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Steel Bolts Strength Designation System
Strength Grade Designation System for Steel Nuts
The strength grade designation system consists of two figures. The first figure is one tenth of the minimum tensile strength in kgf/mm2, and the second figure is one tenth of the ratio between the minimum yield stress (or stress at permanent set limit, R0.2) and the minimum tensile strength, expressed as a percentage.
For example with the strength designation grade 8.8, the first number "8" represents 1⁄10 the minimum tensile strength of 80 kgf/mm2 and the second number "8" represents 1⁄10 the ratio
the numerical values of stress and strength being obtained from the table given below.
Strength Grade Designation System of Steel Bolts and Screws
|Strength Grade Designation||4.6||4.8||5.6||5.8||6.6||6.8||8.8||10.9||12.9||14.9|
|Tensile Strength (Rm), Min.||40||40||50||50||60||60||80||100||120||140|
|Yield Stress (Re), Min.||24||32||30||40||36||48||…||…||…||…|
|Stress at Permanent Set Limit (R0.2), Min.||…||…||…||…||…||…||64||90||108||126|
|All stress and strength values are in kgf/mm2 units.|