<p>The aim of this study is to better understand the form tapping process on thin sheet metal. Elastic–plastic 3D FE models using the Arbitrary Lagrangian–Eulerian (ALE) formulation were developed to investigate the forming kinematics of internal thread. The mechanism of thread formation, the tap-workpiece contact, the tapping torque, and the thrust force were analyzed during forming. Parametric studies were performed to identify the effects of the overlapping deformation due to the manufacturing of successive thread roots, the tap hole diameter, and the friction coefficient as well as the symmetry conditions of the workpiece. The aluminum alloy 1050 in the H14 temper was selected. Some numerical results are validated by the experiments. An alternation between full and partial contact between the workpiece and the tap was identified. Different limits of tap rotation angle were distinguished related to the number of thread roots. The variation of some geometrical characteristics and manufacturing parameters allowed the quantification of the beneficial effects of overlapping and reducing the tap hole diameter to compensate for the lack of metal at the top of the thread. An adequate range of tap hole diameter was ultimately selected to achieve a thread crest correctly formed for a specific case of thin sheet metal.</p>