. Handbook of construction plant, its cost and efficiency. ^ *~.--ki£Nv. Fig. 89. Drilling Down Holes with the Little imp Drill. Fig. 88. Drilling Up Holes with the Little Imp Air Feed Drill. per shift. One blacksmith with a helper will keep 5 to 7drills supplied with sharp bits. In medium rock a bit must besharpened for each 2 ft. of hole, in hard rock, for each iys ft.,and in soft rock for each 4 ft. The direct cost of sharpeningbits by hand is about as follows: HANDBOOK OF CONSTRUCTION PLANT BlacksmithHelperCharcoal . ,$, Total 140 bits at 4 cents = $ Mr. T. H. Proskesays: The
. Handbook of construction plant, its cost and efficiency. ^ *~.--ki£Nv. Fig. 89. Drilling Down Holes with the Little imp Drill. Fig. 88. Drilling Up Holes with the Little Imp Air Feed Drill. per shift. One blacksmith with a helper will keep 5 to 7drills supplied with sharp bits. In medium rock a bit must besharpened for each 2 ft. of hole, in hard rock, for each iys ft.,and in soft rock for each 4 ft. The direct cost of sharpeningbits by hand is about as follows: HANDBOOK OF CONSTRUCTION PLANT BlacksmithHelperCharcoal . ,$, Total 140 bits at 4 cents = $ Mr. T. H. Proskesays: The power drill-sharpener has re-moved many of theshortcomings attend-ant upon the handsharpening process,with the result thatwhere these machinesare used it is possibleto accomplish from 25to 100 per cent moredrilling than underthe old methods. Itake this to mean 25to 100 per cent moredrilling per trip to theshop on the part ofthe drill tender, whichstatement is wellwithin the facts. Es-pecially is this truewhen the machinesharpening is com-bined with the selec-tion of
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbuilding, bookyear191
