| 摘要 |
A drilling head (12) for making a borehole (18) along a predetermined underground path is formed by a tubular body (22) having a guidable rotary drilling sub normally axially mounted in the body by means of a sleeve bearing (36) journalling a drill bit (40) equipped rotary drilling string sub joint moveable with and within the sleeve bearing for disposing the drilling bit (40) on a predetermined angle in a predetermined direction relative to the longitudinal axis of the body (22) by means of diametrically opposite superposed pairs of wedges (28-29), (30-31) interposed between respective end portions of the sleeve bearing and the inner periphery of the body.
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