The University Geological Survey of Kansas Volume 8

The University Geological Survey of Kansas Volume 8

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ...if desired. Two men are generally employed with each drill; one to operate the drill and the other to loosen the bit when it becomes fastened in the hole. The loosening of the bit is accomplished by means of a few strokes'of a hammer, bar, or hand drill, while the power is on. The man who attends to the drill (the driller's assistant) bales out the hole and helps the driller in keeping it straight. There is a greater range in the practice of placing holes when drilling is done by hand than when machines are employed. The usual practice with hand drills is to begin at that point of the face of drift which looks most favorable, while with power drills the center or bottom positions are generally chosen. To accomplish this the column is set vertically in the drift and the drill set at the required height above the floor. Several holes are then drilled to one side of the center, but so slanted as to almost meet at the ends of the completed holes. Other holes drilled between this first row and the wall, on the same side of the drift, in positions ranging from normal with the face of the drift to an angle, the reverse of that of the first set of holes, or slanting outward, complete the arrangement for one side, which is repeated on the opposite side of the drift, but in reverse order. Holes drilled according to such a system require the supporting column to be set up twice for each round of holes. When the condition of the face permits, the arrangement of holes given above will be carried in vertical lines to the top of the drift, which, when charged and fired in the same order in which they were drilled (from the center outward), break down the whole face. However, the more common practice is to break out the lower portion of the face of more

Product details

  • Paperback
  • 189 x 246 x 6mm | 227g
  • United States
  • English
  • black & white illustrations
  • 1236983718
  • 9781236983718