. Transactions. short crosscutis first made by the percussion drills to give a space for the machineand the proper handling of the rods. The rods are square threadedat the ends and come in five foot lengths. They are pulled in lengthsof 5 to 20 feet, according to the space available behind the drill. The holes are cored throughout. The core barrel is 5 feet long,and the frecjuent slips and small seams in the country rock, permit the 454 The Canadian Mining Institute. cores procured to be easily broken off by the usual choker device. Theaverage length of the pieces of core is 5 to 8 inches. In
. Transactions. short crosscutis first made by the percussion drills to give a space for the machineand the proper handling of the rods. The rods are square threadedat the ends and come in five foot lengths. They are pulled in lengthsof 5 to 20 feet, according to the space available behind the drill. The holes are cored throughout. The core barrel is 5 feet long,and the frecjuent slips and small seams in the country rock, permit the 454 The Canadian Mining Institute. cores procured to be easily broken off by the usual choker device. Theaverage length of the pieces of core is 5 to 8 inches. In carefulsampling the core barrel is sometimes pulled out for every six inchesadvanced. The drilling engines are screw fed, and fitted for 300, 1000 revolutions per inch of advance. Their ordinary speed is300 revolutions per minute. The water is pumped through the drillrod by a small independent pump run by compressed air. The averageprogress is 8 feet in an eight hour shift, with a record of 18 ft. 9 Rossland from Mountain. The core is broken up and assayed, after a careful examination by themine superintendent While drilling in ore, sludge samples are takenby running the discharged water for a fraction of the time into a tinpail, in which the sludge settles out. The Rossland rock is very hard on diamonds. The War Eagleand Centre Star companies employ a skilled bit setter to keep the bitsin running order. For the smaller sized bits eight diamonds are used,six on the face and two on the outside. Those on the face are set sothat half of them have a cutting edge extending to the outside of the i Milling in the Rossland District. 455 face, while the other half cut the inside clearance for the core to passup. Whenever the drill is withdrawn from the hole the bit is alwayscarefuliy examined, and if any of the diamonds are found to be looseor the metal worn away, the metal is recaulked around them. Whenthe bit is so badly worn that the diamonds are greatly exposed, th
Size: 1900px × 1315px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, booksubjectmineralindustries, bookyear1895
