1、BRITISH STANDARD BS 1726-3:2002 Cylindrical helical springs made from round wire and bar Guide to methods of specifying, tolerances and testing Part 3: Torsion springs ICS 21.160 BS 1726-3:2002 This British Standard, having been prepared under the direction of the Engineering Sector Policy and Strat
2、egy Committee, was published under the authority of the Standards Policy and Strategy Committee on 25 September 2002 BSI 25 September 2002 The following BSI references relate to the work on this British Standard: Committee reference GME/15 Draft for comment 02/702406 DC ISBN 0 580 39721 1 Committees
3、 responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee GME/15, Mechanical springs, upon which the following bodies were represented: British Impact Treatment Association Institute of Spring Technology Amendments issued since publication A
4、md. No. Date Comments BS 1726-3:2002 BSI 25 September 2002 i Contents Page Committees responsible Inside front cover Foreword ii 1S c o p e 1 2 Normative references 1 3 Terms, definitions and symbols 1 4 Specifying springs for general purposes 2 5T o l e r a n c e s 1 1 6 Methods of testing 14 Figur
5、e 1 Data sheet 1 3 Figure 2 Form of legs 4 Figure 3 Direction of coiling 5 Figure 4 Conventions for describing relative leg orientation 6 Figure 5 Data sheet 2 9 Figure 6 Example torque testing layout 11 Table 1 Calculated free relative leg orientation tolerance ( degrees) 12BS 1726-3:2002 ii BSI 25
6、 September 2002 Foreword BS 1726-3 was first published in 1951 and revised in 1964 to incorporate much of the essential information from ADE Design Data Sheets, which were no longer available from HM Stationery Office and for which copyright permission to republish was obtained. The standard was rev
7、ised in 1987 take account of current manufacturing processes. BS EN 13906-3 was published in 2001 and under the rules of CEN the UK is obliged to withdraw conflicting standards. This edition of BS 1726-3 includes those provisions of the previous edition not included in the EN standard. Together with
8、 BS 8726-2:2002 and BS EN 13906-3:2001, this edition of BS 1726-3 supersedes BS 1726-3:1988, which is withdrawn. BS 1726 is published in three parts: Part 1: Compression springs; Part 2: Extension springs; Part 3: Torsion springs. BS 8726-2:2002 contains the provisions for design of compression spri
9、ngs made from square and rectangular material previously contained in BS 1726-3. 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
10、confer immunity from legal obligations. Summary of pages This document consists of a front cover, an inside front cover, pages i and ii, pages 1 to 15 and a back cover. The BSI copyright displayed in this document indicates when the document was last issued.BS 1726-3:2002 BSI 25 September 2002 1 1 S
11、cope This Part of BS 1726 provides guidance on the specification, tolerancing and testing of parallel sided helical torsion springs manufactured from round wire and bar. It applies to springs which may or may not be stress relieved after forming (hereinafter referred to as group A springs) and to sp
12、rings the material of which has undergone a structural change by heat treatment after forming (hereinafter referred to as group B springs). This standard gives two methods of specifying springs for general purposes and one method of testing springs. NOTE It is not recommended that torsion springs be
13、 loaded in the opposite direction to that of coiling. If this is necessary then discussions should take place between purchaser and supplier. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this British Stand
14、ard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the latest edition of the publication referred to applies. BS 887, Specification for precision vernier callipers. BS 969, Specification for limits and tolerances on p
15、lain limit gauges. BS EN ISO 7500-1, Tension/compression testing machines Verification and calibration of the force measuring system. BS 1726-1, Cylindrical helical springs made from round wire and bar Guide to methods of specifying, tolerances and testing Part 1: Compression springs. BS EN 13906-3,
16、 Cylindrical helical springs made from round wire and bar Calculation and design Part 3: Torsion springs. 3 Terms, definitions and symbols 3.1 Terms and definitions For the purposes of this Part of BS 1726 the definitions given in BS 1726-1 apply. 3.2 Symbols Symbol Term Unit c spring index mm D mea
17、n coil diameter mm D change in mean coil diameter mm D o outside diameter mm D tol. mean coil diameter tolerance mm d material diameter mm d max. maximum diameter of circular section material allowing for material size tolerance Hz e tolerance on size of material cross-section mm E modulus of elasti
