PECK DRILLING OF COMPOSITE/METAL ASSEMBLIES

Under contract with the Department of the Navy, Bell Helicopter Textron Inc. conducted a series of drilling experiments as part of the V–22 Engineering and Manufacturing Development Program. The objective of these tests was a one-step drilling solution for peck drilling close tolerance holes in thick stack-ups of titanium/graphite (Ti/Gr) and aluminum graphite (Al/Gr). Using the current method of drill/ream as a baseline, designed experiments (DOE) were utilized to establish optimum peck drilling parameters and cutter geometries. A one-step drill solution for both Ti/Gr and Al/Gr assemblies would thus minimize equipment and tooling requirements. Various cutter geometries were tested with the best results obtained with a dreamer (combination drill and reamer) design. During 1996, a peck drill test cell was conceived, built, and tested to develop data to be used for tool design purposes and further evaluate dreamer geometry designs for increasing the speed of the drill operation.