1、BRITISH STANDARD BS2457:1975 Specification for Protractors for drawing office use UDC 744.34:531.741BS2457:1975 This British Standard, having been approved by the Office Machines and Equipment Industry Standards Committee,was published underthe authority of the Executive Board on 31January1975 BSI 1
2、1-1999 First published April1954 First revision January1975 The following BSI references relate to the work on this standard: Committee reference OME/8 Draft for comment 72/61394 ISBN 0 580 08089 7 Co-operating organizations The Office Machines and Equipment Industry Standards Committee under whose
3、supervision this British Standard was prepared consists of representatives from the following Government departments and industrial organizations. Association of Certified and Corporate Accountants Business Equipment Trade Association Civil Service Department Confederation of British Industry Depart
4、ment of the Environment* Drawing Office Material Manufacturers and Dealers Association* H M Stationery Office Institute of Chartered Accountants in England and Wales Institute of Chartered Secretaries and Administrators Institute of Cost and Works Accountants Institute of Administrative Management J
5、oint Advisory Committee on Local Authority Purchasing Office Machines and Equipment Federation The Government department and industrial organization marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of th
6、is British Standard. County Surveyors Society Incorporated Association of Architects and Surveyors Institution of Professional Civil Servants Ministry of Defence Ordnance Survey Royal Institute of Chartered Surveyors Society of Motor Manufacturers and Traders Ltd Amendments issued since publication
7、Amd. No. Date of issue CommentsBS2457:1975 BSI 11-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Material 1 4 General requirements 1 5 Dimensions 1 6 Marking 1 Table 1 Preferred sizes for protractors 1 Publication referred to 2BS2457:1975 ii
8、BSI 11-1999 Foreword This British Standard has been prepared under the authority of the Office Machines and Equipment Industry Standards Committee as one of a series in a specialized category needed to meet the requirements of drawing office equipment as distinct from general office equipment. It di
9、ffers from the previous edition published in1954, in that it now specifies a new, metric range of sizes. NOTEA sectional list of other British Standards in this field is published separately as SL37 “Drawing practice”. Certification. Attention is drawn to the certification facilities described on th
10、e inside back cover 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. Sum
11、mary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 and2, 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 fron
12、t cover.BS2457:1975 BSI 11-1999 1 1 Scope This British Standard specifies requirements for protractors of the circular and sem-circular types for drawing office use, made from transparent plastics material. 2 References The title of the British Standard referred to in this standard is given on page
13、2. 3 Material 3.1 Protractors shall be made from transparent plastics material complying with the following requirements. 3.1.1 The change in any linear dimension shall not exceed1% for a variation in ambient temperature from0 C to38 C and in relative humidity from0 to100%. 3.1.2 The material shall
14、possess toughness, hardness and flexibility sufficient to permit constant handling in use without a degree of deterioration of the surface, loss of transparency, or distortion such as to render it unserviceable. 4 General requirements 4.1 Protractors may either be solid or have open centres. Their e
15、dges shall be relieved in thickness by bevelling or other means in such a way that, when viewed from a normal position, no distortion of the graduations is evident. After relieving, the vertical edge thickness shall be not less than1mm. 4.2 The circumference shall be graduated on the underside at“ i
16、ntervals by fine clear radial lines, extending to the working edge. The protractor shall be double-reading and shall be figured at every10 , the outer set of figures running clockwise and the inner set counter clockwise. Two straight lines shall be drawn on the underside across the protractor to for
17、m in the case of the circular protractors, continuation of the0180 and90270 graduations respectively. In the case of the semi-circular protractors the base line shall form a continuation of the0180 graduation and a radial line passing through the90 graduation shall intersect the base line. All marki
18、ngs shall be durably filled with a material of strongly contrasting colour. 4.3 Special care should be taken to avoid confusion between figures of similar form. Reference should be made to BS3693-1. 4.4 Semi-circular protractors shall have an extension of the transparent material to form a straight
19、edge beyond the0180 base line and parallel with it. 4.5 The distance between any two graduations within an angle not exceeding90 , when measured at the circumference, shall not vary from the true distance by more than 0.13mm for sizes less than200mm diameter, or 0.18mm for sizes of200mm diameter and
20、 above. 5 Dimensions 5.1 Preferred sizes are set out in Table 1. 5.2 Protractors shall be flat with a tolerance zone1.0mm wide per300mm of length. 6 Marking Where compliance with this British Standard is claimed, the protractor shall be legibly and indelibly marked with: a) the number of this Britis
21、h Standard i.e.BS2457, and b) the name or trade mark of the manufacturer. Table 1 Preferred sizes for protractors Type Nominal diameter Minimum thickness Minimum extension of material below base line Semi-circular mm 150 200 250 300 mm 1.5 2.0 2.0 2.0 mm 6 6 6 6 Circular 150 200 250 300 1.5 2.0 2.0
22、2.0 BS2457:1975 2 BSI 11-1999 Publication referred to This standard makes reference to the following British Standard: BS3693, Recommendations for the design of scales and indexes. BS 3693-1, Instruments of bold presentation and for rapid reading. BS2457:1975 BSI 11-1999 BSI Certification Trade Mark
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