Single Tube Deep Hole Drilling Offers Shops a Significant Productivity Advantage

Single Tube Deep Hole Drilling Offers Shops a Significant Productivity Advantage

When machining difficult-to-machine materials such as exotics, Inconel, and stainless steels, single tube deep hole drilling offers shops a significant productivity advantage compared to conventional gun drilling.single tube deep hole drilling While converting to this method requires an investment, this can be quickly recouped through higher production rates and ongoing economies of scale.

This innovative drilling technique is based on external cutting fluid supply and internal chip transport. The drill head is attached to a hollow drill tube with a diameter larger than the bore hole being drilled. The space between the drill tube and the drilled bore hole serves as the lubrication channel and the chip transport chamber.

The drill tool’s shank also features a helical groove in which coolant flow flushes the chips from the bore hole as they are being cut. This eliminates the need for a fluted shank and allows the drill head to have an entirely round cross-section, which enhances rigidity and optimizes surface quality. The drill head is a carbide insert, which can be adapted to a wide range of workpiece sizes.

Unlike the V-shaped flutes used by gun drills, which provide an unstable cutting edge, the single-lip design of the BTA drilling tool carries two symmetrical cutting edges and offers a much more stable cut with high feeds. Furthermore, the fact that no asymmetrical cutting edges are in contact with the workpiece improves the achievable drilling depth and hole geometry.

In 1937, Burgsmuller developed a new drilling system called STS (Single Tube System), in which the drill shank’s flutes were replaced by a hollow cylindrical tube. This allowed for greater torsional stiffness and a much faster removal of the chips, while still providing sufficient cooling and lubrication. This method is ideal for long holes with a low depth-to-diameter ratio and can achieve up to six times the productivity of traditional gun drilling.

A key to success for the STS method is ensuring that all components are properly supported, from the machine spindle to the workpiece and drill tube. The drill tube should be rigidly mounted and the machine, the drill head, and the workpiece should all be in perfect alignment to ensure smooth, consistent operation. To minimize vibration, the STS system should be installed on a dedicated deep-hole machine.

To support the STS drilling process, the drill tube is equipped with a coolant inducer at one end and a four-start threaded drill head at the other. The pressurized coolant flows through the annular space between the inner and outer tubes to provide lubrication to the drill head while clearing chips from the inside of the tube. The outer tube also contains a vent for escaping swarf. The result is a highly efficient drilling system that can be used on a variety of universal machines.

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