Exploratory coal seam drilling tool - has two sets of cutting and guide blades for rotation alternately in opposite directions

摘要

The tool for drilling coal seams for test purposes has four cutting blades mounted at its tip. Two blades (1) project sideways from a holder (2) at an upper level, and two further blades (1') extend at right angles to them, but lower down. On the stem (4) of the spindle which carries the holder are two sets of helical feed blades (5, 5). These are made up of short lengths which extend half way around the stem, one set (5) staggered by 90 deg. from the other set (5'). The tool is used by reversing its direction of rotation so that the pairs of blades are operated in turn depending on the direction of rotation.