Gun drilling, also known as deep hole drilling, is a technology for drilling holes that can be up to 200 times deeper than the diameter of the hole. It was initially developed to create standardized holes in armory and projectile weapons. It evolved over the past few decades and is now deemed helpful in a variety of industries.
It is different from other forms of drilling in that it produces holes in metal at high depth-to-diameter ratios of up to 200, compared to traditional drilling techniques that can only achieve a balance of 10:1.
Modern technology demands proper drilling, and this is where gun drilling comes in handy. This technology has broad applicability in a variety of industries. Gun barrels are the obvious; other sectors using them include; aerospace manufacturing, medical technology, hydraulic systems, combustion engines, and musical instruments.
How do they work?
Gun drilling machines are made up of a variety of components. These include a toughened tube drawn into a kidney shape having a tip. This tip has cooling holes that depend on its diameter. The outer edge of the drill is used during the opening cut.
The drilling oil is used both as a coolant and a lubricant during the cutting process. It is also used to expel the waste chips generated from the drilling process. It differs from BTA drilling due to its ability to remove the swarf and introduce a coolant.
Specifications for the gun drilling process
Diameters
1 – 3 mm drills are possible with proper equipment; 30–50 mm are common drills done by the machine. 50–75 mm is doable but less constructive compared to BTA drilling.
Gun Drilling D: d Ratios
5:1 are useful in common twist drills; 10:1 high-performance twist drills with a coolant 20:1 for special deep hole drilling tools with through-tool coolant; 100:1 tools must be on dedicated gun drilling machines; 200:1 gun drilling tools on high performing machinery.
Gun drills differ from typical drills by having a single straight cutting edge and a single hole for the coolant. Pressurized coolant is fed through the internal cavity, and chips are removed through the straight flute along the shaft.
Gun drills can also tolerate material hardness of up to 50Rc. To put this in context, tough steel metals are rated at 60 on the Rockwell hardness scale, which measures how a metal object is resistant to penetration and permanent transformation by another different material.
These gun drills also have an enormous scope of utility as both iron and non-iron materials can be drilled. Powder metals, plastics, and woods will work.
What is the depth limit to which a hole can be drilled using a gun drill? This depends on the precision required; holes with an accuracy of 3 to 5mm can be drilled. On the upper limits, holes deeper than 100 mm can be mined.
What are some of the Advantages of using gun drilling over other methods?
Well, with a single drill, gun drilling creates accurate, precise, and consistent holes. It is also suitable for sustaining clear round holes and straight channels. Gun drilling works in a high tolerance framework for deep holes that demand consistent and specific results.
Another underappreciated feature of gun drilling is that it eliminates further finishing, thanks to the pad.
To top it all, gun drilling is faster and cheaper compared to other methods. Gun drilling has an edge in the most crucial component of drilling; accuracy. Holes drilled by it are all the better in terms of size, finish, and straightness. This gives it an upper hand over other methods such as twist drilling.
Conclusion
Gun drilling machines are ideal for a range of depths and diameters. Their overall length usually defines them. Gun drilling is one of the best processes for creating precise holes. Holes can be drilled with a precision of up to .0005 inches.
Best accuracy is obtainable with counter-rotating work and drill. They can drill on any material with a maximum hardness of 50Rc. Their functioning is optimized on metals rated at 40Rc
