The design of the overburden drilling system does not provide the potential for producing an efficient system below 300mm and so Bulroc has developed an eccentric drilling systems aimed at installing continuous casing for hole sizes down to 115mm.
This design of system is popular for installation of rock anchors or tie back anchors where only temporary casing is required. No separate or sacrificial casing shoe in necessary with this system. The casing shoe is welded into the lead casing and is recovered for further use along with the rest of the casings.
The eccentric system is a 2 piece design and the drill bit has a central pilot in the drilling position that assists in maintaining a straight hole, particularly useful on inclined holes.