Drilling Methods for Controlling Exit Burr Height in CRES Material Stacks

<div class="section abstract"><div class="htmlview paragraph">The Electroimpact Automatic Fan Cowl Riveter uses two novel drill processes to control exit burr height and achieve the required hole quality in CRES (Corrosion-Resistant Steel, also called stainless steel) material stacks. Both processes use piloted cutters on the OML (Outer Mold Line, referring to the exterior surface of an airframe) side, and two different tools are used in a backside spindle on the IML (Inner Mold Line, referring to the inside surface of an airframe) side of the component. The first process uses a shallow-angle shave tool in the IML spindle to directly control the exit burr height after it is produced by the OML spindle and is called the “burr shave” technique. The second process uses a countersink tool in the IML spindle and produces an “intermediate countersink” after the pilot hole is drilled by the OML spindle, but before the final hole diameter is drilled. These drill processes were able to achieve the required hole quality in a challenging CRES material stack, which allows the machine to be qualified for one-up assembly of the component.</div></div>