1、BRITISH STANDARD BS 7776:1995 Glossary of Torque terminology for threaded fasteners UDC 531.232:001.4:621.88BS7776:1995 This British Standard, having been prepared under the directionof the General Mechanical Engineering Standards Policy Committee, waspublished under the authorityof the Standards Bo
2、ardand comes into effect on 15February 1995 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference GME/9 Draft for comment 93/712368 DC ISBN 0 580 23253 0 Committees responsible for this British Standard The preparation of this British Standard was entruste
3、d by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee GME/9, upon which the following bodies were represented: BEAMA Ltd. British Constructional Steelwork Association Ltd. British Industrial Fasteners Federation British Steel Industry British Steel Industr
4、y (Wire Section) Gauge and Tool Makers Association National Association of Fastener Stockholders Society of Motor Manufacturers and Traders Limited Washer Manufacturers Association of Great Britain The following bodies were also represented in the drafting of the standard, through subcommittees and
5、panels: National Centre of Tribology Society of British Aerospace Companies Ltd. Amendments issued since publication Amd. No. Date CommentsBS7776:1995 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii Glossary 1BS7776:1995 ii BSI 07-1999 Foreword This British Standard
6、 has been prepared under the direction of the General Mechanical Engineering Standards Policy Committee and includes definitions of terms relating to the torque terminology of fasteners. In the design, assembly, quality assessment and standardization of threaded fasteners and joints, expressions are
7、 frequently used which relate to the various torque functions which are required to be applied or assessed. Much confusion is generated by the multiplicity of terms used throughout industry. As a basic reference document providing a comprehensive list of terms, this glossary is intended to promote b
8、etter understanding between the various sections of industry and the users of fasteners. Many of the definitions in this glossary are essentially the same as those used in other British Standards already published. As these British Standards are revised and new standards are produced, the use of the
9、 definitions given in this glossary will be encouraged in order to promote wider acceptance and recognition of standard terminology. In this glossary, terms are arranged in alphabetical order. In the definitions, italics have been used to indicate terms that are defined elsewhere in this glossary. A
10、 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 This document comprises a
11、 front cover, an inside front cover, pages i and ii, pages1 and 2 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.BS7776:1995 BSI 07-1999 1 Glossary No. Term Defini
12、tion 1 break loose torque The torque, applied in the reverse direction to tightening, required to initiate rotation of a tightened fastenerthus releasing the assembled clamping force. 2 cam-out torque The maximum torque which can be applied to a fastener assembly tool before the end load required to
13、 maintain functional contact between the tool and the driving recess exceeds that which can be considered as a nominal manual pressure. 3 free-running torque The torque required to rotate a threaded fastener during assembly with a mating threaded component before either of the following occurs: a) a
14、 clamping force is generated; or b) it comes into contact with a device which displays frictional resistance to rotation. 4 prevailing torque The torque necessary to overcome the resistance to rotation generated by a prevailing torque feature, measured with the fastener approximately in constant mot
15、ion and with no clamping force developed against the bearing surface of the fastener. 5 prevailing torque feature A feature of a threaded fastener which displays frictional resistance to rotation due to a self-contained device. NOTEThe frictional resistance is not a consequence of a clamping force d
16、eveloped against the bearing surface of the fastener. 6 removal torque The torque necessary to rotate a threaded fastener, applied in the reverse direction to the tightening torque after the clamping force has been released. 7 self-locking A generic term used to indicate resistance to rotation. NOTE
17、This definition is not intended to imply an indefinite permanency of attachment. 8 snug torque The torque required to clamp together the components of a joint such that the clamped components can then be assumed to behave in approximately the same manner as a single solid component. 9 static audit t
18、orque That torque which, when applied in the direction of tightening, will not cause rotation of a threaded fastener. NOTEIt is usually used to determine whether an adequate tightening torque has been applied by the assembly tool. 10 stripping torque The torque which causes mating screw threads to f
19、ail throughthread stripping. 11 thread forming torque The torque required to rotate a thread forming fastener duringthe process of producing a mating thread. 12 tightening torque The torque applied to a fastener which is required to induce the desired clamping force or pre-load in a joint. 13 torque
20、/angle A technique in which a fastener is tightened to a snug torque then rotated, during which only the angle of rotation is measured. The angle is that which will elongate the male threaded component by an amount relative to the desired tension. 14 torque/clamping force relationship The rate at wh
21、ich the clamping force in a joint increases relative to the increase in applied tightening torque. NOTEIn a correctly designed joint, after the snug torque is exceeded, a graphical representation of the relationship can be assumed to conform to a straight line (atclamping forces which do not cause y
22、ielding of the joint components).BS7776:1995 2 BSI 07-1999 No. Term Definition 15 torsional strength (of a male threaded fastener) The torque at which failure of a fastener occurs, measured with the end of the fastener securely gripped and with at least two full threads exposed to stress. 16 torsion
23、al resistance The torque required to overcome any resistance to rotation other than that generated by a prevailing torque feature or that required to form a mating thread. 17 yield point torque The torque required to tighten a fastener to the point on a graphical representation of the relationship b
24、etween torque and elongation where the relationship ceases to follow a straight line by an agreed deviation. NOTEThis deviation is usually defined as 0.1 % of the free length of the male fastener in the joint.blankBS 7776:1995 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution B
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