1、BRITISH STANDARD BS4656-2: 1988 Accuracy of machine tools and methods of test Part2: Specification for copying lathes and copying attachments UDC621.9.01187.001.4:621.941.244:620.1BS4656-2:1988 This British Standard, having been prepared under the directionof the Machine, Engineers and Hand Tools St
2、andards Committee, was published under the authority ofthe Board of BSI and comesintoeffect on 30December1988 BSI08-1999 First published December1982 First revision December1988 The following BSI references relate to the work on this standard: Committee reference MTE/1 Draft for comment83/76970DC IS
3、BN 0 580 16997 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Machine, Engineers and Hand Tools Standards Committee (MTE/-) to Technical Committee MTE/1 upon which the following bodies were represented: Advanced Manufacturing Technolo
4、gy Research Institute Cranfield Institute of Technology Department of Trade and Industry Mechanical Engineering and Manufacturing Technology Division (MMT) Health and Safety Executive Institution of Production Engineers Ministry of Defence University of Aston in Birmingham Amendments issued since pu
5、blication Amd. No. Date of issue CommentsBS4656-2:1988 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Application of test methods 1 4 Abbreviations 2 5 Diagrams 2 Table 1 Geometrical tests for copying lathes with single-axis copying syst
6、ems 3 Table 2 Geometrical tests for copying lathes with two-axis copying systems 4 Table 3 Practical tests for copying lathes 5 Publications referred to Inside back coverBS4656-2:1988 ii BSI 08-1999 Foreword This Part of BS4656 has been prepared under the direction of the Machine, Engineers and Hand
7、 Tools Standards Committee and implements agreements of the International Organization for Standardization (ISO). This Part of BS4656 supersedes BS4656-2:1982, which is withdrawn. This Part of BS4656 is generally in accordance with ISO8956 “Acceptance conditions for copying attachments, integral or
8、otherwise, for lathes Testing of the accuracy”, ISO8956 was based on a UK proposal. This Part of BS4656 differs from ISO8956 in the following respects. Clauses. Clauses1 and3 contain the same information as is given in ISO8956 but they are presented in accordance with an accepted format that has bee
9、n adopted for the BS4656 series of standards. Clauses4 and5 have been added. A provision is included in clause1, where reference is made to the exclusion of precision category, because neither ISO8956 nor this standard includes such a category. In2.2 “motion” has been qualified by the term “resultan
10、t”. Inch dimensions. In accordance with the UK policy of metrication, inch dimensions given in ISO8956 have not been included in this Part of BS4656. Tables. In column5 of Table 1 reference is made to “thimble micrometer” in place of “micrometer”. In Table 3 test P2, a statement has been included in
11、 column8 indicating that checkc) can be performed using a steel test piece from test P2 of BS4656-1:1981. In column3 of Table 3, test P3 the following text has been retained from BS4656-2:1982. “Machining diameters, shoulders and tapers on cylindrical shaft-type test piece. Only one size of test pie
12、ce is required to be machined. Dependent on the size of the machine, test piecea) orb) is used.” 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 doe
13、s not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This w
14、ill be indicated in the amendment table on the inside front cover.BS4656-2:1988 BSI 08-1999 1 1 Scope This Part of BS4656 specifies, with reference to BS3800, both geometrical and practical tests for copying lathes and centre lathes of general purpose type with copying attachments. The tests in this
15、 standard are supplementary to those (except precision category) in BS4656-1. This standard is applicable to machines of general purpose use and normal accuracy. It applies to hydraulic and electric servo-controlled copying attachments but not to mechanically-controlled ones. It applies to lathes wi
16、th single-axis copying systems and to lathes where two axes are used in conjunction to produce a profile of up to180 included angle. It also applies to capstan and combination turret lathes and vertical boring machines equipped with copying attachments. It deals only with the verification of accurac
17、y of the machine. It does not apply to the testing of the running of the machine (vibrations, abnormal noises, stick-slip motion of components,etc.) nor to its characteristics (speeds, feeds,etc.) which should generally be checked before testing accuracy. This standard does not apply to turning mach
18、ines equipped with two-axis systems of more than180 capability which are considered as special-purpose machines, nor does it apply to single- or multi-spindle automatic lathes fitted with a copying attachment. NOTEThe titles of the publications referred to in this standard are listed on the inside b
