The fiber-reinforced abrasive blade exploded when the operator started up the grinder, injuring the operator and damaging the grinder’s casing and cord. The grinder’s owner was not sure of the history of the blade. Its central hole is too large for the grinder’s arbor, so the operator relied on friction from the washer to hold it in place. In addition, the blade material may not be appropriate for the planned work: cutting a steel rivet.