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Appro To Lauch AppMo 2.0

Appro will shortly be launching AppMo 2.0, which solves the problem of knowing how much clamping force the bolt is exposed to during installation and while “working”! AppMo 2.0 also solves the problem regarding the multiplier effects that arise during installation.
 

“Everyone who has tried to identify the factors affecting the tension force in a bolted joint knows that it is difficult and far from optimal to control the tension force during a specific operation. Therefore, knowledge of the parameters that control the tension force is essential in order to optimise the outcome of the bolted joints tension force. This quote by Björn Malmqvist, technical director at Bult & Fästteknik AB, was taken from Stålbyggnad magazine issue no. 3 – 2010.
 

When fitting bolts with associated nuts and washers, what is required is the tension force (clamping force) between the metal sheets. It is therefore not sufficient simply to add an operation if you do not know what this operation will contribute to the clamping force in the joint. The tension force can vary significantly if you do not keep track of all the parameters, such as the added operation.
 

Of the added assembly operation, approximately 50%, is used to overcome friction between the rotating part’s contact surface. Approximately 40% is used to overcome friction in the threads between the bolt and the nut. This means that only around 10% of the added operation achieves the desired tension force. This can be increased using AppMo Solid Lubrication Paste, but only to just over approximately 20%. 

Applying this knowledge, it is easy to understand that the tension force for the same torque can increase to double using AppMo Solid Lubrication Paste, but with the penalty of having a pause in the assembly.
 

Knowledge of assembly operations and the effect of friction on the tension force is very important in order that the assembly is performed to the correct tension level.
 

Other causes contributing to the multiplier effects include, the installation tools’ repeatability, the mechanical properties of the bolt and nut spread, thread friction, the contact surfaces’ friction characteristics, and the friction-governing nature of the products.
 

With this knowledge, it is easy to understand that, in the past, bolts have been damaged in the assembly of bolted joints due to inaccurate and unverified assembly tools combined with insufficient knowledge of the effect of the coefficient of friction on the tension force.
 

Feel and rule of thumb are now no longer necessary guides during assembly, nor are costly post-tightening inspections of the bolted joints. 
 

The launch of AppMo 2.0 is planned for the spring of 2011.

Related Links:

• Appro