Hydraulic punch tool for heat exchangers

A punch tool for puncturing a hole in a tube comprising:

• a hollow cylindrical member having an open end, a closed end, and a central axis running the length of the cylindrical member;
• a curved surface on said hollow member coaxial with said central axis, said curved surface surrounding a slot positioned to intersect said curved surface of the member at an angle perpendicular with the central axis and substantially near the closed end, whereby the slot communicates with the hollow portion of the cylindrical member;
• a generally rectangular slidable piston fit within the slot, said piston having an upper and a lower side parallel to said central axis;
• means for sealing the space between the slot and the piston;
• an upper and lower surface on said slidable piston, the upper surface being partially rounded to conform to the outside surface of the hollow member and the lower surface providing a support for the sealing means;
• a substantially triangular cutting point attached to the slidable piston at substantially right angles to the upper side of the piston, wherein the base of the point is affixed to the upper surface of the piston whereby the height of the cutting edge will vary according to the thickness of the tube wall;
• and
• means for forcing the slidable piston radially, whereby the cutting point may be displaced from within the hollow member to a point beyond the outside diameter of the hollow member so that a puncture results in the tube in which the tool has been inserted.