The structure of three combined blades used in the cutting edge, unequal division of tooth pitch Special cemented carbide blades are constant “EST “The three combined blades of unique technology are composed of several external edges, middle edges and internal edges. Each blade only takes about 1/3 of the workload in the cutting process. In addition, there are cutting tools on the inner side of each blade. Therefore, chip removal can be very smooth. In addition, because each blade bears part of the cutting work, it is not easy for the hole drill to collapse. The hollow drill can carry out high-precision and high-speed cutting on thick steel plates Cross overlapping holes can also be drilled through the hole. The structure of three combined blades, the unequal division of tooth pitch, and the special cemented carbide blades used in the edge are the crystallization of unique technologies, which make it difficult for the hole drill pole to produce blade breakage. The hollow drill, together with the machine specially equipped with the coring bit, has the characteristics of high efficiency and low cost. The hollow drill bit edge is made of cemented carbide, has three layers of end tooth geometry, and is easy to cut, The steel plate drill has a long service life and a double cut flat handle interface, which is suitable for imported magnetic drill rigs such as FEIN from Germany. Carbide drills are also suitable for various vertical drilling machines, radial drilling machines, milling machines, lathes, etc.
Classification of hollow drills: alloy and tool steel according to material. Hollow drills are mainly used for hard materials, while tool steel is generally used for soft materials. Tool steel for these two types of drills is relatively cheap.
Hollow drill bits can be made of cemented carbide steel, high speed steel, etc., powder metallurgy, tungsten steel drills. In general, cemented carbide is the most widely used in the market, and high-speed steel drills are commonly used. The advantages of cemented carbide hollow drill bits are wear-resistant and durable, and they are not easy to collapse when drilling harder materials, while high-speed steel drills are very sharp, drilling faster, but more brittle, and they are easy to break when drilling harder materials.
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http://www.giant-tools.com/cutting-tools/
Types of hollow bits and precautions for use
I’m sure you know very little about the hollow drill bit. But as the name implies, you will know that it is a kind of drilling drill bit, and it is also hollow. Then you must be wondering how the hollow drill bit can drill things. That is because the hollow drill bit is an efficient multi blade annular cutting drill bit. Because it is annular, the power of the hollow drill bit must be large. Although hollow drill is not as common as other tools in life, it is a very important tool in life. Today’s small edition introduces the types of hollow bits and some important precautions for use.
The types of bits generally include high-speed steel bits, cemented carbide bits, tungsten steel bits. High speed steel drill is a tool for drilling round holes of work pieces through its rotary cutting relative to a fixed axis. It is named after the spiral shape of its chip holding groove, which resembles fried dough twist. Spiral grooves have 2 grooves, 3 grooves or more, but 2 grooves are the most common. High speed steel drills can be clamped on manual and electric hand-held drilling tools or drilling machines, milling machines, lathes and even machining centers. High speed steel fried dough twist drill is made of high speed steel (HSS).
Carbide drills are suitable for use on advanced machining centers. This kind of drill is made of fine grain cemented carbide material. In order to prolong its service life, it is also coated with TiALN. The specially designed geometric edge enables the drill to have a self centering function, and has good chip control and chip removal performance when drilling most work piece materials. The self centering function and strictly controlled manufacturing accuracy of the drill can ensure the
drilling quality of the hole, and no subsequent finishing is required after drilling.
Tungsten steel drill bit is a tool for drilling round holes of work pieces through rotary cutting of its relative fixed axis. It is named after the spiral shape of its chip holding groove, which resembles fried dough twist. Spiral grooves have 2 grooves, 3 grooves or more, but 2 grooves are the most common. Most tungsten steel drills are fried dough twist drills, which can be clamped on manual and electric hand-held drilling tools or drilling machines, milling machines, lathes and even machining centers. Tungsten steel drill bit is made of tungsten steel, which has higher processing hardness, but is more brittle than high-speed steel, and is easy to break when used improperly.
