Mechanical-Metallurgical Improvements in Drill Steel
In this paper a new type of durable 'spiral-rolled' drill set is introduced and its performance discussed. Efficient and economical mine drilling depends to a great extent on durability -0f the drill-set employed. Premature failure Of this element damages the drill bit and is costly when tungsten carbide bits are used. Time of drilling of 'spiral-rolled' drill sets introduced at present in Canada is considerably larger than for the presently used drill steel, but laboratory simulated service tests and practical field tests show that the 'drilli111g life' of the spiral-rolled drill set is several times that of ordinary drill steel. Some features of differential plastic deformation and differential surface rolling, so called 'spiral-rolling', are given. Relations between the drilling machine drill set and characteristics of the ore are discussed. The effect of shims on conical drill rod attachments, the mechanism of failure of drill steel, .and stresses dufi.ng mine drilling, are analysed.
corrosion, drill bit, fatigue, steel, tungsten carbide, Drill, Drilling, Drills, failures, Spirals, steel, Steels, stress