Standard_Parts_Catalogue

Page 2152 | Extract from DIN / ISO Standard DIN EN ISO 898-1 DIN EN 20898-2 Strength Values Extract Extract of Screws / Nuts Material characteristics Property class 4.6 5.6 5.8 6.8 8.8 10.9 12.9 Tensile strength R m in N/mm 2 400 500 500 600 800 1000 1200 Yield point R e in N/mm 2 240 300 400 480 640  900 1080 Elongation at break A in %  22  20  10   8  12    9    8 The property class identification for standard steel screws consists of two figures separated by a point: • The first figure, called the strength index, is equal to 1 / 100 of the tensile strength R m in N/mm 2 • The second fi gure, called the yield point ratio, indicates 10 times the ratio of the yield point R e or the substitute yield point R p 0.2 to the nominal tensile strength R m . If the tensile strength R m is multiplied by 1 / 10 of the second figure, the result is the yield point R e . Example: Screw of the property class 5.8, strength index = 5, yield point ratio = 8 Tensile strength R m = Strength index x 100 = 5 N/mm 2 x 100 = 500 N/mm 2 Yield point R e = Tensile strength R m x 0.8 = 500 N/mm 2 x 0.8 = 400 N/mm 2 The property class identification for standard steel nuts consists of only one figure. It provides information on the test stress S p related to a hardened test mandrel and is specified in the ratio 1 / 100 . The test stress S p is equal to the tensile strength R m . Example: Nut of property class 6 Tensile strength R m = Strength index x 100 = 6 N/mm 2 x 100 = 600 N/mm 2 Test stress S p in N/mm 2 for threads Property class 5 6 8 10 12 … M  4 520 600 800 1040 1150 above M  4 … M  7 580 670 855 1040 1150 above M  7 … M 10 590 680 870 1040 1160 above M 10 … M 16 610 700 880 1050 1190 above M 16 … M 39 630 720 920 1060 1200 Strength values of screws Strength values of nuts Nuts and screws of the same property classes in combination, e.g. nut 8 - screw 8.8, can be loaded up to the yield point of the screw without damaging the nut. If simply one figure is given for standard parts, e.g. “property class 5”, it is equal to the strength index and must be handled correspondingly.