raiseboring pilot tricone bit

A raise borer is a machine used in underground mining to create a circular hole between two mine levels. The raise borer is set up on the upper level and a small-diameter pilot hole is drilled to the level below. The pilot hole is typically 230–445 mm in diameter, which is large enough to accommodate the drill string. Once the pilot hole is achieved to plan, a large diameter reamer is attached and pulled-downwards or pushed-upwards (depending on the method) excavating the hole to the desired width.

Here are some steps in the raise boring process:

1. Drill a pilot hole from the base level to the required level
2. Back ream the pilot hole using a specialist raise bore drill rig
3. Remove the roller bit and replace it with a reaming head when the pilot hole breaks through into the lower level
4. Drill a series of overlapping holes through the ore zone from a raisebore chamber in waste rock above the ore
5. Collect the ore using remote-controlled scoop trams at the bottom of the raises
6. Fill each raisebore hole with concrete

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