ABSTRACT
The published literature on the theoretical aspects of rock drilling is of great value in understanding the process of rock drilling, but of little help in predicting the outputs. Since a large number of factors affect drilling speeds, some of which are still unresolved theoretically, prediction is currently based simply on experience. It is known that work output per minute is related to the air pressure, area of the piston and the stroke. Air pressure can be used as a factor provided that the air consumption is taken at a common pressure level. There is no doubt that in open-fissured rock a considerable loss of footage will result from abandoned holes, from the time taken for extra precautions by the driller and so on. Bad conditions, however, although they may occur for the full depth of a drill hole, represent only a proportion of the total drilling in fissured rock when considered over a series of holes.
