On June 21, 2011, about 0925 mountain standard time, a Cessna 320F, N6160Q, made a precautionary landing on runway 7R at the Phoenix Deer Valley Airport (DVT), Phoenix, Arizona following a partial retraction of the nose landing gear. The pilot/owner operated the airplane under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. The airplane sustained substantial damage to the nose landing gear wheel well and keel. The pilot and two passengers were not injured. Visual meteorological conditions prevailed for the flight and no flight plan had been filed. The pilot reported that during the preflight he observed that the airplane's left main landing gear strut was low. He contacted a maintenance facility to service the strut and to fill the oxygen bottle. Once the maintenance was finished, the pilot and passengers loaded the airplane and tookoff. During the initial climb, the pilot heard a noise while raising the landing gear handle; he looked at a mirror located on the inboard side of the left engine cowling and observed that the nose landing gear was partially retracted. He attempted to cycle the landing gear through the normal procedures and then through the manual procedures, but the nose gear did not change position. The pilot then elected to land the airplane on the runway with the nose gear partially retracted. He approached the runway at a slow speed and as the main landing gear touched down, the pilot held the nose wheel off the ground as long as possible. When the airspeed bled off, the nose of the airplane came down and made contact with the runway and the airplane skidded to a stop. During a post accident examination of the airplane, a Federal Aviation Administration (FAA) Inspector observed that the landing gear actuator push pull tube end bolt was still secured tightly to the rod end, however, it was disconnected from the nose gear door hinge clevis bolt. No damage was noted to the rod end bolt or the clevis bolt. The FAA inspector further reported that he spoke with the airframe and powerplant (A&P) mechanic who conducted the maintenance on the airplane the day of the accident. It was reported that the nose landing gear doors had to be disconnected to gain access to the oxygen bottle valve and control cable. The A&P mechanic reported that he remembers tightening the gear doors, but he must have not secured it to the clevis bolt.