### Blast Hole Drilling: The Basic Process | RPM Drilling

2008-5-22 · A common method for calculating this relationship is: d (inches) < H/5 (in feet). Thus, for example, the maximum recommended drill-hole diameter for a mine that plans to develop a 60-foot bench would be 60/5 or up to 12 inches. From the chart, the range will be 4.5 to 12.3 ... Module 4 - Blasthole Drilling ...

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