What Is the Working Principle of DTH Hammer?

Table of Contents

In modern drilling and mining, the DTH hammer is an indispensable tool. It has won the favor of many construction units with its efficient and stable working performance. But do you understand how the DTH hammer works? This article will unveil the mystery of the DTH hammer for you so that you can easily grasp its working principle.

Overview of DTH hammer

DTH hammer

The DTH hammer is an integral part of the DTH drilling rig. The DTH hammer is an integral part of the DTH drilling rig to connect the DTH drill bit and the drilling rig. It includes low wind pressure DTH hammer, medium wind pressure DTH hammer, and high wind pressure DTH hammer. It is widely used in metallurgy, coal, chemical industry, mining, water conservancy, hydropower, highway, railway, national defense, construction, and other engineering hole forming operations.

The structure of the DTH hammer

Low wind pressure DTH hammer structure

The working air pressure of the low air pressure DTH hammer is lower than 0.7Mpa. It consists of a joint (rear joint), check valve (bonnet, valve body), spring, gasket, pressure pad, valve cover, valve plate, pin, valve seat + valve rod, inner cylinder, piston, outer cylinder (outer sleeve), bushing (guide sleeve), and card drill sleeve.

Typical features

  • The joint threads are mostly rectangular.
  • There is a reversing valve group inside.
  • The piston cylinder has simple rules.
  • The drill bits are mostly pin-locked.

Working principle of DTH hammer

Working principle of low wind pressure DTH hammer

When the hammer works, the compressed air enters the cavity formed by the joint, and the valve covers from the joint through the check valve. Then the compressed air is divided into two paths: one is the direct blowing powder discharge air path, and the compressed air passes through the upper cavity of the valve seat and the piston and the middle channel of the drill bit enters the bottom of the hole and is directly used to purge the rock powder at the bottom of the hole; the other channel is the cylinder working gas distribution channel to achieve periodic reciprocating motion of the piston.

Return stroke working principle:

During the return stroke, first, the stroke air chamber is connected to the outside world and has a low pressure, and from the front connector into the compressed air pressure is large, so that the valve slice tilted to one side, the valve seat and the inner cavity of the inner cylinder connected to the row of holes closed, compressed air from the valve seat on the other row of holes to enter the inner cylinder and the outside of the formation of the cylinder, and then through the cylinder on the row of radial holes into the piston on the front side of the return stroke air chamber, then the compressed air under the action of the piston to accelerate backwards, and the other way is the cylinder working air distribution circuit to realize the piston cycle reciprocating motion. Under the action of compressed air, the piston is pushed backward for acceleration, when the left end of the piston and the valve stem began to cooperate, the exhaust orifice is closed, the stroke air chamber is in a sealed and gradually compressed state, at this time the valve piece is also gradually to the other side of the skewed, the compressed air directly into the seat of the valve and the piston formed by the stroke air chamber, the piston began to do deceleration, when the piston slides out of the liner on the right end of the return air chamber and the outside world atmospheric communication, the loss of pressure, the piston is stopped under the effect of the left cavity back pressure, to achieve the return stroke. The piston stops under the action of the left chamber back pressure, realizing the return stroke.

Stroke working principle:

Piston at the beginning of the stroke, the compressed air continues to enter and through the valve plate from the valve seat and the stroke air chamber connected to the through-hole into the stroke air chamber. At this time, the piston accelerates forward under the action of air pressure until the small head of the piston reaches the lining. The return air chamber of the sleeve is closed, but compressed air still enters the stroke air chamber, and the piston continues to accelerate. When the piston is detached from the valve stem, the stroke air chamber is connected to the outside atmosphere, the valve plate is biased to the other side, and the return air chamber is in the forward position. At this time, the piston impacts the drill bit at a very high speed due to inertia and completes the stroke.

DTH drilling tools

Working principle of high (medium) wind pressure DTH hammer

Take the DTH hammer without a tailpipe as an example. High-pressure gas pushes through the center hole of the fitting to open the backstop valve and the return gas chamber formed by the piston and the outer cylinder and liner. For ventilation, the inner hole of the outer cylinder has an annular groove, and the outer circle of the piston is milled with long grooves and waist-shaped grooves. Because the area of each step of the piston is different, and the high-pressure gas pushes the piston backward. When the piston and liner detach, the high-pressure gas in the return air chamber reaches the bottom of the hole through the bushing and the air hole of the drill bit for slag-blowing. At the same time, the piston decelerates in the opposite direction due to the force. At the same time, due to the force reverse piston for deceleration, the middle of the piston and the outer cylinder to form a stroke gas chamber 1, the pressure effect of the area of pneumatic effect of the annular area difference, the piston continues to return to decelerate, in the piston movement to the tail and the gas distribution seat with the small end of the head with the formation of the stroke of the gas chamber 2, the kinetic energy of the piston reduces the pressure in the gas chamber 2, the piston continues to return, when the piston tail groove at the inner cylinder slot, the gas chamber 1 with the gas chamber 2 connection, at this time the piston is subjected to the stroke of the force to the maximum area of the area of the force is the area of the piston tail area plus the area of the middle of the piston annulus area minus the area of the gas distribution seat head, and then the piston stops the return trip to accelerate forward to impact on the tail end of the drill bit to complete the stroke.

Application advantages of DTH hammers

DTH hammers are extensively utilized in drilling and mining applications owing to the following advantages:

High efficiency

The DTH hammer can quickly break rocks and improve drilling efficiency through high-frequency and high-intensity impact.

High stability

The working process of the down-the-hole hammer is relatively stable and can maintain constant drilling speed and impact force. It allows the DTH hammer to maintain efficient performance in complex formations and harsh environments.


The DTH hammer is highly adaptable to different hardness and nature of rock. 

Long service life

The weight ratio of the piston to the drill bit is close, and the effective action time is prolonged, which is advantageous for enhancing rock-crushing efficiency and extending the life of the drilling tool.

High safety

The DTH hammer fully considers safety factors during the design and manufacturing process and has high safety and reliability.


As an efficient, accurate, and reliable drilling tool, a DTH hammer plays an increasingly important role in modern drilling and mining fields. By understanding its working principle and advantages, we can better apply DTH hammers, improve drilling efficiency, and reduce engineering costs. At the same time, with the continuous advancement of science and technology and the continuous improvement of technology, it is believed that the performance of DTH hammers will be even superior, bringing more convenience and benefits to engineering construction, and mining.

Picture of Kelleg


Your reliable partner in the field of geotechnical engineering.

Get "Kelleg Company Profile and Product Brochure" now

  • 20.9Mb, we will send it to your email after submitting.
  • Your email information is absolutely safe, and we will not disclose it to third parties for any reason.

Can't get enough?

Get all latest news, exclusive offers and updates on new arrivals.



We will contact you within 1 working day, please pay attention to the email suffix “@kellegco.com