The conditions for applying the method of drilling boreholes with simultaneous casing are considered. The most used tool designs, their advantages and disadvantages are shown. Present-day requirements for this tool are indicated. A new design is presented, which allows further drilling through the casing pipe of maximum possible diameter, simulation results are given. The operation of the device is described and a diagram of its use is presented.

This paper presents the design of portable downhole hammers for borehole diameters of 43 and 76 mm when drilling with a combined rotary-percussive method in coal mines. The scope of use is described. Features and advantages of prototypes are shown. The characteristics of DHH and research data are given. The conditions of production tests and operating results are described.