.) NOTEIf squareness of the individual side faces adjacent to working surfaces is required, the purchaser should specify the accuracy. 12 Marking Each straightedge shall be legibly and permanently marked with the following particulars. a) The manufacturers name or trade mark. b) The number of this British Standard, i.e. BS 5204-1. c) An identification
