The drill is available with a diameter between 4.1 and 11.11 mm with the associated countersink step.
Drilling/countersinking dry of CFRP aluminium stacks has been successfully achieved by customers, with a speed of 5,000 rpm and feed of 0.1 mm applied. The tool offers process reliability, good tool life, excellent machining results and delivers a steady boring process.
CFRP aluminium stacks are employed for the fuselage, wing, flaps as well as the horizontal and vertical tail of the latest generation of aircraft. Bores, including countersinking, are drilled in these components for the rivet connections. In most cases, drill feed units are used for machining. Dimensional accuracy of the bores is crucial. The bore must have exactly the same diameter in both materials. Drilling always takes place from the outside to the inside - bore entrance and countersinking in CFRP, bore outlet in aluminium.
Previously minimum quantity lubrication (MQL) was applied for this manufacturing step. After machining, the components had to be disassembled, cleaned and remounted. In addition, machining was often carried out in several successive machining steps. Different tools were used for drilling, reaming to the final diameter and countersinking. The complete process was time-consuming, costly and the required dimensions were often not achieved. For example, the bore and countersinking often did not align on one axis.
The drill has two cutting edges made of solid carbide that combine the properties of a drill for machining aluminium with those of a drill for CFRP machining. It also has a double point angle. This ensures good centring of the drill and minimum burr formation at the bore outlet. Reliable removal of the chips is ensured by the specially designed chip spaces. Any delamination and fibre protrusion is to be avoided for the countersinking in the CFRP. Mapal achieves this with a rake face correction at the countersink step. As CFRP is an extremely abrasive material, the drill is diamond-coated. This means that eight times the tool life is achieved versus an uncoated drill.
