On August 29, 2002, at 1730 eastern daylight time, a Beech 1900B, N81533, registered to Gulfstream International Aviation and operated by Continental Connection, main landing gear failed during landing roll at Tampa International Airport, Tampa. The scheduled flight was operated under the provisions of Title 14 CFR part 121 with an instrument flight plan filed. Visual meteorological conditions prevailed at the time of the accident. The airplane sustained minor damage; the air transport pilots were not injured nor were the thirteen passengers. The flight departed Ft. Lauderdale Airport, Ft. Lauderdale, Florida, at 1445. According to the pilot, as the airplane decelerated to 40 knots during the landing rollout he felt a vibration in the airframe. As the airplane continued to slow down the airplane began to pull to the left. The pilot stopped the airplane on the runway. During the post-flight examination of the airplane the pilot discovered that the left main landing gear had turned 90 degrees to the left. The examination also revealed a fracture in the left main landing gear socket. Examination of the left main landing gear socket assembly fracture revealed, two fatigue regions initiated from the lower corner lug base radii and along the left and right base radii with multiple origins. The fatigue failure occurred at the lower torque knee attach point on the main landing gear socket assembly. Between the two fatigue regions, features consistent with overstress were observed. The lug was stripped of paint to reveal the underlying surface features. Both the lower lug corner radii were confirmed to show marks consistent with repair blending. According to the Raytheon component maintenance manual 32-10-00, pages 18-19 the blend is an allowed repair procedure. According to the blend repair procedure the surface is to be blended to surface finish comparable to that produced by 250 grit sand paper. A comparison was made between the surface finish in the repair area, and the surface produce by 240 grit sand paper on the part, which is slightly coarser than the 250 grit required. The surface finish in the repair region was much rougher than that produced by 240 grit sand paper.