Automatic tapping machines are based on the reversible spindle system, mechanically guided by a lead screw or electronically managed synchronised motors. All the internal threads, of any pitch (from M2 to M36), can be produced with standard male taps, either by rolling or with chip removal. The machines are based on a modular system that enables the installation of one single spindle or a twin spindle with two independent work stations. For the best flexibility, it is also possible to work two different pieces simultaneously on two fully independent work stations. The precision of the operations is ensured by the locking/positioning of the workpiece and the rigidity of the bed frame, to produce perfect orthogonality and excellent concentricity. For maximum productivity with a configuration that sees 4 spindles working at the same time, the tapping rate is up to 200 ppm.