a is retained in the annular recess 80 of the leaf barrel 32 fig8 b by the trip ring retainer 36 best shown in fig1 referring again to fig1 1b and 2 2 b the housing assembly 20 forms a housing for the mandrel assembly 22 which is adapted for telescoping movement relative to the housing assembly 20 between a drilling position and a released position in the drilling position the mandrel assembly 22 is positioned to force the centralizing leaves 34 of the subassembly 11 to move to the expanded position and to transfer torque applied to the mandrel assembly 22 by a drilling rig not shown to the housing assembly 20 and in turn to the drill bit 18 in the released position the mandrel assembly 22 allows the centralizing leaves 34 to move to the collapsed position creates a jarring action within the drill string portion 10 to the housing assembly 20 upon being released from the drilling position is capable of rotating freely relative to the housing assembly 20 and permits fluid circulation through the drill string 12 to be uninterrupted to facilitate these functions the mandrel assembly 22 includes a mandrel 82 a spacer mandrel 84 a spline mandrel 86 and a stinger 88 as shown in fig1 a and 12b the mandrel 82 has an internal bore 90 extending therethrough from an upper end 83 to a lower end 89 the upper end.