Your Guide to DTH Drilling

Pneumatic tools have been used to drill through rock since the 19th century. Back then, drillers would suspend themselves from a rope over a quarry face to put a drill from the right position and use small diameter holes. The process was inefficient and dangerous. It could send rocks flying and the accuracy was subject as much to luck as it was skill. After a while, drilling crews started carrying jackhammers on masts, beautiful boreholes were misaligned, the explosives that followed could be even more dangerous.

Thankfully, we live in the modern era, where down the hole (DTH) drilling has become one of the most efficient and safest methods since its invention in the mid 1950s. Let’s explore what DTH drilling is, why it’s such a successful technique, and how it might be the perfect process for your drilling operation.

What is DTH Drilling and how does it work?

DTH drilling is a drilling method that’s used to crush rock by using a drilling hammer to hit hard rock repeatedly. DTH drills are pneumatic tools that provide power by driving compressed air into a piston inside the hammer. This type of drilling has made it much easier to drill wells quickly and efficiently by allowing contractors to switch from dirt boring to rock boring simply by adding a compressor and hammer to a drill bit.

Before DTH became a widespread drilling technique, contractors would desert a dirt bore project after encountering hard rock, leaving it to a different set of drillers to continue. With DTH drilling, the same drilling team can work through multiple materials.

At its most basic level, DTH drilling involves attaching a drilling hammer to the bottom of a drill string. Small, percussive hammers are placed above the drill bit, allowing drill pipes to exert a feed force necessary to rotate the hammer and bit together with fluid (usually air, water, or mud). This actuates the hammer and flushes the cutting. Drill pipes are then added to the drill string as the hole gets deeper.

Because the air-powered piston strikes the bit directly, energy is transferred down the hole, minimizing any lost energy. This allows drilling to greater depths.

DTH Drilling is most often used in the mining industry, where blast hole drilling is necessary for projects like water well drilling, building construction, and oil and gas processes.

Types of DTH Drilling Hammers

DTH hammers are fully fluid actuated. There are two primary parts: a valve which controls the flow and a piston that strikes the impact surface. The hammer body allows for stable, straight guidance of the bit. There are three types of hammers that depend on the actuation fluid:

  • Air hammers – These are typically limited to shallow holes of less than 200 meters.
  • Water hammers – These require a lost water flow of between 55 and 744 L/min depending on hammer size to actuate the hammer. These allow for better borehole control and greater depth than air hammers.
  • Drilling mud hammers –  These are the newest types of drilling hammers, but they’ve shown a lot of promise so far. They’re able to drill on every existing drilling rig by using classical mud composition. They are fantastic choices for drilling into hard rock in geothermal projects due to their ability to drill extremely deep.

What are the benefits of DTH drilling?

DTH drilling is extremely effective, which is why we’ve been using it for the past seven decades. Some of the major benefits include:

  • The use of air is extremely efficient. You don’t have to buy, source, treat, or transport it for use.
  • DTH systems are simple to adapt to most directional drills, and it doesn’t take long.
  • Very little rotational torque is required to cut rock that will allow the hammer to drill straight.
  • The same drill can be used to drill through both dirt and rock.
  • There isn’t as much wear and tear on a drill bit since the hammer is doing most of the work.
  • There is a smaller carbon footprint than other techniques due to the use of less drilling mud and additives that need to be disposed of.
  • It can be used more often in cities because it produces less noise and vibrations than alternatives. 
  • Fewer amounts of additives and drilling fluids are required than for alternatives.
  • The rate of penetrations is up to five times greater than rotary drilling techniques.

OK Bit has the DTH Drill Bits you need

If you’ve decided DTH is the right drilling method for your project, OK Bit can supply you with whatever bits you need to get the job done. If you aren’t sure if DTH drilling is the best choice or if you need help choosing a specific hammer or bit, our expert staff will be happy to help. Contact us today.