The pilot/owner of the tailwheel-equipped airplane stated that he was conducting touch-and-go landings at the conclusion of a 30-minute local pleasure flight. He noted that the first two landings were normal, and the third touchdown was "smooth." As the pilot lowered the tailwheel, the airplane veered to the left. The pilot corrected, and the airplane made "an abrupt swerve to the right." The left main landing gear collapsed and the airplane came to rest upright in grass off the right edge of the runway. The left wing sustained substantial damage, and closer inspection of the airplane revealed that the left undercarriage outboard attachment bracket had fractured. Examination of the bracket at the NTSB Materials Laboratory indicated that the fracture was the result of overstress. In a subsequent interview, the pilot stated that he typically wore a parachute while flying, but was not wearing one during the accident flight. He stated that the absence of the parachute placed him further from the controls than he was accustomed, and that he was unable to move the rudder pedals through their full range of motion. The pilot stated that there were no deficiencies in the performance or handling of the airplane.