Processing characteristics of deep hole drilling:
1. The tool holder is limited by the diameter of the hole. Small diameter and long length result in poor rigidity and low strength. It is prone to vibration, ripples and tapers during cutting, which affects the straightness and surface roughness of deep holes.
2. When drilling and reaming, it is difficult for the cooling and lubricating fluid to enter the cutting area without using special devices, which reduces the durability of the tool and makes it difficult to remove chips.
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3. In the process of deep hole processing, the cutting condition of the tool cannot be directly observed. It can only be judged by listening to the sound of cutting, watching chips, hand-touch vibration and workpiece temperature, and observing instruments (oil pressure gauge and electric meter) based on work experience. Whether the cutting process is normal.
4. It is difficult to remove chips. Reliable means must be used to break chips and control the length and shape of chips, so as to facilitate smooth removal and prevent chip clogging.
5. In order to ensure the smooth progress of the deep hole during the processing and to achieve the required processing quality, the chip removal device inside (outside) the tool, the tool guiding and supporting device and the high-pressure cooling and lubricating device should be added.
Generally, the depth of the hole is more than 5 times the diameter of the hole, which is called a deep hole. Its difficulty lies in chip removal and cooling. The hole with a relatively small drilling depth can be drilled with a twist drill. and bring out smaller debris while allowing easy access for coolant.
The grinding method of the drill bit can adopt a relatively simple grinding method:
1. Increase the included angle of the drill edge to 130-140 degrees to increase chip thickness and change the direction of chip discharge (the direction of chip discharge is perpendicular to the cutting edge)
2. Grind the chisel edge to reduce the axial cutting tool, and at the same time, the cutting edge forms a corner near the drill core, which is beneficial for chip separation.
4. Invert the outer corner of the cutting edge by 1mm and 45 degrees to reduce wear and improve the finish.
5. The drilling speed should be slightly lower, and the feed rate should be larger, so that the thickened chips are discharged in strips.
6. The nozzle of the coolant should face the hole inward so that the coolant can enter the cutting area.
Common problems and solutions[edit]
rough hole surface
1. Chip bonding: reduce cutting speed; avoid edge chipping; replace with cutting fluid with high extreme pressure and improve filtration; increase pressure and flow of cutting fluid.
2. The coaxiality is not good: adjust the coaxiality of the machine tool spindle and the drill sleeve; use a suitable diameter of the drill sleeve.
3. The cutting speed is too low, the feed rate is too large or uneven: use the appropriate cutting amount.
4. The geometry of the tool is not suitable: change the geometric angle of the cutting edge and the shape of the guide block
The orifice is flared
Poor coaxiality: adjust the coaxiality of the machine tool spindle, drill sleeve and support sleeve; use a suitable drill sleeve diameter, and replace the excessively worn drill sleeve in time.
drill bit broken
1. The chip breaking is not good, and the chips cannot be discharged: change the size of the chip breaker to avoid being too long and too shallow; find out the chipping situation in time and replace it; increase the pressure and flow of cutting fluid; use workpieces with uniform material structure .
2. The feed rate is too large, too small or uneven: use an appropriate cutting rate.
3. Excessive wear of the drill bit: replace the drill bit regularly to avoid excessive wear.
4. The cutting fluid is not suitable: choose a suitable cutting fluid and improve the filtration.
Low bit life
1. The cutting speed is too high or too low, and the feed rate is too large: use an appropriate cutting amount.
2. The drill bit is not suitable: change the tool material; change the position and shape of the guide block.
3. The cutting fluid is not suitable: use a cutting fluid with high extreme pressure; increase the pressure and flow of the cutting fluid; improve the filtration of the cutting fluid.
other
The chips are banded: the geometry of the chip breaker is not suitable; the geometry of the cutting edge is not suitable; the feed rate is too small; the material structure of the workpiece is uneven: change the geometry of the chip breaker and cutting edge; increase the feed rate; use A workpiece with a uniform material structure.
The chip is too small: the chip breaker is too short or too deep; the radius of the chip breaker is too small: change the geometry of the chip breaker.
Too large chips: Chipbreaker is too long or too shallow; Chipbreaker radius is too large: Change the geometry of the chipbreaker
