How to Choose the Right Drill Bit (HDD Drilling Equipment)


A horizontal directional drill (HDD) bit is a special design that helps make directional drilling easier and less expensive. While you will not need this type of tool for all projects, they are ideal for some applications which can be more challenging to reach with standard horizontal directional drilling equipment.

In many cases, the horizontal directional bit will allow you to reach projects that would be inaccessible otherwise. For example, it can help you lay water lines in areas where there is not enough overhead clearance for a standard drill rig. Stubborn rock or soil that cannot be broken with traditional equipment may be easier to break with the bit. This can reduce costs and save both time and energy.

These bits remove soil easily in a horizontal direction, using water or an oil based mud mixture as a lubricant for drilling ease. Given their specialized design, some factors must be considered when choosing a drill bit of this type:

• Drill depth capacity determines how deep the drill can go before hitting a ceiling.

• Shaft length—depends on how far you want to extend your line horizontally. The longer the shaft, the greater this extension will be.

If you are planning to use horizontal directional drilling equipment to drill for water lines, be aware that some have specific requirements for the type of line that will be used. There are some HDD bits that can only support water lines, while others can handle multiple types of pipe (including gas and oil). Be sure to read the specifications carefully before buying your drill bit so you know what you will need for it to work properly.

What Are the Different Types of Drill Bit Materials?

Drill bits are subjected to severe temperatures and pressures. Compression, torque, impact, heat, and friction are all forces that the drill is subjected to as it moves through the soil or rock. Thus, drill bits must be made of a range of materials  in order to be effective in the drilling application.

The most common type of drill bit used in directional drilling applications is steel teeth bits. Steel is a versatile metal that strikes a balance between strength, durability, and cost. Tungsten carbide inserts are typically used in more difficult ground conditions when higher-strength bits are required.

Polycrystalline diamond compact (PDC) bits are suitable for use in projects under extreme conditions. Synthetic diamonds are fastened to carbide inserts to create drill bits 50 times the strength of traditional steel bits. For extremely difficult ground conditions, such as solid rock formations, PDC drill bits are employed.

Hybrids of several drill bit materials are also available, and are built according to the application.

A complete geological report, geological investigation, and rigorous attention to the information provided by geologists and geotechnical engineering professionals are often required for determining the proper type of drill bit.

Drill Bits for Soft Ground Conditions

For projects with mostly soft ground conditions, fixed cutter bits or  drag bits are recommended. These drill bits are made from a single solid piece of steel. Carbide inserts can be utilized, but they are not required.

There are no rolling parts or bearings on these drill bits. As a result, the entire cutting assembly rotates along with the drill string, cutting through the ground as the blades turn. Because there are no bearings or rolling components, the cutting assembly has fewer moving joints and is thus less susceptible to damage.

To suspend and remove cuttings from the bore to the working surface while drilling with drag bits, air or drilling fluids can be employed. The drill bit’s monolithic steel design not only saves money, but it also reduces the chances of it breaking during drilling.

Drill Bits for Medium and Hard Ground Conditions

To efficiently break up dense soil and move it out of the way, bits must have sufficient strength and durability.

The three-cone rolling cutter bit is a common type of directional drilling drill bit for medium to hard ground. It has three revolving cones with their points pointed inwards toward the center. The cones revolve and grind the soil/rock, while the drill string rotates the entire bit at the same time.

The efficacy of the cutting head and its suitability for various ground types are determined by the angle of the revolving cones, its geometry, and the insert materials.

When the cone angle is high, for example, the bit’s penetrating action on the surface is mostly scraping or twisting. Lower angles, on the other hand, have a crushing effect. To avoid excessive bit damage, the cone angle should be reduced as the ground becomes harder. Long and widely spaced teeth are also better for softer ground, whilst short, closely spaced teeth are better for harder rock formations.

The hardness of the ground to be penetrated determines the type of insert material to use. Carbide inserts work best in medium-to-hard terrain, while polycrystalline diamond bits are ideal for solid rock.

Three-cone rolling cutter bits, like drag bits, suspend and remove spoils from boreholes using drilling fluid.


A drill bit’s effectiveness is not just determined by its speed of progress through the ground, but also how much heat it can withstand. A good bit will last longer and cut better because less friction occurs with slower speeds. The best choice may be a trade-off between these two factors depending on what you’re drilling into. If one factor outweighs the other in your case then make sure to do more research before settling for any specific style or size of bits.