scope:

Description of Driving Event:

The Flexovit grinding wheel, National stock number 3460-00-027-0942, abrasive, resin bound, 7" by 1/4", shape 1397, grit 24, was released from a portable air powered grinder, commonly referred to as a "Bayflex Grinder", just after the grinder was turned off. The grinding wheel was propelled across the room by its inertial force created during the grinding operation.

The problem is associated with the size of the flat surface on the nut, which is torqued to the flange on the grinder. The grinding wheels were manufactured with two different flat surface sizes for the nut, 1/16" and 3/8". The 1/16" flat surface may allow the grinding wheel to unthread itself from the grinder when the air is cut off. The grinding wheel with the 3/8" flat surface is the correct one to use.