Underreamer Eccentric (URE) 2018-10-22T11:28:27+00:00

Project Description

Underreamer Eccentric (URE)

Holte’s Eccentric Underreamer’s 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 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 so 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″.

Drilling Bit Underreamer Eccentric
Download URE Brochure
Showing how the Eccentric Underreamer works with a casing driver to underream a borehole larger than the casing for overburden conditions

Eccentric Underreamer Casing Driver Style

The Holte Casing Driver (CD) was designed to be small and compact as well as hard hitting like a Down Hole Hammer (DHH). While the CD cycles fast like a DHH it is able to be designed around a much larger piston since it is above ground, in turn, deriving an extremely powerful impact for driving casing, allowing your DHH to run most efficiently since its energy is not absorbed trying to pull casing along with it.

The Holte Casing Driver is designed to be used with a DHH and underreamer, and is available in four sizes from an easily portable size for light duty rigs to a heavy duty size for the most extreme well and hole conditions.

The casing drive acts similar to a down hole hammer. When the hole is first started, the casing driver sits inactive on top of the casing and acts as a water diverter. When the underreamer advances 1” ahead of the casing the anvil closes and the driver starts operating. The more the anvil is closed, the harder the casing driver hits.  The CD turns on and off automatically and runs only when the casing lags behind the underreamer, causing the anvil to close. There is only 1 1/4” of vertical movement of the CD anvil so the casing will always remain within 3” of the bit.

Charts showing casing diameter, hole depth, and casing driver model. Also shown is the specifications for casing driver models.

Casing Driver Charts

Showing how the Eccentric Underreamer works with a drive shoe to underream a borehole larger than the casing for overburden conditions

Eccentric Underreamer drive shoe style

Maximize your underreaming with a Holte URE designed to have a wider cutting edge where you need it most. The Holte oval shape places more cutting edge on the bore hole wall. The URE Drive Shoe Style Underreamer is similar to the Casing driver style except the driver portion has a drive shoulder. This shoulder drives down the drive shoe that is welded to the casing. With this system, the down hole hammer is used to both drill and drive casing.

Eccentric Overburden Systems are available between 5″ – 12″.

Down Hole Drive Shoes

Drive Shoe