Ligature (technology)
A ligature is a screw the head of which is flattened to form a 'blade' that has just continued. This is used either as a handle for hand-tightened screws (e.g. ligature ) or provided with holes as a (one-dimensionally adjustable) fastening element. While ligatures for manual operation have formed the blade in the middle and wide for better rotation, the blade is often forged as an extension of the outer edge of ligature with holes as a connecting element in order to obtain a flat support for components to be fastened.
history
Even with historical tools and constructions that could be adjusted, ligature screws were used as a construction or operating element that was simple and inexpensive to produce in terms of forging technology, although there was still no differentiation to the wing screw . In the 1950s, the ligature was still defined in the DIN as a manually operated locking element , after which the knurled screw became predominant as a component that could be produced more cheaply and was equally easy to grasp on all sides.
Manual variant
A ligature as a manually operated setting or fastening element has a blade that is as wide as possible, as can be seen, for example, on musical instruments. Due to the increased distance to the axis of rotation, a higher torque is achieved with the same effort. In contrast to wing screws , they have an undivided, possibly slightly notched blade.
A special case are the coffin lid screws, which are also functionally ligature screws as a manually operated, decorated locking element.
Construction variant
With the ligature as a construction and fastening element, it has one or more holes in order to attach another component to the component in which it is screwed.
Demarcation
A distinction must be made between the (constructive) ligature screws , in which the screw neck is bent into a ring, and the eye screw in which the head is forged into a ring or a ring is welded on. Both forms can absorb greater bending forces in the direction of the hole axis than the horizontally flat ligature.