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There are eight types of percussion bits. 1, carbide impact drill can be divided into: straight shank impact drill, taper shank impact drill and hexagonal shank impact drill. Use: for clamping on the impact drill, for drilling concrete foundation, wall, brick wall, granite, in order to install expansion bolts, plastic expansion pipe and other fasteners in the hole. 2, if the electric hammer bit is accidentally broken in the inside, the first user should first open the electric hammer collet to the maximum, if there are screws in the collet, you can remove the screws with a screwdriver; Then insert the collet key and turn the collet counterclockwise. Note that the collet is rotated, not the key. If the key is rotated, the bit will clamp more tightly, so just rotate the collet counterclockwise. 3, the impact drill bit can not be taken off: put the impact drill upside down on the ground, press down the drill sleeve at the root of the drill bit with the left hand, hold the drill bit upward with the right hand, and rotate the drill bit around when lifting. Hand electric drill bit: Equipped with a key, you insert the key into the side hole of the drill sleeve and loosen it to remove the drill bit.

There are four basic types of carbide bits: solid carbide bits, indexable carbide bits, welded carbide bits, and replaceable carbide crown bits. Solid carbide bit Solid carbide bits are suitable for use in advanced machining centers. The drill bits are manufactured from fine grained carbide materials and coated for extended service life. The specially designed geometric edge enables self-centering, providing excellent chip control and removal when drilling most workpiece materials. The self-centering function and tightly controlled manufacturing accuracy of the bit ensure the quality of drilling holes, eliminating the need for further finishing after drilling. Carbide indexable blade bit The drill with indexable carbide inserts has a wide range of processing aperture, and the processing depth ranges from 2D to 5D(D is the aperture), which can be used in lathes and other rotary machining machines. Welded carbide bit The welded carbide drill is made by solidly welding a carbide crown to the steel drill body. This kind of drill uses self-centering geometric edge type, cutting force is small, can achieve good chip control for most workpiece materials, machining hole surface finish is good, dimensional accuracy and positioning accuracy are very high, do not need to carry out subsequent finishing. The bit is internally cooled and can be used in machining centers, CNC lathes or other high rigidity, high speed machine tools. Replaceable carbide crown bit Replaceable carbide crown bit is a new generation of drilling tools developed in recent years. It is a combination of a steel drill body and a replaceable solid carbide crown. Compared with welded carbide bits, the machining accuracy is comparable, but the replaceable crown reduces machining costs and increases drilling productivity. The drill provides precise aperture increments and self-centering capabilities, resulting in high aperture machining accuracy.

Processing effect (1) the diameter of twist drill is limited by the aperture, the spiral groove makes the drill core thinner, the drill bit stiffness is low; With only two ribbed guides, the axis of the hole is easy to skew; The horizontal edge makes centering difficult, axial resistance increases, and the bit is easy to swing. Therefore, the shape and position error of the drilled hole is large. (2) twist drill before and after the tool surface are curved, along the main cutting edge of each point of the front Angle, the rear Angle is not the same, the front Angle of the horizontal edge of -55°. Poor cutting conditions; The distribution of cutting speed along the cutting edge is not reasonable, and the cutting speed of the tip with the lowest strength is the highest, so the wear is serious. Therefore, the hole precision of processing is low. (3) The whole edge of the main cutting edge of the drill participates in cutting, and the cutting speed of each point on the edge is not equal, which is easy to form spiral chips and difficult to discharge chips. Therefore, the chip and the hole wall extrusion friction, often scratch the hole wall, the surface roughness after processing is very low Operation method "Less grinding" is the first "no grinding", get the drill in a hurry to grind, is certainly blind grinding. It is very important to position yourself well before grinding to lay a solid foundation for the next step of "good grinding". Here with four formula to guide the grinding process, the effect is better. Formula one: "edge to balance the wheel surface." This is the first step of the relative position between the drill bit and the grinding wheel. Often, some students lean on the grinding wheel to start grinding before the edge is balanced. This is definitely not going to grind well. The "edge" here is the main cutting edge, and the "leveling" means that the main cutting edge of the part being ground is in a horizontal position. "Wheel surface" means the surface of the grinding wheel. "Lean" means to draw closer slowly. At this point, the drill can not contact the grinding wheel. Formula two: "drill shaft oblique release front Angle." Here refers to the position relationship between the bit axis line and the grinding wheel surface. "Edge Angle" is half of the tip Angle 118°± 2O, about 60° This position is very important, directly affects the size of the tip Angle and the shape of the main cutting edge and the bevel Angle of the edge.Students should be reminded of the common 30°, 60°, 90° triangle board in the 60° Angle, students easy to master. Formula 1 and formula 2 are the relative position of the drill before grinding, both should be taken into consideration, not to balance the edge and ignore the bevel Angle, or to balance the oblique axis and ignore the edge. These errors are often made in practice. At this point, the drill bit is ready to contact the grinding wheel in the correct position. Tip 3: "from the blade to the back grinding back." In this case, grinding is done slowly from the edge of the bit along the entire back surface. This facilitates heat dissipation and grinding. On the basis of stable consolidation of tips 1 and 2, the bit can gently contact the grinding wheel for a small amount of grinding. During grinding, the uniformity of spark should be observed, the pressure should be adjusted in time, and the bit cooling should be paid attention to. When cooling back to grinding, to continue to set the position of formula one and two, which is often not easy to master in the beginning, often can not help but change the accuracy of its position. Formula four: "up and down swing tail do not become warped." This action is also very important in the process of bit grinding, often students in the grinding "swing up and down" to "turn up and down", so that the other main blade of the bit was destroyed. At the same time, the tail of the drill bit should not be tilted above the horizontal center line of the grinding wheel, otherwise the edge will be blunt and unable to cut.

