How Raise Drill Works
Raise drilling is used to create large drill holes -- up to 7.6 meters in diameter. The holes, or tunnels, are used to connect mine shafts, power plant tunnels or channels for rainwater and surplus water, as well as for ventilation between different levels in a mine.This type of drilling is performed in two stages. First you drill a smaller pilot hole and then you swap the smaller drill bit with a reamer. The reamer is equipped with reels made of hardened metal which have the same diameter as the final hole. The hole is expanded as the reamer crushes the rock using both pressure and rotation.
Raise drilling can be used for holes and tunnels of up to 1100 meters in length, which makes this method very practical for many applications. More details