Fast, process-secure ways to complete very deep drilling

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How to make perfect spiral chips

The critical factor in spiral borers is the chip channels. They determine the form of the cuttings at the tip of the drill. Narrow chip channels also mean tightly rolled cuttings. On the other hand, they demand very high pressure in the cooling fluid. “Mapal drills therefore have a sophisticated channel profile, changing from the drill point upwards in such a way that the cuttings can be washed out even with moderate cooling fluid pressure,” Krenzer said. The whole effect is supported by very smooth polished surfaces and coatings. Jürgen Bek, director of drilling tools at TBT Tiefbohrtechnik in Dettingen/Erms, Germany, pointed out the direction the technology has taken. “In the development of deep-hole tools, the trend is clearly towards raising performance through new tool geometry and ultra-smooth coatings, in order to enable a reduction in the number of machine tools and in the machine footprint space.”

In the development of deep-drilling machines, the structures are determined predominantly by finite element methods and simulations. Further development of such methods, specially matched to the needs of deep drilling, plays a central role. According to Lothar Künzel, deep-drilling product manager at Gühring, Albstadt, Germany: “Customers would primarily like to achieve the best possible machining results.” Here, he distinguishes between two different requirements: the highest possible machining speed and the highest possible drilling precision. Spiraled deep-hole drills have clear advantages regarding machining speed (cutting speed and feed), while classical deep-hole drills provide maximum bore quality. The main goal in further development at Gühring is said to be continuously optimising the machining parameters of classical deep drills.

Simplicity is the key to deep boring

Moreover, there are demands for improvements in the processing quality of spiraled deep drills. “Increasingly significant are deep-drill processes,” Künzel said, “in which bores of up to 75 × D are carried out on conventional machines.” The range of nominal diameters where this is demanded is between 2 and 16mm.

Thomas Bruchhaus, drilling processes and tool holder product manager at Sandvik Coromant Germany in Düsseldorf, described the requirements on the tools. “Today’s deep-drilling tools must be simple to use and offer a choice of different geometries, hard metal types and coatings.” Few wearing parts and short delivery times are further positive points. Regarding machining processes, a distinction must be made between serial production and one-off production: in serial production of low-cost components, the cost per bore is the factor in the foreground, while more elaborately produced, higher-cost components call for process security and reproducibility. Furthermore, with some components, a good chip break and straight bores with low deviation are desirable.

“All our deep-hole tools are suitable for machining high-performance working materials,” Bruchhaus said. “For high heat-resistance alloys, for example, we have developed special cutting materials.” He added: “In standard processes, our tool solutions effortlessly achieve bore depth ratios of up to 150, but we have also already realised processes with ratios over 300.”

Bert Bleicher, a former manager at the Hoffmann Group, Munich, discussed one of the company’s products. “Our new Garant deep-hole boring system is designed for bores of up to 50 × D.” Geometries, tip angle and cut tolerances are exactly matched to each other for the required bore depth. In this way, a series of tools can be employed in uninterrupted succession during a production process. In choosing the right tool, a coloured ring system offers support: for light working materials such as aluminium, products with yellow rings are suitable; for steel, including rust and acid-resistant steels, those with green rings.

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Technology

Fast, process-secure ways to complete very deep drilling

How to make perfect spiral chips

Simplicity is the key to deep boring