Twist drill is a tool used to drill round holes of workpiece by rotating cutting of its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. Twist drill can be clamped on manual, electric hand-held drilling tools or drilling machines, milling machines, lathes and machining centers. Drill material is usually high - speed tool steel or carbide. Standard twist drill. Twist drill is composed of shank, neck and working part. (1) Spiral Angle β Spiral Angle is the Angle between the most round spiral line on the spiral groove of the bit and the axis of the bit after it expands into a straight line. As the lead of each point on the spiral groove is the same, so the spiral Angle at different diameters of the drill bit is different, the spiral Angle at the outer diameter is the largest, the closer to the center of the spiral Angle is smaller. When the screw Angle increases, the rake Angle increases, which is beneficial to chip removal, but the bit stiffness decreases. The screw Angle of standard twist drill is 18° ~ 38°. For the drill with smaller diameter, the screw Angle should be smaller to ensure the stiffness of the drill. (2) rake Angle γOm [ Because the twist drill rake surface is helical, the rake Angle at each point on the main cutting edge is different. From the outer circle to the center, the rake Angle gradually decreases. The rake Angle at the tip is about 30°, and the rake Angle near the cross edge is about -30°. (3) after the Angle alpha Om the twist drill master choose fixed point of cutting edge Angle, by that point in the column section after the feed Angle alpha Om. Column section is the main cutting edge selected point m, and a bit axis parallel to the line, the line formed by the rotating drill axis cylinder. Alpha Om also changes along the cutting edge, the closer it gets to the center, the greater the alpha Om. The back Angle α at the twist drill's outer circle is usually 8° ~ 10°, and the back Angle at the cross edge is 20° ~ 25°. This can compensate for the effect of the actual working back Angle at each point on the main cutting edge decreased due to the axial feed movement of the bit, and can adapt to the change of the front Angle. (4) Main deflection Angle κ RM The main deflection Angle is the included Angle between the tangent line of the selected point M of the main cutting edge and the feed direction on the base plane. The base plane of the twist drill is the plane containing the drill axis past the selected point of the main cutting edge. Because the main cutting edge of the drill does not pass the axis line, the base plane of each point on the main cutting edge is different, and the main Angle of each point is also different. When the vertex Angle is ground out, the main declination Angle of each point is also determined. The main declivity Angle and the vertical Angle are two different concepts. (5) Front Angle 2φ front Angle is the included Angle of the two main cutting edges projected on the plane parallel to it. The smaller edge Angle is easy to cut into the workpiece, the axial resistance is small, and the cutting edge working length increases, the cutting layer nominal thickness decreases, is conducive to heat dissipation and improve tool durability; If the front Angle is too small, the bit strength is weakened, deformation is increased, torque is increased, and the bit is easy to break. Therefore, according to the strength and hardness of the workpiece material to grind a reasonable front Angle, the front Angle of the standard twist drill 2φ 118° The bevel Angle of the bevel edge is the included Angle projected between the main cutting edge and the bevel edge on the plane perpendicular to the bit axis. When the twist drill tool surface is ground out, the ψ is formed naturally. As can be seen from FIG. 3-5, when the bevel Angle of the transverse edge is increased, the length of the transverse edge and the axial resistance decrease. Standard twist drill edge bevel is about 50° ~ 55°.

