Handbook of construction plant, its cost and efficiency (1918)
Dana, Richard Turner, 1876-1928 · New York, McGraw-Hill book company, inc., [etc., etc.] · leaf 259
Fig. 89. Drilling Down Holes with the Little !mp 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 lYz…
Contractors' operations · Building
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