Chicago : Engineering and Contracting Pub. Co. · leaf 312
classified as fairlysoft rock. From April 5 to May 1, 25 days a crew ofone drillman and one mucker, advanced a 4x6 ft. tunnel 254.5 ft. The cost of labor andsupplies on the machine amounted to $1.54,or $.006 per ft. of tunnel. The tool used, aSullivan DB-15, weighs 25 lbs., uses %-in.hollow steel,… … 298 ENGINEERING & CONTRACTING Vol. XXXVI. No. 12. hand feed tool. The great advantage in usinghammer drills in work of this class, as instoping, consists in the fact that no time islost in mucking for the set-up, as in thecase of piston drills, or in mounting the drillafterwards on the bar or…
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