After knowing the types of hollow bits, you must be eager to know the precautions for the use of hollow bits. First of all, the most important thing is that the installation of the tool should not be loose or too tight. Secondly, there should be no iron filings under the magnetic block of the drill and the surface should be flat and clean without adsorption. In addition, the drill should be kept cool throughout the use process, and it is best to fully cool. The blade collision and impact should also be avoided in the process of use. If the iron scraps on the drill begin to become more, tools should be used to remove them.
What are the standards for hollow drill bits
At present, the main handle types on the market are divided into universal handle, right angle handle, overtone handle and threaded handle.
Hollow bits are also called coring bits, hole openers, center bits, steel plate bits, magnetic drill bits, rail bits, etc. Classification of bits: high-speed steel bits, cemented carbide bits, tungsten steel bits.
Suitable for drilling rigs: German overtone and other imported magnetic drills and domestic hollow drills.
How many holes can be drilled with a hollow drill
A hollow drill can generally drill 50 to 60 holes. Generally speaking, the cumulative drilling depth of a high-quality hollow bit is about 8-15m.
For example, drilling 5mm thick steel plate and drilling 15mm thick steel plate will not have the same number of holes. Therefore, we can only calculate roughly with effective drilling depth to be more accurate.
Since the rotation speed of the drill bit is high during drilling and the drill bit will rise rapidly when planing the working face, the water supply is insufficient once the watering cooling can not keep up with the blue iron chips drilled, and the water supply needs to be increased in time; If you delay for a while and find that the iron chips are black, it means that your drill bit should be replaced.
Before drilling, it must be ensured that the tool is completely installed in place without looseness or clamping. When drilling with a magnetic base drill, it must be ensured that there is no iron filings under the magnetic block of the drill, the adsorption surface is flat, and the machine is free of swing or incomplete adsorption. The whole process from drilling to drilling completion should be kept cool enough. If conditions permit, it is better to use internal cooling, and insufficient cooling may cause tool damage.
Material inspection of hollow drill
We have developed a special hollow drill for users to process difficult to machine materials. The processed material code is U-Mn, and its main chemical composition includes: carbon (0.56% ～ 0.68%), manganese (1.35% ～ 1.65%), silicon (0.2% ～ 0.35%), etc; The tensile strength of the material is ≥/mm2, and the hardness and wear resistance are high. This drill is used to process Ø 30+0.5mm through-hole on thick materials. The power of portable drill is<, Required bit life>, The drill bit material is. In the process of developing the hollow bit, by repeatedly adjusting the design parameters of the bit and conducting drilling tests, the geometric parameters of the bit are finally determined as: front angle g=12 °, rear angle a=9 °, and auxiliary rear angle a1=3 °.
The following is a brief analysis of the influence of hollow bit design on cutting performance.
Influence of Front Angle Change on Cutting Performance of Drill
The influence of rake angle on cutting force
The change of rake angle will affect the deformation degree of the chip material, thus changing the cutting force. The greater the chip deformation, the greater the cutting force; The smaller the chip deformation, the smaller the cutting force. When the current angle changes in the range of 0 °~15 °, the change range of the cutting force correction coefficient is 1.18~1.
Effect of Front Angle on Bit Durability
When the rake angle of the drill bit is increased, the strength and heat dissipation volume of the tool tip will be reduced, and the force on the tool tip will also be affected. When the current angle is positive, the tool tip is subject to tensile stress; When the current angle is negative, the tool tip compression stress. If the selected rake angle is too large, although it can increase the sharpness of the drill bit and reduce the cutting force, the tool tip is subject to a large tensile stress, which reduces the strength of the tool tip and is easy to break. In cutting test, many drill bits are damaged due to excessive front angle. However, due to the high hardness and strength of the materials to be machined, and the low rigidity of the main shaft and the whole machine of the portable drilling machine, if the front angle is too small, the increase of the cutting force during drilling will cause vibration of the main shaft, obvious vibration marks on the machined surface, and the durability of the drill will also be reduced.
