Strength class

Using the strength classes materials and building materials are classified according to their strength and named.

Lumber

For construction timber , the strength classes of solid timber in EN 338 and of glued laminated timber in EN 1194 were re-regulated in the course of European standardization . The new DIN 1052: 2004 contains the same strength classes with different strength values.

screws and nuts

For screws and nuts , the classification is based on strength classes.

For screws, these consist of two numbers separated by a point, e.g. B. 4.6 or 8.8, from which the properties of tensile strength and yield point or 0.2% yield point can be determined very easily. Up to and including strength class 6.8, the yield point is specified, from strength class 8.8 the 0.2% yield point. ${\displaystyle R_{\mathrm {m} }}$ ${\displaystyle R_{\mathrm {e} }}$ ${\displaystyle R_{p=0,2}}$

Only one number is used for nuts. This indicates that z. B. a nut of class 10 can be used with a screw of strength class 10.9.

Example 1: Screw of strength class 4.6

1. Determination of tensile strength : The number in front of the point is multiplied by 100: ${\displaystyle R_{\mathrm {m} }}$

   ${\displaystyle R_{\mathrm {m} }=4\cdot 100\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}=400\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}}$

2. Determination of the yield point : The two numbers are multiplied together and then multiplied again by 10: ${\displaystyle R_{\mathrm {e} }}$

   ${\displaystyle R_{\mathrm {e} }=4\cdot 6\cdot 10\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}=240\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}}$

Example 2: Screw of strength class 12.9

1. Determination of tensile strength : The number in front of the point is multiplied by 100: ${\displaystyle R_{\mathrm {m} }}$

   ${\displaystyle R_{\mathrm {m} }=12\cdot 100\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}=1200\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}}$

2. Determination of the 0.2% yield strength : The two numbers are multiplied together and then multiplied again by 10: ${\displaystyle R_{p=0,2}}$

   ${\displaystyle R_{p=0,2}=12\cdot 9\cdot 10\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}=1080\,{\frac {\mathrm {N} }{\mathrm {mm^{2}} }}}$

Web links

• Screw primer Overview of the old and new strength classes for screws and nuts
• The strength class - what does it say? Blog post on the calculation of strength classes for bolts and nuts
• Overview of strength classes for screws and nuts ( Memento from March 25, 2015 in the Internet Archive )