Drilling tools and methods for producing drill holes, especially in composite materials, are known. Composite materials comprise at least two layers of different materials. At least one layer preferably comprises fiber-reinforced plastic, especially carbon fiber-reinforced plastic. At least one second layer preferably comprises metal, especially aluminum or titanium. Such composite materials are especially employed when high loads are to be transferred with the least possible weight. This may be for instance connection points between structural components or other highly stressed points, for instance in aircraft design. Consequently, composite materials are primarily, but not exclusively, used in the aircraft industry. It has been demonstrated that, due to the different specific machining properties and other physical parameters for the various material layers in the composite materials, also known as stacks, it is extremely difficult to produce drill holes whose the diameter is sufficiently precisely defined in the individual layers. In particular, the different elasticities of the individual materials lead to a drill hole that runs through different layers but does not have the same diameter in the individual layers. This can mean that especially a drill hole with very narrow tolerances may fall outside of tolerances in at least one layer. Even if the drill hole is initially pre-bored to a smaller dimension and then it is finish reamed to the final dimensions in a known manner, there may be a deviation in the diameter in the individual material layers, which is problematic, especially for drill holes with very narrow tolerances. In addition, it is a disadvantage in such a method that there are two work steps. During reaming there is the additional problem that typical reaming tools have only small chip spaces, while composite materials frequently include tough layers, and long chips are produced when the materials are machined. This is the case with aluminum, for instance. Especially if the diameter of the drill hole that is to be reamed is small, long chips may clog the chip spaces of the reaming tool and/or damage the surface of the drill hole. This problem also occurs with drill reamers, that is, combined drilling and reaming tools. In general the chip spaces in this case are smaller than in tools that are only for reaming.
USPTO Backgrounds
USPTO Backgrounds