with reference to fig1 and 6 the middle portion of the present tool is enclosed within piston housing 65 and piston spline housing 80 threadedly connected together as shown piston 45 moves as aforesaid back and forth along the polished outer surface of the piston mandrel 50 in response to the flow of hydraulic fluid through channels 38 and 39 the lower end of the piston is threaded to a piston spline 55 which follows the piston to also move back and forth in the direction of arrows a and b the piston spline shown separately in fig7 and 8 includes on its outer surface a plurality of spaced apart longitudinally extending splines 56 that mate with opposed splines 81 formed on the inner surface of spline housing 80 shown separately and most clearly in fig9 and 10 the meshing of the splines prevents rotation of the piston spline and attached piston 45 relative to the tool 39 s outer housing with reference once again to fig5 and 7 the downhole end of piston spline 55 is formed with one or more threaded apertures 57 for a matching number of correspondingly threaded guide pins 59 each pin having a tip 60 extending radially inwardly to engage a respective helical groove 70 formed in the opposed outer surface of orienting mandrel 75 these left hand grooves spiral around the outer surface of the mandrel preferably to provide 540 u00b0 and up to perhaps 750 u00b0 of mandrel rotation the.