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What is Gun Drilling: Process, Applications & Benefits
Gun drilling is a widely used machining method for creating precise holes with a high length-to-diameter ratio. In this process, long hollow drills with internal coolant systems are used to drill deep, straight holes in metals. This article discusses what gun drilling is, its process, benefits, and applications across different industries.
Contents
What is Gun Drilling?
Gun drilling is a deep hole drilling method used to produce deep, precise holes using single lip-cutting tools. What sets gun drilling apart is the use of a hollow shaft that delivers coolant internally. This preserves the accuracy of holes. Consequently, a gun drill can drill holes with length-to-diameter ratios of up to 300:1, while twist drills are limited to 5:1.
Gun drilling comes from the firearm industry back in the early 20th century. At that time, manufacturers were in need of a reliable process to drill rifle barrel holes. The requirement for perfectly straight holes with high length-to-diameter ratios led to gun drilling. Eventually, this method extended across different industries.
How Gun Drilling Works?
The main component of gun drilling is the gun drill tool. It is designed to achieve long, deep holes. Here are the elements of this tool:
- Tip: It is the sharp end of the gun drill that removes the material from the workpiece. It has a single carbide cutting edge attached at an angle.
- Coolant Channel: It is the internal passage that runs through the body of the drill. It passes coolant to the cutting area. This removes heat from the cutting area and avoids chip buildup.
- Shank: Shank is the back portion of the gun drill that connects to the spindle of the drilling machine. It transmits rotational power from the drilling machine to the tip of the drill.
Step-by-Step Process
Here’s how the gun drilling process works:
- First, the workpiece is securely attached to the fixture of the drilling machine. This alignment is important since we want the hole to start in the proper position. The gun drill is installed in the spindle and checked for straightness.
- The drill point is adjusted to the start point of the hole. The drilling parameters (speed, feed rate, and depth) are set by the machine operator.
- The gun drill begins to rotate at high speed and slowly advances into the workpiece.
- Coolant is supplied through the internal channel at a very high rate to the cutting tip. This coolant pulls heat away from the cutting and flushes chips from the work area.
- The drill has enough depth and stops feeding into the workpiece. The tool is withdrawn slowly while the coolant continues to flow. The hole is then inspected for size and surface finish.
Advantages of Gun Drilling
Gun drilling provides many advantages over the traditional methods. Here are the key benefits of gun drilling:
- Hole Straightness: Gun drilling offers extreme hole accuracy, even for deep holes. Gun drilling produces straight holes that achieve close tolerance along the entire hole depth.
- Depth Capability: Gun drills can create holes significantly deeper than most traditional drilling methods allow. This feature provides opportunities for the design of complex components.
- Surface Finish: Gun drilling creates exceptionally smooth hole walls. Due to the monitored cutting action and the continual flow of coolant, the surface of the hole remains without surface distortions.
- Diameter Control: Gun drilling provides consistency in the diameter of the holes drilled from start to finish. This exactness in the diameter of holes is necessary when creating components with a tight tolerance, such as hydraulic pistons and fuel injectors.
- Chip Removal: Gun drilling’s internal system continuously flushes chips as the hole is drilled. Therefore, it eliminates chip clogging from shutting down the process.
Applications Of Gun Drilling
The applications of gun drilling are found in a range of industries. Across all the industries, one common thing is the manufacturing of critical components. These components demand precision, tight tolerances, and excellent surface finish. Here are some of the notable applications of gun drilling in some industries.
Automotive Industry
In the automotive industry, numerous components require passages for the flow of oil, fuel, etc. Gun drilling is used in the manufacturing of engine blocks, fuel injectors, fuel pumps, hydraulic cylinders, and various other components.
Aerospace Industry
The components of an aircraft endure extreme conditions that require near-perfect internal structures. These components include turbine blades, fuel lines, and hydraulic passages in landing gear systems.
Medical Device Manufacturing
Medical applications demand high cleanliness and dimensional accuracy. To name a few, gun drilling produces hollow surgical instruments, creates internal channels in orthopedic implants, needles, endoscopic instruments, and dental implants.
Mold Industry
In the injection molding industry, gun drilling provides cooling and heating channels within mold bodies. These channels provide temperature control during the molding cycle.
Gun Drilling vs Other Methods
Here is how gun drilling compares with twist drilling and BTA drilling:
Gun Drilling vs Twist Drilling
Twist drilling uses two cutting edges that work well for drilling shallow holes, but can face challenges in deeper drilling. The spiral design can cause chips to pack in the flutes. This can lead to tool breakage and poor hole quality. Gun drilling eliminates this issue by utilizing a single cutting edge, as well as cooling delivered through the flute as a coolant.
Gun Drilling vs BTA
BTA drilling uses large diameter tools fitted with external chip disposal systems. BTA drilling is suitable for drilling holes over 20mm in diameter. Whereas BTA drilling requires pre-loaded pilot holes and large and complicated setups. Gun drilling offers more flexibility in starting with solid material or even smaller diameters, as small as 1mm in diameter and above.
Conclusion
In the manufacturing industry, gun drilling is the preferred technique for internal passage creation. It can achieve extreme length-to-diameter ratios while maintaining accuracy. Major industries, including medical, automotive, and aerospace, rely on gun drilling for precise components. For professional gun drilling solutions, contact us
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