{"id":31031,"date":"2020-02-01T18:27:24","date_gmt":"2020-02-01T17:27:24","guid":{"rendered":"https:\/\/bolting.eu\/torque-at-expansion-bolt\/"},"modified":"2025-02-11T14:15:43","modified_gmt":"2025-02-11T13:15:43","slug":"torque-at-expansion-bolt","status":"publish","type":"page","link":"https:\/\/bolting.eu\/en\/torque-at-expansion-bolt\/","title":{"rendered":"Torque at expansion bolt"},"content":{"rendered":"\n

Torque at expansion bolt<\/h2>\n\n
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The torque at expansion bolt<\/a> is a very important thing. It is sometimes also referred to as the “torque for bolt anchors”. In simple terms, it describes the force with which a bolt should ideally be donned. The corresponding unit is “Newton meter” = Nm. Firstly, this force must be great enough. Because only then will a expansion bolt hold properly in solid ground. And secondly, it must not be too great. Otherwise there will be too much tension in the steel and the bolt may break. If you want to bolt a climbing route<\/a>, you should definitely know about this term!<\/p>\n\n

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Explanation of the torque (M). M = length of the lever “r” x force “F”:Taken from wikipedia; graphic: Pietz<\/figcaption><\/figure>\n\n
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In the diagram above, “r” would therefore be the wrench. And “F” is the force with which we “donned” the expansion bolt. The torque (“M”) is calculated as follows:M = r x FTorque = lever arm x force<\/p>\n\n

The rock has to be right…<\/h2>\n\n
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If you want to set up a climbing route with expansion bolt <\/a>, you should be familiar with the basics. For example, the following two factors. A solid rock base and the correct torque for expansion bolt. Firstly, the rock must be solid. With a fall factor of 2, the resulting force is approx. 6 kN. The UIAA standard 959 for expansion bolt or bolt hanger<\/a> requires at least 15kN axial and 20kN radial breaking load. This means that the forces occurring almost never reach the maximum breaking load of the bolts. Consequently, if a fixed point rarely fails, it is more likely to be the rock that gives way. Not the bolt that breaks! Further information can be found in our specialist article “What do expansion bolt hold?”Secondly, the hook must be donned with the correct torque. <\/p>\n\n

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Knowing the torque at expansion bolt is simply part of bolting! Image: bolting.eu <\/figcaption><\/figure>\n\n
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… and the torque at expansion bolt<\/h2>\n\n
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Two things happen simultaneously with the right torque. On the one hand, the expansion links slide over the cone of the expansion bolt. In doing so, they exert the necessary expansion effect. On the other hand, the expansion bolt is also put under tension. This threshold tension only remains below a critical value with the correct torque. If it is exceeded, it will break. This is why the correct torque is so important for bolt anchors! The Fischer FBN II, for example, has the following torque recommendation:<\/p>\n\n