To facilitate aligning and setting of a punch in a die of a press machine, a module cam assembly comprises a cam unit and an L-shaped module base. The cam unit comprises a cam driver, a cam slider equipped with a positive return to be driven by the cam driver, and a cam base holding the cam slider. The cam slider has a punch retainer on its vertical side. The L-shaped module base bears the cam unit, and is adapted to be fastened to the lower die holder. The L-shaped module base has a button die on its vertical leg in confronting relation with the punch retainer of the cam slider. This arrangement facilitates the centering and fastening of any tool to the press machine.