Deep hole drilling is a drill bit specially used for processing deep holes. It divides into two types: outer chip discharge and personal chip discharge. The gun drill is a typical external chip deep hole drill, and the BTA drill belongs to the inner chip deep hole drill. What are the advantages of BTA deep hole drilling, what are the precautions and common problems when using BTA deep hole drilling? This article takes you to find out.
Advantages of BTA deep hole drilling
BTA deep hole drilling is a typical structure of deep hole drilling with internal chip removal. It is a deep hole machining system (single tube drill) that supplies cooling oil from the outside and discharges iron chips from the inside. The BTA deep hole drill is suitable for drilling deep holes with a hole diameter of more than 6 mm and a ratio of hole depth to hole diameter of less than 100. Since iron chips discharged from the inside, no external chip flutes like a gun drill are needed, so no matter from processing efficiency or processing Quality must be excellent.
The table of the BTA deep hole drilling machine fixed so that drilling can perform regardless of the weight and shape of the workpiece. Especially suitable for the processing of heat exchanger tube sheets, marine engine parts, large molds, hydraulic devices, and parts for construction and chemical plants.
Compared with the gun drill, BTA deep hole drill has the following advantages:
- Drill bit and drill rod are easy to load and unload;
- The difficulty of chip removal reduced accordingly, making the BTA drilling system suitable for processing large diameter deep holes;
- Because the relative oil supply area of the BTA is much larger than that of the gun drill and the chip removal space is large, the pressure of the cooling system of the BTA drilling system reduced significantly;
- Under the premise that the drill bit diameter, drill rod length, and drill rod material are the same, the torsional rigidity of the BTA drill rod is about 2.4 times that of the gun drill rod, and the bending stiffness is much higher than that of the gun drill rod. The feed rate and the anti-vibration ability of the drill pipe are better than the gun drill, which is beneficial to improve the drilling efficiency and processing quality;
- The center of gravity of the drill rod coincides with the central axis, and the torsional strength and rigidity are more significant than the V-shaped drill rod of the gun drill. This advantage makes the BTA drill particularly suitable for deep hole drilling with “workpiece fixed and drill bit rotated”;
- Since the chips discharge from the inside of the drill pipe, the chips will not scratch the processed surface, and the treated surface has good quality.
Precautions for BTA deep hole machining
Because deep hole machining has different characteristics from ordinary hole machining, the following points should note when using BTA deep hole drilling:
- Deep hole machining can not directly observe the cutting situation, so you can only judge the condition of chip discharge by listening to the sound, looking at the chips, watching the load of the machine tool and the pressure of the cutting fluid.
- It is difficult to dissipate heat in deep hole machining, and a competent and reliable cutting heat cooling method must be adopted.
- It is challenging to arrange deep holes, such as chip clogging is very easy to damage, so the amount of cutting must be reasonably selected to ensure reliable chip breaking and smooth chip evacuation.
- The hole is prone to deflection during deep hole processing, so the guiding device and measures should consider when designing the structure of the liquid inlet.
- In the process of deep hole processing, the length of the drill rod, poor rigidity, and smooth vibration will directly affect the machining accuracy and production efficiency, so it is imperative to choose the cutting amount reasonably.
- Among the above problems, chip evacuation, guidance, and cooling are the most important. Solving these problems well can prolong life and improve processing efficiency.
Common problems and solutions of BTA deep hole machining
When processing deep holes in BTA, we often encounter the problems of rough drilling surface and broken drill bit. For these two problems, we can take corresponding countermeasures.
The surface roughness of BTA deep hole drilling
In general, there are several reasons for the roughness of the drilled surface:
- Cutting bond.
- Poor concentricity.
- Cutting speed is too low, the feed rate is too large or uneven.
- Tool geometry is not suitable.
- Reduce cutting speed, avoid chipping, replace with cutting fluid with high extreme pressure performance, and improve filtration, increase cutting fluid pressure and flow.
- Adjust the concentricity of the machine tool spindle and the drill sleeve, and use the appropriate diameter of the drill sleeve.
- Use the right amount of cutting.
The problem of a broken bit of BTA deep hole drill
In general, there are several reasons for the breakage of the drill bit:
- Chip breaking is not right, the chip can not be discharged.
- The feed rate is too large, too small, or uneven.
- Excessive bit wear.
- Cutting fluid is not suitable.
- Change the size of the chip breaker to avoid being too long or too shallow, and find and replace the chipping situation in time. Increase the pressure and flow of the cutting fluid, and use the material to organize the workpiece uniformly.
- Use the right amount of cutting.
- Replace the drill bit regularly to avoid wear.
- Use suitable cutting fluid and improve filtration.