Abstract: At 3:15 p.m. on December 8, 1999, Employee #1 suffered a serious disfiguring injury when a 12-inch DeWalt chop saw blade flew off the saw and into his face. Employee #1 was assigned a project of building a 6-foot- by-6-foot mock-up window frame, constructed out of 2-inch by 8-inch lumber. Employee #1 set up the DeWalt Model DW-705 chop saw on a stand in the rear shop yard. The saw had a metal cutting blade that did not cut the lumber well. Employee #1 decided to change the blade over to a 32-tooth wood cutting blade. The factory saw arbor bolt wrench was missing and the head of the arbor bolt was rounded from misuse. Employee #1 could not remove the arbor bolt. With the assistance of the shop foreman the two men were able to remove the bolt to change the blade. The two men discussed the hazards of using the damaged bolt, but together decided that the saw blade would tighten under use. The employees installed the new blade using the damaged arbor bolt but were unable to completely tighten it because of the rounded bolt head. Employee #1 also failed to completely reinstall and secure the saw hood before the saw was put back in service. Employee #1 held the hood guard opened with his right thumb as he cut the lumber at a 45-degree angle. Once Employee #1 finished the cut through the lumber he released the trigger, which engaged the machine's arbor brake. Once the arbor brake engaged, the damaged arbor bolt loosened, allowing the blade to spin clockwise on the arbor, backing out the reverse threaded arbor bolt. Since the hood guard was not reinstalled and secured, the bolt came out of the arbor and released the saw blade. The unguarded, unrestrained saw blade flew out from the saw and into the face of Employee #1 operating the saw. Employee #1 was hospitalized.