1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1996 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTSubmitted for recognition as an American National Stand
4、ardJ1701MISSUEDJUL96Issued 1996-07TORQUE-TENSION TIGHTENING FOR METRIC SERIES FASTENERSForewordFundamentally, threaded fasteners are required to create a clamping force or load on the assembledjoint to prevent loosening. To accomplish this, a tensile loading is applied onto a bolt or screw by itself
5、 or by a nuttightened on the bolt or screw.The axial stress in them produces a clamping force equal to the product of the proof-load stress, reduced by adesign factor, and the core area of the bolt or screw.Although clamping or tension load can be measured by load cells and strain gauges, these meth
6、ods areimpractical on the production line. The most practical methods of achieving control of joint clamp load involvetorque control, angle (tightening) control, or combinations of torque and angle. In some cases, a torque versusangle yield method is utilized, particularly when tightening 16 mm and
7、larger sizes. But measurement andassembly equipment is sensitive. Therefore, it becomes very important to understand the relationship betweentorque and tension.1. ScopeThis SAE Information Report is provided as an advisory guide. Individual application discretion isrecommended. The content has been
8、presented as accurately as possible, but responsibility for its applicationlies with the user. The document covers the variables in the torque-tension relationship: friction, materials,temperature, humidity, fastener and mating part finishes, surfaces, and the kind of wrenching employed.Also describ
9、ed in this document is the torque management required to achieve correct fastener jointtightening.The thread fit of fasteners must be in accordance with Class 6g for external and 6H for internal metric threads.2. References2.1 Related PublicationsThe following publications are provided for informati
10、on purposes only and are not arequired part of this document.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J174Torque-Tension Test ProceduresSAE J1648Protective Coatings for FastenersCopyright SAE International Provided by IHS under license with SAEN
11、ot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE J1701M Issued JUL96-2-3. Explanation of Tightening Terms3.1 TorqueIs the product of force x lever arm length. It is the moment resistance of the fastener and itscomponents to tightening, expressed in newton-meters (N
12、m).3.2 Turn Screw or Bolt and Turn Nut TermsDescribe which mating part is tightened. For turn screw, the headof the screw or bolt is turned against a panel into either a panel with a tapped thread or separate nutcomponent.For turn nut, the nut is threaded onto a screw or bolt and is tightened agains
13、t the panel surface.3.3 Clamping LoadOccurs when the screw or bolt is stretched when the fastener is tightened. It is equal andopposite to the tensile force developed in the screw or bolt and is expressed as newtons (N).3.4 InertiaIs the tendency of a body to continue in motion after being subjected
14、 to a force in a specific directionuntil acted upon by an outside force. In tightening, friction between mating parts and bearing against panel orpart surfaces is the major contributing outside force and has to be overcome. Inertia of the rotating power toolis another factor which must be considered
15、.4. Variables in the Relationship of Clamping Load to Applied Torque4.1 FrictionThe friction resistance torque is the most important of all of the variables. It has two components,the friction resistance of the applied nut fastener with respect to mating part threads, and the bearing surfaceagainst
16、joint members. Increasing the clamping tension force on the screw or bolt increases the frictionresistance to turning.4.2 Fastener MaterialsCharacteristic properties of hardness and surface condition can contribute to frictionvariability thus affecting tightening torque to obtain the same clamping l
17、oad.4.2.1 Nonheat-treatable low-carbon stainless steels and other soft alloys cause increased friction resistanceresulting in higher tightening torque for a given clamp load.4.2.2 Hardened steel or hard alloy fasteners have a harder slippery surface reducing friction and thereby requiringlower tight
18、ening torque.4.2.3 Special materials, rubber, plastics, etc., either as fabricated fasteners or attached to them, also affect torqueif they contact the rubbing surfaces during the tightening.4.3 Surface Conditions, such as coatings or effects of the environment applied to fasteners and bearing surfa
19、ceswill affect tightening torque requirements for a given clamp load.4.3.1 The roughness, coarseness, or abrasiveness of coatings will increase torque required resistance.4.3.2 Decreased friction due to the nature of the coating including oil, wax, teflon, or other lubricants will reducetorque requi
20、red resistance.4.3.3 Interferences due to dirt, rust, burrs and galling, or seizing caused by soft coatings (zinc is an example) onfasteners, mating parts, and panels increases torque resistance.4.3.4 Hardness of the fastener, its mating part, or the joint material panel will reduce required torque.
