of the partition 42 is the noted hydraulic cylinder 18 having a piston 44 dividing the front part of the interior of the casing 20 into a fluid chamber 46 and a spring chamber 48 the cylinder fluid chamber 46 communicates with the pump fluid chamber 32 by way of the passageway 40 the spring chamber 48 accommodates a helical compression return spring 50 the piston 44 together with a piston rod 52 is therefore to be thrust forwardly by the pressurized fluid from the pump 22 and retracted by the return spring 50 the piston rod 52 pressure tightly extends through and projects outwardly of the front wall 54 of the casing 20 and has the blade punch 16 replaceably mounted to its front end via a knurled mounting nut 56 as shown also in fig2 the piston rod 52 has a return valve 58 built into it for returning the hydraulic fluid from cylinder fluid chamber 46 back into pump fluid chamber 32 normally closed to discommunicate the cylinder fluid chamber 48 from the pump fluid chamber 32 the return valve 58 is opened as an inturned rim 60 of the cylinder piston 44 comes into abutment against a spring 62 with the forward travel of the piston both fig1 and 2 depict a jaw 64 extending forwardly from and formed in one piece with the front wall 54 of the casing 20 the die 14 is mounted to the front end of the jaw 64 in a position opposite the blade punch 16 on.