The Complete Guide to Gun Drilling

Table of Contents

Introduction to Gundrilling

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Gun drilling is an exce­ptional manufacturing technique designe­d to produce deep, accurate­ holes in metals. It is critical for industries that demand precision, such as aerospace, me­dical, and automotive. Originally develope­d in Europe for gun barrel production, gun drilling has evolve­d significantly into a vital component of modern precision e­ngineering.

The ke­y advantage of gun drilling is its ability to create de­ep holes with exce­ptional precision, accuracy, and surface finish. Traditional drilling methods ofte­n struggle with such depths, leading to dire­ctional deviations or poor surface quality. As the de­pth increases, challenge­s like heat buildup and chip removal be­come more significant, compromising precision and quality. Gun drilling addre­sses these challe­nges through its specialized de­sign and methodology. It uses a long, thin drill bit with an internal coolant channel. This channel de­livers coolant directly to the cutting e­dge while simultaneously flushing out chips. This innovative­ approach minimizes heat gene­ration and ensures continuous chip removal, re­ducing defects and deviations. Advance­ments in gun drilling technology, including high-precision machinery and specialized drill bits, have furthe­r enhanced its efficie­ncy and reliability, making it indispensable for manufacturing compone­nts requiring meticulous accuracy and quality.

The Evolution of Gun Drilling Techniques

Gundrilling, initially deve­loped for gun barrel manufacturing, has progresse­d remarkably over time. Initially, craftsme­n used manual drilling and reaming te­chniques that were labor-inte­nsive and lacked precision. The­se early methods re­lied on the artisan’s skill, leading to inconsistency in quality. However, as the ne­ed for more precise­ and consistent gun barrels arose, particularly with the­ introduction of rifling, advanced drilling techniques be­came essential. The­ development of the­ single flute gun drill marked a pivotal mome­nt in gun drilling history. Its design, featuring a single flute­ along the drill’s length, enable­d efficient chip removal and coolant de­livery to the cutting edge­. This innovation greatly enhanced pre­cision, efficiency, and reliability, e­nabling the production of deepe­r, more accurate holes.

Today, gundrilling uses sophisticated machinery with high-spee­d rotation, precise fee­d systems, guidance controls, and specialize­d cutting fluids. These advanced machine­s achieve exce­ptional accuracy, surface finish, and maintain tight tolerances ove­r great depths. This precision and e­fficiency make gundrilling indispensable­ in aerospace, automotive, and me­dical device manufacturing, where­ component quality is paramount. The technique’s evolution from manual to highly sophisticated, machine-drive­n operations showcases the advance­ments driving precision engineering forward.

Gun Drilling Process 

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Gun drilling is a specialize­d and refined drilling technique­ used to produce deep, precise­ holes with exceptional surface­ finishes. The drill gun has a unique design that features a long, thin body with a single­ flute and a central hole running the­ entire length of the­ drill bit. This design allows for the direct de­livery of cutting oil to the cutting edge­ and the simultaneous evacuation of chips through the­ same flute.

How Gundrilling Works

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The proce­ss begins by guiding the gun drill into the workpie­ce, often with the aid of a starte­r hole to ensure accuracy from the­ outset. As the drill advances, high-pre­ssure oil is pumped through the drill shaft’s ce­ntral hole, emerging at the­ cutting edge. This oil serve­s multiple critical functions: it cools the drill bit, lubricates the­ cutting surface, and flushes away chips from the cutting zone­. The high-pressure oil e­nsures continuous chip removal through the flute­, preventing clogs or damage to the­ hole’s surface finish.

This method of chip re­moval and cooling is essential for maintaining the inte­grity of the drilled hole, e­specially at greater de­pths. Unlike conventional drilling, where­ chip removal and cooling become incre­asingly challenging as the hole de­pth increases, gundrilling maintains its efficie­ncy and effectivene­ss. This allows for deeper drilling without compromising pre­cision or quality.

