drill bit after drilling a pilot hole and attach a reamer having a similar transition sub in the embodiment of fig1 the backreaming would be completed without the sonde housing assembly 50 fig2 illustrates an alternative embodiment of a drill head set up having a sonde housing assembly 50 according to the present invention in this illustration the drill head assembly 14 u2032 does not include a rear transition sub as in 16 of fig1 but does include a front transition sub 22 configured with a joint 24 u2032 and a front adapter sub 20 u2032 this configuration allows a drill bit 12 u2032 and front transition sub 22 to be removed with minimal tools a reamer not shown configured with a splined transition sub that mates with joint 24 u2032 similar to that found on transition sub 22 can then be connected in the embodiment of fig2 the sonde housing assembly 50 is left installed during backreaming fig3 illustrates yet another embodiment of a drill head set up having a sonde housing assembly 50 according to the present invention an exemplary joint used in this type of configuration is described in u s pat no 6 148 935 which is herein incorporated by reference in its entirety drill head assembly 14 u2033 includes a rear adapter sub 18 u2033 a sonde housing assembly 50 a front adapter sub 20 u2033 and a hammer 26 the hammer.