Twist drill is the most important hole processing tool, it is a kind of double spiral groove complex cutting tool, its main cutting performance (such as processing quality, processing efficiency and tool durability, etc.) and its geometric parameters are closely related. Therefore, people have been committed to the improvement of drill and drilling process research. Twist drill and its Forming Method systematically describes the twist drill's basic structure, geometric Angle and common tool materials; On the basis of studying the forming method of standard twist drill groove and the forming method of twist drill rear cutter surface, the method of forming the rear cutter surface of twist drill by electric discharge wire cutting machine tool is put forward, its forming principle and forming device are introduced, and the experimental study of wire cutting method is carried out. Combined with the simulation research of cutting process, the 3d solid modeling method of twist drill, the finite element simulation and analysis method of drilling process are introduced in detail, and the reasonable selection of drilling processing conditions and drill tip geometric parameters are studied through drilling test.

Materials and classification Hollow bit material Hollow drill material can be divided into hard alloy steel, high-speed steel, powder metallurgy, tungsten steel drill class, general use most is cemented carbide on the market, and high speed steel is commonly used type, hard alloy hollow drill its advantages of wear-resisting durable, not easy to crash when playing a hard material, type and high speed steel is very sharp, drilling is faster, but more brittle, easily broken when playing a hard material. Hollow bit classification In addition to the traditional twist drill in the market, there are specialized for magnetic seat drill coring drill (also called hollow drill), this kind of drill adopts the principle of milling cutter, with high efficiency, good precision effect. General customers are choosing hollow bits (coring bits), specifications are: Ø 12-160 - mm. Only small holes must be made with a twist bit. Hollow drill types generally have HSS drill, carbide drill, tungsten steel drill. HSS drill is a tool used to drill round holes of workpiece by rotary cutting with its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. HSS drill bits can be clamped on manual or electric hand-held drilling tools or on drilling machines, milling machines, lathes and even machining centers. HSS twist drill is made of HSS. Carbide bits are suitable for use in advanced machining centers. The bits are manufactured from fine grained carbide and TiAlN coated for extended service life. The specially designed geometric edge enables self-centering, providing excellent chip control and removal when drilling most workpiece materials. The self-centering function and tightly controlled manufacturing accuracy of the bit ensure the quality of drilling holes, eliminating the need for further finishing after drilling. Tungsten steel drill is a tool used to drill round holes of workpiece by rotating cutting its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. Tungsten steel drill bits for twist drill can be clamped in manual, electric hand-held drilling tools or drilling machines, milling machines, lathes and processing centers. Tungsten steel drill material is tungsten steel, processing hardness is higher, but compared with high-speed steel is more brittle, not easy to fracture when used

Take stainless steel as an example, the two are mainly different in three aspects, such as feed, speed and linear speed. First, the amount of supply Common bit: feed 0.03~0.08. U drill: the feed is 0.06~0.18. Second, the speed Normal bit: rotating speed from 200 to 800 RPM. U drill: the rotating speed is much higher than ordinary drill. 1500~3000 RPM. Three, linear speed Normal bit: linear speed of 8. U drill: line speed is much higher than ordinary drill, 115~165. Shovel drill is a tool improved on the basis of U drill. The range of equipment used is wide (can be used in rocker drill, vertical drill, bed, processing center and other equipment) the rigidity of the equipment is not high. The whole cutter head can be accurately centering, the cutter head is equipped with chip separating groove and chip breaking groove, which can process deep holes. Shovel drill is generally used for U drill processing and ordinary drill processing of intermediate speed processing, the general blade is high speed steel, speed is generally below 1000, compared with ordinary drill does not need to grind the workers' skills are low. The shovel drill consists of a steel shank and a blade with a removable head. The handle part of the knife rod has two structures: side fixed handle and Mohs handle. The side fixed shank is often used in CNC lathes, CNC machine tools in machining centers, etc. Mohs shank is used in vertical drill, rocker drill, car and other traditional equipment. By simply installing a set of cooling rings, external cooling can be turned into internal cooling. Cooling water enters the tool rod through the cooling ring, and directly cools to the blade part through the internal cooling hole. And the high-pressure cooling water is more conducive to chip removal. The chip removal form of the cutter bar has two kinds of straight groove and spiral groove. When the workpiece rotating tool is stationary, straight groove is more conducive to chip removal, such as lathe processing. When the tool at high speed rotating workpiece static, the more choice of spiral chip groove, such as CNC machine tools, rocker drill and so on. According to the length to diameter ratio (that is, the ratio of length to diameter) of the cutter bar, it can be divided into 3D,5D,7D,9D or even higher. Shovel drill blade is divided into carbide blade and high-speed steel blade two kinds.

