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Knowledge of “deep hole drilling”

Processing characteristics of deep hole drilling:

1. The tool holder is limited by the aperture, the diameter is small, and the length is large, resulting in poor rigidity and low strength. It is easy to produce vibration, ripples, and taper when cutting, which affects the straightness and surface roughness of the deep hole.

2. During drilling and reaming, the cooling lubricating fluid is difficult to enter into the cutting area without a special device, which reduces the durability of the tool and makes chip removal difficult.

 

3. During the processing of deep holes, the cutting condition of the tool cannot be directly observed. You can only rely on work experience to listen to the sound of cutting, look at the chips, touch the vibration and workpiece temperature by hand, and observe the instruments (oil pressure gauge and electric meter) to determine whether the cutting process is normal.

4. Chip removal is difficult. Reliable means must be used to break the chips and control the length and shape of the chips to facilitate smooth removal and prevent chip clogging.

5. In order to ensure the smooth progress of deep holes in the processing process and achieve the required processing quality, the inner (outer) chip removal device of the tool, the tool guide and support device, and the high-pressure cooling and lubrication device should be added.

Generally, a hole with a depth of more than 5 times the aperture is called a deep hole. Its difficulty lies in chip removal and cooling. Holes with a relatively small hole depth can be drilled with twist drills. In order to remove chips smoothly, the iron shavings must be straight out in thin strips and bring out smaller fragments. At the same time, the coolant is easy to enter.

The grinding method of the drill bit can use a relatively simple grinding method:

1. The angle between the drilling edges is increased to 130-140 degrees to increase the chip thickness and change the direction of chip discharge (the direction of chip discharge is perpendicular to the edge)

2. Sharpen the horizontal edge to reduce the axial cutting tool. At the same time, the cutting edge is close to the drill core to produce an angle that is conducive to chip separation.

4. Pour a 45-degree angle of 1 mm at the outer angle of the edge to reduce wear and improve the finish.

5. The speed of drilling is slightly lower, and the amount of feed should be larger, so that the chips are thickened and discharged in strips.

6. The nozzle of the coolant should be facing the hole inward to facilitate the coolant to enter the cutting area.

Common Problems and Solutions Edit

Rough surface of the hole

1.Chip bonding: reduce the cutting speed; avoid chipping; switch to cutting fluid with high extreme pressure and improve filtration; increase the pressure and flow of cutting fluid.

2.Poor coaxiality: adjust the coaxiality of the machine tool spindle and the drill sleeve; use a suitable drill sleeve diameter.

3.The cutting speed is too low, the feed is too large or uneven: use the appropriate cutting amount.

4.Inappropriate tool geometry: 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; adopt a suitable drill sleeve diameter and replace the worn drill sleeve in time.

 

The drill bit is broken

1.The chip breaking is not good, and the chips cannot be discharged: change the size of the chip breaking groove to avoid being too long or too shallow; find the chipping edge in time and replace it; increase the pressure and flow of the cutting fluid; use a workpiece with uniform material organization.

2.The feed is too large, too small or uneven: use the appropriate cutting amount.

3.Excessive wear and tear of the drill bit: Replace the drill bit regularly to avoid excessive wear and tear.

4.Inappropriate cutting fluid: choose the right cutting fluid and improve the filtration situation.

Low drill life

1.The cutting speed is too high or too low, and the feed is too large: use the appropriate cutting amount.

2.The drill bit is not suitable: replace the tool material; change the position and shape of the guide block.

3.Inappropriate cutting fluid: switch to 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 breaking groove is not suitable; the geometry of the cutting edge is not suitable; the feed volume is too small; the material organization of the workpiece is not uniform: change the geometry of the chip breaking groove and the cutting edge; increase the feed volume; use a workpiece with uniform material organization.

Chip is too small: the chip breaking groove is too short or too deep; the radius of the chip breaking groove is too small: the geometry of the chip breaking groove is changed.

Excessive chip cutting: the chip breaking groove is too long or too shallow; the radius of the chip breaking groove is too large: the geometry of the chip breaking groove is changed.

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