Difficulties in deep hole machining
(1) The cutting condition can not be observed directly. The chip removal and bit wear can be judged only by listening to the sound, looking at the chip, observing the machine load, oil pressure and other parameters.
(2) Cutting heat is not easy to spread out.
(3) It is difficult to remove chip, and the bit will be damaged if it is blocked.
(4) Because of the long length, poor rigidity and easy vibration of drill pipe, the hole axis is easy to deflect, which affects the machining accuracy and production efficiency.
Matters needing attention in deep hole processing
(1) Key points of deep hole processing operation: the coaxiality of the center line of the spindle and tool guide sleeve, tool bar support sleeve, workpiece support sleeve should meet the requirements; the cutting fluid system should be smooth and normal; there should be no central hole on the processing end face of the workpiece, and drilling on the inclined plane should be avoided; the chip shape should be normal to avoid the formation of straight band chip; the through-hole should be processed at a higher speed when the drill bit is ready When drilling through, the drilling speed should be reduced or shut down to prevent damage to the bit.
(2) Cutting fluid for deep hole machining: a large amount of cutting heat will be generated in the process of deep hole machining, which is not easy to diffuse, and sufficient cutting fluid is needed to lubricate and cool the tool. Generally, 1:100 emulsion or extreme pressure emulsion is selected; when higher machining precision and surface quality or toughness materials are required, extreme pressure emulsion or high concentration extreme pressure emulsion is selected. The kinematic viscosity of cutting oil is usually (40 ℃) 10 ~ 20cm2 / s, and the cutting fluid flow rate is 15 ~ Cutting oil with low viscosity should be selected when machining diameter is small; cutting oil with 40% extreme pressure sulfurized oil + 40% kerosene + 20% chlorinated paraffin can be selected for deep hole machining with high precision.
(3) Precautions for using deep hole drill:
A. The end face of the workpiece is perpendicular to the axis line of the workpiece to ensure the reliable sealing of the end face.
B. A shallow hole is pre drilled on the hole position of the workpiece before the formal machining, which can play a guiding and centering role during the pilot drilling.
C. In order to ensure the service life of the tool, it is better to adopt automatic tool feeding.
D. If the guide elements in the liquid feeder and movable center support are worn, they should be replaced in time to avoid affecting the drilling accuracy.