The Bureau of Mines studied the self-advancing reamer concept as a potential application as a shaft or raise borer, as a stabilizer for straight holes, and as a reamer for blastholes. Over 8,000 ft of 15- in blastholes were drilled in hard taconite with a conical reamer blasthole bit (CRBB) and penetration rates were compared with those from a standard 15-in bit used on the same drill at the same rotational speed and thrust. The penetration rate of the CRBB was 20 pct greater than that of the standard bit. However, an economic analysis shows that the additional equipment substantially increases the drilling cost.
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