Method of tapping on a press, and apparatus for implementing the method

A method of automatically tapping parts disposed in a metal strip which is displaced stepwise between a fixed table of a cutting press and a moving element thereof, said method comprising the steps of:

• providing a tapping apparatus comprising a tapping head having an axis of rotation, a tap-carrier connected to said tapping head for carrying a tap, said tap-carrier being movable relative to said tapping head;
• motion transforming means mounted on a movable element of a press for transforming a stroke of said movable element into a rotary motion of said tapping head to thereby apply a rotary couple to said tap as said movable element moves said tapping head along said axis of rotation, said rotary motion having an amplitude proportional to said stroke;
• force applying means for applying an axial pneumatic force to said tap-carrier in a direction towards the part to be tapped;
• and interruption means for interrupting application of said axial pneumatic force when the tap is engaged in said part over a sufficient length, thereby ensuring the tap continues to penetrate in said part solely under the effect of the rotary couple applied thereto;
• before each tapping operation, applying said axial pneumatic force to said tap-carrier, said force being selected to be substantially constant and directed towards the parts to be tapped;
• interrupting application of said axial pneumatic force at a moment when said tap is engaged in said part over a sufficient length for ensuring said part continues to penetrate in said part solely under the effect of said rotary couple which is communicated thereto.