Cooperative Mining Series; Bulletin Volume 13

Cooperative Mining Series; Bulletin Volume 13

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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. 1915 edition. Excerpt: ...machines is supposed to be snubbed for a depth equal to one-half the depth of the undercut. Snubbing usually is only 18 inches deep however, and the height of face snubbed varies from 18 to 24 inches. In No. 6 seam the face is snubbed to the blue band. Fig. 33 shows a common method of placing holes after chain machines where black powder is used and fig. 34, where permissible explosives are used. The position of drill holes and their number vary between wide limits. The usual practice with chain machines is to use one-third pick bits and twothirds chisel bits. In District IV seam No. 5 has always been considered hard and in this district only chisel bits are used in the chain. In a mine in District VI where entries are driven on two benches, shooting is done with size F black powder, and the PLAN Fig. 34. Method of placing holes where permissible explosives are used holes are arranged as shown in fig. 35. At another mine in this district all holes are drilled with air-drills. Unless the miner desires to point his own holes all holes are pointed by the drill-runner. The operator of this mine states that on account of the differential in wage scale he finds no advantage in the use of power drills. Hydraulic mining machines have been tried in one or two districts but the machines did not perform successfully on account of the strength of the coal and the lack of cleat. There are used in blasting coal annually in Illinois about 32 million pounds of black powder and about one million pounds of permissible explosives. The standard sizes of black powder according to the Revised Mining Statutes of Illinois are the following: The larger the grain, the slower combustion proceeds and the slower does the force of the explosion develop. The sizes in...
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Product details

  • Paperback | 60 pages
  • 189 x 246 x 3mm | 127g
  • United States
  • English
  • black & white illustrations
  • 1236799704
  • 9781236799708