1、FORD WORLDW IDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 1 of 3 Printed copies are uncontrolled .Systems Engineering (ESSE)WE 990Surface Discontinuities of Nuts1. SCOPE. This standard defines limits for various types of surface discontinuities on nuts with threaddiameters from 5 up t
2、o and including 39mm.NOTE: The term “permissible discontinuity“ only applies provided that all requirements of WE 950and WE 952 are satisfied. The visual inspection requirements of Clause 3.2 are mandatory. All otherrequirements are for reference purposes unless otherwise specified on the Ford stand
3、ard or utility partdrawing.REFERENCES.ISO 1 - Standard reference temperature for industrial length measurement.ISO 468 - Surface RoughnessISO 1302 - Technical Drawings - Method of Indicating Surface Texture.ISO 4288 - Rules and Procedures for the measurement of surface roughness parameters usingstyl
4、us instruments.ISO 6157/2 - Fasteners - Surface discontinuities - Part 2: NutsISO 10485 - Cone proof load test on nuts.QS-9000 - Quality System StandardWE 950 - Prevailing Torque-Type Steel Hexagon Nuts and Hexagon Flange Nuts - Mechanicaland Performance PropertiesWE 952 - Mechanical Properties of N
5、uts with Specified Proof Load Values2. REQUIREMENTS General requirements for surface discontinuities are defined in ISO 6157 - Part 2.3. INSPECTION AND EVALUATION PROCEDURE.3.1 GENERAL REQUIREMENTS. Sampling shall be carried out in accordance with QS-9000 usingthe following procedures. Surface coati
6、ngs shall be removed if identification of the surfacediscontinuities is impaired. The manufacturer may use any inspection procedures provided duecare is taken to ensure that products conform to this standard.3.2 NON-DESTRUCTIVE TESTING. A representative sample shall be taken from the lot inaccordanc
7、e with QS-9000 and must be subjected to a visual examination at 10X magnification. Ifdefective parts are suspected but not confirmed, then further tests such as magnetic or eddy currenttechniques must be carried out for confirmation. If no defective product is found the lot shall beaccepted. If surf
8、ace discontinuities are found exceeding the allowable limits, these shall form thelot size for the procedure shown in Clause 3.3.If, during the visual inspection, a product is found with quench cracks or other unacceptablediscontinuities, the lot shall be subject to rejection or 100% sorting to remo
9、ve all parts withevidence of that defect.3.3 DESTRUCTIVE TESTING. If defective products are detected by the procedures given in Clause3.2, then a secondary sample shall be taken from these defective products in accordance with QS-9000, consisting of the parts containing the most severe discontinuiti
10、es. These shall be subject tothe Performance Test requirements as defined in ISO 6157/2. If any part fails the appropriatedestructive test, the lot shall be subject to rejection or 100% sorting and re-test.FORD WORLDW IDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 2 of 3 Printed copies
11、 are uncontrolled .Systems Engineering (ESSE)WE 990Surface Discontinuities of Nuts4. PERFORMANCE TESTS. For referree purposes nuts must satisfy the widening test specified in Clause4.1. The cone proof load test according to ISO 10485 may be applied in addition to the widening test byagreement betwee
12、n manufacturer and user.4.1 WIDENING TEST.4.1.1 PRINCIPLE After removal of the thread up to the nominal diameter a tapered mandrel ispushed into the nut. The widening is measured as a percentage of the hole diameter.4.1.2 TEST MANDREL.The test mandrel shown in Figure 1 shall be used for measurement
13、of widening of 6% or4% respectively (See Clause 2). It shall have minimum hardnesses of not less than 45HRC and the cone shall be polished (roughness depth R a = 2.5 m).4.1.3 TEST NUT.Nut to be subjected to the widening test shall have the thread removed to a diameter equalto the nominal diameter of
14、 the thread.4.1.4 PROCEDURE.Prior to the test, lubricate the mandrel with molybdenum disulphide (MoS 2 ).Insert the mandrel int o the nut as shown in Figure 2 and apply a load axially in a slowand continuous manner until the mandrel is pushed through the hole up the cylindricalpart. The mandrel shal
15、l be tightly clamped at the upper end. For referee purposes thespeed of insertion shall not exceed 25mm/min.4.2 CRITERIA.The total widening of nuts shall be:6% for nuts of property classes 8, 10, or 12, and4% for nuts of property classes 04 to 05Failure of a nut occurs when the wall of the nut break
16、s entirely before the minimum specifiedwidening value is obtained. In cases of doubt, the fracture may be recognized when the nut is cuton the opposite side and then falls into two single parts.4.3 SPECIAL CASES.4.3.1 PREVAILING TORQUE TYPE NUTS.For prevailing torque type nuts the minimum value of w
17、idening shall be 20% below thevalues specified for hexagon nuts.FORD WORLDW IDE FASTENER STANDARDDate: 1996-10-01Engineering Standards & 3 of 3 Printed copies are uncontrolled .Systems Engineering (ESSE)WE 990Surface Discontinuities of NutsFigure 1. Test mandrel for widening up to 6% (or up to 4% respectively)Figure 2. Test assembly