There are many kinds of real drill bits, mainly according to their different uses and distinguish, that is, what kind of drill bits to drill. Common drill bits are twist drill, flat drill, deep hole drill, reaming drill, countersink drill, center drill, etc., the following in detail. 1 Flat drill The cutting part of flat drill is spade form, structure is simple, manufacturing cost is low, in cutting fluid leads into hole easily, but performance of cutting and discharge chip is poorer. Flat drill structure has two types of integral and assembled. The whole is mainly used for drilling 0.03 ~ 0.5 mm diameter micro hole. Prefabricated flat drill blade can be changed, can use internal cooling, mainly used for drilling 25 ~ 500mm diameter of large holes. 1 Twist drill Twist drill is the most widely used hole machining tool. The usual diameter range is 0.25 to 80 mm. It is mainly composed of bit working part and shank. The working part has two spiral grooves, shaped like a twist, hence the name. In order to reduce the friction between the guide part and the hole wall when drilling, twist drill from the drill tip to the handle direction gradually reduce the diameter of the inverted cone. The screw Angle of twist drill mainly affects the size of cutting edge Angle, edge edge strength and chip removal performance, which is usually 25° ~ 32°. Spiral grooves can be processed by milling, grinding, hot rolling or hot extrusion, and the front end of the drill bit forms a cutting part after grinding. The cutting Angle of the standard twist drill is 118, the bevel Angle of the cross edge is 40° ~ 60°, and the back Angle is 8° ~ 20°. Due to structural reasons, the rake Angle is large at the outer edge and gradually decreases to the middle, and the transverse edge is negative rake Angle (up to about -55°), which acts as extrusion when drilling. In order to improve the cutting performance of twist drill, the cutting part can be ground into various shapes according to the properties of processed materials (such as group drill). Twist drill shank form has straight shank and cone shank two kinds, processing the former clip in the drill chuck, the latter inserted in the machine tool spindle or tail seat of the cone hole. The general twist drill is made of high speed steel. Insert welding carbide blade or crown twist drill for the processing of cast iron, hardened steel and non-metallic materials, such as the whole cemented carbide small twist drill for the processing of instrument parts and printed circuit boards. 1 Deep hole drilling Deep hole drilling is usually refers to the processing of hole depth to aperture ratio greater than 6. Commonly used gun drill, BTA deep hole drill, jet drill, DF deep hole drill and so on. Sleeve drills are also commonly used for deep hole machining. 1 Center drill The center drill is used for drilling the center hole of shaft type workpieces. It is essentially composed of screw Angle small twist drill and countersink drill, so it is also called compound center drill. 1 Economic drill Shaving drill has more cutter teeth, in order to form the hole end processing into the required shape, used for processing various countersunk head screw hole, or flat hole outer end face. 1 Reaming drill Reaming drill has 3 to 4 cutter teeth, its rigidity is better than twist drill, used to expand the existing hole and improve processing accuracy and finish.

1. Different materials Alloy is a kind of ultra-high hardness and very wear-resistant material, the only disadvantage is easy to break, but the wear resistance is very strong, good alloy material is very easy to use, and the price is very high. HSS drill a is not easy to break and wear resistance is very good and so on, generally for factory in need of high speed steel drill bit is more cost-effective, because the unit price is low and the quality also, still can be generally adopts high speed steel drill bit, unless encounter and rigid material, high speed steel drill bit processing, select alloy bit again. 2. Different physical properties Alloy bit generally refers to carbide bit, can be divided into integral, welding, indexable blade type and removable head type. The main components of the alloy are tungsten carbide, cobalt and so on. The hardness is relatively high, generally above HRC90 degrees. It is suitable for processing steel parts after heat treatment and difficult to process materials. Alloy drill itself high hardness, heat treatment after the product hardness must be used alloy drill. HSS bit material is a kind of alloy steel with complex composition, containing tungsten, molybdenum, chromium, vanadium, cobalt and other carbide forming elements. The total alloying element is about 10 ~ 25%. It can maintain high hardness under the condition of high heat generated by high speed cutting, HRC can be more than 60. HSS drill bits can maintain high hardness and HRC above 60 even when high heat is generated by high speed cutting. Carbide drill has a series of excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance and corrosion resistance, especially its high hardness and wear resistance, even at 500℃ is basically unchanged, still has a high hardness at 1000℃.

Carbide bits are divided into four basic types: solid carbide bits, indexable carbide inserts, welded carbide bits and convertible carbide crown bits. Each bit has the benefit of being suited to a particular machining premise. Carbide bits break rock by weight on bit and impact load generated by rotation. In rock drilling, the drill bit is subjected to high frequency impact load, and is subjected to torsion, bending, stretching, compression and other complex stresses. In the environment of high-speed rotary collision, the drill bit is subjected to wear and corrosion of rock, rock powder and mineral water and other working media. Usage and characteristics of carbide drill: 1, can be suitable for more complex material drilling, can choose higher cutting speed. 2. The high performance alloy blade specially selected for alloy drill can effectively reduce the blade breakage and maintain good wear resistance. 3, multi-layer geometric cutting edge, improve drainage performance, maintain a small cutting resistance. 4, in addition to the usual right Angle handle, equipped with a variety of handle, suitable for a variety of drill, drilling machine.

