Apparatus and method are disclosed for feeding a cablehead assembly into the side of a drill string. The cablehead is passed through a low angle side entrance in a side entry sub into the drill string. A cartridge assembly is seated in the side entrance around the cable to prevent pressure loss through the entry port. The cable is clamped to the outside of the sub to lock the cable in place. The cartridge assembly is thereafter tightened about the cable to seal against pressure loss. A cover plate is secured to the outside of the sub adjacent to the entry port to prevent expulsion of the cartridge.
