1、BRITISH STANDARD CONFIRMED NOVEMBER 1959 BS 1734:1951 Incorporating Amendment Nos. 1, 2 and 3 Specification for Micrometer headsBS1734:1951 This British Standard, having been approved by the MechanicalIndustry StandardsCommittee and endorsed by the chairman of theEngineering Divisional Council, was
2、published undertheauthority ofthe GeneralCouncil on 16April1951 BSI02-2000 ISBN 0 580 35798 8 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government depa
3、rtments and scientific and industrial organizations: Admiralty Air Ministry Associated Offices Technical Committee Association of Consulting Engineers Incorporated British Chemical Plant Manufacturers Association British Compressed Air Society British Electrical and Allied Manufacturers Association
4、British Engineers Association British Internal Combustion Engine Manufacturers Association British Iron and Steel Federation British Railways, The Railway Executive Crown Agents for the Colonies Department of Scientific and Industrial Research Engineering Equipment Users Association Institute of Mar
5、ine Engineers Institute of Petroleum Institution of Civil Engineers Institution of Gas Engineers Institution of Heating and Ventilating Engineers Institution of Mechanical Engineers Institution of Mechanical Engineers (Automobile Division) Institution of Production Engineers Locomotive Manufacturers
6、 Association Machine Tool Trades Association Ministry of Labour and National Service Ministry of Supply Ministry of Transport Ministry of Works Office of the High Commissioner for India War Office Amendments issued since publication Amd. No. Date of issue Comments 1218 June 1951 1240 September 1951
7、3455 August 1959 Indicated by a sideline in the margin BS1734:1951 BSI 02-2000 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Nomenclature 1 3 Material 1 4 Micrometer screw 1 5 Spindle 1 6 Thimble and barrel 3 7 Graduations 3 8 Adjustments 3 9 Measuring face 4
8、10 Accuracy 4 11 Case 5 12 Packing 5 13 Marking 5 Figure 1 1 Figure 2 Nomenclature for micrometer heads 2 Figure 3 Detail of barrel and thimble bevel 3 Table 1 Dimensions for Type 1 micrometer heads with rotatable spindles 4 Table 2 Dimensions for Types 2 and 3 micrometer heads with rotatable spindl
9、es 4 Table 3 Maximum permissible errors for Type 1 micrometer heads 5 Table 4 Maximum permissible errors for Types 2 and 3 micrometer heads 5BS1734:1951 ii BSI 02-2000 Foreword Other British Standards for engineers precision tools are as follows: BS 817, Cast iron surface plates and tables. BS 818,
10、Cast iron straightedges. BS 852, Toolmakers straightedges. BS 863, Steel straightedges of rectangular section. BS 869, Toolmakers flats and high precision surface plates. BS 887, Vernier callipers. BS 888, Slip (or block) gauges and their accessories. BS 906, Engineers parallels (steel). BS 907, Dia
11、l gauges for linear measurements. BS 939, Engineers squares. BS 957, Feeler gauges. BS 958, Precision levels. BS 959, Internal micrometers. BS 1054, Engineers comparators. BS 1643, Vernier height gauges. BS 1685, Bevel protractors. BS 1790, Combination length bars. This British Standard for micromet
12、er heads 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 and is a further development of work which was done in connection with the revision of BS870, “External micrometers
13、.” The standard relates to micrometer heads supplied independently for assembly with measuring tools or machine tools. It forms one of a series of specifications for engineers precision tools which has been prepared with the co-operation of the manufacturers and in close collaboration with the Natio
14、nal Physical Laboratory. 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
15、 This document comprises a front cover, an inside front cover, pages i and ii, pages1 to5 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.BS1734:1951 BSI 02-2000 1
16、1 Scope This British Standard relates to micrometer heads having measuring ranges of: a) 1 / 2in. b) 1 in. c) 13 mm. d) 25 mm. It applies to micrometer heads with rotatable spindles and with non-rotatable spindles, classed according to the following ranges of thimble diameter (dia. D, Figure 1): Typ
