Flat drill is a simple structure, easy to manufacture processing tool. With the emergence of some new tool materials and the use of the new tool structure, flat drill can be used for deep processing.
　　(1) applies only to an aspect ratio of less than 10 deep.
　　(2) generally applies to the processing of larger diameter aperture (ie diameter of 20-30mm), the greater the diameter of the economy.
　　(3) use machine folder knife block structure, wide adjustment range, easy to use.
　　(4) applies only to horizontal deep hole drilling.
　　(5) The internal cooling structure, cooling fluid can flow directly into the cutting area, cooling and chip discharge push outward.
　　(6) is not stable drilling, processing quality, and is generally used for roughing.