Drilling Machines – The Selection Of Percussion

SINCE the introduction of the first percussion rock drill in about 1850, drilling equipment has undergone a progressive evolution so that a wide range of special classes of machines now are marketed by several manufacturers. Essentially all of the drilling machines presently employed for blasthole drilling are of the hammer-drill type. They are classified as hand-held hammers (jackhammers, sinkers, etc.), drifters (light or heavy), and stopers and are of many sizes; varying in weight and rotative and blowing power. Most makes of drill machines fundamentally are the same in principle of operation as they are designed to strike a blow on the end of a drill rod in the manner of early-day hand drilling. However, beyond this common characteristic, the similarity among different makes ceases. In choosing between similar machines of one make or another, it is important to remember that rock drill manufacturers have not attempted to standardize drill parts, the result being that a mine operator must approach, because of replacement parts, standardization by limiting the makes of machines used. The present-day selection of any particular drilling machine is dependent fundamentally on its inherent ability to make a hole, or series of holes, as speedily and as cheaply as is possible. Two categories of controlling elements become apparent in any analysis devoted to making the choice of a drill, namely: 1-Conditions under which the equipment is to be used, such as mining method practiced, type of labor available, character of rock material. 2-Physical characteristics or features of the given drilling machine. Regardless of the controls of class 1, above, the elements of this category are fixed by several factors. All of them are interrelated and, though some often are more important in one case than in another, an unfavorable variation of any-others being essentially equal-is sufficient to discredit the optimum applicability of the particular drill machine. The relative factors in the selection of a machine are as follows: First cost-This is not generally an important item on a comparative basis as the marketing of drill machines is highly competitive and most makes are priced closely.