19、ack cover. 2 Definitions For the purposes of this Part of BS4656 the following definitions apply. 2.1 single-axis copying system a copying system in which a component shape is produced by the resultant motion of two slides, one of which is under servo-control from the contact of a stylus against a t
20、emplate whilst the other has a pre-set constant feed motion. In this case the axis of the stylus is always parallel to the axis of the copying slide 2.2 two-axis copying system a copying system in which a component shape is produced by the resultant motion of two slides, both of which are under serv
21、o-control from the contact of a stylus against a template 3 Application of test methods 3.1 In applying the tests detailed in Table 1 and Table 2, reference should be made to BS3800, especially concerning the installation of the machine before testing, warming up of spindles and other moving parts,
22、the description of measuring methods and the recommended accuracy of testing equipment. 3.2 The tests may be applied in any order that is practicable and that makes for ease of mounting of instruments or gauging. The sequence in which the geometrical tests are listed in Table 1 is related to the sub
23、assemblies of the machine and it is not intended to impose the practical order in which the tests are to be done. 3.3 It is not always necessary for all the tests specified in this standard to be carried out. The purchaser shall be at liberty to select, in agreement with the manufacturer, those test
24、s relating to the properties that are of interest to him. The appropriate tests are to be clearly stated when the machine is ordered. 3.4 When establishing the tolerance for a measuring range different from that given in this standard (see2.311 of BS3800:1964), it should be taken into consideration
25、that the minimum value of tolerance is0.005mm for geometrical and practical tests. 3.5 Tests carried out on copying lathes which purport to comply with BS4656-1 shall be performed with the copying unit in position. 3.6 Unless otherwise stated, geometrical tests shall be performed at each end of, and
26、 also at the mid-point of, the copying slide stroke.BS4656-2:1988 2 BSI 08-1999 4 Abbreviations For the purposes of this standard, various methods of expressing permissible deviations are employed, each having a particular type of application. The methods are as follows. 5 Diagrams For reasons of si
27、mplicity the diagrams in this standard illustrate only one type of machine. This type of expression applies to deviations of perpendicularity that are ratios. This type of expression applies to deviations of straightness and parallelism, and is used in fact for local permissible deviations, the meas
28、urement length being obligatory. This type of expression applies to deviations of straightness and parallelism and is used to recommend a measurement length, but in this case the proportionality rule comes into operation if the measurement length differs from that indicated.BS 4656-2:1988 BSI 08-199
29、9 3 Table 1 Geometrical tests for copying lathes with single-axis copying systems (see3.6) All dimensions are in millimetres. 1 2 3 4 5 6 No. Diagram Object Permissible deviation Measuring instruments Observations 1G1 Assessment of repeatability of positioning 0.005 in 5 repeats Dial gauge Run the s
30、tylus up to the template, retract and repeat. Template and stylus set normal to copying axis 1G2 Measurement of dead zone 0.02 Dial gauge and thimble micrometer Mount dial gauge in cutting tool position, mount micrometer against stylus. Rotate micrometer slowly towards stylus and in reverse directio
31、n. Observe total movement of micrometer for zero movement of dial gauge 1G3 Measurement of sensitivity Number of discrete movements of dial gauge: W 10 for a0.05 displacement of the micrometer Dial gauge and thimble micrometer Rotate micrometer very slowly in one or other direction of copying slide
32、stroke. Observe number of discrete movements of the dial gauge in specified movement of micrometer Carry out tests in both directionsBS 4656-2:1988 4 BSI 08-1999 Table 2 Geometrical tests for copying lathes with two-axis copying systems (see3.6) All dimensions are in millimetres. 1 2 3 4 5 6 No. Dia
33、gram Object Permissible deviation Measuring instruments Observations 2G1 Assessment of repeatability of positioning in each axis a 0.005 in 5 repeats Dial gauge and template Each axis is to be tested independently Run the stylus up to the template, retract and repeat. Template and stylus set normal
34、to copying axis. 2G2 Measurement of dead zone a 0.03 normal to spindle axis 0.05 parallel to spindle axis Dial gauge and thimble micrometer Each axis is to be tested independently Micrometer and dial gauge are to be mounted parallel with the servo-controlled axis under test Mount dial gauge in cutti
