CNC Knowledge: Do you really understand “deep drilling”?

Processing characteristics of deep hole drilling:

1. The tool holder is limited by the opening, with a small diameter and a large length, resulting in poor rigidity and low strength. It is prone to vibration, ripple and cone during cutting, which affects the straightness and roughness of the surface of deep holes.

2. When drilling and reaming holes, it is difficult for the cooling lubricant to enter the cutting area without using special devices, which reduces the durability of the tool and makes the removal of difficult chips.

3. During deep hole processing, you cannot directly observe the cutting conditions of the tool. You can only judge based on your work experience by listening to the sound while cutting, looking at the chips, touching the vibration and temperature of the workpiece, and. by observing the instruments (oil pressure gauge and electric meter). Is the cutting process normal?

4. It is difficult to remove chips. Reliable means should be used to break up chips and control chip length and shape to facilitate smooth removal and avoid chip clogging.

5. In order to ensure the smooth running of deep holes during processing and achieve the required processing quality, internal (external) chip removal devices, tool guiding and supporting devices and devices Cooling and high pressure lubrication should be added to the tool.

Generally, a hole with a depth greater than 5 times the diameter of the hole is called a deep hole. The difficulty lies in chip removal and cooling. For holes with a relatively shallow drilling depth, twist drills can be used to remove chips. chips smoothly, the iron filings should come out in thin strips and bring out small debris, while the coolant can easily penetrate.

The drill bit can be ground using a relatively simple grinding method:

1. Increase the angle of the drill blade to 130-140 degrees to increase the chip thickness and change the chip discharge direction (the chip discharge direction is perpendicular to the cutting edge).

2. Grind the edge of the chisel to reduce the axial cutting edge while creating an angle where the cutting edge is close to the sprue to facilitate chip separation.

4. 1mm camel at a 45 degree angle on the outer corner of the cutting edge to reduce wear and improve smoothness.

5. The drilling speed should be slightly lower and the feeding quantity should be larger, so that the chips are thickened and discharged in strips.

6. The coolant nozzle should face the hole inward to facilitate coolant entry into the cutting area.

Frequently asked questions and solutions

Rough hole surface

1. Chip adhesion: reduce the cutting speed; avoid edge chipping; Switch to extreme high pressure cutting fluid and improve filtration, increase cutting fluid pressure and flow;

2. Poor coaxiality: Adjust the coaxiality between the machine tool spindle and the drill bush; use an appropriate drill sleeve diameter;

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

4. Bad tool geometry: change the geometric angle of the cutting edge and the shape of the guide block

Flared port

Poor coaxiality: Adjust the coaxiality of the machine tool spindle, drilling bush and support bush; use a suitable drill bush diameter and replace excessively worn drill bushes in a timely manner.

Broken drill bit

1. The chip breaking is not good and the chips cannot be discharged: change the size of the chip breaker to avoid it being too long or too shallow; detect chips in time and replace it by cutting fluid pressure and flow; with a uniform material structure.

2. Feed amount is too large, too small or uneven: Use appropriate cutting amount.

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

4. Inappropriate cutting fluid: Choose the appropriate cutting fluid and improve filtration.

Drill life is short

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

2. The drill bit is inappropriate: change the tool material; change the position and shape of the guide block.

3. The cutting fluid is inappropriate: replace with extreme high pressure cutting fluid; increase the pressure and flow of the cutting fluid; improve filtration of cutting fluid;

other

The chips are in strips: the geometry of the chipbreaker is inappropriate; the geometry of the cutting edge is inappropriate; the advance is too small; the structure of the workpiece material is uneven: modify the geometry of the chipbreaker and increase the feed; .

The chips are too small: the chipbreaker is too short or too deep; the radius of the chipbreaker is too small: modify the geometry of the chipbreaker.

Chips too large: the chipbreaker is too long or too shallow; the radius of the chipbreaker is too large: modify the geometry of the chipbreaker.