Down the Hole (DTH) bits are used with down the hole hammers to drill holes through a variety of rock types. When used with a down the hole hammer, the drill bits are designed with a slot drive to rotate the bit in the ground. Drill bits come in different sizes and styles to allow for drilling of different hole sizes.
The many down the hole (DTH) bits we offer are made from high-quality materials to provide a good balance between drilling capacity and bit life. We offer a range of standard and custom bits, with a variety of options for drill stem and head designs to suit different project needs.
The choice of down the hole drill bits is almost limitless, thanks to working with flexible bit manufacturers. The ability to customize the bit to your geology and other drilling environments makes this method unique from other drilling methods.
The first thing to consider when choosing a drill bit is the rock formation. The type of rock formation determines which drill bit face shape and carbide (tungsten carbide) configuration we need to choose.
The DTH drilling method is best suited for drilling in medium-hard rock formations, but not all hard rocks are the same. Some rock formations are harder than others, and some are more abrasive due to their high silica content.
Here, we will focus on how to customize drill bits for different formation conditions to increase the life of the drill bit and improve drilling performance.
Choosing a drill bit face design
First, let's consider the face design of the drill bit. There are several different types of face designs we can choose from: flat, concave, convex, convex-concave, and drop-center designs.
Flat design: This design works well in all rock formations, especially in hard rock formations. However, some deviations may occur in soft rock formations. Overall, the drilling speed is good.
This design may be difficult to find in stock, you may need to customize it, usually require a minimum order quantity, and need to wait for delivery. Be prepared in advance.
Concave design: Concave is the most common design type, and almost all manufacturers have it in stock. It is suitable for medium-hard rock formations, can maintain good hole straightness, and has average drilling speed.
It is considered the standard drill bit design and works in almost all rock formations, with only some adjustments for harder rock formations, such as adding wear pads or using high-grade tungsten.
Convex Design: The convex design is used in hard and abrasive rock formations. The design consists of two different outer ring angles, which can effectively reduce outer ring wear.
This design is particularly suitable for situations where rapid outer ring wear is encountered. It performs well in medium-hard rock formations and drills very quickly. It may be custom ordered.
Concave-convex design: This new design combines the advantages of convex and concave surfaces to provide better hole straightness. It performs well in multiple drilling conditions, especially in hard rock formations.
This design is becoming more popular and many top manufacturers have this design as an off-the-shelf product, although they may have their own naming methods.
Drop-on-center design: This design is more outdated and less available in stock, but it still performs well for certain conditions. It is suitable for sloped or broken rock formations and has good hole straightness.
This design is generally custom-made and may require a minimum order quantity. Not all manufacturers offer this design.
Air Supply and Bit Hardness
Next, we have to consider flushing the hole. An important aspect of drill bit design is the ability to effectively clean the hole. This can only be achieved with adequate air supply
If you have a high air supply, consider using a three-hole flushing system, which can help quickly remove cuttings from the bottom of the hole.
I prefer to use deep and wide flushing holes, especially in high air pressure applications. If the cuttings are not removed quickly and effectively, the drill bit will re-grind the cuttings, causing premature wear or failure, and the drilling speed will also be slower.
In addition, we can adjust the hardness of the drill bit itself. There are many heat treatment options on the market, such as induction hardening and carburizing. These different heat treatment methods will harden the drill bit to different depths, thereby extending the life of the drill bit steel.
Unlimited Options
The shape, grade, and size of the tungsten carbide is another option in DTH drill bit design that is unique to this drilling method. The options are almost endless.
Common tungsten carbide shapes are dome/spherical and parabolic. Dome buttons are typically used in hard and abrasive rock formations, while parabolic buttons are suitable for soft to medium hard rock formations.
There are also multi-point, chisel-tooth, conical and ballistic tungsten carbide buttons, which some manufacturers offer. Tungsten carbide also has different hardness grades, and standard grades and upgraded high-hardness tungsten carbide buttons can provide better performance for harder and more abrasive rock formations.
If you need more specific information about custom drill bits, you can visit leanoms. The high-performance DTH drill bits we provide are widely used by stone mining companies such as Forustone, helping them improve efficiency and stability in the mining process of soft stone and hard rock. Whatever your needs, we can provide you with customized solutions to ensure smooth operations.
