1、 WORLDWIDE FASTENER STANDARD WE950 2015 03 06 Printed copies are uncontrolled Copyright 2015, Ford Global Technologies, LLC Page 1 of 6 PREVAILING TORQUE-TYPE STEEL HEXAGON NUTS AND HEXAGON FLANGE NUTS MECHANICAL AND PERFORMANCE PROPERTIES 1. SCOPE This standard specifies the mechanical and performa
2、nce requirements for prevailing torque-type steel hexagon nuts, hexagon nut and washer assemblies and hexagon flange nuts, tested at room temperature as specified in ISO 1. a) with nominal diameters M4 to M24 inclusive. b) with strength requirements of property classes 8 and 10, according to ISO 898
3、/2. c) with dimensions as specified in the Worldwide Product Standards or on Worldwide Utility Part drawings. d) within the following temperature ranges: 1) -50 to +300 C for all-metal nuts. 2) -50 to 120 +120 C for non-metallic insert nuts. NOTE: This specification is not applicable to parts which
4、do not have a coating incorporating a self-lubrication constituent or which are not lubricated to meet the requirements of WZ100, unless otherwise specified. Unless stated otherwise, all reference to nuts in this standard are to both all metal and non-metallic insert prevailing torque hexagon nuts,
5、hexagon nut and washer assemblies and prevailing torque hexagon flange nuts. NOTE: These products shall be capable of being assembled on bolts with pilot points in accordance with WA 900. 2. REFERENCES ISO 1 - Standard reference temperature for industrial length measurement. ISO 1302 - Technical dra
6、wing - Method of indicating surface texture on drawings. ISO 965/1 - ISO general purpose metric screw threads - Tolerances - Part 1: Principles and basic data. ISO 898/1 - Mechanical properties of fasteners - Part 1: Bolts, screws and studs. ISO 898/2 - Mechanical properties of fasteners - Part 2: N
7、uts with specified proof load values. ISO 2320 - Prevailing torque type steel hexagon nuts - Mechanical and performance properties. WSK-M4D671-A/A2 - Polyamide (PA) 4.6, Heat Stabilized Molding Compound WX100 - Finish specification. WZ100 - Steel hexagon ISO metric threaded fasteners torque/clamping
8、 force performance. WORLDWIDE FASTENER STANDARD WE950 2015 03 06 Printed copies are uncontrolled Copyright 2015, Ford Global Technologies, LLC Page 2 of 6 3. DEFINITIONS 3.1 PREVAILING TORQUE-TYPE NUT A nut which is frictionally resistant to rotation due to a self-contained prevailing torque feature
9、, and not because of a compressive load developed against the bearing surface of the nut. 3.2 PREVAILING TORQUE DEVELOPED BY A NUT The torque necessary to rotate the nut on its mating externally-threaded component, with the torque being measured while the nut is in motion, and with no axial load in
10、the mating component. 4. FINISH Prevailing toque nuts for prevailing torque and torque/clamping force testing must satisfy the requirements of the specified protective coating (if any) including lubrication requirements. NOTE: Prevailing torque nuts which are specified without supplementary lubricat
11、ion may not satisfy the requirements of this specification unless the lubrication is an integral property of the specified coating. 5. MECHANICAL AND PERFORMANCE REQUIREMENTS 5.1 MATERIALS AND PROCESSES 5.1.1 MATERIALS The material used to produce all metal prevailing torque nuts must be steel. The
12、choice of steel shall be at the discretion of the manufacturer provided that finished parts meet the mechanical and performance requirements specified in Clause 5.3. The body of prevailing torque nuts with non-metallic inserts must be made from steel as above. The insert material must be heat stabil
13、ized Polyamide 4.6, 6, or 6.6 with a minimum moisture content of 1.5%. If the nylon is inserted prior to coating and the cure temperature of the coating is in excess of 180 C but not exceeding 250 C, heat stabilized Polyamide 4.6 with a minimum moisture content of 3% in accordance with WSK-M4D671-A/
14、A2 must be used. Table 2. Nut/bolt assemblies 1)If an all metal nut is combined with a bolt of a lower property class, the prevailing torque characteristics may be significantly altered and thread damage may occur. Property class of the nut1)8 10 Property class of the mating bolt or screw. - all met
15、al 8.8 10.9 Property class of the mating bolt or screw. - non-metallic insert 8.8 and lower 10.9 WORLDWIDE FASTENER STANDARD WE950 2015 03 06 Printed copies are uncontrolled Copyright 2015, Ford Global Technologies, LLC Page 3 of 6 5.1.2 HEAT TREATMENT Class 8 nuts may be hardened and tempered at th
16、e option of the manufacturer. Class 10 nuts must be hardened and tempered. 5.1.3 LUBRICATION Nuts finished in accordance with WX100 requiring no lubrication may be lubricated at the discretion of the manufacturer. Nuts finished in accordance with WX100 with a finish which requires lubrication must b
17、e lubricated. All nuts with or without lubricant must meet the requirements of Clause 5.3. There must be no significant change in the appearance or performance of parts treated with a lubricant after storage indoors in a dry condition for a period of six months. 5.2 MECHANICAL REQUIREMENTS 5.2.1 PRO
18、OF LOAD Nuts shall withstand the proof load specified in Table 1 for the applicable class when tested as specified in Clause 6.1. 5.3 PERFORMANCE REQUIREMENTS 5.3.1 PREVAILING TORQUE The prevailing torque developed by nuts (See Clause 3.2) during their first fixing, or any subsequent fixing or remov
19、al, shall not exceed the maximum prevailing torque specified for the applicable class in Table 1 when tested as specified in Clause 6.2. In addition, the prevailing torques developed by nuts during their first and fifth removals shall be not less than the minimum prevailing torques specified in Tabl