The influence of the change of back angle on the cutting performance of drill bit
Increasing the back angle can reduce the friction between the back face and the cutting material, and reduce the extrusion deformation of the machined surface. However, if the back angle is too large, it will reduce the strength and heat dissipation of the blade.
The size of the back angle directly affects the bit durability. In the process of drilling, the main wear forms of the bit are mechanical scratch and phase change wear. Considering the mechanical abrasion, when the cutting life is fixed, the larger the back angle is, the longer the available cutting time is; Considering the phase change wear, the heat dissipation capacity of the drill bit will decrease with the increase of the back angle. After the drill bit is worn, with the gradual widening of the wear band of the rear tool face and the gradual increase of the cutting power, the heat generated by friction will gradually increase, which will increase the temperature of the drill bit. When the temperature rises to the phase change temperature of the drill bit, the drill bit will be rapidly worn.
3. The influence of drill design on grinding
The amount of hollow drill is small and the processing batch is small. Therefore, the processing technology should be considered when designing the drill, and the common machining equipment and tools should be used as far as possible to achieve processing and grinding.
The chip flows out through the rake face, so the shape of the rake face directly affects the chip shape and chip removal performance. The chip is further deformed due to the extrusion and friction of the rake face during the out flowing process. The metal deformation of the chip bottom layer is the largest, and it slides along the rake face, making the chip bottom layer longer, thus forming various curly shapes. When using a hollow drill bit to drill holes, it is hoped that the chips will become chips or banded chips to facilitate chip removal. In order to facilitate machining and grinding, the rake face must be designed as a plane without breaking the chip groove. The rake face does not need to be reground in use.
The back face of the hollow drill is the most easily reground face and also the fastest worn face. Therefore, the grinding of the hollow drill is realized by sharpening the back face.
The auxiliary rear cutter face is divided into internal auxiliary rear cutter face and external auxiliary rear cutter face. From the perspective of regrinding, regrinding the internal and external auxiliary rear tool faces is not easy to achieve, so the auxiliary rear tool face should be designed to be non regrinding.
According to the above analysis, the hollow drill blade is designed as shown in Figure 1. The machining practice proves that the design can completely meet the requirements of use and tool regrinding.
4.Use of cutting fluid and its influence on cutting performance of drill bit
The main feature of the hollow drill is that the inner core of the hole is not cut during machining, so the cutting amount of the hollow drill is significantly reduced compared with that of the fried dough twist drill, and the power of the drill and the heat generated in cutting are also small.
When drilling with a high speed steel hollow drill bit, the temperature in the processing area has a great influence on the hardness of the drill bit, so coolant must be used to cool down the drilling process (if coolant is not used, the drill bit will wear mainly due to phase change wear at the beginning, but fast wear). At first, we used the external spray cooling method, but because the drill station is processed in the horizontal axis direction, the coolant is not easy to enter the drill blade, so the coolant consumption is large, and the cooling effect is not ideal. By redesigning and changing the structure of the main shaft of the drill, the external spray cooling is changed into the internal spray cooling, and the coolant is added from the core of the hollow drill bit, so that the coolant can smoothly reach the cutting part of the drill bit, thus significantly reducing the coolant consumption and improving the cooling effect.
5.Use effect of hollow bit
The well-designed hollow drill shall meet the following requirements:
①It is easy to manufacture and can be processed by common machine tools and general cutters; ② It is convenient for re grinding, and can be grounded with ordinary grinder;
③ High production efficiency and long service life;
④ Low price.
The hollow bit developed by us basically meets the above requirements. In actual use, the bit durability can reach 50 minutes, and the hole diameter tolerance and surface roughness meet the design requirements. Because only the rear cutter face needs to be reground, the back angle of the drill bit is easy to control, and the grinding can be easily realized on the ordinary grinder.
Diane
Phone/Whatsapp:8618622997325
Post time: Sep-30-2022