Modern Trends in Hollow Drill Steel
B. M. HAMILTON
THE PROCEDURE and technique for drilling holes has probably undergone as great a change during the pas t ten years as any one of the other operations conducted in hard-rock mining. During this period, we have seen a change from the heavy leyners and drifters to the light jackleg type of drill machine; from steels that were forged and hardened on the bit end to the inserted carbide-tipped rod, from the necessity of providing special bit-end fabrication and beat treatment of shank steels to the simple grinding or turning of a plain section on a shank with no heat treatment required for bit attachment.
alloy, carbon steel, fatigue, heat treatment, molybdenum, Alloys, Bits, Drill, Drills, Fatigue, Grade, steel, Steels, stress