35、ng tool position, mount micrometer against stylus in axis under test. Rotate micrometer very slowly towards stylus and in reverse direction. Observe tool movement of micrometer for zero movement of dial gauge 2G3 Measurement of sensitivity a Number of discrete movements of dial gauge: W 5 for a0.05
36、displacement of the micrometer Dial gauge and thimble micrometer Each axis is to be tested independently Micrometer and dial gauge are to be mounted parallel with the servo-controlled axis under test Rotate micrometer very slowly in one or other direction of copying slide stroke. Observe number of d
37、iscrete movements of the dial gauge in specified movement of micrometer Carry out tests in both directions a This test is to be performed at the end of each stroke and midway along the copying slide stroke.BS 4656-2:1988 BSI 08-1999 5 Table 3 Practical tests for copying lathes All dimensions are in
38、millimetres. 1 2 3 4 5 6 7 8 No. Diagram Nature of test Cutting conditions Checks to be applied Permissible deviation Measuring instruments Observations Single-axis Two-axis P1 Test-piece material: steel This test is for machines with chucking facilities only and without a tailstock Machining three
39、diameters, two shoulders and two tapers on cylindrical test pieces in chuck D =0.5D a aup to a maximum of200 For single-axis copying machines: D 1=D 1 D 2=D 20 D 3=D 2 1 D 4=D 3 20 For two-axis copying machines: D 1=D 1.5 D 2=D 20 D 3=D 2 1.5 D 4=D 3 20 The axis of the template shall be set parallel
40、 to the axis of the spindle The inclination angle of the copying unit to the axis of the machine and the measuring pressure shall be specified by the manufacturer a) Taper surfaces b) Measurement of deviation D D 1compared to template c) Measurement of deviation D D 2compared to template d) Change i
41、n shoulder to shoulder length50 compared to template To be regular and without steps Micrometer, depth gauge and profile projector c) Includes the effect of dead zone twice 0.025 0.06 0.04 0.03 0.08 0.05 a D ais the maximum swing over cross-slide.BS 4656-2:1988 6 BSI 08-1999 Table 3 Practical tests
42、for copying lathes All dimensions are in millimetres. 1 2 3 4 5 6 7 8 No. Diagram Nature of test Cutting conditions Checks to be applied Permissible deviation Measuring instruments Observations Single-axis Two-axis P2 Test piece material: steel This test is for machines which have facing capabilitie
43、s Facing profile consisting of three faces and one taper and a chamfer on a cylindrical test piece in the chuck D =0.5D a aor160 whichever is the greater For single-axis copying machines: H =0.5 For two-axis copying machines: H =0.75 D 1=D 40 D 2=D 90 D 3=D 110 D 4=D 150 a The axis of the template t
44、o be set perpendicular to the axis of the machine The inclination of the copying unit of the axis of the machine and the measuring pressure is to be specified by the manufacturer The facing is to be carried out from the outside diameter to the inside a) Taper surfaces b) Depth of recess H compared t
45、o template c) Alignment of inner and outer faces (adjacent to diameters D and D 4 ) compared to template. Deviation should be allowed only in a concave direction To be regular and without steps Depth gauge, straightedge, and gauge blocks b) Includes the effect of dead zone c) Can be performed using
46、a steel test piece from test P2 of BS4656-1: 1981 0.04 0.04 0.06 0.05 a D ais the maximum swing over bed. L D a 8 - =BS 4656-2:1988 BSI 08-1999 7 Table 3 Practical tests for copying lathes All dimensions are in millimetres. 1 2 3 4 5 6 7 8 No. Diagram Nature of test Cutting conditions Checks to be a
47、pplied Permissible deviation Measuring instruments Observations Single-axis Two-axis P3 a) Minimum size test piece L =200 For single-axis copying machines X =D 1 For two-axis copying machines X =D1.5 Test piece material: steel b) Maximum size test piece L =500 For single-axis copying machines X =D 1
48、 For two-axis copying machines X =D1.5 Test piece material: steel This test is for machines which produce shaft-type workpieces and is to be used instead of test P1 Machining diameters, shoulders and tapers on cylindrical shaft-type test piece Only one size of test piece is required to be machined.
49、Dependent on the size of the machine, test piecea) orb) is used. For intermediate capacities, test piece dimensions may be suitably scaled The workpiece shall be mounted between centres or ina work-holding device and supported by a tailstock. The axis of the template shall be parallel to the axis of the machine The inclination angle of the copying unit to the axis of the machine and the measuring pressure shall be specified by the manufacturer a) Taper surfaces b) All D diameters compared to template
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