1、BRITISH STANDARD BS 906-1: 1972 Specification for Engineers parallels Part 1: Metric unitsBS906-1:1972 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee, was published under the authorityof the Executive Boardon 16June1972 BSI 03-1999 First publishe
2、d, 24th June, 1940 First revision, Part1, June, 1972 The following BSI references relate to the work on this standard: Committee reference MEE/59 Draft for comment 70/4282 ISBN 0 580 07053 0 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision t
3、his British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Technical Committee Electricity Council, the Central Electricity Association of Consulting Engineers Generating Board and the Area
4、Boards in Association of Hydraulic Equipment England and Wales Manufacturers Ltd. Engineering Equipment Users Association Association of Mining Electrical and Gas Council Mechanical Engineers Institution of Civil Engineers British Chemical Plant Manufacturers Institution of Gas Engineers Association
5、 Institution of Heating and Ventilating British Compressed Air Society Engineers British Electrical and Allied Manufacturers Institution of Mechanical Engineers Association Institution of Mechanical Engineers British Gear Manufacturers Association (Automobile Division) British Internal Combustion En
6、gine Institution of Plant Engineers Manufacturers Association Institution of Production Engineers* British Mechanical Engineering Locomotive and Allied Manufacturers Confederation Association of Great Britain British Pump Manufacturers Association London Transport Executive British Steel Industry Ma
7、chine Tool Trades Association Crown Agents for Oversea Governments and Ministry of Defence Administrations Ministry of Defence, Army Department* Department of Employment and Productivity National Coal Board (H.M. Factory Inspectorate) National Physical Laboratory (Department of Department of the Env
8、ironment Trade and Industry)* Department of Trade and Industry Royal Institute of British Architects Department of Trade and industry National Telecommunications Engineering Engineering Laboratory Manufacturing Association Water Tube Boilermakers Association The Government departments and the indust
9、rial organization 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
10、publication Amd. No. Date CommentsBS906-1:1972 BSI 03-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Material 1 3 Finish 1 4 Accuracy 1 5 Marking 1 6 Protection 4 Appendix Derivation of tolerances stated in Table 1 and Table 2 Inside back cover Figure 1 2
11、Figure 2 2 Table 1 Tolerances on grade A parallels 2 Table 2 Tolerances on grade B parallels 3 Table 3 Basis of tolerances Inside back coverBS906-1:1972 ii BSI 03-1999 Foreword In order to keep abreast of progress in the industries concerned, British Standards are subject to periodical review. Sugge
12、stions for improvements will be recorded and in due course brought to the notice of the committees charged with the revision of the standards to which they refer. A complete list of British Standards, numbering over 5000, fully indexed and with a note of the contents of each, will be found in the Br
13、itish Standards Yearbook, which may be purchased from BSI Sales Department. It may also be consulted in many public libraries and similar institutions. This standard makes reference to the following British Standards: BS 860, Tables for comparison of hardness scales. BS 891, Method for Rockwell hard
14、ness test. Part 1: Testing of metals. BS 906, Engineers parallels. Part 2: Imperial units. BS 1133, Packaging code, Section 6: Temporary prevention of corrosion of metal surfaces. This British Standard, prepared under the authority of the Mechanical Engineering Industry Standards Committee, is part
15、of the BSI programme to produce standards in metric units. An earlier British Standard, BS 906, BS 1940, specified engineers parallels in imperial units. This has been revised to become Part 2 of this standard, and will be withdrawn when the change to metric has been completed. It should therefore b
16、e considered as obsolescent. Part 1 of this standard lists a small number of standard sizes which have been chosen consistent with using the parallels individually or in combination over a useful range of reasonably small increments. The sizes are easily called to mind. The tolerances in this Part o
17、f this standard are based on formulae shown in an appendix and are inter-related for different dimensions and for the two grades. It should be noted that the tolerances shown in the two parts of the standard differ slightly. A British Standard does not purport to include all the necessary provisions
18、 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 inside front cover, pages i and ii, pages1to 4, an inside
19、 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.BS906-1:1972 BSI 03-1999 1 1 Scope This British Standard applies to parallel sided steel blocks of six si
20、zes in Grade A and eight sizes in Grade B, namely: 2 Material Parallels shall be made of high quality steel, hardened and stabilized by a stress relieving process; the finished parallel shall give a hardness number of not less than 800 HV 1)for Grade A and not less than 640 HV 1)for Grade B. NOTEThe
