Blind rivets
WHAT IS A BLIND RIVET
| The blind rivet is an immovable mechanical fastener that allows two or more parts to be joined by operating from one side only. | It consists of two entities: Rivet body (joining element) and Nail or Mandrel (element allowing deformation) |
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MAIN JOINING TECHNIQUES
| Joining techniques can be classified into demountable and fixed.By fixed or immovable, we mean those unions in which the parts do not require predictable disassembly over time. When choosing the joining technique, one must also | take into account whether or not there is access from both sides of the material to be joined and the possibility of their retrieval after the possible removal of the fastener. |
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WHY BLIND RIVETS
| The rivet is the preferred solution whenever two materials must be joined permanently, as it allows:
■ Permanent fastening ■ Quick installation ■ Presence of filler material ■ Removal and reinstallation possible ■ Easy installation |
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OPERATING PRINCIPLE
| The properly dimensioned rivet is inserted into a hole calibrated according to the diameter of the chosen rivet. A specific tool (riveting tool) clamps and pulls the nail, its head radially deforms the rivet body until it meets the first element of the parts | to be joined. At this point, opposing forces cause the joining of the components and the subsequent breaking of the nail at a defined point and load. |
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DIAMETER AND LENGTH DIMENSIONING
| Depending on the stresses and loads to which the materials to be joined will be subjected and the environmental conditions of use, the rivet must be defined in terms of its dimensions: | rivet diameter d and rivet body length L dimensioned according to the grip range, and to the type of materials making it up. |
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CHOICE OF MATERIAL BY MECHANICAL OR PHYSICAL CHARACTERISTICS
| The choice of rivet manufacturing material must be made according to certain parameters such as: Chemical compatibility between the material to be assembled and the rivet material in order to avoid electrolytic corrosion.For the same rivet size, choose the most suitable material based on its mechanical strength | depending on the stresses to which the part to be riveted will be subjected, the environment in which it will be placed (exposure to atmospheric agents, exposure to acid atmosphere environments, possibility of contact with food or chemicals). |
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| The main mechanical stresses to which blind rivets are subjected are: |
| TRACTION: | SHEAR: |
| the direction of the stress coincides with the geometric axis of the workpiece and tends to elongate it. | the stress lies in the plane of the section subject to sliding with respect to the immediately adjacent section. |
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| In order to determine the resistance of rivets to such stresses, tests are carried out on them with equipment in accordance with the international technical reference standard UNI EN ISO 14589. |
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| Tests are carried out with two equally sized thicknesses (S), which give the maximum grip range (SM) of the rivet. |
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SURFACE TREATMENTS
| Protection against corrosion, especially in a fastening system, becomes one of the most important features to be considered when designing a joint in particularly aggressive | environments. The choice of the surface treatment must be carried out depending on the material of the rivet, the environment in which it is used and the aesthetics required. |
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How the blind rivet works
