1、BRITISH STANDARD BS906-2:1972 Specification for Engineers parallels Part2: Imperial unitsBS906-2:1972 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee,was published underthe authority of the Executive Board on 16 June 1972 BSI 09-1999 First publish
2、ed 24 June 1940 First revision Part2 June 1972 The following BSI references relate to the work on this standard: Committee reference MEE/59 Draft for approval71/34901 ISBN 0 580 07043 3 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision this B
3、ritish Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations. Associated Offices Technical Committee Engineering Equipment Users Association Association of Consulting Engineers Gas Council Association of Hydraulic Equ
4、ipment Institution of Civil Engineers Manufacturers Ltd Institution of Gas Engineers Association of Mining Electrical and Institution of Heating and Ventilating Mechanical Engineers Engineers British Chemical Plant Manufacturers Institution of Mechanical Engineers Association Institution of Mechanic
5、al Engineers British Compressed Air Society (Automobile Division) British Electrical and Allied Manufacturers Institution of Plant Engineers Association Institution of Production Engineers* British Gear Manufacturers Association Locomotive and Allied Manufacturers British Internal Combustion Engine
6、Association of Great Britain Manufacturers Association London Transport Executive British Mechanical Engineering Confederation Machine Tool Trades Association British Pump Manufacturers Association Ministry of Defence British Steel Industry Ministry of Defence, Army Department* Crown Agents for Over
7、sea Governments and National Coal Board Administrations National Physical Laboratory (Department of Department of Employment and Productivity Trade and Industry)* (H.M. Factory Inspectorate) Royal Institute of British Architects Department of the Environment Telecommunications Engineering Department
8、 of Trade and Industry Manufacturing Association Department of Trade and Industry National Water Tube Boilermakers Association Engineering Laboratory Electricity Council, the Central Electricity Generating Board and the Area Boards in England and Wales The Government departments and the industrial o
9、rganization 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 and were assisted by a number of individual members: Gauge and Tool Makers Association Amendments issued since public
10、ation Amd. No. Date CommentsBS906-2:1972 BSI 09-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Material 1 3 Standard sizes 1 4 Finish 1 5 Accuracy 1 6 Protection 1 7 Marking 1 Table 1 Tolerances on Grade A parallels 2 Table 2 Tolerances on Grade B parallel
11、s 3BS906-2:1972 ii BSI 09-1999 Foreword This standard makes reference to the following British Standards: BS860, Tables for comparison of hardness scales. BS891, Method for Rockwell hardness test Part1: Testing of metals. BS906, Engineers parallels Part1: Metric units. BS1133, Packaging code, Sectio
12、n6. Temporary prevention of corrosion of metal surfaces. This British Standard has been prepared under the authority of the Mechanical Engineering Industry Standards Committee in response to a request received from the Institution of Production Engineers. It forms one of a series of specifications f
13、or engineers precision tools, and has been prepared with the co-operation of the manufacturers and in close collaboration with the National Physical Laboratory. Originally published as BS906,1940, this Part of this British Standard will eventually be withdrawn when the change to metric is complete.
14、It should therefore be considered as obsolescent. Part1 of this standard specifies dimensions for engineers parallels in metric units and it should be noted that the tolerances shown in the two parts of the standard differ slightly. The specification lays down standard sizes of parallels and their g
15、eneral accuracy of dimensions. With regard to the latter, provision is made for two grades of accuracy, one for high precision work and the other for general tool room use. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are respo
16、nsible 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 to3 and a back cover. This standard has been updated (see copyrigh
17、t date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS906-2:1972 BSI 04-1999 1 1 Scope This British Standard applies to parallel steel blocks of the following grades and sizes: Grade A accuracy. Sizes! in“ in 4in to1“ in 3in 12in.
