During the landing roll, after a wheel landing, the airplane veered left and departed the runway. The airplane's tailwheel fork assembly fractured. Postaccident inspection revealed the tailwheel offset to the left of the fuselage. Inspection at the NTSB metallurgical laboratory showed overstress separations with no evidence of preexisting cracking. The airplane and assembly had both accumulated 29,846 hours in operation at the time of the accident.