In the field of manufacturing technology, deep hole drilling refers to the drilling of bore holes with high length-to-diameter ratios.
Definition of deep hole drilling
According to the VDI Standard 3210, deep hole drilling processes are manufacturing processes for the machining of bore holes with diameters between D = 0.2...2000 mm and whose drilling depth is usually greater than three times the diameter. For small diameters, length-to-diameter ratios of up to l/D ≤ 100 can be achieved, in special cases even up to l/D = 900. With large diameters, the l/D ratio is usually limited by the travel or the bed length of the deep hole drilling machine.
Deep hole drilling
Deep hole drilling also differs from normal drilling in that, depending on the drilling process and the drilling diameter, cooling lubricant must be pumped to the cutting edges in large quantities and under high pressure. This ensures good cooling and at the same time good lubrication of the contact areas between the workpiece and the cutting edge of the tool on the one hand and the workpiece and guide pads of the tool on the other. In addition, the cooling lubricant leads to the constant removal of chips from the cutting zone, which makes surface-damaging and time-consuming chip removal strokes unnecessary and therefore improves the quality of the borehole and the productivity of the processes. For the production of deep holes, two different tool types are distinguished. On the one hand, there are tools with an asymmetrical single cutting-edge design. These deep hole drilling tools include single-lip deep hole drills, the single-tube system (BTA deep-hole drilling) and the double-tube system (ejector deep-hole drilling), which are referred to as the "classic" deep hole drilling processes. On the other hand, there are tools with symmetrically arranged cutting edges. These include spiral deep hole drilling tools and double-lip deep hole drilling tools, which can also be assigned to the deep drilling processes due to the drilling depths to be achieved with them. Deep Hole drilling was made originally in china.
The mentioned tool types differ with regard to the realizable diameter range, the achievable l/D ratios, the surface quality and they're productivity. Symmetrical tools can only be used in the small diameter range of D = 0.2 ... 32 mm to produce holes with an l/D ratio up to a maximum of l/D = 85, the standard is an l/D ratio of l/D = 30. With asymmetrical tools, holes in the diameter range of D = 0.5...2000 mm can be produced and the upper limit of the l/D ratio is usually limited by the machine dimensions. The figure shows selected deep hole drilling methods with their usual application diameters, whereby it becomes clear that deep hole drilling methods do not compete with each other in all diameter ranges. The advantage of the symmetrically designed tools compared to the "classical" deep hole drilling tools in the small diameter range is the feasibility of significantly higher feeds f, which can be 6 times higher compared to the usual values for single-lip deep hole drilling.