Gun drill – the main body of deep hole processing technology

Introduction of carbide gun drill

The gun drill can not only be used to process deep holes (L / D ratio > 10), but also can be used to process precision shallow holes. Gun drill generally consists of drill stem, drill pipe and drill bit. There is a through hole in the middle of the gun drill, which is the channel for cutting fluid to enter the cutting area.

Drill is the key part of gun drill. The material is cemented carbide. Its unique and scientific combination structure ensures that it can complete the cutting work and also play the role of self guiding. It can get a high-precision deep hole through one time.

The drill shank transmits torque between the machine tool and the drill bit, and seals high-pressure oil. The high rotary accuracy between the drill stem and the drill pipe can avoid the extra vibration and improve the machining accuracy and reliability. There are smooth arc grooves to eliminate stress in the neck where the drill handle is connected with the cutter rod to avoid damage due to stress concentration.

The drill pipe is made of high quality alloy steel by rolling, heat treatment, straightening and other processes. The drill pipe rolled 118 °～ one hundred and twenty ° V-shaped groove for chip removal.
In order to ensure the straightness and deviation of the drilling hole, the drill pipe must have enough strength to provide the torque required for cutting under the condition of small torsional deformation. At the same time, the blade body must be resilient enough to absorb the vibration caused by the high-speed rotation of the blade. Therefore, the material selection, heat treatment and rolling process of drill pipe are very strict.

The drill has two basic angles, the outer angle and the inner angle. The most appropriate combination can be selected according to the material and aperture of the workpiece to be cut, so as to better balance the cutting force and chip breaking in the work, and transfer the cutting force to the support shoulder to ensure good straightness and coaxiality.
The bit has a very small inverted cone with a slightly larger diameter than the tool holder. The drill pipe can rotate freely in the cutting hole without rubbing the inner wall of the hole.

Use of gun drill
Gun drill processing is forced chip removal. The high-pressure cutting oil enters the bore of gun drill from the drill shank and reaches the cutting area to cool and lubricate the drill edge. The iron chips and cutting oil are discharged along the “V” groove of the drill pipe. Also known as the external discharge chip.
The material range of gun drilling is very wide. From glass fiber, Teflon and other plastics to carbon steel, alloy steel, non-ferrous metals and then to high strength alloy steel (such as high temperature heat resistant alloy, titanium alloy), it can be used for deep hole processing. Due to its excellent hole processing performance, gun drill is widely used in shipbuilding, automobile, engine, locomotive, military industry, chemical machinery, nozzle oil pump, mining machinery, hydraulic parts and other industries.Machining accuracy of gun drill

The following processing effects can be achieved by using suitable deep hole processing machine tools and cutting parameters

Aperture size: it6-it611

Inner hole roughness: ra0.2-ra6.3

Skewness: 1 / 1000 × The depth of the hole is fixed and the tool rotates

0.5/1000 × The depth of the hole, workpiece rotation, tool reverse rotation

Processing efficiency of gun drill
Because of the special tool structure of gun drill, in deep hole processing, there is no need to remove the chip, once processing to the depth. The deeper the hole is, the more efficient the machining is. According to the different materials and aperture, the processing speed can reach more than 30-100 mm / min.

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