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.