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Different deep hole drilling systems

In deep hole drilling, a combination of tool design and cutting fluid pressure are used to flush the chips out of the hole. Three different drill systems are commonAll three systems can produce holes with excellent surfacefinish, close dimensional tolerance and concentricity.

The Ejector system

Is similar to STS, except that the drill is connected to an inner and outer tube. Cutting fluid is pumped down the drill between the two tubes, ie. entirely within the drill body rather than externally, and the chips are flushed back out through the inner one, also within the drill body. This self-contained system requires less fluid pressure thanthe STS system and can usually be installed in conventional machine tools without major reconstruction.

The single tube system or STS

High pressure pumps supply cutting fluid down the outside of the drill tube, between the drill and the drilled hole. The drill shank itself is hollow, and the fluid pressure flushes the chips into the drill body through chiprooms in the drill head, and back out through the drill tube.The high cutting fluid pressure makes the STS-system morereliable than the Ejector system especially when drilling materials where good chipbreaking is difficult to obtain i.e. low carbon steels and stainless.The STS-system is always the first choice for long series production.

The Gun drill system

The gun drill shank is hollow, and cutting fluid is pumped inside it down the length of the tube from an external supply, and forced out through holes in the cutting head. The drill shank has an exterior V-shaped groove or flute along its length, and the fluid pressure flushes the cut chips back along this groove, along the outside of the drill, and so out of the hole. The gun drill can be applied to a conventional machining centre, but high cutting fluid pressure is required.For more information about the systems see Applicationguide page 118.
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