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BTA drilling Process

SingleTube System STS

BTA stands for Boring and Trepanning Association which developed this deep hole drilling system. It involves a single drill tube in which high pressure coolant is supplied to the drill through the annular area between the drilled hole and the tube outer diameter. The chips are evacuated through the I.D. of the tube. The drill head is screwed to this drill tube which is much stronger compared to the kidney shaped shank of a gun drill, hence much higher metal removal rates are possible. This involves the use of a Pressure head which is basically a high pressure seal between the workpiece and the drill bush. BTA/STS drilling is generally used for ф19 and above.
Since the chip removal is internal, no v shaped groove is required in the shank, so its cross-section is completely round and this provides more rigidity to the entire system. BTA drilling finds its application in Industries like Oil & Gas, Defence, Steel, Aircraft, Aerospace, Hydraulic Cylinders, and Power etc. For larger diameter deep hole drilling, BTA drilling is the only available option which provides high productivity and precision.
Another system which evolved from BTA single tube system is the Ejector drilling system. It is a system with twin tubes where the coolant is pumped through the space between the inner and outer tube. This eliminates the use of Pressure head and simplifies the system. This was introduced mainly to tool up conventional machines to do Deep hole Drilling.

Profimach® STS Deep Holes drilling Machines

High quality affordable deep hole machines

These high precision deep hole BTA drilling machines (STS: Single Tube System) have been specially developed and improved in recent years. All essential castings are made of high grade of cast iron that is stress relieved through annealing to eliminate internal stress. With the greatest stiffness and stability of the castings, these machines are suitable for precision deep hole working.

These deep hole BTA machines are offered with twofull-year limited warranty .

BTA: Single Tube Systems - STS

The single tube system STS or sometimes referred to as the “BTA” system of drilling, is the reverse of a gun drilling system.  Unlike the gun drill, the STS or “BTA” drilling system assembly consists of a drill head that is attached to a ground cylindrical tube. This is by either an internal or external fast lead thread.  The drill tube or boring bar is smaller in diameter than the drill head which forms an annular space between the hole being drilled and the OD of the drill tube or boring bar.  This space is known as “oil room” and in conjunction with a coolant induction unit or a pressure head. In addition, it makes it possible to direct filtered high volume coolant to the drill head cutting edge.

Single Tube Systems Features

This pressure head seals against the entry side of the part to be drilled. Also, this directs the coolant to the detachable drill head.  The coolant provides lubrication for the drill head and assures that all of the chips produced by the drill head are directed through the detachable cutting head are flushed internally through the ID of a cylindrical hollow drill tube or boring bar.  This is better known as an external coolant supply / internal (ID) chip exhaust method of drilling.

The STS / BTA system supports tools ranging from 12 mm – 850mm diameter. These tools and this system allow depth to diameter ratios in excess of 100 x’s dia. In most cases, the STS / BTA system is set up on dedicated deep hole drilling machines. This system is the best choice for extremely deep bores. And, for materials with poor chip forming properties such as stainless steel, Titanium, and low carbon steel.

BTA deep hole drilling is a process that accurately drills holes from 20 – 1250 mm in diameter with higher feed rates.

BTA drilling is a deep hole drilling process that uses a specialized drilling tool on a long drill tube to produce deep holes in metal, from holes with a diameter of 20 mm and larger, up to depth-to-diameter ratios of 400:1. BTA drilling is the most effective method of drilling deep holes, as it is a cleaner, more reliable and capable process than conventional twist drills, and can achieve larger diameters and higher feed rates than the alternative gundrilling.

BTA drilling tool heads are threaded or mounted onto long drill tubes, and use multiple cutting surfaces on a single tool to remove chips efficiently, exhausting them using high-pressure coolant through holes in the tool head, then out the drill tube and through the machining spindle. 

BTA stands for Boring and Trepanning Association, and is also sometimes referred to as STS (single tube system) drilling, as it uses one single drill tube for the BTA tool, compared to other processes such as ejector drilling, which use two.

Ejector Drilling Process

Ejector Drilling is similar to BTA Drilling operation with the difference that it has Twin tubes instead of a single tube.  The high pressure Coolant is pumped to the cutting face through the annular area between the outer tube and the inner tube. There is a special connector for holding both the tubes and also to feed the high pressure coolant.The pressure head with rear coolant sealing that is required in BTA drilling is eliminated here and only a guide bush is needed.  The Chips generated are evacuated through the inner tube where ejection effect is generated at the rear end to help in chip evacuation.  The area for chip discharge is comparatively less than BTA and hence the evacuation is not as efficient particularly in smaller sizes.  Since the tube diameter is larger than BTA Drilling the torsional strength also goes up. This can be an advantage to go for higher feeds. This is usually used to retrofit conventional machines for deep hole drilling.


EJECTOR DRILLING can be build on our standard BTA drilling machines!


BTA Drilling vs Gun Drilling

BTA drilling can achieve drill feed rates of typically 5-7 times faster than gundrilling

BTA drilling can achieve drill feed rates of typically 5-7 times faster than gundrilling at the same diameter, due to the tool design, more efficient chip exhaust, and machine design and power. BTA drilling machines introduce coolant around the tool head, and evacuate chips through the drill and machine spindle, compared to gundrilling, where coolant is introduced internally and chips exit through an external groove. BTA boring/drilling is VERY effective in holes from 20 – 350 mm (till 1200 mm we will use trepanning tools), a greater size range than gundrilling.

BTA drilling machines

BTA deep hole drilling machines PDHB-100 Series

Boring diameter till 100 mm

BTA deep hole drilling machines PDHB-160 Series

Boring diameter till 160 mm

BTA deep hole drilling machines PDHB-200 Series

Boring diameter till 200 mm

BTA deep hole drilling machines PDHB-360 Series

Boring diameter till 360 mm

BTA deep hole drilling machines PDHB-500 Series

Boring diameter till 500 mm

BTA deep hole drilling machines PDHB-800 Series

Boring diameter till 800 mm

BTA deep hole drilling machines PDHB-1000 Series

Boring diameter till 1000 mm

BTA deep hole drilling machines PDHB-1200 Series

Boring diameter till 1200 mm

The Art of Deep Hole Drilling - The Art of Deep Hole Boring