Advantages: (1) Good rigidity, high strength, easy to obtain higher drilling accuracy. (2) Can be suitable for more complex material drilling, can choose higher cutting speed. (3) Effectively reduce blade breakage, with good wear resistance. (4) Multi-layer geometric cutting edge, improve chip removal performance, keep small cutting resistance. (5) In addition to the usual right-angle handle, equipped with a variety of handle, suitable for a variety of drill, drilling machine. (6) Compared with indexable blade bit, the whole carbide bit can be repaired for 7 ~ 10 times. Disadvantages: to grind well, grinding is not easy to collapse, the two main cutting edge height, Angle is the same, it is best to use grinding drill machine. Extended information Carbide bits are divided into four types of foundation: solid carbide bits, carbide indexable blade bits, Welded carbide bits and convertible carbide crown bits. Each bit has the benefit of being suited to a particular machining premise. (1) Solid carbide drill bit (2) Carbide indexable blade drill The drill with indexable carbide inserts can process a wide range of aperture sizes, and the processing depth ranges from 2D to 5D (D is the aperture), which can be used in lathes and other torsional machining machines. (3) Welded carbide drill bit The welded carbide bit is made by smoothly welding a carbide crown to a steel drill body. This kind of drill uses self-centering geometric edge type, cutting force is small, for most of the workpiece materials can achieve excellent chip control, machining the hole profile smooth degree is good. Dimensional accuracy and positioning accuracy are very high, no need for subsequent finishing. The bit adopts internal cooling system and can be used in machining centers, CNC lathes or other high rigidity, high speed machine tools. (4) Carbide crown bit can be changed Convertible carbide crown bit is a new generation of drilling tools. It is composed of a steel drill body and a removable solid carbide crown. Compared with t

Carbide steel drilling edit Multipoint steel drill is mainly used for drilling of steel members, such as steel structure engineering, rail transportation, Bridges, ships, machinery manufacturing, aerospace, and other areas of the hole drilling, the drilling performance is superior to the traditional two blade twist drill, drilling drilling with high efficiency, light energy, the characteristics of blade steel drill and magnetic bridge drilling rig can form a complete set of large workpiece multi-faceted, Easy to operate and flexible, effectively shorten the construction time, become the modern steel member drilling and annular groove processing of the preferred tool. Performance of the editor 1, can be suitable for more complex material drilling, can choose higher cutting speed. 2, select special steel plate drill high performance alloy blade, effectively reduce blade breakage and maintain good wear resistance. 3, multi-layer cutting edge geometry, improve chip removal performance and maintain a small cutting resistance. 4, in addition to the usual right-angle handle type, with a variety of handle type, suitable for a variety of drill, drilling machine. 5, specifications from ф 12mm~ ф 150mm, cutting depth 35mm, 50mm, 75mm, 100mm series. 6, can be customized ф 150mm~ ф 200mm cutting depth can be expanded to 200mm special occasions demand.

Carbide bits are divided into four basic types: solid carbide bits, indexable carbide inserts, welded carbide bits and convertible carbide crown bits. Each bit has the benefit of being suited to a particular machining premise. (1) Solid carbide drill bit (2) Carbide indexable blade drill The drill with indexable carbide inserts can process a wide range of aperture sizes, and the processing depth ranges from 2D to 5D (D is the aperture), which can be used in lathes and other torsional machining machines. (3) Welded carbide drill bit The welded carbide bit is made by smoothly welding a carbide crown to a steel drill body. This kind of drill uses self-centering geometric edge type, cutting force is small, for most of the workpiece materials can achieve excellent chip control, the processing of the hole profile smooth, dimensional accuracy and positioning accuracy are very high, there is no need to carry out subsequent finishing. The bit adopts internal cooling system and can be used in machining centers, CNC lathes or other high rigidity, high speed machine tools. (4) Carbide crown bit can be changed Convertible carbide crown bit is a new generation of drilling tools. It is composed of steel drill body and changeable integral carbide crown. Compared with welded carbide bit, its processing accuracy is 82.5 jin, but because the crown can be changed, it can reduce the processing cost and improve the drilling yield. The drill provides accurate aperture increment and self-centering capability for high aperture machining accuracy. Between the drill body and the carbide crown, the interlocking V-groove adjacent mechanism made of detailed grinding is used to lock each other, which can ensure that the bit assembly has the same dimensional accuracy and overall rigidity as the welded carbide bit. At the same time, the locking mechanism has only one exact matching position, so that the crown is easy to be installed on the matching rod, so as to ensure the repeated positioning accuracy when changing the crown. When the rod is pulled through the locking screw, the crown/drill body assembly is locked smoothly to each other, and its adjacent stiffness is sufficient to meet the requirements of rapid and high speed cross-yield hole machining. Seco-carboloy adopts the advanced needle molding process to produce carbide crowns with extremely high material evenness, resulting in even strength and uniform thermal deformation. Seco currently offers three CrownLoc bits with specific geometric edges. The first is a universal geometric edge with a conventional edge passivation radius, edge width, and taper Angle, suitable for processing a wide variety of steel materials. The second is the geometric edge with a wider edge belt and chamfering, suitable for processing cast iron materials; The third geometric edge reduces cutting heat and work hardening for stainless steel and super alloy materials. The total life of the bit should also be taken into account when considering the cost per hole. Generally speaking, a solid carbide bit can only be reground 7 ~ 10 times, a welded carbide bit can only be reground 3 ~ 4 times, and the steel crown of the convertible carbide crown bit can be changed at least 20 ~ 30 times when processing steel.

