ODDS’N’SODS — A busy little drill bit

When the Helen mine at Wawa, Ont., first underwent an underground stope development program, a series of diamond drill holes was required to locate the F.W. contact over a rather large area.

Using the Pajari down-the-hole survey equipment, it was found that some of the holes had wandered all over the place, by as much as 50 ft. off the drilling line.

The engineering department took a dim view of this situation, and the diamond drill bits had some bad things said about them. However, all of this was about to change — a busy little drill bit on another project was due to pull off a stunning event.

A deep probe was under way to intersect the Victoria orebody at a depth of 5,000 ft. This deposit was a pet project of Sir James Dunn, president of Algoma Steel. As a world businessman, Dunn wanted only to look ahead as far as he could, and he did not want to be surprised by anything unpleasant. Once the hole had reached a depth of 3,000 ft., a serious cave occurred at 2,500 ft., at a time when the drill rods were out of the hole. A decision was made to write off 500 ft. of the hole and start a new hole with a small-angle wedge above the cave.

When the new hole was out about 40 ft., the drillers had the impression that the busy little drill bit was trying to get back to the old hole. This suspicion was confirmed 30 ft. farther on, when the bit occupied all of the old hole and the drill string could be lowered again to the old bottom at 3,000 ft.

This busy little drill bit had managed to pull off one of the most stunning reversals in diamond drilling history. It deserves a place somewhere in the annals of world mining.

At 3,000-ft., a full shift was required to lower the rods, fill the core barrel and raise the drilling string to the surface staging. Using all their ingenuity and competitive energy, the drillers managed to keep to the routine until the hole bottomed at 5,015 ft.

The contractor was Boyles Drilling and the area manager was Al Haxthou. The drill foreman was the unflappable Angus MacIssac, who showed the younger driller how to run a drill program.

And yes, the hole intersected the Victoria orebody in the target area. — D.A. Campbell is a resident of Orillia, Ont.