GUNDRILL Type and structure


 1. Types and structures of gun drills


Generally speaking, the current types of gun drills mainly include brazedcarbide gun drills, solid carbide gun drills, indexable gun drills and mosaic gun drills.


1.brazed carbide gun drill  

brazed carbide gun drills are currently the most commonly used gun drills, which include three parts: a carbide head, a drill rod, and a drill handle (as shown in the figure below). The cutter head is made of tungsten carbide after sintering and grinding. The cutter head is brazed with the heat-treated drill pipe as a whole.

For example, the gun drill of KBD Company belongs to this kind of gun drill, and the diameter of the drill bit is from Ф 3 mm to 50 mm.


2. Solid carbide gun drill

 The cutter head and the drill pipe of the solid carbide gun drill are made of carbide alloy as a whole, and the cemented carbide drill pipe and the steel drill shank are brazed together (as shown in the figure below). The solid carbide gun drill has higher rigidity and lower torsional vibration, which not only improves the cutting reliability, but also improves the service life of the tool, but the price is more expensive.

At present, the solid carbide gun drills on the market are none other than KBD in terms of technical quality and minimum diameter. KBD company's solid carbide gun drill has a minimum diameter of Ф 1mm

3. indexable gun drill


The overall structure of the indexable gun drill is the same as the ordinary gun drill, except that the cutter head is partially assembled, the cutter head body is made of tool steel, the cutting edge is made of replaceable carbide insert, and the guide part is made of carbide guide blocks. The set screw assembles the whole cutter head together (see the figure below for the structure). indexable gun drills are generally suitable for holes with a diameter of 10 mm -60mm

The clip-on gun drill adopts indexable inserts, which can be quickly indexed or replaced after the tool is worn out, which is convenient and quick. The indexable insert has a chip splitting edge and a chip breaker, which reduces the chip force and produces smaller chips, making chip removal more stable and smooth, more suitable for high-speed cutting, and improving processing efficiency. In addition, for different workpiece materials, indexable inserts and guide strips with different coatings can be used, which can improve the wear resistance and tool life of the tool and improve the roughness of the processed surface.

KBD machine gun drill is suitable for indexable type range Ф 10 - 60 mm, customers can choose according to the needs of different working conditions.

According to our actual processing experience, the feeding efficiency of the 01 machine-added gun drill is increased by more than 40% compared with the ordinary gun drill.


4. Inlaid welding gun drill


When the diameter is more than 6mm, the gun drill head can also adopt the welded structure as shown in the figure below, that is, the body of the cutter head is made of alloy tool steel, but the cutting edge and the guide strip are welded with hard alloy to save hard alloy materials. . Or gun drills with PCD or CBN inserts for the cutting edge processed by aluminum alloy, graphite and other materials.

When the PCD gun drill is processing aluminum alloy, it produces debris and iron filings. The cutting axial force and torque are lower than those of ordinary gun drills. The tool wear resistance is strong, and the service life is as long as 4000m. The hole length greatly saves tool replacement and grinding, and improves the efficiency Machine efficiency.

2. Calculation of gun drilling tool length


The gun drill is a non-standard tool. Since the holes processed by customers are different and the machine tools used are different, the length of the gun drill required is also different. Generally, when the processing depth can be satisfied, the shorter the length, the higher the rigidity of the gun drill and the higher the stability of the drilling, which is beneficial to ensure the accuracy of the hole. The length of the gun drill is an important parameter when purchasing the gun drill.

When drilling with a pre-drilled pilot hole and without a drill pipe support device, generally the maximum depth-to-diameter ratio does not exceed 30-40 times. When ordering, the gun drill length should be as shown in the figure:

Total length of gun drill = regrindable length + drilling depth + chip removal zone length + shank length

When the special deep hole drilling machine is used for gun drilling, it is equipped with a guide chip removal device, and the hole processing with a depth-to-diameter ratio of 30-40 times deeper also needs to be equipped with a drill pipe support device (as shown in the figure below).


*Note: L1=gun drill regrindable length; L2=drilling depth; L3=gun drill guide chip removal box width; L4=reserved margin; L5=drill shank length; L6=drill pipe cylindrical part length; L7 = Drill pipe support width

3. The geometric structure and angle of the gun drill head



1. Analysis of gun drilling cutting process


The gun drill is single-edged cutting, and the cutting edge composed of inner and outer edges is subjected to cutting resistance in the diameter direction during the cutting process, which can only be offset by the guide strip part of the cutter head distributed on the outer circular contour surface.

When the drill bit starts drilling, it needs a guide drill sleeve or a guide hole to support the guide part of the cutter head. After drilling into the hole, the tool head is guided by the machined bore surface support.

Therefore, there will be extrusion and friction between the guide strip of the cutter head and the guide drill sleeve or the wall of the processed inner hole, and sufficient coolant lubrication is necessary (as shown in the figure below).


2. The end structure of the gun drill head

 The cutter head is the part for drilling and cutting. Its geometric structure is as shown in the figure below. The end mainly passes through five surfaces (namely, the first relief surface, the second relief surface, the tool nose relief surface, and the inner edge relief surface) , over the oil surface) and cylindrical surface chamfering, forming the end structure of the gun drill's outer cutting edge, inner cutting, drill tip and so on. The side cutting edge of the gun drill plays a role in smoothing the hole wall during machining, so re-sharpening does not need to be considered.


3. Outline structure of gun drill head


The contour structure of the outer circle of the cutter head reflects the distribution of the guide strips. The figure below is the profile structure type of KBD gun drill head.

G type is the most general profile structure for gun drill outer circle, suitable for almost all workpiece materials and processing occasions.

If there is no requirement or specification, the gun drill generally adopts the G-shaped profile.

of the gun drill


In daily production and processing, deep hole processing is required in different processing occasions.

The following is the tool grinding angle of the botek gun drill in normal processing. Please refer to the figure below. If you have special processing requirements and materials to be processed, please contact KBD .

If you have any questions about deep holes, please contact us.



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