Hollow drill material can be divided into hard alloy steel, high-speed steel, powder metallurgy, tungsten steel drill class, general use most is cemented carbide on the market, and high speed steel is commonly used type, hard alloy hollow drill its advantages of wear-resisting durable, not easy to crash when playing a hard material, type and high speed steel is very sharp, drilling is faster, but more brittle, easily broken when playing a hard material. Hollow bit classification In addition to the traditional twist drill in the market, there are specialized for magnetic seat drill coring drill (also called hollow drill), this kind of drill adopts the principle of milling cutter, with high efficiency, good precision effect. General customers are choosing hollow bits (coring bits), specifications are: Ø 12-160 - mm. Only small holes must be made with a twist bit. Hollow drill types generally have HSS drill, carbide drill, tungsten steel drill. HSS drill is a tool used to drill round holes of workpiece by rotary cutting with its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. HSS drill bits can be clamped on manual or electric hand-held drilling tools or on drilling machines, milling machines, lathes and even machining centers. HSS twist drill is made of HSS. Carbide bits are suitable for use in advanced machining centers. The bits are manufactured from fine grained carbide and TiAlN coated for extended service life. The specially designed geometric edge enables self-centering, providing excellent chip control and removal when drilling most workpiece materials. The self-centering function and tightly controlled manufacturing accuracy of the bit ensure the quality of drilling holes, eliminating the need for further finishing after drilling. Tungsten steel drill is a tool used to drill round holes of workpiece by rotating cutting its relative fixed axis. Because of its capacity chip groove into spiral shape and shape like hemp and named. Spiral grooves have 2, 3 or more grooves, but 2 grooves are the most common. Tungsten steel drill bits for twist drill can be clamped in manual, electric hand-held drilling tools or drilling machines, milling machines, lathes and processing centers. Tungsten steel drill material is tungsten steel, processing hardness is higher, but compared with high-speed steel is more brittle, not easy to fracture when used.

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Hollow drill also known as core drill, hole opener, center drill, steel plate drill, magnetic drill, rail drill and so on. The main materials of drill are: high speed steel; Powder metallurgy; Cemented carbide. Hollow drill types and specifications are complete, suitable for all kinds of imported magnetic seat drill (magnetic drill) and general drilling, milling, boring, etc. The drilling efficiency is 8~10 times that of ordinary drill. Hollow drill (multi blade steel drill or core drill) is more efficient bit of annular cutting blade, the hole diameter from 12 mm to 150 mm, it is mainly used for drilling of steel members, such as steel structure engineering, rail transportation, Bridges, ships, machinery manufacturing, aerospace, and other areas of the hole drilling, the drilling performance is superior to the traditional two blade twist drill, With the characteristics of high drilling efficiency, light drilling and labor-saving, multi-blade steel plate drill and magnetic seat drill can be used for multi-directional drilling of large workpiece, convenient and flexible operation, effectively shorten the construction time, and become the preferred tool for drilling and annular groove processing of modern steel components [1].

Hollow drill also known as core drill, hole opener, center drill, steel plate drill, magnetic drill, rail drill and so on. Bit classification: HSS bit, carbide bit, tungsten steel bit. Cutting depth: 25mm, 35mm, 50mm, 75mm, 100mm. Suitable for drilling RIGS: Germany overtone and other imported magnetic drilling and domestic hollow drilling. Specification: 12MM to 100MM.

