On September 28, 1994, at 1400 mountain daylight time, a Bellanca 7KCAB, N53844, sustained substantial damage when the left main landing gear separated during landing roll at a private airstrip near Frederick, Colorado. The pilot and student pilot were not injured. Visual meteorological conditions prevailed and no flight plan was filed for this local area instructional flight. Based on a pilot report, the event was originally classified as an incident. It was upgraded to an accident following examination by an FAA airworthiness inspector. According to the pilot, he was conducting a student training flight and during landing roll, following a practice full stall landing, the left main landing gear axle broke and the aircraft nosed over. Examination of the axle was conducted by the National Transportation Safety Board Materials Laboratory who found that the axle failed in fatigue. Their report is attached. A review of FAA Service Difficulty Reports was conducted. This review provided information that over the life of the 7KCAB type aircraft there have been only four previous failures of this type reported by that method. No other information concerning previous failures was found.