Deep Hole Drilling: Definition, Technologies, Benefits & Applications

The engineering space would be incomplete without deep hole drilling operations. Ever since the technique emerged in the 18th century, it continues to revolutionize engineering processes and manufacture globally.

Deep hole boring is a simple process that combines speed and precision. The main tool here is a high speed drill bit, but the setup and execution of the drilling operation requires expertise. There is also a lot of details regarding this drilling process that most people don’t know.

The essence of this post is to highlight the intricacies of this fundamental process, including the various applications and versions.

What Is Deep Hole Drilling?

Deep hole Drilling

Deep hole drilling is a method of cutting metal to produce a new bore hole or alter bore hole diameter and depth of an existing one. Engineers use the depth to diameter (D:d ratio) to determine whether a hole is a deep hole or not. For a deep hole, the D:d ratio is more than 10:1.

To create such a hole diameter and depth, you need special tools and method. That’s critical because there must be a way of removing the chips drill the deep holes effectively. You can drill a deep hole in several materials including aluminum and its alloys.

While deep hole boring is a core machining process in many industries today, it was originally only a gun manufacturing technology. Manufacturers used deep hole boring to create deep gun barrels.

As with any other technologies, the drilling operation is now present in many industries. Automotive, aerospace, and oil & gas are now some of the many industries with deep hole drilling applications.

Deep Hole Drilling Tools and Technologies

Below are some of the popular drilling tools and technologies:

Twist Drilling

Twist Drilling

Twist drilling technology involves the use of a special tool that has a chisel point. Rotary and axial force creates the deep hole, while the grooves guide the chips out of the hole. Twist drills are usually of cemented carbide or high speed steel material.

BTA Drilling

DTA Drilling

Created by the Boring and Trepanning Association several decades ago, BTA drilling entails using a special machining tool with an inner tube. This tube helps in the removal of debris and cutting fluid from the 15.6 mm – 300 mm diameter holes.

Gun Drilling

Gun Drilling

The gun drilling operation features a long slender tool rotating at high speeds to produce a deep hole. The name of this tool is gun drill. To remain at the set point, this slender tool connects to a tool holder. Another role of the tool holder is to remove debris from the hole. Manufacturers looking for very deep hole boring with pinpoint accuracy prefer the gun drilling operation. The process is also cost-effective.

Ejector Drilling

Ejector drilling is comparable to BTA drilling, but comes with two tubes instead of one. To add to the tubes, this system comprises the drill head, an adapter, and a rotary connector. Ejector drilling is effective on irregular surfaces. Compared to gun drilling, ejector drilling operations are typically faster and have tighter tolerances.

Bottle Boring Tooling

Bottle-boring tooling comes in handy when you need to machine an internal profile in a deep hole. Tool inserts under the control of the CNC control unit do the deep hole boring. The boring bar in this type of deep hole drilling comes with internal tie rod.

Counter Boring Tooling

Where a hole existed but you want to alter the hole diameter to parameters that are more exact, you need to use counter boring tooling. You can use a drill bit with a smaller diameter to drill a small hole. Follow that with counter boring tooling to acquire the required hole diameter.

Benefits And Limitations Of Deep Hole Drilling

Automotive, aerospace, and many other industries use deep hole boring for its many benefits. That’s despite the process having several limitations.

Precision of Deep Hole Boring

The automation component of deep hole drilling is the main reason this process is highly precise. It is easy to achieve the exact depth-to-diameter ratios with this process. That explains the industries mentioned above and many other manufacturing setups prefer this deep hole boring option.

Outstanding Surface Quality

Compared to what twist drill bits and other traditional techniques offer in terms of surface finish, deep hole drilling is much better. The quality of the tooling and setup alone gives this method an upper hand. The method offers better cooling and chip evacuation, thus contributing to the ease of making the surface finish high quality.

High Cutting Performance

The cutting performance in deep drilling largely depends on the tooling aspect. Deep hole boring utilizes advanced tools with extended tool life. These tools can last long and bring unique geometries.

Speed & Efficiency

Since this method of creating holes is automated, it works fast and saves energy. It can form small and sizeable holes without losing speed and efficiency.

Deep Hole Drilling Services For Various Industries

If you are looking for the most dependable, modern, and affordable deep hole drilling services, look no further than our company. Our machinist are highly experienced and we have the most advanced CNC machines.

As a mark of quality combined with versatility, our services cut across different industries. In the automotive industry, deep hole drilling services are instrumental in making crucial components. Examples of these are hydraulic cylinders and fuel injectors.

The aerospace industry is also a prominent customer for these services. Using our rich expertise and world-class machines, we help make landing gears and other industry components.

You will also find our footprints in the oil & gas industry. The long parts in the industry feature holes, which need deep hole drilling.

Tips For Deep Hole Drills

Due to its complexity, the deep hole boring process requires a few tips for success. Issues like workpiece instability, material challenges, and genera mistakes are bound to happen. Fortunately, there are ways to avoid such and have quality deep holes.

Consider the following points:

Use the right drill bits

Poor holes can occur due to incompatibility of the drill bit.

Ensure equipment lubrication and cooling

Coolants and lubricants play an important role in enhancing tool life and general equipment life. Cooling is also good for the quality of the deep hole and safety of the process.

Choose the right drilling Operation

The suitability of a machine or technique for a certain deep hole differs. Different parameters call for different approaches.

Use quality fixtures for Drilling Operations

Workpiece stability during hole drilling is instrumental to the quality of the results. Enhance the quality of the holes by using high quality fixture mechanisms. These mechanisms ensure that the workpiece remains steady regardless of the amount and nature of forces.

Deep Hole Drilling Service Provider

An experienced company that uses advanced drilling equipment is your best bet to avoiding expensive mistakes for your machining operations.


How do you drill a hole deeper?

To drill a hole deeper, you need to first choose a drilling technique that delivers such depth. Some machines are capable of drilling holes over 100 times the diameter. Therefore, choose a machine and tool with a higher capability.

What is the maximum depth of a gun drill?

The gun drill depth is typically between 50 and 100 times the diameter of the hole.

What is the best drill bit for deep holes?

The best drill bit for deep holes depends on the material you are drilling. For instance, if you are drilling granite (tough material), the best option would be a concrete drill bit. In the same breath, a carbide drill bit is the best solution for deep hole drilling in steel. Note that there is a broad range of drill bits.


Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.