QUARRYING. 99 



Opinions differ as to the weight of hammers best suited for 

 drilling. Some quarriers use hammers weighing as much as 16 

 or 18 Ibs. for the larger drills say from 2 to 3 inches and lighter 

 hammers for the smaller ones. 



In the Aberdeen and Peterhead districts, long hammers, 

 measuring about 10 inches in the head and weighing about 9 

 Ibs. each, are almost universally used, and are considered to work 

 better than those of greater weight. 



In my opinion, a man is what is termed " overtooled " with a 

 hammer of 16 or 18 Ibs. weight, and I much prefer those which 

 are not so heavy. 



Quarry drills are now generally made of solid octagon cast- 

 steel, the sizes commonly used varying from 1 to 1 \ inch, accord- 

 ing to the size of drills. For small drills, employed in drilling 

 plug-holes, f or f inch steel is used. 



The waste of steel at the head of solid steel drills is so much 

 less in quantity than the waste of iron used to be, when the 

 drills were made of iron and steeled only at the point, that, 

 notwithstanding the higher price of steel, it is found to be 

 economical to make the entire drill of it ; moreover, the labour 

 and cost of constantly " steeling " the point is thus saved. 



With good smiths, the consumption of steel in a quarry is 

 very small. 



In the Port Elizabeth quartzite quarries, it amounted to 

 0-024 Ibs. per ton of rock quarried, and averaged 0'06 Ibs. per 

 foot of hole drilled. The greater portion of this was, however, 

 chargeable to the steam-drills, which were much more waste- 

 ful of steel than the hand-drills. 



In drilling granite of ordinary hardness, such as that in the 

 Peterhead district, by hand, the consumption of steel is only 

 about one-third of the above. 



In drilling hard rock, the drills usually require to be sharp- 

 ened once for each 12 or 18 inches bored, 



Forms of Drills. The forms of drills shown in Fig. 18, p. 100, 

 are those which, from experience, I have found well suited for 

 boring hard rock by hand. For softer rock similar drills may be 

 used, but the angle of their cutting edges should be made more 

 acute. 



Standard gauges ought to be worked to in making and sharp- 

 ening drills, otherwise they are very liable to give trouble by 

 becoming jammed in the holes. 



