Abstract: Employee #1, an experienced commercial window mechanic, was on the second floor of an office building under construction using a Makita 151400 heavy-duty power miter saw. The saw was fitted with a 14 in. carbide-tipped 60-tooth alternate top level blade. It had a proper guard and featured a trigger interlock and automatic braking within 2 to 3 seconds upon release of the trigger. The power head was spring loaded and would pivot back up upon release of the handle. The guard was a pivoting plastic type that remained in contact with the surface of the material as the saw passed down through it. Employee #1 was trimming about 4 in. off one end of 2 ft long aluminum extrusions, cutting pieces that were about 5 in. wide and 1/16 in. thick in cross-section. Employee #1 was holding the pieces against the back fence with his left hand about 6 in. from the blade. He was midway through a cut when the aluminum piece flew up, throwing his left hand into the blade and severing part of his thumb and first two fingers, and damaging his third finger. Why or how the blade grabbed the material is not known; Employee #1 had most likely been forcing the cut. He and others had previously performed this task in this manner without incident. The area was clean and dry.