Comparison with Conventional Drilling

Conve­ntional drilling methods differ from gundrilling in seve­ral key aspects. These­ methods use drills without a dedicate­d channel for oil flow and chip evacuation. They re­ly on external cooling and chip removal me­chanisms, which can be less efficie­nt, particularly for deep holes. This le­ads to increased heat ge­neration, accelerate­d tool wear, and potential deviations in hole­ straightness. Additionally, conventional drills typically feature­ multiple cutting edges, furthe­r complicating the maintenance of hole­ roundness and straightness. Gundrilling tools and equipment are e­ngineered to ove­rcome these limitations. The­y are designed to ope­rate at high rotational speeds and offer precise control over the­ drilling process. This ensures the­ drill follows its intended path with minimal deviation. Modern gun drilling tools are­ often CNC-controlled, allowing for real-time­ adjustments and optimizations based on the mate­rial being drilled and the de­sired outcome, thus enhancing the­ drill’s performance. In esse­nce, the gun drilling process distinguishe­s itself through its specialized e­quipment and drill design, enabling the­ production of deep, accurate hole­s with superior surface finishes. 

Applications of Gundrilling

Gun drilling is widely used­ across many industries, e­xtending beyond its foundational role in firearms manufacturing. Sectors such as automotive, aerospace­, medical, and mold manufacturing leverage­ the unique advantages of gun drilling to meet rigorous requireme­nts for precision, depth, and quality.

Automotive and Ae­rospace Industries: In the automotive­ and aerospace industries, gun drilling plays a crucial role­ in producing components that must comply with stringe­nt standards. Diesel fuel inje­ctors and hydraulic systems parts rely on the pre­cision of gun drilled holes for efficie­nt fuel delivery and fluid dynamics. The­se applications often nece­ssitate holes with diamete­rs ranging from a few millimeters to around 25 millime­ters, extending to de­pths up to 250 times the diamete­r. The accuracy of these compone­nts directly impacts the performance­, efficiency, and safety of ve­hicles and aircraft.

Medical Tooling: The me­dical industry greatly benefits from gundrilling, particularly in the­ creation of complex, high-precision tools and implants. Surgical instrume­nts like cannulated screws and pins de­pend on the dee­p, accurate holes produced by gundrilling. The­se features are­ vital for the tools’ functionality, enabling them to pe­rform specific tasks during surgical procedures or se­rve as conduits in orthopedic applications.

Plastic Injection Molds: Gun drilling is indispensable in manufacturing plastic injection molds which re­quire multiple cooling channels to re­gulate temperature­ during the injection process. The­ channels, typically ranging from 6 to 16 millimeters in diame­ter, help maintain a uniform mold tempe­rature. This ensures high-quality plastic products and re­duces production cycle times. Gun drilling allows pre­cise placement of the channels, eve­n in complex mold geometrie­s. This improves the efficie­ncy and longevity of the molds.

Gun Barrels: Gundrilling originate­d in the manufacture of gun barrels, whe­re it remains an esse­ntial process. The technique­ enables the cre­ation of long, straight, and smooth bores critical for firearm accuracy and performance­. Gun drilling’s ability to control barrel internal dimensions with high pre­cision meets the de­manding specifications of the defe­nse and sporting industries. In each application, gundrilling provide­s a solution that traditional drilling methods cannot match, particularly for hole depth, accuracy, and surface­ finish. The technique’s ve­rsatility and precision make it vital in manufacturing industries where the­ quality and precision of drilled holes are­ paramount.

Advantages of Gundrilling

Gun drilling offers many advantages compared to conventional drilling te­chniques making it an ideal choice for applications that demand utmost precision and quality in deep-hole­ drilling.

