subterranean drilling applications embodiments of the invention include a connector assembly that facilitates increased torsion and bending capacity in any shaft comprising connected joints referring now to fig3 a longitudinal cross section of one exemplary embodiment of a connector assembly 100 according to the present invention is shown as shown in fig3 and described above with respect to fig2 one exemplary application is depicted in which a downhole steering tool 200 is coupled to a downhole sub 50 via connector assembly 100 in the exemplary embodiment shown connector assembly 100 includes a mating sleeve 110 deployed about cylindrical shaft 220 of steering tool 200 and threadably coupled with downhole sub 50 via a conventional box 114 and pin 52 connection in the embodiment shown mating sleeve 110 includes a threaded inner surface 109 for threadably coupling with a threaded outer surface 219 of cylindrical shaft 220 connector assembly 100 further includes a center sleeve 130 deployed between the cylindrical shaft 220 and the mating sleeve 110 the center sleeve 130 is rotationally engaged with cylindrical shaft 220 and mating sleeve 110 via radial splines 136 138 shown on and described in more detail below with respect to fig4 on its inner 133 and outer 134 surfaces respectively with continued reference to fig3 cylindrical shaft 220 is disposed to rotate about axis 60 in the substantially.