Abstract

A cutting tool assembly including an elongated pilot holder and a cutter blade adapted to be transversely positioned in a transverse slot in the pilot holder. The cutter blade includes cutting edges along one transverse edge of the blade and notches in the upper and lower transverse edges of the blade for respective coaction with a set scrw received in a threaded central axial bore in the lower pilot end of the pilot holder. In use, the lower pilot portion of the pilot holder is positioned in a previously provided pilot hole in a plate member, and the pilot holder is lowered and simultaneously rotated to move the cutting edge of the cutter blade into the upper face of the plate member to perform a cutting operation in the upper face, whereafter the pilot holder and cutter blade are raised, the set screw is loosened to allow removal of the cutter blade from the pilot holder, the pilot holder is lowered to dispose the slot below the lower face of the plate member, the cutter blade is rotated through 180° and reinserted into the slot in the pilot holder, the set screw is threadably advanced to engage the notch in the other transverse edge of the blade holder, and the pilot holder is raised and simultaneously rotated to perform a cutting operation in the lower face of the plate member. A novel peripheral cutter blade is also disclosed, as well as a method whereby the novel peripheral cutter blade may be utilized to form a hole in a plate member.