When joining lightweight metals, the focus is on the installation space available and on optimizing performance and cost, as well as on the reliability of the fastening. And in light of that, an important point is the optimization of the fastening’s load capacity.

Arnold Umformtechnik GmbH & Co. KG developed the Powertite fastener to cope with such situations — a round self-tapping screw with a trilobular tapping zone. Where the forming work is taking place, the screw has a slightly triangular cross section (with rounded edges) to reduce the tapping torque. At a length of 3 x p (p=pitch) the tapping zone is optimized, allowing the forming work during the tapping process to be

The Powertite screw is a round thread-forming screw with a polygonal tapping tip and a trilobular tapping zone. The round load cross-section has a defined overlap. Source: Arnold Umformtechnik GmbH & Co. KG distributed over several thread flights, and ensuring that the screw is optimally set and centered. The round load cross-section has a defined overlap; the external diameter of the screw is always greater than the nominal dimension. This enables a greater overlap on the thread flanks of the screw and of the tapped nut thread. By combining this trilobular shape in the tapping zone, and the round cross-section in the bearing zone, we achieve a significant improvement in thread-tapping screw fastenings, because, on one hand, the tapping torques are low, and on the other, the overturn torques and load-bearing capacity of the tapped nut thread are greatly increased.

It is possible to create a computerized preliminary design for a specific application using the Fast Designer Metals tool. Here, Arnold Umformtechnik always makes a recommendation for a suitable core hole layout.

Huge savings potential possible
There are many examples of ways in which thread tapping Powertite can be used. They are applications, for example, where there is a need to implement maximum clamping forces with over-elastic assembly. And the Powertite is also suitable for component assemblies where the screw-in depth is low, yet high hole tolerances are necessary. And in many cases, it is possible to reduce weight by reducing the length of the screw and optimizing the weight of the screw heads.