from a first end 10a of body portion 10 tapering to a minimum cross sectional area at its extremity likewise the second connecting portion 14 extends coaxially from a second end 10b of body portion 10 and is tapered in a similar manner referring to fig2 and 4 the enlarged views of the cutting means clearly depicts the unique formation of the first cutting means 16 incorporated at the extremity of the first connecting portion 12 while enlarged details of the second cutting means 18 are not shown it is understood that said second cutting means 18 is formed in an identical manner although it may be proportionally scaled to a size larger or smaller than that of the first cutting means 16 as depicted in fig2 the cutting means 16 comprises a portion 17 having a generally curvilinear cross section laterally extended with respect to the tool and more specifically the longitudinal axis of the connecting portion 12 the portion 17 decreases in thickness as the distance from the tool axis increases ultimately forming a cutting edge 22 at the intersection of outer and inner curvilinear surfaces 22a and 22b respectively as shown in fig2 and the third angle projection of fig4 surfaces 22a.