The

CROSS-BIT

The cross bit can perform a crushing action - as in this case - or a chopping action when shaped differently. The bit screws to the bottom of a suitable sinker bar - or bars. The chopping or crushing action is performed as the tool string is lifted a short distance and allowed to fall freely onto the material being drilled.

The picture shows the crushing version of the cross-bit. Bits like this can be refurbished on site by adding hard-facing welding to worn parts, or to change the shape. Longer and heavier bits can be used as well as ones studded with Tungsten-carbide inserts, which are primarily used for drilling longer distances through hard rock. A 6-inch button bit may require 500 kg in sinker bars as the driving force.

Different sized cross-bits are made to suit the casing in which they are intended to operate. The one pictured is intended to suit working in 6-inch casing. Cross bits may also be used without casing, or in advance of casing, where appropriate.