17、e 1Below 1 in. thimble diameter. Type 21 in. and below 2 in. thimble diameter. Type 32 in. thimble diameter and over. NOTEMicrometer heads of the larger types with non-rotatable spindles may be supplied to special orders with dimensions approximately similar to those given inTable 2 and to an accura
18、cy similar to that shown inTable 4 2 Nomenclature For the purpose of this standard the nomenclature given inFigure 2 has been adopted. 3 Material The barrels and thimbles, if of Type1, shall be of a suitable quality steel; if they are of larger diameter they may be made of a suitable light alloy. Th
19、e spindle shall be of high grade tool steel. Its measuring face shall be hardened to not less than800D.P.N. 1)The measuring face may be tipped with tungsten carbide or other suitable hard material. 4 Micrometer screw The micrometer screw shall have a pitch of 1 / 40of an inch, or of0.5mm. NOTEIt is
20、recommended that the threads of the screw and nut be truncated so as to confine contact to the flanks of the thread. 5 Spindle The front parallel portion of the spindle of micrometer heads with rotatable spindles shall be a good free turning fit in its bush without appreciable shake. There shall be
21、at least one turn over-run at each end of the screw beyond the graduated range. The micrometer head shall be supplied with the spindle and screw lubricated with a thin light non-corrosive oil, and in this condition the spindle shall run freely and smoothly throughout the length of its travel. There
22、shall be no perceptible backlash between the spindle screw and nut. When the micrometer head is at its maximum reading there shall still be full engagement of the nut and micrometer screw. Figure 1 1) The approximate equivalent hardness number on the Rockwell C scale is62.BS 1734:1951 2 BSI 02-2000
23、Figure 2 Nomenclature for micrometer headsBS1734:1951 BSI 02-2000 3 If a spindle clamp is provided on Type1 micrometer heads, the design shall be such that it effectively locks the spindle without resulting in an alteration of measurement greater than0.0001in., or0.003mm. If a friction or ratchet dr
24、ive is fitted to the spindle, the force it exerts shall lie between 1 1 / 2lb. and 2 1 / 4lb. NOTEIt is not customary to fit friction or ratchet drives to Types2 and3 micrometer heads as these are generally used in conjunction with a fiducial indicator. The projection of the spindle (dimension C, Fi
25、gure 2) shall be in accordance with Column5 ofTable 1 andTable 2. 6 Thimble and barrel The thimble and barrel may be of Type1 diameter or may be of the larger type (seeFigure 2). In the case of micrometer heads having 1 / 2 in. or13mm. range of measurement the diameter of the graduated edge of the t
26、himble (dimension D, Figure 1) shall be not less than 3 / 8 ; in. and in the case of micrometer heads having1in. or 25mm. range of measurement this diameter shall be not less than 7 / 16in. It is recommended that, for ease of reading, the angle of the bevel (angle ! Figure 3) should be15 but in no c
27、ase shall this angle be more than20 . The distance from the outside of the barrel to the reading end of the graduation on the thimble (dimension B, Figure 3) shall not exceed0.015in. 7 Graduations The thimble shall be graduated to read in the units shown in Columns6 and7 ofTable 1 andTable 2. NOTEA
28、vernier enabling readings to be taken to0.0001in. may be incorporated in Type1 micrometer heads if required. All graduation lines shall be clearly cut. In the case of Type1 micrometer heads the graduation lines on the thimble and the fiducial line, and vernier lines when applicable, on the barrel sh
29、all have a width of not less than0.006in. and not more than0.008in. For larger heads the thickness of the graduation lines on the thimble and the fiducial line on the barrel shall be approximately one-fifth of the distance between the adjacent lines with a minimum thickness of0.004in. Whilst the thi
30、ckness of the remaining graduations on the barrel for all types is not of prime importance, it is recommended that these graduations should not vary in thickness from the others by an obvious amount. NOTEIt is recommended that, for ease of reading, the surfaces of the thimble and barrel should have
31、a dull finish and that the graduation lines should be blackened in. 8 Adjustments Each micrometer head shall be provided with means for adjusting the zero setting and for compensating for wear between the screw and nut. On Types2 and3 micrometer heads provision shall be made for adjusting the zero s
