Blind rivet nuts
WHAT IS A BLIND RIVET NUT
| The blind rivet nut is a fastener that places a thread where it would not be economical or possible to drill a thread with a tool. The main elements that distinguish the blind rivet nut are: |
| ■ Head |
| ■ Shank |
| ■ Knurling |
| ■ Deformation chamber |
| ■ Thread |
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WHY THE BLIND RIVET NUT
| The blind rivet nut is the preferred solution in all cases where it is necessary to have threads on surfaces that are thin and/or located in a position that is difficult to access, and therefore impossible to machine by tooling. |
| Main advantages of blind rivet nuts are: the speed of application, the ease of installation even with hand tools, the single-sided fastening which allows application even in blind structures, the resistance to rotation (especially with hexagonal rivet nuts),higher thread strength compared to the application material. |
| ■ Permanent fastening |
| ■ Quick installation |
| ■ Presence of filler material |
| ■ Single-sided fastening |
| ■ Easy installation |
OPERATING PRINCIPLE
| The properly dimensioned rivet nut is screwed onto the riveting tool tie rod, then inserted into a hole calibrated to the chosen diameter. |
| The riveting tool exerts a traction force on the tie rod, which radially deforms the compression chamber of the rivet nut, until it is locked onto the material. |
| Once the rivet nut is tightened, the tie rod of the riveting tool is unscrewed to release the thread that will accommodate the screw. |
| Setting phases: |
| ■ Screwing |
| ■ Introduction / Clamping |
| ■ Unscrewing |
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CHOICE OF TYPE OF RIVET NUT
| The choice of rivet nut type can be determined by characteristics such as: |
| ■ Type of head |
| ■ Body shape |
| ■ Grip range |
| ■ Screw diameter |
| ■ Material |
| The TYPE OF HEAD is to be chosen according to its protrusion, i.e. the thickness between the fastening surface and the material to be assembled, |
| FAR blind rivet nuts are available with dome head, countersunk head or reduced head. |
| The BODY SHAPE is available cylindrical, hexagonal or half hexagonal. |
| Rivet nuts with a cylindrical shank generally have a knurling that increases resistance to rotation. |
| The hexagonal shank or half hexagonal shank, due to its geometry, inserted in hexagonal seats completely prevents rotation of the blind rivet nut inside the hole. |
| The body of the blind rivet nut can be open or closed if a blind thread is to be applied. |
| The GRIP RANGE determines the choice of rivet nut length, depending on the type. FAR blind rivet nuts are available in, three different lengths (L - C - M ) for the same diameter, thus increasing the range of thicknesses that can be tightened. |
| The DIAMETER OF THE SCREW determines the choice of thread: depending on the type FAR blind rivet nuts are available with threads from M3 to M12. |
| The MATERIAL is to be chosen according to its mechanical strength, the stresses to which it will be subjected and the environment in which it will be placed.Depending on the type FAR, blind rivet nuts are available in aluminium, steel, A2 or A4 stainless steel. |
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DIAMETER AND LENGTH DIMENSIONING
| In function of the stresses and loads to which the materials to be joined will be subjected and theenvironmental conditions of use, the rivet nut must be defined both in terms of its dimensions: thread diameter d, geometry of the housing hole (round or hexagonal), body length L/, dimensioned according to the clamping thickness, and in terms of the type of materials it is made of. |
| Rivet nuts with a hexagonal or half hexagonal body should only be housed in holes with hexagonal punching. |
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CHOICE OF MATERIAL BY MECHANICAL OR PHYSICAL CHARACTERISTICS
| The choice of manufacturing material of the rivet nut must be made according to certain parameters such as: Chemical compatibility between the material to be assembled and the rivet nut material in order to avoid electrolytic corrosion. |
| For the same the rivet nut size, choose the most suitable material based on its mechanical strength depending on the stresses to which the part to be secured will be subjected, the environment in which it ill 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 FAR rivet nuts are tested are: |
| TORQUE: |
| Indicates the maximum tightening force expressed in Nm, beyond which the thread may be permanently deformed. |
| TRACTION: |
| The value (expressed in N ) is determined with hanging load and indicates the limit stress that causes the insert to fail. |
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IMPROPER USES
| Values stated in the catalogue are unreliable in case of improper uses. The rivet nut should always be used by inserting the screw from the side of the insert rivet nut head and never the other way around. |
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| During installation, the tool must be adjusted in order to obtain the deformation of the blind rivet nut to ensure its correct clamping on the material. |
| Insufficient deformation would result in rotation of the insert rivet nut within the housing, impairing its use and strength. |
| Excessive deformation can result in damage to the insert rivet nut and the tool with possible breakage of both components. |
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| For the correct choice of material, size and type of insert rivet nut, please refer to the technical tables in our price lists and on our website www.far.bo.it. |
| PLEASE NOTE: The concepts and values given in our publications require correct installation and the use of tools with stroke and force appropriate to the thickness to which the blind rivet nut is applied. |
MATERIALS AND SURFACE TREATMENTS
| Corrosion protection, especially in a fastening system, becomes one of the most important features to consider when designing a joint in particularly aggressive environments. |
| The choice of surface treatment must be made according to the material of the rivet nut, the environment in which it is to be used, and the aesthetic performance required. |
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FINISHES ON REQUEST
| Liquid PVC gasket applicable under the head (only for dome head rivet nuts), compared to traditional gaskets, it has the characteristic of not pulling out and not being “pinched”, allowing the following advantages: |
| ■ Dampening the contact between two metal surfaces |
| ■ Reduce fluid penetration between the coupled parts |
| ■ RReduction of contact noise between coupled parts |
| ■ Vibration reduction. |
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How the rivet nut works
