1、FORD WORLDWIDE FASTENER STANDARDDate: 1993-01-01Engineering Standards & 1 of 2 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 950APPENDIX AMaterial and Performance Requirements for Case Hardened Carbon Steel Thread Cutting Screws - Type D1. SCOPE.This appendix covers the requirements
2、for Thread Cutting Screws not specified in the body of WD 950. Unless otherwise specified all other requirements of WD 950 apply.1.1 REFERENCES.ISO 1502 - General purpose metric screw threads - Gauging.2. MATERIAL.Screws shall be made from cold heading quality, killed steel wire suitable for case ha
3、rdening.3. METALLURGICAL REQUIREMENTS.3.1 CORE HARDNESS, SURFACE HARDNESS AND MICROSTRUCTURE. These shall bespecified in Clauses 3.1, 3.2 and 3.4 of the specification.3.2 TOTAL CASE DEPTH. A microhardness test shall be carried out at the thread flank mid-pointbetween crest and root or, in the case o
4、f smaller screws up to (M)4, in the root of the thread. Thecase depth shall be at the point where the hardness exceeds the actual core hardness by HV25 andshall be in accordance with the following:Screw Size Total Case Depth(M)2 and (M)3(M)4 and (M)5(M)6 and larger0.05 - 0.018mm0.1 - 0.23mm0.15 - 0.
5、28mm4. PERFORMANCE REQUIREMENTS.4.1 DRIVE TEST. Thread cutting screws shall meet the same thread forming requirements as thespaced thread tapping screws when tested in a test plate of the material specified in Clause 4.1 ofthe specification. Test plate thickness and the diameter of holes shall be as
6、 specified in Table 1 ofthis Appendix.Table 1. Standard test plate thickness and hole size for drive testinspection of thread cutting screws (Type D) - Metric threadThreadCuttingPlate Thickness Hole DiameterScrews 1) Min. Max. Min. Max.(M)4(M)5(M)6(M)8(M)10(M)121.853.14.674.675.56.52.063.235.055.056
7、27.23.34.25.56.88.510.23.354.255.556.858.5510.251) Although the designation for these screws are M4, M5, M6 etc., the thread formdimensions vary from ISO metric screws. However, the female thread formed bythese screws must meet the requirements of the 6H gauging system specified inISO 1502.FORD WOR
8、LDWIDE FASTENER STANDARDDate: 1993-01-01Engineering Standards & 2 of 2 Printed copies are uncontrolled .Systems Engineering (ESSE)WD 950APPENDIX AMaterial and Performance Requirements for Case Hardened Carbon Steel Thread Cutting Screws - Type D4.2 TORSIONAL STRENGTH TEST.Using the same method and e
9、quipment detailed in Clause 4.3 of the specification, the torque tocause failure of the thread cutting screw shall equal or exceed the minimum value shown in Tableof this Appendix for the size of screw being tested.Table 2. Torsional strength requirements for thread cutting screwsThread CuttingScrew
10、 1)Minimum TorsionalStrength (NM)(M)4(M)5(M)6(M)8(M)10(M)125.210.517.743871521) Although the designation for these screws are M4, M5,M6 etc., the thread form dimensions vary from ISOmetric screws. However, the female thread formed bythese screw s must meet the requirements of the 6Hgauging system specified in ISO 1502.
