The Composition of Tapered Drill Rods

Table of Contents

According to the way of connecting with the drill rod, there are tapered drill rods, threaded extension rods, and integral drill rods. The tapered drill rod is a relatively widely used type and belongs to the category of small cross-section rods. During the rock drilling process, the main parts of the tapered drill rod, rock drill, and drill bit are the end of shank and the taper part. Therefore, the overall drill rod and its connection with the part of the geometry and parameters of the choice for the efficiency of rock drilling is crucial.

tapered drill rod

Shank adapter handle

The shank adapter handle of the drill rod includes the shank adapter, drill shank, and drill shoulder parts.

Shank adapter

The shank adapter refers to the end of the shank about 30mm. During the drilling process, the end face of this end is in contact with the end face of the rock drill piston, bears the impact of the rock drill piston, and transmits the impact power of the rock drill to the drill rod. Since the impact frequency of the rock drill piston is about 2000~3000 times/min, it is required to have moderate hardness and wear resistance, reasonable geometric structure, and machined dimensions with a certain degree of accuracy, especially the end face should be flat and have a low machining roughness. Therefore, the end part must have the fatigue strength to resist the high-frequency impact of the rock drill piston.

Drill shank

During the drilling process, the drill shank is directly connected and matched with the hexagonal sleeve of the rock drill. Therefore, whether its matching performance is good or not is closely related to the geometric structure of the drill shank and the selection of parameters.

Drill shoulder

The drill shoulder mainly plays the role of fixing the drill rod on the rock drill during the rock drilling process.

Rod body

The rod body of the tapered drill rod generally refers to the part from 50mm in front of the drill shoulder to 50mm behind the cone. It is not processed in the brazing process, and its geometric structure and parameters are consistent with those of hollow steel.


The cone structure and parameters of the tapered drill rod vary from country to country. Considering the requirements for the connection and coordination between the drill rod-cone and the drill bit taper hole, the smaller the cone angle α of the cone is, the greater the expansion stress of the cone on the taper hole will be; the greater the cone angle α is, the greater the expansion of the drill bit shell stress is reduced, but the connection is slack.

The geometric structure and parameters of each part of the tapered drill rod affect its rock drilling efficiency and service life, and its quality has a great relationship with the steel type and rolling quality of the drill steel. In addition, Whether the manufacturing process is reasonable and whether the forging equipment is advanced and sophisticated is also extremely important. In particular, since the hollow brazing steel type adopts alloy steel, the material performance is significantly improved, and brazing technology and equipment on the quality of brazing rod is more prominent.

Process flow of tapered drill rod

Although the degree of mechanization and automation of the production process of each drill rod manufacturer is different, the basic manufacturing process is similar. The typical process flow is:

Selection of hollow steel – Quality inspection of incoming steel – Sizing material – Straightening – Induction heating – The end of shank adapter reaming and sizing – Flat end chamfering of the shank end – Induction heating – Forging drilling shoulder – Finishing drill shoulder – Forming of brazing cones (machining or forging) – Inspection of drill rod geometry – Induction heating – Shank adapter end quenching – Shank adapter end tempering – Shot peening treatment for the whole surface of drill rod – Anti-corrosion treatment for the whole drill rod – Quality inspection of finished drill rod – Packaging-Storage.

In short, the tapered drill rod is an essential tool in engineering construction, and its performance and quality directly affect the safety and stability of the project. By understanding its composition, manufacturing process, and other aspects, we can better understand it, and using the product, we can also choose the product parameters that are more suitable for our project and escort the engineering construction.

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