Coring drill is mainly used for steel plate and other products drilling tools, hollow drill with specialized machine coring drill. Thin-wall diamond coring bit: concrete core sample is drilled directly on structural concrete, and the compressive strength test is carried out after processing the core sample. This method is recognized as a more intuitive and reliable test method for testing concrete strength. For coring method and technical operation, please refer to "Technical Specification for Testing concrete Strength by Drilling Core method" officially issued in China. Hollow core bit and drill bit, mainly used for drilling tools for steel and other products, hollow drill with core bit on special machine, has the efficiency of fast, the characteristics of low cost, core drill bit blade is made of carbide end tooth geometry with three layers, brisk cutting, steel bit service life is long, the double smoothing handle interface, is suitable for the drill of the bell, etc. Carbide drill is also suitable for all kinds of vertical drilling machine, radial drilling machine, milling machine, lathe and so on. Coring bit classification: according to the material alloy bit, tool steel bit. Alloy bits are mainly used for hard materials, while tool steel bits are usually used for soft materials. Tool steel is relatively cheap for these two types of bits. Price: the market price ranges from more than 100 to more than 200.

Hollow bit is a kind of hole machining tool suitable for portable tools. But because the hollow bit manufacturing process is more complex, and can not process blind hole, so it is not widely used in metal cutting processing, usually only in the processing of some large diameter or precious metal workpiece through hole or drilling equipment power is limited. Since there is no standard product for hollow bits, most hollow bits used for special material processing need to be developed by themselves. The influence of the posterior Angle The influence of rake Angle on cutting force: the change of rake Angle will affect the deformation degree of chip material, so as to change the cutting force. The larger the chip deformation, the greater the cutting force; The smaller the chip deformation, the smaller the cutting force. When the current Angle varies from 0° to 15°, the cutting force correction coefficient varies from 1.18 to 1. Influence of rake Angle on bit durability: when the rake Angle increases, the strength and heat dissipation volume of the tool tip will decrease, and the force on the tool tip will be affected. When the current Angle is positive, the tip is subjected to tensile stress. When the current Angle is negative, the compression stress of the tool tip. If the front Angle is too large, although it can increase the edge of the drill bit and reduce the cutting force, the tensile stress of the tip is large, the strength of the tip is reduced, and it is easy to break. Many drill bits are damaged due to excessive rake Angle in cutting tests. However, due to the high hardness and strength of processed materials, coupled with the portable drill spindle and machine rigidity is low, such as the selection of the front Angle is too small, drilling when the increase of cutting force will make the spindle vibration, processing surface appears obvious vibration, drill durability will also be reduced. Influence of cutting performance Increasing the back Angle can reduce the friction between the back tool surface and the cutting material and reduce the extrusion deformation of the machined surface. However, if the back Angle is too large, the blade strength and heat dissipation capacity will be reduced. The size of the back Angle directly affects the bit durability. In drilling process, the main wear forms of drill bits are mechanical abrasion and phase change wear. Considering mechanical abrasion, when the cutting life is constant, the larger the back Angle, the longer the available cutting time; Considering phase change wear, the increase of back Angle will reduce the bit heat dissipation capacity. After bit wear, with the gradual broadening of the wear zone on the back tool surface, the cutting power gradually increases, and the heat generated by friction gradually increases, which increases the bit temperature. When the temperature rises to the bit phase transformation temperature, the bit will appear rapid wear. Influence of grinding process Hollow drill bit consumption is less, processing batch is small, so the design of drill bit should consider its processing technology, as far as possible with common machining equipment and common tools to achieve processing and grinding. The chip flows out through the front cutter surface, so the shape of the front cutter surface directly affects the chip shape and chip removal performance. The chip is extruded and rubbed by the front cutter surface in the process of outflow, further deforming. The chip bottom metal deformation degree is the largest, and slippage along the front knife surface, so that the chip bottom length is longer, thus forming a variety of crimped shapes. When drilling with a hollow bit, it is hoped that the chips will become debris or ribbon chips to facilitate the removal of chips. In order to facilitate machining and grinding, the front cutter face must be designed as a plane, and chip groove is not broken. The front face does not need regrinding in use. The back cutting surface of hollow bit is the most easily reground surface, and also the fastest wear surface, so the grinding of hollow bit is realized by the back cutting surface. The auxiliary rear tool surface is divided into the internal auxiliary rear tool surface and the external auxiliary rear tool surface. From the point of view of regrinding, it is not easy to regrind the inner and outer rear surfaces, so the rear surfaces should be designed in the form of non-regrinding. Cutting fluid and drill bit The main characteristic of the hollow bit is that the inner core of the hole is not cut when machining, so the cutting amount of the hollow bit is significantly reduced than the twist drill, and the required rig power and the heat generated in the cutting is also smaller. When drilling with HSS hollow bit, because the temperature of the processing zone has a great influence on the hardness of the bit, it is necessary to use coolant to cool down the drilling process (if no coolant is used, the bit wear will be mainly phase change wear and rapid wear at the beginning). At the beginning, we adopted the external spray cooling method, but because the drill position was processed in the horizontal axis direction, the coolant was not easy to enter the blade part of the drill, so the coolant consumption was large, and the cooling effect was not ideal. After the redesign, the main shaft structure of the drilling machine was changed from external spray cooling to internal spray cooling, and the coolant was added by the core of the hollow bit, so that the coolant could reach the cutting part of the bit smoothly, so that the coolant consumption was significantly reduced and the cooling effect was improved.

