Rock Drill Bit Types
There are two basic rock drill bit types – PDC and diamond. Each is suitable for drilling different types of rock. Both types of bit use shearing motions to drill. Penetrating force is transmitted to the cutters vertically and horizontally and varies depending on the strength of the rock.
- Mechanics length
The first step in choosing the right rock drill bit is to determine the drill’s shank configuration. There are several options for shank configuration. The smallest common pneumatic drills use a one-piece bit/drill steel combination. These drills can be found in a wide range of lengths and flute lengths.
In directional drilling, the rotational parameters of a rock drill bit are not as important as those of a standard drill bit. In fact, industry experience suggests that the optimal rotational speed is about 20 rpm or 4-5 degrees per impact. In hammer drilling, the outer row of cutters moves at about half the diameter of the bit during each stroke.
- Tapered drill bits
A forged drill shoulder and shank adapter is used to join this drill rod to the rock drill. Of all drill rod kinds, the tapered drill rod is the one that is most frequently used. Small cross-section drill rods with hollow hexagonal ends fall into this category. Internationally, 19mm, 22mm, 25mm, and 28mm are most frequently utilized.
- Top hammer threaded drill bit
Top hammer-threaded drill bits are designed to increase drilling efficiency and service life. These bits are typically made of cemented carbide. This material offers superior wear and impact resistance and has a longer service life. This type of drill bit is ideal for large-scale construction projects.
Top hammer-threaded drill bits are designed for use in a variety of rock drilling applications. They are suitable for open pits, underground, and quarry work. These tools can be used to drill through both soft and hard rock. They are also capable of drilling a much longer distance per impact.
- Conical inserts
Conical inserts are one of the most common types of rock drill bits and are used extensively in geothermal and oilfield drilling. Although they are not as strong as PDC bits, they are cheaper and can drill through harder materials like limestone and dolomite. They also have a higher impact resistance than PDC drill bits. However, PDC bits account for nearly half of the footage drilled in the United States.
Conical bits are typically made of steel. They are made from high-carbon steel that has been heating treated but is generally softer inside. This means that they can be more forgiving in tough drilling conditions.
- Three-blade PDC bits
There are three basic types of PDC rock drill bits. These bits are used in mining, water well drilling, oil well drilling, and cathodic protection applications. They are designed with a one-piece 4140 alloy steel body for maximum strength and bit stability. They also feature Force-Balanced PDC cutter locations that reduce bit whirl and an asymmetric blade layout that reduces drilling harmonics.
PDC bits can be used in soft and medium rock formations. For hard formations, you may want to use diamond bits. The blades of a PDC bit work through shearing, which transfers a horizontal or vertical penetrating force into the rock formation. This process cuts the rock at an initial angle relative to the thrust, depending on the strength of the rock formation.