21、Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE J1701M Issued JUL96-3-4.3.5 Temperature contraction, especially if the assembly tightening was made while warm, will reduce clampingload. If the fast
22、ener is at a higher temperature than the assembly, then the clamping load increases uponcooling. Adjustments to assembly torque must accommodate these conditions.4.3.6 Humidity will cause reduced friction and stickiness reducing required torque.4.3.7 Joint relaxation can occur if joint material defo
23、rms under load and/or time. In such cases, special torquesequencing may be required.4.4 WrenchingThe method of tightening has a profound influence on required torque.4.4.1 The slow deliberate turning by hand wrenching allows the assembly to settle somewhat during tighteningthus negating some of the
24、effects of joint relaxation.4.4.2 High air pressure or electric power tool fastener tightening involving rotation inertia and sudden stoppagecontribute to lower torque. The use of inertia lessens the affect of static friction but can increase torsionalloading of bolts or screws.5. Torque ManagementT
25、o determine how much hand or power tool torque should be applied to a fastenerassembly or how much turn-of-the-nut tightening is required, consideration must be directed to thedevelopment of these methods.5.1 Theoretical Calculations to Obtain Torque Guide5.1.1 EMPIRICAL EQUATION(Eq. 1)where:T = Tor
26、que (Nm)D = Screw or bolt nominal size (mm)W = Screw or bolt tension (kN)K = Torque factor5.1.2 The tension of the screw or bolt is calculated by multiplying the usable screw or bolt tensile strength by thetensile-stress core area of the screw or bolt. The nominal clamp load stress is assumed as 75%
27、 of proof loadstress.5.1.3 The torque factor is the critical parameter in Equation 1 influenced primarily by the frictional conditions alongthe thread flank and at the bearing surfaces.The other influence on “K” is the relative resiliency of the fastener and joint material.a. Therefore:(Eq. 2)TKDW=K
28、K1 K2 K3+=Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE J1701M Issued JUL96-4-where:K1 represents the torque factor wasted by friction on the bearing surface of the nut or bolt,approximately 50%
29、of the total torque factor.K2 factor represents the wasted friction on the contact flanks of the threads, about 40% of the total “K”.K3 factor represents the useful torque producing the bolt tension, about 10% of the total “K”.b. K is 0.15/0.20 when bolts, nuts, and washers of the fastener joint are
30、 clean and coated with a thin filmof protective oil.When dirt, rust, and other defects of field storage and environmental exposure are present, K can be 0.25/0.40. Refer to Table 1 for torque K factors for other conditions.5.2 Clamp load and torque calculations based on the Equation 2 formula for dr
31、y and lubricated conditions aretabulated in Table 2.5.3 Turn-of-the-Nut MethodThe previous sections dwelled on tightening torque to produce clamping tension.The turn-of-the-nut method can produce satisfactory clamping when the joint is completely closed prior to theturn movement.Since the basis for
32、tightening threaded fasteners is screw or bolt tension, stretching the bolt by turning the nuta number of degrees clockwise after finger or snug tight will accomplish this. The bolt stretch is the degreesturned portion of the 360 degree pitch dimension. The number of degrees turned depends upon the
33、strengthof the bolt and the joint thickness.This document has not elaborated on the method because it is not effective unless the joint is closed under thebolt head or nut. Nevertheless, turn-of-the-nut is the most practical for M16 and larger fastener sizes.5.4 Check procedure for correct tightenin
34、g torque because assembly conditions such as mismatching componentsand pull-up tightening occur, the calculated guide torques previously discussed may overpower the fastener orits mating part causing failure to each other or both. Therefore, the following procedure on assimilatedassemblies can be a
35、practical method of establishing installation torque.5.4.1 First determine the torque at which any of twelve or statistically determined number of fasteners selectedfrom the same lot or their mating parts fail when they are applied by either hand or power tool wrenching tobe used in production.TABLE
36、 1TORQUE FACTORS FOR SURFACE CONDITIONSOF MATING FASTENERSMating Parts KDry, clean with thin film of oil 0.15/0.20Additional lubricating coatings of oil,wax, or dissimilar plating or hard washer 0.10/0.15Thread and head bearing surfacescovered with high-performance lubricantsor with anti-seize compo
37、undscan be aslow as 0.05Combinations of certain materials such asAustenite stainless steel screws/boltsand parts not lubricated or coatedcan be ashigh as 0.35Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from I
38、HS-,-SAE J1701M Issued JUL96-5-TABLE 2TORQUE-TENSION RELATIONSHIP FOR METRIC PROPERTY CLASSESMajorDiameterandThreadPitchStressAreamm2Class 4.6ClampLoadkNClass 4.6TorqueDry K = 0.2NmClass 4.6TorqueLub K = 0.15NmClass 4.8ClampLoadkNClass 4.8TorqueDry K = 0.2NmClass 4.8TorqueLub K = 0.15NmClass 5.8Clam
39、pLoadkNClass 5.8TorqueDry K = 0.2NmClass 5.8TorqueLub K = 0.15Nm3.0 x 0.5 5.03 0.85 0.50 0.40 1.17 0.70 0.503.5 x 0.6 6.78 1.14 0.80 0.60 1.58 1.10 0.804.0 x 0.7 8.78 1.48 1.20 0.90 2.04 1.60 1.205.0 x 0.8 14.20 2.40 2.40 1.80 3.30 3.30 2.50 4.05 4.00 3.006.0 x 1.0 20.10 3.40 4.00 3.00 4.67 5.66 4.2
40、0 5.73 6.90 5.208.0 x 1.25 36.6 6.18 9.90 7.40 8.51 13.60 10.20 10.40 16.70 12.5010.0 x 1.50 58.0 9.79 19.60 14.70 13.48 27.00 20.00 16.50 33.10 24.8012.0 x 1.75 84.3 14.22 34.10 25.60 19.60 47.00 35.00 24.00 58.00 43.0014.0 x 2.00 115.0 19.41 54.30 40.80 26.74 75.00 56.00 32.80 92.00 69.0016.0 x 2.
