Punch press

A punch press comprising:

• an upper assembly including an upper main shaft having a lower end detachably mounting an upper die, said upper assembly including an upper clamping means for automatically clamping and unclamping said upper die by an action in an axial direction of said upper main shaft;
• a lower assembly including a lower main shaft having an upper end detachably mounting a lower die, said lower assembly further including a lower clamping means for releasably clamping said lower die on the upper end of said lower main shaft;
• and
• an angular phase adjusting means for adjusting angular phases of said upper and lower dies to a predetermined phase relationship relative to each other;
• wherein said upper clamping means includes an axially movable member extending coaxially within said upper main shaft, a clamping mechanism mounted to a lower end of said axially movable member, a mechanical spring means for normally biasing and axially movable member in an upward direction to provide a clamping force for clamping said upper die, and a means for moving said axially movable member and said clamping mechanism in a downward direction against the bias of said mechanical spring means to an unclamping position for unclamping said upper die.