21、 two largest sizes of Grade B parallels may be made with a series of lightening holes drilled through the thickness, provided that the accuracy of the parallels is not thereby affected. The requirements in this specification may be applied to parallels made of materials other than steel, e.g. granit
22、e, provided they are durable. 3 Finish The sides of Grades A and B parallels shall have a finely ground, or lapped finish. The ends of both grades of parallels shall be smoothly finished by milling or grinding. All sharp edges shall be removed. 4 Accuracy 4.1 Each parallel and pair of parallels shal
23、l comply with the requirements for accuracy for the appropriate grade stated in Table 1 and Table 2. 4.2 Additionally, the maximum errors in squareness of adjacent width and thickness faces shall not exceed 0.005mm per 25mm for both Grade A and Grade B parallels.(For widths less than 25mm the tolera
24、nce is 0.005 mm over the width W for both grades.) (See Table 1 and Table 2.) 5 Marking Each parallel shall have legibly and permanently marked on it the following information: the nominal dimensions of T and W (see Table 1 and Table 2), the grade of accuracy, the manufacturers name or trade mark, t
25、he serial number common to each parallel of the pair, e.g. 20 mm 40 mm A X Co. 1234 NOTEAttention is drawn to certification facilities offered by BSI; see the back cover of this standard. GRADE A 5 mm 10 mm 100 mm 10 mm 20 mm 125 mm 15 mm 30 mm 150 mm 20 mm 40 mm 200 mm 25 mm 50 mm 250 mm 30 mm 60 m
26、m 300 mm GRADE B 5 mm 10 mm 100 mm 10 mm 20 mm 125 mm 15 mm 30 mm 150 mm 20 mm 40 mm 200 mm 25 mm 50 mm 250 mm 30 mm 60 mm 300 mm 40 mm 80 mm 350 mm 50 mm 100 mm 400 mm NOTE 1See also 2, Material. NOTE 2The titles of the British Standards referred to in this standard are listed on page ii. 1) The eq
27、uivalent hardness numbers on the Rockwell C scale are 64 for 800 HV, and57.6 for640HV. When Rockwell values are used, tests should be carried out in accordance with BS891, and it should be noted that conversion values may vary as shown in BS 860.BS906-1:1972 2 BSI 03-1999 Table 1 Tolerances on grade
28、 A parallels 1 2 3 4 5 6 7 Nominal size Calliper measurements for individual parallels (see Figure 1) Functional requirements (see Figure 2) Departure from nominal T and W Variations in calliper measurements of T and W for individual parallels for a pair T W L parallelism of T and W matching mm mm m
29、m mm mm mm mm 5 10 100 0.005 0.002 0.004 0.006 10 20 125 15 30 150 20 40 200 25 50 250 0.010 0.003 0.006 0.010 30 60 300 NOTETolerance on L is 1mm throughout. Figure 1 Figure 2 Calliper measurement is the perpendicular distance from any point on one surface to the corresponding point on the opposite
30、 surface. When resting on a true plane, either way up in turn, the variation at any point shall be within the values shown in Column 6 for a single parallel. For matching, the maximum variation over the two parallels, however associated, shall not exceed the tolerance in Column 7.BS906-1:1972 BSI 03
31、-1999 3 Table 2 Tolerances on grade B parallels 1 2 3 4 5 6 7 Nominal size Calliper measurements for individual parallels (see Figure 1) Functional requirements (see Figure 2) Departure from nominal T and W Variations in calliper measurements of T and W for individual parallels for a pair T W L para
32、llelism of T and W matching mm mm mm mm mm mm mm 5 10 100 0.010 0.004 0.008 0.012 10 20 125 15 30 150 20 40 200 25 50 250 0.020 0.006 0.012 0.020 30 60 300 40 80 350 0.025 0.007 0.014 0.020 50 100 400 0.030 0.008 0.016 0.025 NOTETolerance on L is 1mm throughout. Figure 1 Figure 2 Calliper measuremen
33、t is the perpendicular distance from any point on one surface to the corresponding point on the opposite surface. When resting on a true plane, either way up in turn, the variation at any point shall be within the values shown in Column 6 for a single parallel. For matching, the maximum variation ov
34、er the two parallels, however associated, shall not exceed the tolerance in Column 7.BS906-1:1972 4 BSI 03-1999 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.
35、Grade A parallels shall always be supplied in pairs and in a suitable protective box. 2) Temporary (easily removable) corrosion preventatives are dealt with fully in BS 1133, Section 6: Guidance on sealed packs with dessicants is given in Section 19, “Use of dessicants in packaging”.BS906-1:1972 BSI
36、 03-1999 Appendix Derivation of tolerances stated in Table 1 and Table 2 The tolerances given in Table 1 and Table 2 of this standard have been calculated on the basis shown in Table 3. Table 3 Basis of tolerances Grade B parallels The tolerances for Grade B parallels are double the respective toler
37、ances calculated for Grade A using the above formulae and the appropriate nominal values of W and L. Tolerances in 4m (0.001 mm = 1 4m) Grade A parallels Calliper measurements for individual parallels (see Figure 1) Functional requirements (see Figure 2) Departure from nominal T and W Variations in
38、calliper measurement of T and W for individual parallels for a pair parallelism of T and W matching Expressed to minimum tolerance 5 1 1 1 5 2 4 4 W 10 - L 100 - + L 100 - 2 L 100 - 3 L 100 - BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
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