Rotary Hole Openers Overview


The Mills Machine Holeopener is used to enlarge or ream an existing pilot hole or can be run above a pilot bit to simultaneously drill and enlarge a hole. These rugged tools are built for the toughest drilling applications. For most drillers, the use of Hole Openers has gone from being an optional operation to becoming a standard practice. Several advantages to using Holeopeners is described on the reverse side of this page. The primary reasons for using holeopeners are economy, accuracy, speed and flexibility of size. With over 60 years of experience, Mills Machine can custom design and manufacture the exact tool for your individual requirements.

  • Fabricated Roller Cone (see Rotary Holeopeners, in this catalog)
  • Fixed Arm Roller Cone (see Rotary Holeopeners, in this catalog)
  • Drag Bit, fixed and replaceable blade (see Rotary Drag Bit in this catalog)
  • Claw Bit (see Rotary Claw Bit in this catalog)

Holeopeners or Roller Back Reamers are available for Horizontal Road Boring or Horizontal Directional Drilling applications. Configurations include Roller Cone, Drag (blade) Type or Claw (bullet) Type in any size and with any connection. These rugged units are manufactured with a reverse pitch on the cutters for pulling back through the pilot hole. We also manufacture a line of Free Bore Bits and Casing Push Bits for the Horizontal Road Boring market. Configurations include Roller Cone, Drag (blade) Type or Claw (bullet) Type in any size and with any hex connection. The Roller Cone type features a special Positive Cam Lock Design for pushing casing as you drill. This type of bit is made to cut very hard rock formations. Blade and Bullet configurations are offered with flip-out cutters for soft to medium formations.

Advantages of Hole Openers

1. Cost and availability of large tricone rock bits. Large diameter rock bits are expensive and difficult to find compared to the economy of Holeopeners using smaller rock bit segments. 2. Large diameter holes with small rigs. Large holes can be drilled with smaller rigs by opening the hole up in stages. A smaller hole requires less power. 3. Straighter hole. Drill a straighter hole by drilling a pilot hole, then attaching the pilot bit to the bottom of a holeopener, which will then follow the existing hole. 4. Cutter replacement. To extend the initial cost investment of a Holeopener, the cutters on most any design can be replaced. Bolt-on drag bit and claw holeopeners can be replaced in the field. Fixed blade and roller cone holeopeners may require factory replacement. 5. Sizes and formations available. Holeopeners can be manufactured in any size and made to drill any formation from soft clay to hard granite. 6. Surface casing and starter holes. Holeopeners provide a convenient way to drill larger diameter holes for setting surface casing and shallow starter holes. 7. New jobs. With the capability of drilling larger diameter holes, several job markets could open up. For example: mining air shafts, elevator holes, power line holes, municipal water wells, foundation holes and mouse or rat holes for drill pipe storage.