41、00 157.020.0 x 2.50 245.024.0 x 3.00 353.030.0 x 3.50 561.036.0 x 4.00 817.0Tensile Strength 400 MPa 420 MPa 520 MPaProof Load Stress 225 MPa 310 MPa 380 MPaMajorDiameterandThreadPitchStressAreamm2Class 8.8ClampLoadkNClass 8.8TorqueDry K = 0.2NmClass 8.8TorqueLub K = 0.15NmClass 9.8ClampLoadkNClass
42、9.8TorqueDry K = 0.2NmClass 9.8TorqueLub K = 0.15NmClass 10.9ClampLoadkNClass 10.9TorqueDry K = 0.2NmClass 10.9TorqueLub K = 0.15Nm3.5 x 0.6 6.784.0 x 0.7 8.785.0 x 0.8 14.206.0 x 1.0 20.108.0 x 1.25 36.6 16.50 26.40 19.80 17.80 28.50 21.40 22.80 36.50 27.3010.0 x 1.50 58.0 26.10 52.20 39.20 28.30 5
43、6.60 42.40 36.10 72.20 54.2012.0 x 1.75 84.3 37.90 91.00 68.00 41.10 99.00 74.00 52.50 126.00 94.0014.0 x 2.00 115.0 51.80 145.00 109.00 56.10 157.00 118.00 71.60 200.00 150.0016.0 x 2.00 157.0 70.60 226.00 170.00 76.50 245.00 184.00 97.70 313.00 235.0020.0 x 2.50 245.0 110.20 441.00 331.00 119.40 4
44、78.00 358.00 152.50 610.00 458.0024.0 x 3.00 353.0 158.90 762.00 572.00 172.10 826.00 620.00 220.00 1055.00 791.0030.0 x 3.50 561.0 252.40 1515.00 1136.00 273.50 1641.00 1231.00 349.00 2095.00 1572.0036.0 x 4.00 817.0 367.60 2647.00 1985.00 398.30 2868.00 2151.00 509.00 3662.00 2746.00Tensile Streng
45、th 830 MPa 900 Pa 1040 PaProof Load Stress 600 MPa 650 Pa 830 PaCautionThe previously listed torque and resulting tension are provided as an advisory guide. Individual application discretion is recommended. The content has been presented as accurately as possible, but responsibility for its applicat
46、ion lies with the user.Note 1The stress area of threaded series not included in Table 2 may be computed from the equation:As = 0.7854 (D - 0.9382 P)2where:As = Stress area in mm2D = Diameter in mmP = Pitch in mmCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reprod
47、uction or networking permitted without license from IHS-,-SAE J1701M Issued JUL96-6-5.4.2 Average the twelve individual torques. Then apply 85% safety factor and repeat the previous with a new setof twelve fasteners until no failures occur.5.4.3 Retest a new set of fasteners on the assemblies utiliz
48、ing the design factor established torque to confirminstallation is satisfactory or make minor adjustments until it is so.PREPARED BY THE SAE FASTENERS COMMITTEECopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from
49、 IHS-,-SAE J1701M Issued JUL96RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThis SAE Information Report is provided as an advisory guide. Individual application discretionis recommended. The content has been presented as accurately as possible, but responsibility for itsapplication lies with the user. The document covers the variables in the torque-tension relationship:friction, materials, temperature,
