DTH (Down - The - Hole) drill bits are essential tools in the field of rock drilling. They are designed to be used in conjunction with DTH hammers and are directly sent down the hole using a drill rod. These bits play a crucial role in various applications such as mining, quarrying, water well drilling, geothermal well drilling, and foundation piling.
Bit Face Designs:
Convex: This design is suitable for most drilling applications, especially in hard, abrasive rock. It offers a good combination of high penetration rates and long service life. The convex shape helps to concentrate the impact force on the rock surface, enabling efficient rock breaking.
Flat: Traditionally used for general - purpose drilling, the flat - face design is effective in very broken ground, hard formations, and soft formations where there is a tendency to over - drill. The flat surface provides a larger contact area with the rock, which can help in stabilizing the drilling process in unstable or broken ground conditions.
Concave: It is an excellent all - round bit design suitable for both hard and soft formations. The cone - shaped face provides good stability during drilling, ensuring straightness and low vibration. Carbide placement on the concave face enhances penetration rates in most ground conditions.
Carbide Insert Types:
Dome: This is a tough shape suitable for hard, abrasive rock and deep - hole drilling. It can withstand high impact forces and is suitable for nearly all rock - drilling applications.
Semi - ballistic: It is a combination design that provides a speed increase over the conventional domed button and has a higher longevity than the more - aggressive ballistic carbide design. However, it is less suited for broken ground conditions.
Ballistic: Ideal for less - abrasive sedimentary deposits where speed is vital. It is not recommended for badly broken ground or extremely hard rock.
Other Features:
DTH drill bits are designed for high air pressures and good flushing capacity, which is essential for efficient rock drilling. The simple structure design of DTH drill bits can reduce downtime to a large degree. For example, some DTH drill bits have a patent - designed structure that maximizes the transmission efficiency of the percussive force, and the surface of parts is enhanced to be anti - fatigue, thus extending the service life of DTH hammers.
DTH drill bits come in a wide range of specifications. The diameter can range from 60 mm to 775 mm, and the number of buttons can be between 8 and 24. Different shank types are available to fit various DTH hammers. For example, common shank types include those compatible with Atlas Copco's Cop 32, 34, 44, etc., and Ingersoll - Rand's DHD 3.5, DHD 340a, etc.
