tissue from the sharp distal edge of the intermediate tube 104 until the intermediate tube 104 is advanced distally outside the distal end of the outer tube 106 a releaseable lock can be used to maintain the axial or longitudinal position of the intermediate tube 104 relative to the outer tube 106 until punching is required a releaseable lock can further be used to maintain the rotational position of the intermediate tube hub 116 and thus the intermediate tube 104 relative to the outer tube hub 118 and the outer tube 106 all components of the punch assembly 100 can be fabricated from metals such as but not limited to stainless steel elgiloy u2122 cobalt nickel alloy titanium nitinol or the like the nitinol can be shape memory or it can be superelastic the metals used in the obturator wire 102 the intermediate tube 104 and the outer tube 106 are advantageously cold rolled heat treated or otherwise processed to provide a full spring hardness the intermediate tube 104 the outer tube 106 or both are relatively rigid resilient structures polymeric materials such as but not limited to polycarbonate abs pvc polysulfone pet polyamide polyimide and the like can also be used to fabricate the stopcock 110 the intermediate tube hub 116 the outer tube hub 118 the intermediate tube pointer 112 and the outer tube pointer 114 the materials are.