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For a long time, the machining efficiency of single edged deep hole drill (gun drill) is limited due to its low rigidity and grinding defects. The innovative high efficiency single edged deep hole drill can significantly improve the machining efficiency.


When the depth of the hole is more than 20 times the pore diameter, deep hole drilling method must be used for processing. Over the years, single edged deep hole drilling (gun drill) is a common tool for machining deep holes less than 40mm. It can be seen from the experiment that the advantage of single edged deep hole drilling is that the drilling quality is high, and the shortcoming is that the feedrate can be achieved. If the feed rate is increased when machining quenched and tempered steel, the tool wear will increase and produce bad chip shape. Therefore, low machining efficiency and short tool life are the disadvantages of ordinary single edged deep hole drilling.
 
Slight edge and round coating can prolong tool life without affecting machining accuracy.
 
On the premise of keeping the quality of single edged deep hole drilling, the tool is optimized to improve its machining efficiency without reducing tool life. For example, for stainless steel processing, not only should we pay special attention to the design of cutting tools, but also the performance of different coating materials and coating structures will be studied. A large number of practices have proved that the wear of the whole coating is smaller than that of ordinary coatings. In most cases, a slight roundness of the blade can improve tool life compared with a single edged deep hole drill using a sharp edge.
 
The common uncoated monolithic cemented carbide single edged deep hole drill is used as a benchmark for evaluating the performance of single edged deep hole drill. Through the cutting test, the tool wear and chip shape of the ordinary cemented carbide single edged deep hole drill indicate that when the feed length is f=0.02mm, when the drilling length reaches 30m, the tool has slight wear. Because the cutting heat and cutting force load of the cutter are small, there are only slight crescent wear and flank wear, and the chip produced is oblique helical chip. It is easy to drain from the hole. By increasing the feed rate, the tool tip at the outer edge of the tool has shown severe wear after the drilling length reaches lf=9m, so that the test has to be interrupted. In addition, increasing feed rate also affects chip shape. There is also a strip of chip on the skew spiral chip, while the flat strip chip segment is sandwiched between the cutter and the workpiece, causing tool breakage.
 
According to the actual effect of industrial application, ordinary single edged deep hole drill can be reliably applied to deep hole processing. But to improve the processing efficiency, it must be limited by certain conditions, especially if the feed rate is increased, the tool will wear out too quickly. When the feed rate of the single edged deep hole drill varies, it can be seen that the measured value increases with the increase of feed rate, almost linearly. When the feed rate is f=0.34mm, the feed force is Ff=950N and the torque is Mb=4.3Nm; at f=0.36mm, the tool is damaged due to the excessive torsion load.
 
Besides cutting force load, chip shape is of great significance for deep hole drilling process. Using a single edged deep hole drill, a suitable length of oblique spiral chip is formed at the feed f=0.04mm, and there is no unfavorable strip chip segment. When the feed is increased to f=0.1mm, a single chip roll appears, which is also suitable for chip type and shape smoothly discharged from the hole. When the feed rate was further increased to f=0.2mm, a lot of thermal loads were obviously generated. The chip color changed significantly and the shape became irregular. This phenomenon becomes more prominent when the feed rate is further increased to f=0.3mm. The chip is not only curly, but also has a flat chip. It can be seen that the chip is very thick. The magnitude of the mechanical load can be used to judge the tool wear condition. With the increase of wear value, the measuring value of feed force and torque also increases.
 
According to the predetermined tool life, the feed can be increased by 10 times. The measurement results show that in the drilling length of 30m, because the ordinary single edged deep hole drill can reach the drilling length of 30m when the feed rate is f=0.02mm, increasing the feed rate will result in the accelerated wear of the single edged deep hole drill. The single edged deep hole drill uses a 10 times higher feed rate, that is, f=0.2mm, and still achieves the predetermined life index. SEM analysis shows that the tool is still in normal wear condition and can continue to be used.
 
Besides the tool wear, the quality of the hole is also an important index to describe the performance of deep hole drilling. For the eccentric error of hole, the measured value shows the influence of tool structure and feed rate. For different single edged deep hole drills, the measured values are at a comparable level. This indicates that the improvement of tool sharpening does not adversely affect the eccentricity error of holes. In addition, for single edged deep hole drilling, increasing the feed rate or increasing the hole eccentricity error is also important. With the increase of feed rate, the feed force and torque value increase, resulting in the radial force increasing, causing the offset of the tool and increasing the eccentric error of the hole.
 
By improving the tool structure and processing technology, the hole eccentricity error can reach a very good level. In short, the improvements in the structural design, coating and cutting edge of the cutting tool proved effective, enabling the efficient processing of single edged deep hole drilling.
 
Fixed word: 189-3829-0275 Fax: 0769-81090104
Dongguan Li Kun CNC Co., Ltd.
Miss Lin: 189-3829-0275
Mr. Luo: 136-6578-2166
No. 1, Chau Tun old road, Changping Town, Dongguan
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