18、city N/mm 2 F T tolerance factor for torque K o stress correction factor for circular section wire l combined effective length of legs mm L o free body length of spring mm L o, tol. tolerance on free body length mm L t loaded body length of spring mm m shape factor mmBS 1726-3:2002 2 BSI 25 Septembe
19、r 2002 4 Specifying springs for general purposes 4.1 General There are two methods by which a customer may specify a spring. In the first method the customer presents the supplier with a complete design and indicates what manufacturing processes, such as stress relieving, prestressing and shot peeni
20、ng, should be carried out. In this case the information should be supplied on Data Sheet 1 (Figure 1). When the customer does not have the information to complete Data Sheet 1, the customer should complete Data Sheet 2 (Figure 5). This is an application for a spring design in which the customer shou
21、ld specify the requirements from an operational point of view, giving such information as dimensional constraints, forcelength parameters, fatigue life, resistance to corrosion, in order that the supplier can produce a spring design to meet these requirements. When the spring supplier has prepared a
22、 design from the information on Data Sheet 2, the supplier will complete Data Sheet 1 and submit it to the customer for approval. 4.2 Method one (customer design) 4.2.1 Use of Data Sheet 1 Details of the required spring should be supplied on Data Sheet 1 (Figure 1) using standard nomenclature. Only
23、the essential dimensions and properties, for which the spring is to be inspected, should be toleranced, although other features may be included for information. n number of active coils in spring n change in number of active coils during loading N total number of coils in spring p pitch mm R min. mi
24、nimum allowable inside radius of any bend mm S nominal torsional rate N mm/degree t thickness of any surface coating mm T torque at any angle N mm T tol. tolerance on torque N mm T change in torque N mm relative leg orientation under torque degrees o relative leg orientation in free state degrees to
25、l. tolerance on relative leg orientation degrees angular rotation of spring degrees Bending stress in spring N/mm 2 Symbol Term UnitBS 1726-3:2002 BSI 25 September 2002 3 S P E C I F I C A T I O N F O R H E L I C A L T O R S I O N S P R I N G S BS 1726-3:2002 DATA SHEET 1 Part Serial No. This form s
26、hould be completed with reference to BS 1726-3:2002 Clause 4.2 Torque test layout if required 5 Thermal treatment (a) Stress relieving (group A) No Yes If yes Time min Temperature C (b) Heat treatment and hardness (group B) 6M a x i m u m d e f l e c t i o n Maximum deflection Rev degree 7 Dimension
27、al tolerances Outside diameter, mm Free body length, mm Leg length: 1 mm 2 mm Free relative leg orientation, mm 1M a t e r i a l 8 To be completed only if torque testing is a requirement Specification No. 8.1 Rate Diameter mm S N mm/degree; 2 Direction of coiling 8.2 Torque Right Hand Left Hand at T
28、est position 1 (TP1) N mm at Test position 2 (TP2) N mm 3 Form and length of legs 8.3 Property tolerances (Select only 2) Leg 1 Leg 2 Rate, N mm/degree Axial Free relative leg orientation, degree Tangential Torque at TP1 N mm Radial Over-centre Torque at TP2 N mm Radial Over-centre 9 Surface coating
29、 Lengths mm mm 10 Identification 4 Nominal dimensions 11 Special requirements Outside diameter D omm Mandrel diameter (max.) mm Free body length, L omm Number of coils, N Free relative leg orientation, omm Sheet 1 of Serial/design/Part No. Figure 1 Data sheet 1BS 1726-3:2002 4 BSI 25 September 2002
30、A detailed drawing is not necessary where the required spring conforms to the standard types, as shown in Figure 2. Only for those springs that require special leg geometry is a detailed drawing necessary. Figure 2 Form of legsBS 1726-3:2002 BSI 25 September 2002 5 Before completing Data Sheet 1, th
31、e designer should determine whether torque testing is a requirement. This decision affects tolerances for certain parameters (see 5.2 and 5.3), which boxes are to be completed, and the need or otherwise for a torque testing layout. If torque testing is a requirement then a test layout should be pres
32、ented either on, or as a supplement to, Data Sheet 1. Complete the data sheet in accordance with 4.2.9.1. The designer should be fully aware of the aforementioned guidelines and comply with the following. a) Specify only those particulars which are of functional importance by marking the appropriate
33、 squares and/or by entering the relevant values in each box. NOTE Box 8 is only to be completed if torque testing is required. b) Avoid redundant dimensioning. c) Refer to BS EN 13906-3 for the methods of calculation used to determine values for rate, torque, stress, etc. d) If space is insufficient
