Tightness is one of the parameters of the quality of pipe drill string. Consequently, the reduction of hydraulic costs and wear of the tool-joint tapered thread of the drill string can be achieved by changing the cutting part of the cut tools. It is precisely because of the reduction of the tightness we have bigger expense of hydraulic energy on the one hand and the wear on the surface of the thread is accelerated, since the drilling fluid together with the abrasive, moves along the screw threaded channel at a high speed (over 50 m/s) on the other side. To date, the tightness of tool-joint tapered thread provided in two ways. The second is the filling of the spiral channel, which is formed due to the standard gap between the box and the pin by a special lubricating and sealing filler. Typically, such fillers in the presence of significant pressure and untightness when contacting the ends of the box and pin are displaced from the channel. The authors of the article propose to reduce the cross-sectional area of the specified gap to achieve a sharp decrease in the speed of the drilling mud in the channel formed by the gap. As a result of the virtual experiment, actual data were obtained regarding the speed of the drilling mud, which became 40-50 times smaller in the case of a decrease in the height of the channel by 4 times and its width by 1.6 times. In the article it is shown that the existing sizes and tolerances for the gaps in the standard are of an optional nature and are presented for the design of a cutting tool for cutting. Consequently, the reduction of hydraulic costs and wear of the tool-joint tapered thread of the drill string can be achieved by changing the cutting part of the cut tools.
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