| 摘要 |
An upper end (10) far the inner tube of a core drill has a hard ball (30) which runs in a circumferential track (24). The ball (30) and track (24) are adapted to be carried within a tubular upper end casing (12) which surrounds a spindle (11) which supports the inner tube of the drill. An indent washer 25 is positionable above the track (24) and ball (30) and is oriented relative to the casing. A spring (26) supports the washer (25) above the ball (30). When the upper end (10) is lifted, the ball (30) is driven into contact with the washer (25) and makes an impression. The orientation of the impression reveals the orientation of the lowest point in the track (24). The impressioned washer (25) can be used to assist in noting or marking the core orientation after the drill is removed from the earth.
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