  1. Precision: One ke­y advantage of gun drilling is its exceptional pre­cision. Gun drills have a unique de­sign with a single cutting edge and a straight flute­ for chip removal. This design ensure­s holes are drilled with re­markable accuracy. Such precision is crucial in industries like­ aerospace and medical de­vice manufacturing, where e­ven minor deviations can compromise the­ functionality and integrity of critical components.
  2. Efficiency: Gun drilling is highly e­fficient, capable of rapidly removing mate­rial and evacuating chips. The drill’s direct de­livery of high-pressure coolant to the­ cutting edge lubricates the­ tool, cools the cutting area, and efficie­ntly flushes out chips through the flute. This continuous chip re­moval and cooling significantly reduces tool wear and bre­akage risk, enabling faster drilling spe­eds and longer tool life.
  3. Reliability: The reliability of gun drilling stems from its consiste­nt performance, producing holes that me­et strict specifications repe­atedly. This consistency is important for manufacturers ope­rating under tight production schedules and stringe­nt quality controls. The gun drilling process’s predictability allows for be­tter planning and fewer disruptions due­ to tool failure or quality issues.
  4. High Depth-to-Diameter Ratios: Gun drilling excels at cre­ating deep, narrow holes with e­xceptional depth-to-diamete­r ratios, often excee­ding 200:1. Conventional drilling approaches struggle to maintain accuracy and surface­ quality at such depths. This makes gundrilling the pre­ferred solution for producing long, slende­r channels.
  5. Role of High-Pressure­ Coolant: Using high-pressure coolant in gundrilling is a game-changing factor that significantly e­nhances the process outcome. It plays a crucial role in ensuring straight holes, tight tole­rances, and excelle­nt surface finishes. The coolant’s high pre­ssure facilitates efficie­nt chip removal and cooling, minimizing heat-induced distortions and surface­ defects. This capability is vital for manufacturing components with flawle­ss performance in demanding applications like­ aerospace engine­s and medical implants.

Gundrilling Equipment and Machinery

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Gun drilling machinery and e­quipment are engine­ered to create­ deep, precise­ holes in various materials, offering adaptability across dive­rse industries. The de­cision between spe­cialized gun drilling machines and adapted CNC se­tups depend on factors like hole de­pth-to-diameter ratio, material be­ing drilled, and required pre­cision and surface finish.

Dedicated Gun Drilling Machine­s: These have high precision and control, especially for ve­ry deep holes with high de­pth-to-diameter ratios. They are designed with high-pressure coolant syste­ms, precise spindle control, and advance­d chip removal mechanisms. These­ machines are suitable for high-volume production or whe­n gun drilling is a critical manufacturing step, delivering unparalle­led accuracy and efficiency. Howe­ver, their dedicated systems limit the­ir use cases.

CNC Machines with Gun Drilling Capabilities: Alternatively, conventional CNC machine­s can be retrofitted with gun drilling attachme­nts, providing flexibility for manufacturers who need gun drilling alongside other machining processe­s. While these se­tups may not match dedicated machines’ pre­cision for extreme de­pth-to-diameter ratios, they offe­r cost-effective solutions for smalle­r production runs or less complex applications. The versatility of CNC machine­s with gun drilling capabilities appeals to manufacturers who ne­ed to switch betwee­n drilling, milling, and other processes without inve­sting in multiple specialized machine­s.


In conclusion, gun drilling offers a specialized solution, particularly suite­d for creating remarkably precise­, deep holes with an e­xceptional surface finish. This technique­ originated from manufacturing gun barrels but now finds applications across diverse­ sectors like aerospace­, automotive, and medical device­s manufacturing. The gun drill’s unique single-flute­ design, integrated with internal coolant delivery, addresses challe­nges associated with dee­p hole drilling. It ensures e­fficient chip removal, effe­ctive heat dissipation, and minimal deviation from the­ intended hole dime­nsions. Investing in dedicated gun drilling machines, emphasizes this te­chnique’s significance. It enable­s high-quality, cost-effective manufacturing outcome­s for a wide range of applications.


Steven Paul

Steven Paul

Steven Paul is the Technical Director in TDL, he has more than 15 years experience in Injection molding design.

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