The riveting processiet
The history of riveting technology
In the beginning there were: man, his hammer and a rivet head maker (riveting die).
Riveting as one of the oldest methods of connecting two components in an inseparable way is already known since early history.
Riveted unions were produced by peening bolt rivets over with a hammer.
As industrialisation was on the rise, also presses or mechanical hammers for metal working were gaining ground but were soon replaced by specific riveting machines. The great amount of force to be exerted along with high noise levels on the one hand and, on the other hand, the changes in the structure of the rivets and their embrittlement were less and less accepted by users who demanded higher quality standards.
Though the orbital riveting technology did bring some improvements in its wake, the hardenings of the rivet structure and the damage to the closing head surface still remained.
New riveting method
The invention that revolutionised the riveting world
The Radial Point Riveting Technology by Friedrich
In the year 1966, Friedrich's engineers layed the foundation for a technology which to this date remains the most efficient and economic one:
The advantages of the radial point riveting technology:
- low effort combined with a high riveting power
- low-noise and uniform rivet shaping
- low transverse forces, therefore workpiece fastening is easy
- particularly suited to meet quality assurance requirements due to the vertical riveting die
- minimum friction, little heat development and a smooth rivet surface
- gentle change to the rivet material structure
- no rotation of the die, therefore also stamping is possible
- allows to achieve an easily dimensionable bearing stress
A comparison of riveting methods
These microsections show the differences in structural conditions obtained by the different riveting methods for shaping the rivets. It is with the radial point riveting method only that the material structure remains unchanged to the greatest possible extent.
Pressing and hammering
The rivet is shaped either by pressing or by hammering. Pressing uses a one-time pressure applied to the rivet, while in hammering the rivet is beaten several times in axial direction. The disadvantages: both methods need great efforts and cause much noise.
Describing an orbital path K, the end E of the riveting die rotates about the centre line Z of the riveting spindle. The longitudinal axis of the riveting die intersects the riveting spindle axis in point M. The shaping of the rivet takes place on a contact line whose length is identical to the riveting die radius.
Radial Point Riveting
The end E of the riveting die describes a hypocycloid loop-path S. Here, too, the longitudinal axis of the riveting die intersects the riveting spindle axis in point M. Due to the hypocycloid drive the angle of attack of the die constantly changes between 0° and X°. The shaping of the rivet is done by point contact, forming the rivet material outward from the centre.
Riveting dies and closing head shapes
flat into countersunk
tubular rivet crimped externally
tubular rivet crimped internally