18、 Grade B accuracy. Sizes! in“ in 4 in to2in 4in 16in. The parallels of Grade A accuracy are high precision parallels primarily intended for inspection; those of Grade B accuracy are primarily intended for general tool room work. NOTE 1The larger sizes of parallels may be made with a series of lighte
19、ning holes drilled through their thickness, provided that the accuracy of the parallels is not thereby affected. NOTE 2The titles of the British Standards referred to in this standard are listed on pageii. 2 Material The parallels shall be made from high quality steel. They shall be hardened and sha
20、ll be suitably heat treated to remove any stresses resulting from the hardening process. The diamond pyramid hardness number of the finished parallels shall be not less than800HV 1)for Grade A parallels and not less than640HV 1)for Grade B parallels. 3 Standard sizes The British Standard sizes of pa
21、rallels are as given in Columns1,2 and3 of Table 1 and Table 2. The parallels shall always be supplied in pairs. 4 Finish Grade A and Grade B parallels shall have a finely ground or preferably lapped finish on all faces within the limits specified for each grade in 5. In both grades the ends shall b
22、e finished by milling or grinding. All sharp edges shall be rounded off or bevelled. 5 Accuracy Each parallel and pair of parallels shall conform to the following requirements for Grade A or Grade B accuracy. 5.1 Width and thickness. The maximum permissible errors in width and thickness shall not ex
23、ceed the amounts given in Table 1 for Grade A parallels and Table 2 for Grade B parallels. 5.2 Squareness of faces. The maximum errors in the squareness of adjacent faces shall not exceed0.0001 in per inch with a minimum tolerance of0.0001in for Grade A parallels, and0.0002 in per inch with a minimu
24、m tolerance of0.0002 in for Grade B parallels, measured over the width W. 6 Protection Grade A and B steel parallels shall be protected against climatic conditions by being covered with a suitable corrosion preventative preparation 2)during storage and transit. Each pair of Grade A parallels shall b
25、e supplied in a suitable protective box. 7 Marking Each parallel shall have legibly and permanently engraved upon it, on one or both ends, the following particulars: its general dimensions (Columns1,2 and3 of Table 1 and Table 2), the grade of accuracy, the manufacturers name or trade mark, a serial
26、 number common to each pair of parallels, e.g. # 1“ 8 A Co. 1234. 1) The approximate equivalent hardness numbers on the Rockwell C scale are64 and57.6 respectively. When Rockwell values are used, tests should be carried out in accordance with BS891 and it should be noted that conversion values may v
27、ary as shown in BS860. 2) Temporary (easily removable) corrosion preventatives are dealt with fully in BS1133, Section 6. Guidance on sealed packs with dessicants is given in Section19, “Use of dessicants in packaging”.BS 906-2:1972 2 BSI 04-1999 Table 1 Tolerances on Grade A parallels 1 2 3 4 5 6 7
28、 General dimensions Maximum permissible errors for each parallel The two parallels of a pair shall have equal mean thicknesses (T) and equal mean widths (W) to within T W L a(minimum) Tolerances on T and W Maximum variations in T and W not to exceed Maximum permissible error in straightness from mea
29、n true plane in in in in in in in ! “ 4 0.0001 0.00005 0.00005 0.00005 ) # 6 0.0001 0.0001 0.0001 0.0001 “ 1 6 0.0001 0.0001 0.0001 0.0001 # 1“ 8 0.00015 0.00015 0.00015 0.00015 1 2 10 0.00015 0.00015 0.00015 0.00015 1! 2“ 10 0.0002 0.00015 0.00015 0.00015 1“ 3 12 0.0002 0.0002 0.0002 0.0002 a The t
30、wo parallels of a pair shall agree in length to within0.01in.BS 906-2:1972 BSI 04-1999 3 Table 2 Tolerances on Grade B parallels 1 2 3 4 5 6 7 General dimensions Maximum permissible errors for each parallel The two parallels of a pair shall have equal mean thicknesses (T) and equal mean widths (W) t
31、o within T W L a(minimum) Tolerances on T and W Maximum variations in T and W not to exceed Maximum permissible error in straightness from mean true plane in in in in in in in ! “ 4 0.00025 0.0001 0.0001 0.0001 ) # 6 0.00025 0.00015 0.00015 0.00015 “ 1 6 0.00025 0.00015 0.00015 0.00015 # 1“ 8 0.0004
32、 0.0002 0.0002 0.0002 1 2 10 0.0004 0.00025 0.00025 0.00025 1! 2“ 10 0.0005 0.00025 0.00025 0.00025 1“ 3 12 0.0005 0.0003 0.0003 0.0003 1# 3“ 14 0.0006 0.00035 0.00035 0.00035 2 4 16 0.0006 0.0004 0.0004 0.0004 a The two parallels of a pair shall agree in length to within0.01in.BS906-2:1972 BSI 389
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