Abstract: A testing for screw connections, comprising a sensor carrier plate with sensors on both sides and being mounted on a base plate, whereby the sensors are sandwiched between a torque introduction plate and a torque sustaining plate, the sensors detecting separately both head and thread friction forces and a preload force.

Abstract: The test device for determining the friction and prestress values of screwed connections consists of a transportable device having a central support plate (1), whereby shearing force sensors and axial force sensors (7, 8, 11) are arranged on both sides of said plate. The sensors are screwed between an application plate (2) and a torque receptor plate (3) and can be replaced or provided with adapters (4, 5). The sensors (7, 8, 11) can be extension sensors or piezoelectric sensors. The amplifiers of the piezoelectric sensors can be miniaturized in such a way that they can also be placed in the central support plate (1). During tightening, the following values are determined: total torque Mtot, head friction torque MK, thread friction torque MG, prestress force Fz, to obtain the following values: thread friction value &mgr;G and head friction value &mgr;K.