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Presently direct material deep-hole machining systems in common use classified by cutter system mainly include: Gun drilling system, BTA single-tube drill system and ejector drilling system. They represent the advanced, efficient hole processing technology. So, good precision effect can be achieved just through one-time feeding, and the machined hole position is accurate and precisely sized, having high straightness and coaxiality as well as very good surface smoothness and repeatability; various deep holes can be machined easily. Special deep holes such as cross holes, inclined holes, blind holes and flat-base blind holes can be solved very well.
In deep-hole drilling, combination of any cutter structure, cutting fluid pressure and flow aims for removing cutting chips from the hole in a better way. Viewed from machining principle and practice, any cutter system can drill out holes of excellent surface quality, small tolerance and good concentricity. Three common deep-hole drilling systems are introduced as follows.
BTA single-tube drilling system adopts external cooling and internal chip removing method; cutting fluid enters from between the external drill stem wall and machined work piece surface through oil disperser, reaching the cutter end for cooling and lubricating as well as pushing out cutting chips from inside the drill stem. Besides functioning as a guide, oil disperser can also provide a passage for feeding oil to cutting area; this system is widely used; however, as limited by the chip-removing space inside the drill stem bore, it is mainly used for deep-hole machining of diameter over Ф12mm. Compared with ejector drill, the high cutting fluid pressure makes single-tube drilling system more reliable, especially when drilling materials whose cutting chips are hard to break (such as low-carbon steel and stainless steel etc). Among GSM series machine types, ZK21D is BTA single-tube drill machine.
