Introduction To The Classification, Working Principle, And Application Scope Of Deep Hole Drilling Machines

In modern society, to efficiently and economically produce various high-quality products, people will use multiple machines, instruments, tools, and other technical equipment. Different equipment for processing metal parts must manufacture this specialized equipment, such as casting, forging, welding, stamping, and cutting equipment.

The shape and size of mechanical parts mainly process by cutting. Features with complex conditions, high precision requirements, and small surface roughness requirements often require several or even dozens of cutting processes on the machine tool. Therefore, machine tools are the most critical processing equipment in modern machinery manufacturing.

The deep hole drilling machine is different from the traditional hole processing method. It mainly relies on specific drilling technology (such as a gun drill, BTA drill, ejector drill, etc.) to drill deep holes and precision shallow holes with an aspect ratio greater than 10 Processing.

bta deep hole drilling machine
bta deep hole drilling machine

Deep hole drilling machine represents advanced and efficient hole processing technology, processing with high precision, high efficiency, and increased consistency. The precise machining effect can obtain through one pass. The machined hole’s position is accurate, the dimensional accuracy is good, the straightness and coaxiality are high, and the surface finish and repeatability are high.

The deep hole drilling machine can conveniently process various forms of deep holes, and it can also solve the particular conditions of deep holes, such as cross holes, inclined holes, blind holes, and flat-bottom blind holes.

The deep hole drilling machine can process deep holes with a large aspect ratio (up to 300 times) and process precision shallow holes, with the smallest drilling hole diameter up to 0.7mm. Deep hole drilling machines occupy a critical position in mechanical processing, accounting for more than 40% of the hole processing volume.

With the advancement of science and technology, new types of high-strength, high-hardness, and high-value difficult-to-machine deep-hole parts continue to appear. The processing depth requirements, processing accuracy, and processing efficiency of processed workpieces continue to increase, making deep-hole processing the key to machining Process and processing difficulties.

Due to the rigidity of the processing system, the problems of cutting discharge and cooling and lubrication, traditional machining methods are becoming challenging to meet or even fail to meet the current, in-depth hole machining requirements precision, efficiency, and materials. Therefore, deep hole processing requires the support of specific drilling technology.

First of all, let’s take a look at the classification of deep hole drilling machines. Different categories have different functions.

  1. According to the layout of the spindle, it can be divided into deep horizontal hole drilling machines, deep vertical hole drilling machines, and three deep coordinate hole drilling machines;
  2. According to the current commonly used deep hole drilling processing systems, there are mainly gun drilling machines, BTA single tube drilling machines, and spray drilling machines;
  3. Classification according to the movement form: workpiece rotates, the tool does feed movement, the workpiece does not move, the device rotates and then feeds; the workpiece rotates, the tool rotates in reverse to do the feed movement. (The characteristics of the workpiece and the machining hole situation determine which method is used.)
  4. Classified by chip removal method: cutting fluid passes through the hollow drill rod, reaches the head of the drill bit for cooling and lubrication, and discharges the chips from the drill bit and the V-groove outside the drill rod (such as gun drills);

The cutting fluid enters between the drill pipe’s outer wall and the workpiece’s surface, reaches the tool head for cooling and lubrication, and pushes the chips out of the drill pipe (such as BTA drills).

Let’s take a look at the working principle and application range of deep-hole drilling machines.

1. Gun Drill System

The gun drilling system mainly uses to drill small diameter (generally less than 35mm) deep holes, and the required cutting fluid pressure is high. This is the most common method of deep hole drilling.

The gun drilling system belongs to the internal cooling and external chip removal method. The cutting fluid passes through the hollow drill pipe, reaches the drill head for cooling and lubrication, and discharges the chips from the drill bit and the V-shaped groove outside the drill pipe. This method is suitable for small and medium batch hole processing.

2. Bta Single Tube Drilling System

The BTA single tube drilling system is an external cooling and internal chip removal method. The cutting fluid enters between the drill pipe’s outer wall and the machined surface of the workpiece through the oil applicator, reaches the tool head for cooling and lubrication, and pushes the chips out of the drill pipe. In addition to its guiding function, the oil applicator also provides a channel for oil delivery to the cutting area.

This system is widely used but limited by the chip removal space of the drill rod. It mainly uses for deep hole drilling with a diameter of ¢﹥12mm.

Compared with jet drilling, the high cutting fluid pressure makes the single-tube drilling system more reliable, incredibly when drilling materials difficult to break (such as low carbon steel and stainless steel). Compared with jet suction drilling, the BTA single tube drilling system is the first choice for continuous processing of large batches and high loads.

3. Ejector Drilling System

The ejector drilling system belongs to deep hole drilling with internal chip removal. The cutting fluid enters from the oil delivery port on the coupling. Most of the cutting fluid enters the annular space between the inner and outer drill rods forward, reaches the tool head for cooling and lubrication, and pushes the chips into the inner drill rod’s internal cavity to discharge backward. Also, a small part of the cutting fluid utilizes the jet effect of fluid mechanics. The crescent-shaped nozzle on the inner drill rod is sprayed into the rear of the inner drill rod at high speed, forming a low-pressure zone in the drill rod’s internal cavity to discharge the cutting fluid from the cutting area. The chips produce backward suction, and under the double action of pushing and suction, the chips promptly release outward.

This relatively independent system requires lower cutting fluid pressure than the BTA system while also reducing the drilling system’s sealing requirements. Due to the inner tube, jet suction drilling’s minimum diameter range is limited, generally not less than ¢18mm.

The above is an introduction to the working principle and application range of deep hole drilling machines. We must pay attention to safety when applying deep-hole drilling machines. Deep hole processing is in a closed or semi-closed state, and the cutting situation of the tool cannot directly observe.

At present, the operator can only judge whether the cutting process is normal by listening to the sound, watching the cutting, observing the machine load and pressure gauge’s appearance, and touching vibration. It cannot take teste under the condition of mechanical work.

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