The increasingly widespread use of composite materials brings with it new and increasingly complex challenges, not least the need for ever more innovative tooling solutions.

One of the more common problems facing manufacturers is the machining of composite-metal alloy hybrids or 'stack' materials. Because both material types exhibit very different machining characteristics, the key here is finding a one-shot drilling solution that provides a clean hole without causing damage to the component or necessitating additional processes.

Engineers from Dormer are working with customers worldwide to develop specialised cutting tools capable of meeting this growing need.

One such example occurred when Dormer was asked to advise on a drilling application involving a wing skin assembly. Here, the customer needed to drill a stack material comprising of 10mm thick aluminium and 4mm thick carbon fibre.

"Ordinarily", says Ricky Payling, Dormer's European key account manager for aerospace and composites, "the customer would have to cut a smaller diameter hole first, gradually opening this out to the finished size. This not only takes time but also involves the use of several different tools.

"However, with Dormer's R790 carbide composite drill we were able to machine through-holes with no delamination or splintering on the carbon fibre and no exit burr on the aluminium."

Other significant achievements have included machining composite stacks with a glass cloth exit face. "With this type of material", Ricky explains "it is extremely difficult to produce a hole with a perfectly clean periphery. However, after consideration of the required geometry, we were able to manufacture prototype tools that consistently delivered holes with excellent exit quality, showing no signs of delamination, splintering or fraying of the glass cloth."