At some point it may be necessary to increase the size of a pre-drilled hole to a larger diameter or to drill large diameter holes. Hole opener bits are designed specifically for this purpose. Bits are custom manufactured in a wide range of styles to meet field requirements. A custom hole opener is an effective way of enlarging holes, hence the name "Hole Opener".
There are many variations, all of which are tailored to the driller's specific needs. Hole openers can be fabricated with steel tooth cutters, tungsten carbide insert cutters or for Hole Openers, DTH hammers, all either new or rebuilt. Bearing may be open or sealed and the hole opener may utilize either standard or reverse circulation. Hole openers may be the answer to your hole enlargement problems.
TCI(Tungsten Carbide Inserts) Cutters are available along with diamond enhanced features. Fixed cutter hole openers are made from sections of tricone bits as shown left (TCI cutters) and below (Tooth cutters). Steel Tooth Cutters are available with carbide tipping.
Steel Tooth Tricone Cutters - Today, drillers are more adept at replacing their own cutters. Your supplier can provide the replacement cutters which saves you shipping the hole opener to and from the manufacturer for repair.
The Hole Opener Advantage
- Straighter Holes - By drilling a smaller hole with a "pilot" bit, then attaching that said bit onto the bottom of the the hole opener. The hole opener will follow the path of the hole drilled by the smaller bit.
- Larger Holes with Smaller Rigs - By drilling a hole in stages, larger holes can be drilled with smaller rigs. A smaller hole requires less power.
- Replacing Cutters and Cutting Cost - On most Hole Opener designs, the cutters can be easily replaced. The cost to replace a cutter is a fraction of the cost to replace a large tricone rock bit.
- Cost of Large Rock Bits - Larger diameter rock bits not only cost a lot, they can be difficult to find. A more economic solution is to use a hole opener that uses smaller tricone rock bit segments..
- Flexibility - Hole Openers can be fabricated in just about any size, and can be configured to drill through any formation.
- Drilling Weight - The choice of drilling weight is determined based on the recommendations of the bit manufacturer and the number of cutters on the hole opener.
Number of Cutters
- The number of cutters placed on a hole opener is governed by the following facts:
- Maximum number which will fit around the perimeter.
- The greater the number of cutters, the less the weight, which therefore reduces the penetration rate.
- In softer formations, less weight is needed to penetrate.
- The greater the number of cutters, the smoother the tool will run.
- The greater the number of cutters, the greater the cost.
- The greater the number of cutters, the longer the cutters will last
- Rotary Speed - Maximum speed is determined by the manufacturer's recommendation and the calculation to account for the linear distance the cutter is moving per revolution.
- Hole Cleaning - A frequently over looked point of hole opener operation is hole cleaning. The volume of cuttings to remove from a hole increase by a squared factor with an increase in hole diameter.