32、etting by turning the barrel, which shall be a stiff friction fit. Both adjustments shall be such that they remain secure after setting and do not impair the original accuracy of the instrument. Suitable spanners or keys shall be supplied for these adjustments. Figure 3 Detail of barrel and thimble
33、bevelBS1734:1951 4 BSI 02-2000 Table 1 Dimensions for Type 1 micrometer heads with rotatable spindles Table 2 Dimensions for Types 2 and 3 micrometer heads with rotatable spindles 9 Measuring face In the case of 1 / 2in. and13mm. range micrometer heads the measuring face of the spindle shall be not
34、less than 3 / 16in. in diameter. In the case of1in. and 25mm. range micrometer heads the measuring face of the spindle shall be not less than 1 / 4in. in diameter. The measuring face shall be finished by lapping and shall be flat to within the tolerances given in Column2 ofTable 3 andTable 4 and squ
35、are to within the tolerances given in Columns3 and4 ofTable 3 andTable 4. 10 Accuracy When tested at the standard reference temperature of68 F. each micrometer head shall comply with the tolerances given inTable 3 andTable 4. Repetition of reading. Micrometer heads of Types1 and2 shall be capable of
36、 repetition of reading over any portion of the scale to0.000 05 in. (0.001 mm.). Type3 micrometer heads shall be capable of repetition of reading over any portion of the scale to0.000 02 in. (0.0005 mm.). 1 2 3 4 5 6 7 Diameter of thimble Measuring range Diameter of shank A Length of shank B Project
37、ion of spindle C Unit of thimble graduations Tolerance +0.0000 0.0004 Tolerance +0.000 0.005 English Metric in. in. in. in. mm. Type 1 Below 1 in. 1 / 2in. or 13 mm. 0.375 3 / 8 1 0.001 a 0.01 Type 1 Below 1 in. 1 in. or 25 mm. 0.500 3 / 4 2 0.001 a 0.01 a 0.0001 by vernier if required. 1 2 3 4 5 6
38、7 Diameter of thimble Measuring range Diameter of shank A Recommended length of shank B Recommended projection of spindle C Unit of thimble graduations Tolerance +0.0000 0.0002 Tolerance +0.000 0.005 English Metric in. in. in. mm. Type 2 1 in. and below 2 in. 1 in. or 25 mm. 0.500 or 0.5625 3 / 4or
39、1 3 / 8 2 a 0.0002 0.005 Type 3 2 in. and over 1 in. or 25 mm. 0.500 or 0.5625 3 / 4or 1 3 / 8 2 a 0.0001 0.002 a 2 5 / 8in. where length of shank is increased to 1 3 / 8in.BS1734:1951 BSI 02-2000 5 Table 3 Maximum permissible errors for Type 1 micrometer heads Table 4 Maximum permissible errors for
40、 Types 2 and 3 micrometer heads 11 Case Each micrometer head shall be supplied in a suitable protective case or box. 12 Packing As a protection against climatic conditions each micrometer head shall be coated with a suitable thin non-corrosive light oil and shall be securely wrapped in suitable wrap
41、ping material. 13 Marking Each micrometer head shall have legibly and permanently marked upon it, in characters not less than0.025in. high, the manufacturers name or trade mark. 1 2 3 4 5 Diameter of thimble Flatness of measuring face Squareness of measuring face to axis of spindle (measured over di
42、ameter of face) Squareness of measuring face to outside diameter of shank (measured over diameter of face) Maximum error of traverse of measuring face at any position Type 1 Below 1 in. 0.000 05 in. (0.001 mm.) 0.000 05 in. (0.001 mm.) 0.0003 in. (0.008 mm.) 0.0001 in. (0.003 mm.) 1 2 3 4 5 Diameter
43、 of thimble Flatness of measuring face Squareness of measuring face to axis of spindle (measured over diameter of face) Squareness of measuring face to outside diameter of shank (measured over diameter of face) Maximum error of traverse of measuring face at any position Type 2 1 in. and below 2 in.
44、0.000 03 in. (0.0008 mm.) 0.000 03 in. (0.0008 mm.) 0.0001 in. (0.003 mm.) 0.0001 in. a (0.003 mm.) a Type 3 2 in. and over 0.000 02 in. (0.0005 mm.) 0.000 03 in. (0.0008 mm.) 0.000 03 in. (0.0008 mm.) 0.0001 in. a (0.003 mm.) a a The periodic error shall not exceed 0.000 05 in. ( 0.001 mm.) for Typ
45、e 2 micrometer heads and 0.000 02 in. ( 0.0005 mm.) for Type 3 micrometer heads.BS 1734:1951 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at
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