20、e 1 when tested as specified in Clause 6.2. 5.3.2 TORQUE/CLAMPING LOAD The torque necessary to develop the clamping load specified in Table 1 must be measured as specified in Clause 6.2 and must meet the applied torque specified in Table 1. (Except nut and washer assemblies where only the clamping f
21、orce shall be achieved.) 6. TEST METHODS Prevailing torque nuts shall meet the requirements for proof load testing and prevailing torque and torque/clamping force specified in Clauses 6.1 and 6.2. WORLDWIDE FASTENER STANDARD WE950 2015 03 06 Printed copies are uncontrolled Copyright 2015, Ford Globa
22、l Technologies, LLC Page 4 of 6 6.1 PROOF LOAD TEST Proof load testing shall be completed as specified in ISO 2320 except that the test bolt shall be as specified in Clause 6.6 with a property class higher than the nut to be tested. It is permissible to test nuts on the hardened mandrel described in
23、 ISO 2320 but this shall be completed prior to the introduction of the prevailing torque feature. 6.2 PREVAILING TORQUE AND TORQUE/CLAMPING FORCE TESTS The torque shall be measured using a device as specified in Clause 6.3 and the clamping force shall be measured using a device as specified in Claus
24、e 6.4. For referee purposes the device must not exceed 30 r.p.m. A test bolt (Clause 6.6) shall be inserted in the clamp force measuring device, a test washer (Clause 6.5) placed on the bolt and sample nut then assembled on the bolt. The nut shall be advanced on the bolt until two or three full bolt
25、 threads protrude through the nut. The maximum torque occurring while the nut is advanced through the next 360oof nut rotation shall be measured. For the nut to be acceptable, this torque shall not exceed the maximum prevailing torque value specified for the applicable nut in Table 1. Tightening sha
26、ll be continued until the clamping force specified in Table 1 appropriate to the property class of the nut is achieved. The length of the test bolt shall be such that when the required clamping force is achieved a length equivalent to four to seven thread pitches of the test bolt protrudes through t
27、he nut, measured form the end of the test bolt. For referee purposes an automatic electronic sensing device shall be used and rotation shall continue until the specified clamping force is exceed within a tolerance of +10%. A continuous record of the torque and clamping force shall be evaluated to de
28、termine the torque for the clamping force specified in Table 1. The applied torque shall be recorded. (Except nut and washer assemblies - See Clause 5.3.2). NOTE: All prevailing torque measurements shall be taken with the nut in motion and with the test washer prevented from turning during nut tight
29、ening. The applied torque shall be within the values specified in Table 1. (Except nut and washer assemblies where only the clamp force need be achieved.) The nut shall then be slackened by the application of reverse torque until the tensile load in the bolt has been reduced to zero. The maximum tor
30、que occurring through the next 360oof rotation after this slackening shall be measured. For the nut to be acceptable, these torques shall not be less than the “first removal“ torque value specified for the appropriate nut in Table 1 nor greater than the maximum prevailing torque recorded during the
31、initial assembly of the nut. After the “first removal“ prevailing torque has been measured, the nut shall be further slackened until the prevailing torque element is disengaged from the bolt thread. The nut shall then be rotated in a tightening and then slackening direction four more times. Each tim
32、e the nut shall be advanced in the tightening direction sufficiently to allow a length equivalent to four to seven thread pitches to protrude through the nut without generating a clamping force, and each time the nut is rotated in the slackening direction the prevailing torque element shall be disen
33、gaged from the bolt thread. This portion of the test need not be carried out in the clamping force measuring device. During the last rotation of the nut in the slackening direction the prevailing torque shall be measured through the first 360oof rotation and the torque recorded. For the nut to be ac
34、ceptable, this torque shall not be less than the “fifth removal“ torque value specified in Table 1. In addition, at no time during these four subsequent tightening and slackening movements shall the torque exceed the maximum prevailing torque value specified in Table 1. WORLDWIDE FASTENER STANDARD W
35、E950 2015 03 06 Printed copies are uncontrolled Copyright 2015, Ford Global Technologies, LLC Page 5 of 6 6.2 PREVAILING TORQUE AND TORQUE/CLAMPING FORCE TESTS (Continued) To avoid overheating of the test assembly, sufficient time shall elapse between the torque application cycles. The speed of inst
36、allation and removal of the nut shall not exceed 30 r.p.m. and shall be continuous and uniform. Table 1. Proof loads, clamp loads, applied torques and prevailing torques for nuts with a coarse pitch Nom Size Proof Load Clamp Load Applied Torque, Nm Prevailing Torque, Nm kN kN All Metal Non Metallic
37、Insert Class Class Class 8 Class 10 Class 8 Class 10 Class 8 and 10 8 10 8 10 1st 5th 1st 5th 1st 5th removal removal removal mean +/- mean +/- max. min. min. max. min. min. max. min. min. M4 7.0 9.15 3.8 5.5 3.1 0.6 4.5 0.8 0.9 0.2 0.1 1.2 0.22 0.11 0.45 0.15 0.1 M5 12.1 14.8 6.2 8.9 6.2 1.2 8.9 1.
