An apparatus and method for monitoring the assembly of threaded components including a station (13) at which two threaded components are to be threadably interengaged, a heat sensor (11) located at the station and positioned to sense the temperatures of the threaded coupling (15) whilst being threadably engaged or disengaged, an output associated with the sensor which is adapted to display (17) an indication of the temperatures of the coupling (15) during assembly or disassembly of the components.