Deep hole processing is a difficult technology, which is mainly manifested in the large ratio of hole depth to diameter (generally ≥10), slender drill rod, poor rigidity, easy to 

produce deflection and vibration during operation, so the accuracy and surface quality of the hole are difficult to control; secondly, there are many chips and the chip 

removal channel is long. If the chip breaking is not good and the chip removal is not smooth, the drill bit may be damaged due to chip blockage, and the processing quality 

of the hole cannot be guaranteed; thirdly, the drill bit works in a nearly closed state, and the time is long, the heat is high and not easy to dissipate, and the drill bit is very 

easy to wear. In addition, due to the large ratio of hole depth to diameter (even up to 100 and above), the working condition of the drill bit cannot be observed during 

drilling, which makes deep hole processing difficult.

According to the above characteristics, deep hole drilling should have the following requirements:

1) Good chip breaking and smooth chip removal. At the same time, there must be a smooth chip removal channel, and the chips must be forced to be discharged with the 

help of a certain pressure of cutting fluid.

2) Good guidance to prevent drill bit deflection. In order to prevent the drill from deflecting and vibrating during operation, in addition to the drill itself needing a good 

guide device, the workpiece is rotated and the drill only performs linear feed motion to reduce the deflection of the drill during drilling.

3) Adequate cooling. The cutting fluid plays the role of cooling, lubrication, chip removal, vibration reduction and noise reduction during deep hole processing. Therefore, 

deep hole drilling must have a good cutting fluid channel. The cutting fluid used for deep hole processing must have good fluidity, and its viscosity should not be too large 

to accelerate the flow rate and flush the chips. The flow rate of the cutting fluid should not be less than 5 to 8 times the cutting speed, generally 480 to 720 m/min.

According to the above requirements for deep hole drilling, the new deep hole drills that are widely used at present mainly include single-edged external chip removal deep 

hole drills, internal chip removal deep hole drills, and ejector drills.