34、 in any box, details should be entered on a supplementary sheet and attention drawn to this fact in the appropriate box. 4.2.2 Material Complete box 1, by giving the material type and specification code quoting the relevant British Standard wherever possible. In cases where torsion springs are produ
35、ced from annealed material or are manufactured by a hot coiling method, they may require subsequent heat treatment (group B). If this is the case, specify the final hardness required and the process to be used, e.g. austemper, harden and temper. 4.2.3 Direction of coiling The action of the spring is
36、 dependent on the direction of coiling. Enter the direction of coiling in box 2. Figure 3 shows the convention for defining direction of coiling. 4.2.4 Form and lengths of legs Where the legs are of a standard form (see Figure 4), indicate the form in box 3 together with the appropriate lengths. Alt
37、ernatively, provide a detailed drawing on Data Sheet 1 or attach a supplementary drawing sheet. A fully dimensional drawing showing clearly the shape of the legs with their relationship to the body should be provided and attached to Data Sheet 1 or 2. In view of the wide variety of leg forms it is i
38、mpractical to give tolerances for these dimensions in this standard, but some guidelines are suggested in Clause 6. Figure 3 Direction of coilingBS 1726-3:2002 6 BSI 25 September 2002 4.2.5 Nominal dimensions The dimensions to be entered in box 4 are for information only unless a corresponding toler
39、ance is to be applied in box 7 and, in the case of relative leg orientation when torque testing is required, when entries should be made in box 8. 4.2.5.1 Outside diameter, D o Enter the outside diameter of the coil. 4.2.5.2 Mandrel diameter Enter the maximum diameter over which the spring is to ope
40、rate. This is also the size of mandrel that will be used for testing the spring if torque testing is a requirement. Due allowance should be made for a reduction in inside diameter during loading. 4.2.5.3 Free body length, L o Enter the free body length. Group B springs cannot generally be produced w
41、ith completely closed coils and account of this should be taken when stating free body length. 4.2.5.4 Number of coils, N Only enter the number of full coils. NOTE A fully dimensioned drawing showing clearly the shape of the legs with their relationship to the body should be provided and attached to
42、 data sheet 1 or 2. In view of the wide variety of leg forms it is impractical to give tolerances for these dimensions in this standard, but some guidelines are suggested in Clause 5 Figure 4 Conventions for describing relative leg orientationBS 1726-3:2002 BSI 25 September 2002 7 4.2.5.5 Relative l
43、eg orientation, o The convention for the description of relative leg orientation is directly related to the number of part coils in the spring. Examples of this are shown in Figure 4. 4.2.6 Thermal treatment 4.2.6.1 If stress relieving is required for group A springs, the duration and temperature sh
44、ould be given in box 5(a). 4.2.6.2 Heat treatment and hardness requirements for group B springs should be given in box 5(b). 4.2.7 Maximum deflection Indicate in box 6 the maximum elastic deflection, in revolutions and degrees, through which the legs have to move relative to each other. A degree of
45、prestressing is automatically present in a cold coiled torsion spring as a result of winding the coils. Consequently, it is rarely necessary to carry out a secondary prestressing operation. Springs that are hot coiled or hardened and tempered after coiling do not contain an element of prestress. If
46、prestressing is required this should be stated in box 11. 4.2.8 Dimensional tolerances The tolerances to be entered in box 7 will depend on whether torque testing is a requirement. 4.2.8.1 Outside diameter Refer to either 5.2.2 or 5.3.1 for the appropriate tolerance. 4.2.8.2 Free body length Refer t
47、o 5.2.3 for tolerance on free body length. This tolerance is only to be stated if torque testing is not required. 4.2.8.3 Leg length Refer to 5.4.4 for leg length tolerances. 4.2.8.4 Relative leg orientation Refer to 5.2.4 or 5.3.3 for the relative leg orientation tolerance. This is only to be enter
48、ed if torque testing is not required. 4.2.9 Properties 4.2.9.1 Torque testing Only complete box 8 if torque testing is required. However, to avoid over-dimensioning the spring it is necessary to be aware that no more than two parameters are needed to define torque performance. In addition to the det
49、ails in box 8 a torque testing layout should also be provided either on or as a supplement to Data Sheet 1. The example in Figure 6 indicates the information that should be included, in accordance with the following. a) Test angles and radii should be shown relative to the anchorage points and test mandrel, not relative to the spring (except in the case of nominal prewind from the nom
