The Hole Opener Advantage fully heat-treated alloy steel. With cutters for Soft,Medium Hard format Straighter Holes - By drilling a smaller hole with a "pilot" bit, then attaching that said bit onto the bottom of the the hole opener. The hole opener will follow the path of the hole drilled by the smaller bit. Larger Holes with Smaller Rigs - By drilling a hole in stages, larger holes can be drilled with smaller rigs. A smaller hole requires less power. Replacing Cutters and Cutting Cost - On most Hole Opener designs, the cutters can be easily replaced. The cost to replace a cutter is a fraction of the cost to replace a large tricone rock bit. Cost of Large Rock Bits - Larger diameter rock bits not only cost a lot, they can be difficult to find. A more economic solution is to use a hole opener that uses smaller tricone rock bit segments..