Underreamer Eccentric (URE)
Holte’s Underreamer Eccentric oval shape is designed to have a wide cutting edge on the borehole wall to maximize the underreaming. It is ideal for sensitive overburden conditions. The Holte Percussion Underreamer Eccentric is a two piece tool, a driver section & a bit section. The driver, or splined section fits into a down hole hammer. Available in a Drive Shoe Style or for use with a Casing Driver.
The bit section has a pilot portion that is out of center to the rest of the bit and the drill string. Due to this, it will drill a larger hole than the OD of the drive shoe on the casing.
The whole bit swings out and has a short heavy pin on the top side that fits into a pocket on the driver. A small portion of the air escapes between the wall of the driver pocket and the pin portion of the bit. This keeps the bit free from sticking in place so that a very minimum of reverse rotation will swing the bit back in alignment with the drill string for retraction.
Eccentric Overburden Systems are available between 5″ – 12″.