Tightening Calculator

Tightening of Bolts

The program Tightening of Bolts helps you to find or check the tightening procedures of threaded joints using the relationship between torque, clamp load, friction and the property class of the fastener. It also takes different thread and under head friction into account.

Input
The calculations can be performed for tightening into the elastic or the plastic area. Choose elastic or plastic. Torque tightening is usually performed in the elastic area and yield and angle controlled tightening in the plastic area.

The Input bolt dimensions for the calculations consists of 3 main parameters:
• The nominal metric thread diameter d
• The pitch of the thread P
• Effective diameter for the friction moment at the bearing area under the bolt head (when bolt tightening) or at the nut bearing area (when nut tightening), or bearing diameter Db

Below the Input parameters a field containing another 5 parameters is shown:
• The equivalent stress σred, representing the total stress acting on the bolt (a combination of axial stress because of the clamp force and torsional stress caused by the tightening torque)
• The clamp force F acting on the bolt
• The tightening torque T applied to the bolt
• The bearing friction µb
• The thread friction µth

IMPORTANT
If you fill in any 3 of these 5 parameters, the 2 parameters that are left open are calculated automatically. The results (all 5 parameters) are shown in the Output field. If less than 3 or more than 3 parameters are filled in no result will be shown.

Additionally to these results the following parameters are also calculated and shown in the Output bolt dimensions:
• The nominal minor diameter of the bolt thread d3
• The nominal pitch diameter of the bolt thread d2
• The nominal stress area of the bolt thread AS