This ring portion of the bit is larger in diameter than the casing and has a smooth round outer surface. This is unlike eccentric underreamer bits which get stuck in a hole more easily requiring more torque. This smooth O.D. bit hardly registers on the torque gauge.

This system uses no drive shoe or shoulder when driving casing down from the bottom. Instead the driving is done from the top by the Holte casing driver which turns on and off automatically.

Straps or reinforcement patches are not needed on the welds. The welds do not get the same abuse as when casing is pulled down from the bottom. Another benefit from not driving from the bottom is there being no threat of wearing through the shoe or driving it off the casing. This leaves the down hole hammer free to do only drilling.

The cuttings go up through slots in the center piece or bit driver which is also the stabilizer for the unit.

To remove the ring bit, the casing driver is lowered so the casing sits on the ring portion. The downx hole hammer is then pulled up while the casing driver is hammering. This drives the ring off so the down hole hammer can be removed, leaving only the ring and the casing in the hole.

The ring bit system is available in 6" through 12". Other sizes are available upon request.