The pilot stated that he departed and proceeded to a nearby airport where he performed 6 touch-and-go landings followed by one full-stop landing; all were uneventful. The flight departed to return and after lowering the landing gear using the normal system, there were no landing gear down and locked indications. Additionally, the landing gear circuit breaker (CB) tripped. He reset the CB, raised then lowered the landing gear; however, the landing gear failed to fully extend and the landing gear CB tripped again. Attempts to extend or retract the landing gear using the emergency extension lever in accordance with the Pilot’s Operating Handbook, and also G-loading were unsuccessful. Guidance from maintenance personnel was also unsuccessful in lowering the landing gear. He performed a fly-by and was informed that the landing gear appeared to be partially extended. The pilot returned for landing and on short final had the passenger get in the back of the airplane as the airplane did not have shoulder harnesses. The cabin entry door was opened slightly, the fuel and master were turned off, and the mixture controls were placed to idle-cutoff.At touchdown, the right gear collapsed, followed by the left, then the nose. The airplane came to rest on the runway right of center line and both evacuated the airplane. Postaccident inspection of the nose landing gear by an FAA inspector revealed a screw part number (P/N) 411 349 was broken off in the first thread of the bellcrank assembly P/N 21708-00. The head of the screw, bushing P/N 14976-15, and bushing P/N 14976-16 were separated and not located. No determination was made as to the reason for the fractured screw. Piper Aircraft personnel reported there have been no service difficult reports pertaining to the screw.