Double-tube(ejector) drilling system in deep hole drilling processing

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.

Ejector drilling system is a deep-hole drilling system adopting external cooling and internal chip removing; cutting fluid enters from the upper oil-filling mouth of the coupler, most of the fluid goes forward into the ring space between the internal and external drill stems, reaching the cutter end for cooling and lubricating; it pushes cutting chips into the internal chamber of the internal drill stem and then removes them out; a small amount of cutting fluid, by utilizing injection effect of fluid mechanics, is injected to the rear part of the internal drill stem at high speed from the upper crescent nozzle on the internal drill stem, forming a low-pressure area in the chamber of internal drill stem, sucking back the cutting fluid and chips generated in the cutting area, pushing cutting chips to the outside quickly under double forces of sucking and pushing. Compared with BTA system, this relatively independently system needs lower cutting fluid pressure and reduces the requirements for drilling system sealing. For the sake of internal tube, ejector drill has a limited min diameter scope normally no less than Ф18mm. Among GSM series machine types, ZK21S is a double-tube ejector drill machine.