1. Poor quality of taps: Main materials, CNC tool design, heat treatment, machining accuracy, coating quality and so on. For example, too big size difference at the transition of tap section or no design of transition fillet leads to stress concentration, which is easy to fracture at the stress concentration. The section transition at the junction of handle and blade is too close to the welding joint, resulting in the superposition of complex welding stress and stress concentration at the section transition, resulting in large stress concentration, resulting in the fracture of taps in use. Metal processing wechat, good content, worth paying attention to. For example, improper heat treatment. During the heat treatment of taps, cracks may occur if the taps are not preheated, overheated or overburned, tempered or cleaned prematurely before quenching. To a large extent, this is an important reason why the overall performance of domestic taps is not as good as that of imported taps. 2. Improper tap selection: The hardness is too large tapping parts should choose high-quality taps, such as cobalt high speed steel taps, carbide taps, coating taps and so on. In addition, different tap designs are used in different workplaces. For example, tap chip slot number, size, Angle and so on have an impact on chip removal performance 3. The taps do not match the processed materials: This problem is taken seriously more and more in last few years, before domestic manufacturer always feels what import is good, expensive is good, it is suitable actually good. With the increase of new materials and difficult to process, in order to adapt to this need, the variety of tool materials is also increasing. This requires a good selection of suitable tap products before tapping. 4. Small bottom hole: For example, when machining the M5×0.5 thread of ferrous metal material, the cutting tap should be used to select the diameter of 4.5mm drill hole, if the 4.2mm drill hole is misused, the cutting part of the tap is bound to increase when tapping, and then the tap is broken. It is recommended to choose the right bottom hole diameter according to the types of taps and different tapping materials. If there is no drill that completely matches, you can choose a larger one. 5. Material problems of attacking parts: Tapping material is not pure, local hard points or pores, resulting in the tap instantly lost balance and broken. 6. The machine tool does not meet the precision requirements of taps: Machine tools and clamps are also very important, especially for high-quality taps, as long as a certain precision of machine tools and clamps can play the performance of taps. What's common is not enough concentricity. At the beginning of tapping, tap starting positioning is not correct, that is, the spindle axis is different from the center line of the bottom hole, too much torque in the process of tapping, which is the main reason for tap fracture. 7. Poor quality of cutting fluid and lubricating oil: This domestic many enterprises began to pay attention to, many of the procurement of foreign tools and machine tools of the company has a very deep experience, cutting fluid, lubricating oil quality problems, processed product quality is easy to appear burr and other adverse conditions, at the same time, the life will also have a great reduction. 8. Unreasonable cutting speed and feed: When processing problems, most of the domestic users is to reduce cutting speed and reduce feeding, such tap propulsion strength is reduced, the production of thread accuracy was greatly reduced, it increased the roughness on the surface of the screw thread, thread aperture and cannot control precision, burr problem, of course, such as more inevitable. However, too fast feed speed, resulting in too much torque will easily lead to tap fracture. Machine tapping cutting speed, general steel 6-15m/min; Tempered and tempered steel or hard steel material is 5-10m/min; Stainless steel, 2-7m/min; Cast iron is 8-10m/min. In the same material, the tap diameter is small and the tap diameter is large, the tap diameter is low. 9. The operator's technology and skills do not meet the requirements: These problems above, all need operators to make a judgment or feedback to the technical staff, but at present the vast majority of domestic operators do not pay enough attention to. For example, when processing blind hole thread, when the tap is about to contact the bottom of the hole moment, the operator did not realize that the tap speed is still not to the bottom of the hole, or when the chip discharge is not free, forced into the tap resulting in tap fracture. It is suggested that operators strengthen their sense of responsibility. It can be seen from the above that the causes of tap fracture are various, such as machine tools, fixtures, workpieces, processes, collets and tools, etc., and the real reason may never be found only by armchair armchair soldiers. As a qualified and responsible tool application engineer, the most important thing is to go into the field, not just by imagination.