Abstract: The invention relates to an assembly device by screwing with tightening torque limiting, comprising a screw provided with a screw head and with a threaded shank defining a geometric reference axis, a sectile monoblock tightening end-piece provided with a tightening head having a tightening profile, with a coupling profile to operate in conjunction with the screw head and with a breaking zone. An insulating sleeve is molded onto the tightening end-piece and the screw head. The sleeve is provided with first coupling means to secure the tightening head and the coupling profile and with second coupling means to secure the screw head and the coupling profile. Said second coupling means comprise a first portion securedly fixed in rotation to the tightening head, a second portion securedly fixed in rotation to the screw head, and a sectile third intermediate portion.