What is a Gun Drill Bit? – All You Should Know!

The gun drill bit is the tool for gun drilling. Gun drilling is referred to as deep drilling in small diameter precisely. So when you need to drill a narrow hole deeper, you should use a gun drill bit. But gun drill bits are not able to use in regular drilling machines. It needs a special mechanism to fix the drilling machine.

Normally a gun drill bit can drill 400mm – 1200mm deep holes. It is 40D – 80D (D- drill bit diameter). Gun drill bits are made with carbide material and there is a flushed liquid flow to eject the chips from the drill bit. Due to the carbide material, it can be used in high RPM and feeding rates.

Gun drill bits are self-centering, and it helps to make a deep, accurate hole in the metal. Bits are designed with bearing pads for keeping the gun drill bit on center. Those pads help to drill a bit to move forward while maintaining smooth contact along the surface of the hole.

What are the Parts of Gun Drilling?

First of all, you should know the parts of a gun drill bit.

A gun drill bit has 3 main parts,


The tip is the drilling head of the drill bit. It has made with different materials according to the drilling requirements. When it is prepared with carbide, it can drill 40×D. But when the whole drill bit is made with solid carbide, it can drill 80×D with a single drill bit.


Shank is named as flute area. Normally spiral flute design is not essential in the gun drill bit. The flute can be spiral or straight. There is a flush flow to remove the chips easily.


The driving head is the connection with the drilling machine.

The gun drill bit is longer drill bits such as 400mm to 1200mm. Due to the length of the gun drill bit it needs additional equipment to hold the drill bit.

You will need this equipment for gun drilling.

  1. Drill bush
  2. Sealing disc
  3. Steady rest bushes
  4. Adjusting screws
gun drill bit
Gun Drilling Equipments

Where to Use Gun Drill Bits?

Generally, you can use gun drill bits for drilling smaller diameter deep holes. The depth of diameter ratio can be even greater than 40D. Gun drill bits are basically used with metal materials and plastic.

You can use gun drill bits on conventional machines (CNC), special-purpose machines, medical appliances, , and gas and oil industry manufacturing.

You can also use gun drill bits to make air holes into the motor racing engines.

You can start with a pilot hole using a spotting hole drill bit for the highest accuracy if you need.

What are the Color and Material Of Gun Drill Bit?

When you choose a gun drill bit, it is important to find out about the gun drill bit’s material and its coated color because it helps to maintain your gun drill properly.

There are many coated gun drill bits. According to the coated color, its price also changed.

Normally gun drill bits are coated with diamond powder, titanium nitride, black oxide, titanium carbonitride, and titanium aluminum nitride. According to theses coating color drill bit tip color is changed.

Gun drill bits are mostly bright finished in color because it has made with solid carbide, which is harder material for all metals.

Cheap gun drill bits are made of carbon steel. Carbon steel gun drill bits can be sharpened well, but carbon steel loses its temper faster due to the friction of cutting, and when it uses for hard drilling, faster becomes dull.

The gun drill made of High-Speed steel Alloys (HSS) is better than carbon steel. They are hard and keep a sharp cutting edge longer than carbon steel. They can withstand heat better and cut faster than carbon steel.

The long-lasting drill bit is made of HSS with tungsten carbide. Those are very hard, and their edge longer than HSS. But those drill bits are quite expensive.

What Materials Can be Drilled Using Gun Drill Bit?

As I have mentioned above, generally, gun drill bits are used for metal materials. Among the metal materials, you can drill by using gun drill bits on aluminum, iron, titanium, steel, bronze, and brass materials.

You can also use gun drill bits on plastic, and fiber materials if you need.

What are the Sizes of Gun Drill Bits?

Normally gun drill bits have different sizes. According to the drill bit diameter, there are 6mm – 12mm drill bits are available with 400mm – 1200mm in length.

Due to the length, these are not able to use in hand drills.

What is the Drilling Depth of Gun Drill Bits?

Normally drilling depth of the gun drill bit depends on its diameter and material. When the tip is made with solid carbide, it can drill 40D maximum depth. But when the whole drill bit is manufactured with solid carbide, it can drill 80D in a single drill.

It is recommended to that drill to 40D at a time. Then use another drill bit for the rest of the length.

Gun Drilling vs. BTA Drilling – What is the Difference?

Gun drilling was originally developed to drill out gun barrels. Gun drilling is commonly used for drilling smaller diameter deep holes. The depth-to-to-diameter ratio can be even greater than 300:1.

The BTA drilling system was created by the Boring & Trepanning Association. BTA drilling is a deep-hole drilling process. It uses a long drill tube to make a deep hole in the metal. It can make a hole with a diameter of 20mm and larger, up to a diameter ratio of 400:1.

BTA drilling is cleaner, more reliable, and can achieve larger diameters and higher feed rates than gun drilling. Typically BTA drill feed rates 5-7 times faster than gun drilling.

BTA drilling machines have coolant around the drilling bit head, and it helps to evacuate chips through the drill and machine spindle, but when you use grilling, its coolant is introduced internally, and chips exit through an external groove.

Gun Drilling Machine
Gun Drilling Machine

Read More About – What is Center Drill Bit?


A gun drill bit is high-quality drill bit that is highly used in small-diameter deep holes. Due to the length, it needs additional supportive equipment.

Normally a gun drill can drill 400mm – 1200mm depth with using a single drill bit. Solid carbide gun drill bits are the best for any metal and are highly efficient.

Tom Mackency

Tom Mackency

Hi, I am Tom Mackency. It has been 10 years that I have been working as a professional woodworker since 2013. I am really enjoying my carrier by creating many kinds of projects in my workshop. But mostly I like for home improvement projects. Home improvement and DIY projects are the most interesting things for me. More than that, the coolest things are power tools. Those are very precious and efficient than a decade ago. So I try to introduce so many things about power tools, woodworking, DIY projects, home improvement and many more interesting topics here.