How does a blind rivet nut work?

Blind rivet nuts have become an indispensable part modern installation engeneering. They allow to:

• - install bolt threads of different types into ...
  ... thin or low rigidity components
  ... hollow sections or other components not accessible from both sides
  ... components which already have a coated surface,
• connect different components to each other at the same time and
• attach additional parts.

The continous development of new types, forms and dimensions documents the nearly unlimited fields of applications. The HONSEL-Group has been one of the leading companies in this progress for decades.

d - shank diameter
d_k - setting head diameter
k - setting head hight
l_g - thread length min. 1 x M
l - shank length
M - thread diameter

l₁ - projection length
g - grip length

KLSK - small countersunk head

Countersinking of the bores is generally not necessary for setting blind rivet nuts with small countersunk head.

If technically necessary, countersink so that the countersunk head protrudes by min. 0.1 mm after setting.

HEADLESS - without head

• The blind rivet nut is used with 0 mm protrusion in smooth-walled bores without countersinking.
• parts can be assembled without interference edges or can slide over each other.

Round shank blind rivet nuts

• Universal nut type with a high level of availability and a wide material spectrum
• Use with dry and grease-free parts

Blind rivet nuts with continuous hexagonal shank (HEXAFORM) or partial hexagonal shank (HEXATOP)

• Shank design with positive locking twist lock
• Preferred use with coated parts
• High twist resistance even with insufficient setting device stroke
• Suitable for multiple screwing

Blind rivet nuts with knurled shank

• Shank design with positive locking twist lock
• preferred use in parts with low strength (part material less “hard” than material of the blind rivet nut)

Blind rivet nuts with closed shank

• Closed nut shank prevents liquid and gas passing through the nut
• Additional sealing possible between nut shank and part borehole
• Mechanical properties identical with comparable nut with open shank

Blind rivet nuts are characterised by very quick and simple installation.

To set the nut, it is screwed onto the threaded mandrel of the setting tool, inserted into the part borehole, and set by the tool stroke. This causes the closing bead of the nut to form. After the threaded mandrel is removed, the parts can be screwed tight.

Various tools are available for setting the nut which allow setting to be carried out efficiently. Setting tools can be manually-, battery operated or pneumatically/hydraulically operated.

In order to guarantee the correct functioning of the blind rivet nuts, the following points should be observed:

Set the blind rivet nuts up to complete formation of the blind head

It must be easy to unscrew the threaded mandrel after setting

Installation at right-angles to the part surface

Countersink blind rivet nuts with standard countersunk head with a slight protrusion

When using blind rivet nuts with small countersunk head (e.g. UNIVERSAL), it is not necessary to countersink the borehole

For blind rivet nuts without an additional positive locking twist lock, the part surfaces must be dry, clean and grease-free

The specified part bores must be observed; oversized bores result in problems with the torque and load-bearing strength

To measure the tightening torque, the nut to be tested is inserted into a test plate, a twist-locked steel washer is placed on it and the screw tightened.

The following conditions apply during the test
Test plate: structural steel – uncoated, dry, grease-free, thickness approx. maximum clamping length of the nut
Part bore: nominal size of the nut shank + 0.2 mm
machine screw: oiled, strength class min. 8.8

The minimum value at which failure of the nut can occur under the defined conditions is indicated.

Rotation of the nut and/or recognisable plastic deformation of the blind rivet nut is regarded as failure. In practical use, partially different operating conditions may apply which can lead to a change in the tightening torques. We therefore generally recommend an examination of each specific individual case.

Tightening toque - measured values (PDF)

The axial tensile force is determined using the test device to DIN EN ISO 14589. The nut is riveted into a steel washer that is placed on an insert bushing; then the two parts are screwed together.

The following conditions apply during the test

• Test device in accordance with DIN EN ISO 14589
• Deformation rate approx. 3 mm/min.
• Strength class of the bolt min. 8.8
• Tensile direction against the blind head of the nut

The measured minimum value at which failure of the nut can occur under the defined conditions is indicated.

Tearing out of the thread or tearing off of the closing head of the nut is regarded as failure. The values shown should be regarded as indicative values for the design of the joint. In practice, different operating conditions generally prevail that can lead to a change in the failure mode and the forces. We therefore generally recommend an examination of each specific individual case.

Axial tenisile force - measured values (PDF)