38、7 1.6 0.3 0.15 2.1 0.35 0.18 0.8 0.25 0.15 M6 17.2 20.9 8.7 12.9 10.4 2.0 15.2 2.7 3 0.5 0.25 4 0.55 0.28 1.5 0.4 0.25 M8 31.8 38.1 15.9 22.8 25 5.0 36 7.0 6 0.9 0.45 8 1.15 0.58 3 0.7 0.45 M10 50.5 60.3 25.3 36.1 50.5 9.5 72 13 11 1.6 0.8 14 2 1 5.5 1.2 0.8 M12 74.2 88.5 36.7 52.5 88 17 126 24 16 2
39、.4 1.2 21 3.1 1.6 8 1.8 1.2 M14 101.2 121 50 71.6 140 28 200 40 24 3.2 1.6 31 4.4 2.2 12 2.4 1.6 M16 138.2 165 68.2 97.5 217.5 42.5 310 61 32 4.4 2.2 42 6 3 16 3.3 2.2 M18 177 204 86.2 119 313.5 58.5 433 80 42 5.9 3 56 8 4 21 4.4 3 M20 225 260 110 152 437.5 82.5 605 114 55 7.6 3.8 72 10.5 5.3 28 5.7
40、 3.8 M22 279 321 136 189 602.5 102.5 832 157 68 9.5 4.8 90 13 6.5 34 7 4.8 M24 325 374 159 220 774 154 1070 213 82 12 6 106 15 7.5 41 9 6 NOTE: The applied torque figures are tests results and may not be suitable for assembly. 6.3 TORQUE MEASURING DEVICE The torque measuring device (torque wrench or
41、 power device) shall be accurate to +/- 2% of the maximum specified torque range of the device. For referee purposes, the measuring device shall be chosen so that all readings fall within the upper half of its torque range. A recommended method using manual torque wrenches is described in Appendix A
42、 but for referee purposes an automatic electronic sensing device shall be used. 6.4 LOAD MEASURING DEVICE The load measuring device used in the prevailing torque test shall be an instrument capable of measuring the actual tension induced in the test bolt as the nut is tightened. The device shall be
43、accurate to +/- 3%. The bolt clearance hole in the backing plate shall have the same internal diameter and tolerance as the test washer. The face against which the test washer bears shall be smooth, flat within a tolerance of 0.1/100 and square with the axis of the test bolt within a tolerance of 0.
44、1/100. WORLDWIDE FASTENER STANDARD WE950 2015 03 06 Printed copies are uncontrolled Copyright 2015, Ford Global Technologies, LLC Page 6 of 6 6.5 TEST WASHER Test washers must be made from carbon steel quenched and tempered to a surface hardness of 500-600HV and a core hardness of 450-490HV and must
45、 be unplated; both faces shall be clean and lubricant free. The dimensions must be as specified in WZ100. The faces must be flat and parallel within a tolerance zone of 4% of the specified minimum thickness. The surface roughness of the abutment face shall fall within the range N4 - N5 to ISO 1302.
46、Test washers must be designed such that when assembled into the test equipment, rotation of the washer is prevented during tightening of the nut. Any device used to prevent rotation must not intrude into a diameter equal to the maximum bearing face diameter of the prevailing torque nuts. Alternative
47、ly, multi-holed plates may be used provided that they conform to the requirements for hardness, hole dimensions, surface condition, thickness, flatness and parallelism. The abutment face shall be re-prepared in accordance with the above between each test or a new washer used. 6.6 TEST BOLT Threads s
48、hall be in accordance with ISO 965/1 within a tolerance of class 6g min. to 4h max. Threads on all bolts shall be produced by rolling. Bolt length shall be such that 4 to 7 thread pitches, as measured from the end of the bolt, will protrude through the nut when the nut is seated against the test was
49、her. Thread length shall be such that a minimum of two full threads are within the grip after the nut is seated. The bolt shall have a point which is flat and chamfered. The thread surface shall be free of burrs or other contamination that might affect an accurate determination of the performance of the nut. The bolt shall have an ultimate strength related to the specified property class of the nut to be tested (except for proof load testing - See Clause 6.1) and the properties shall be in accordance with ISO 898/1. A new bolt shall be used for testing each nut. The bol
