| 摘要 |
A drill bit includes discs with same diameters on axis that is fixed without possibility of motion at the lower section of pads. The drill bit has additional discs with different diameters on common axis that is immovably fixed over the discs in the upper section of legs, respectively, and toothed chain that is destructive element that connects additional upper, and discs in the lower section of the legs, respectively. At that the discs and additional discs are fit on the axis wit possibility of rotation. |
