1、BRITISH STANDARD CONFIRMED AUGUST1959 BS 852:1939 Incorporating amendments issued August1946and December1949 Specification for Toolmakers straightedgesBS852:1939 This British Standard having beenapproved by the MechanicalIndustry Committeeand endorsed by theChairman of the EngineeringDivisional Coun
2、cilwas published undertheauthority of the GeneralCouncil on 19 June1939 BSI 08-1999 ISBN 0 580 35098 3 Co-operating organisations The Mechanical Industry Committee under whose supervision this British Standard was prepared consists of representatives from the following Government Departments and Sci
3、entific and Industrial Organisations: Admiralty Crown Agents for the Colonies Department of Scientific and Industrial Research High Commissioner for India H.M. Office of Works Home Office Ministry of Transport War Office Agricultural and Road Machinery Manufacturers Association Association of Consul
4、ting Engineers British Chemical Plant Manufacturers Association British Electrical and Allied Manufacturers Association British Engineers Association British Iron and Steel Federation British Marine Oil Engine Manufacturers Association Engineering Insurance Companies Institute of Marine Engineers In
5、stitute of Petroleum Institution of Automobile Engineers Institution of Civil Engineers Institution of Gas Engineers Institution of Heating and Ventilating Engineers Institution of Mechanical Engineers Institution of Production Engineers Locomotive Manufacturers Association Machine Tool Trades Assoc
6、iation Railway Companies of Great Britain Amendments issued since publication Amd. No. Date of issue Comments August 1946 December 1949 Indicated by a sideline in the marginBS852:1939 BSI 08-1999 i Contents Page Co-operating organisations Inside front cover Foreword ii 1 Scope 1 2 Material 1 3 Gener
7、al features 1 4 Finish 2 5 Accuracy 2 6 Glass test plate 3 7 Handles 3 8 Case 3 9 Packing 3 10 Marking 3 Appendix Testing of toolmakers straightedges 4 Figure 1 1 Figure 2 1 Figure 3 1 Figure 4 2 Figure 5 2BS852:1939 ii BSI 08-1999 Foreword This Specification has been prepared under the authority of
8、 the Mechanical Industry Committee in response to a request received from the Institution of Production Engineers. It forms one of a series of Specifications in course of preparation for engineers precision tools, 1)and has been prepared with the co-operation of the manufacturers and in close collab
9、oration with the National Physical Laboratory. This Specification requires reference to the following British Standard: BS869,Toolmakers Flats and High Precision Surface Plates. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are
10、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 4 and a back cover. This standard has been updated (see co
11、pyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover. 1) Other Specifications for engineers precision tools published are as follows: BS 817, Cast iron surface plates and tables. BS 818, Cast iron straightedges. BS 863, Steel
12、straightedges of rectangular section. BS 869, Toolmakers flats and high precision surface plates. BS 870, Micrometers (external). BS 887, Vernier callipers. BS 888, Slip (or block) gauges and their accessories. BS 906, Engineers parallels (steel). BS 907, Dial gauges for linear measurements. BS 939,
13、 Engineers squares. BS 957, Feeler gauges. BS 958, Precision levels. BS 959, Internal micrometers. BS 1054, Engineers comparators. BS 1643, Vernier height gauges.BS852:1939 BSI 08-1999 1 1 Scope This Specification applies to toolmakers straightedges of short length intended for very accurate work, a
14、nd having one working edge, which is bevelled and very slightly rounded off (commonly described as a “knife-edge”). NOTEThe attention of the purchaser is drawn to the necessity for indicating, in his enquiry and order, his particular requirements in regard to type and length, and whether a test plat
15、e (see Clause6) is required. 2 Material The straightedges shall be made from high quality cast or alloy steel. The straightedges shall be hardened and they shall be suitably heat treated to remove any stresses resulting from the hardening process and to give stability. The diamond pyramid hardness n
16、umber of the hardened straightedges, measured adjacent to the working edge, shall be not less than800. 2) 3 General features Typical sections of straightedges of the type covered by this Specification are given inFigure 1 toFigure 4 inclusive. 2) The approximate equivalent hardness number on the Roc
17、kwell C scale is62. Figure 1 Figure 2 Figure 3 BS852:1939 2 BSI 08-1999 The faces adjoining the working edge may be ground flat or may be hollow ground. It is desirable that the included angle of these faces (seeFigure 5) be not more than30 . The working edge shall be very slightly rounded off, to f
18、urnish what is commonly described as a “knife-edge.” (See Note to Clause4.) It is recommended that straightedges from2in. to6in. in length should have one end finished at an angle as shown inFigure 2 andFigure 3. 4 Finish The working edge shall be finished by grinding, and lapping within the toleran
19、ces specified in Clause5. NOTEThe radius on the working edge shall be uniform from end to end so that accuracy of straightness is retained even when the straightedge is inclined (see Clause5). 5 Accuracy Each straightedge shall conform to the following requirements for straightness of the working ed
20、ge. Straightedges up to and including5in. in length shall be tested on toolmakers Flats (BS869), and straightedges longer than5in. on high precision altered surface plates (BS869). When the straightedge is placed on a British Standard Toolmakers Flat or on a British Standard High Precision Surface P
21、late (BS869) against a well-illuminated background, no white light shall be visible at any point along its length. This test shall apply for any angle of application of the straightedge to the test plate up to10 on either side of the normal. NOTEThis test is sensitive to the order of0.00003in. Figur
22、e 4 Figure 5 BS852:1939 BSI 08-1999 3 6 Glass test plate It is recommended that a black glass test plate be supplied with each set of straightedges of lengths up to6in. The straightness of the reference face of this test plate shall be such that when a true straightedge is applied to the face agains
23、t a well-illuminated background, no white light shall be visible at any point along its length. The reference face shall be indicated by means of an arrow and the words “test face” etched as shown in the following diagram: NOTEWhen using a glass test plate, care should be taken as far as possible to
24、 avoid handling it, as the resultant local temperature effects may introduce errors in the flatness of the working face. 7 Handles Each straightedge of length from6in. to12in. inclusive shall have a permanently attached heat-insulating handle. It is recommended that a suitable form of handle be supp
25、lied with each set of straightedges of lengths fromin. to1 in. inclusive. 8 Case It is desirable that each straightedge, and particularly sets of straightedges be supplied in a suitable protective case. 9 Packing All surfaces of the straightedges shall be protected against climatic conditions by bei
26、ng covered with a hard-drying lanolin or other suitable non-corrosive preparation. 10 Marking Each straightedge shall have legibly and permanently engraved upon it the manufacturers name or trade mark.BS852:1939 4 BSI 08-1999 Appendix Testing of toolmakers straightedges The National Physical Laborat
27、ory is prepared to accept straightedges for examination for conformity with this British Standard. Full particulars of the tests and fees charged may be obtained on application to the Director, The National Physical Laboratory, Teddington, Middlesex.blankBS 852:1939 BSI 389 Chiswick High Road London
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