Journal - South African Institute of Mining and Metallurgy . anner in whichrotation is affected. The large Leyner machineuses a ratchet and rifle bar like those of |drills. The Leyner Rock Terrier drill aspositive geared rotation worked off the feedscrew. The Gordon machine has a positive ition worked by a central spindle ending in ahandle and ratchet at the rear of the machine,if the other drills are pivoted on the handleor airfeed, and are oscillated orrevolved byahandleon the front which often contains the air valve,The drawings show a typical mal: imple American hammer drill and its air fe
Journal - South African Institute of Mining and Metallurgy . anner in whichrotation is affected. The large Leyner machineuses a ratchet and rifle bar like those of |drills. The Leyner Rock Terrier drill aspositive geared rotation worked off the feedscrew. The Gordon machine has a positive ition worked by a central spindle ending in ahandle and ratchet at the rear of the machine,if the other drills are pivoted on the handleor airfeed, and are oscillated orrevolved byahandleon the front which often contains the air valve,The drawings show a typical mal: imple American hammer drill and its air feedattachu(see ). Nearly all the* - of drills are working with success in America, and iof them have been tried here without big Leyner drill is at present, I believi .work on only two mines, the Jupiter and thei Ions .lidated Main Reef. The Rock Terrier drillis not at work anywhere here. What are thecauses of failure ? Why is a machine that is 114 The Journal of The Chemical, Metallurgical and Mining Society oj Smith Africa. Oct. 1P(V7. \J | «=