Underreamer Gauge (URG) 2018-10-19T09:47:51+00:00

Project Description

Underreamer Gauge (URG)

  • Underream on all sides of the hole simultaneously with a wing bit system
  • URG Underream for Reverse Circulation or Conventional Drilling
  • Retract the arms with slight reverse rotation

The Holte URG® (Underreamer Guard) Underreamer has an extendible arm bit and is considered superior to a one-sided UR because three (3) to four (4) arms extend to ream a full gauge (360 degree) hole. The underreamers which swing out on only one side drill slower and not always straight.

This bit design was developed at Holte Manufacturing while researching faster ways to drill large diameter holes. Because there is bit surface reaming the full gauge of the hole, this bit wears much better than an eccentric style bit which only reams with about a 50 degree portion of the hole.

The Full Gauge UR resembles a conventional hole opener. The extendible arms cover 360 degrees of the hole circumference, minus three air slots, similar in size to a conventional bit. We offer URG Overburden Systems between 10″ – 42″ configured with three (3) or four (4) arms for both conventional and reverse circulation drilling.

URG in the dirt
Showing how the Eccentric Underreamer works with a casing driver to underream a borehole larger than the casing for overburden conditions

Underreamer Gauge URG 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

Underreamer Gauge URG drive shoe style

Maximize your underreaming with a Holte URG designed to have a wider cutting edge where you need it most. The Holte extendible arms underreams 360 degrees of the bore hole wall. The URG 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.

Down Hole Drive Shoes

Drive Shoe