Wire electric discharge machine

A wire electric discharge machining apparatus in which machining liquid is interposed between a wire electrode and a work piece and said work piece is machined by discharge energy, said wire electric discharge machining apparatus comprising:

• electrically conductive means supported so that a state of said electrically conductive means is switched over between a contact state where said electrically conductive means comes into contact with said work piece and a non-contact state where said electrically conductive means does not come into contact with said work piece;
• drag generating means for generating drag acting on said electrically conductive means in a direction to make said electrically conductive means move away from said work piece;
• machining liquid pressure controlling means for changing and controlling a hydraulic pressure of said machining liquid;
• and
• electrical conduction switch-over means for switching over power supply to said work piece from said electrically conductive means and/or from the means other than said electrically conductive means,
• wherein said hydraulic pressure of said machining liquid during electric discharge machining is changed and controlled by said machining liquid pressure controlling means so that the state of said electrically conductive means is switched over between the contact state where said electrically conductive means comes into contact with said work piece and the non-contact state where said electrically conductive means does not come into contact with said work piece in accordance with a desired machining speed and desired machining accuracy to thereby carry out machining.