The core drill bit is a hole machining tool that is more suitable for portable tools. However, due to the complicated manufacturing process of the hollow drill bit and the inability to machine blind holes, it is not commonly used in metal cutting. It is usually used only when the power of through holes or drilling equipment for processing large diameter or precious metal workpieces is limited. . Since the hollow drill bit does not have a standard setting product, most of the hollow drill bits used for special material processing need to be developed by themselves. We have developed a special hollow drill bit for the user to process difficult materials. The processed material code U-Mn, the main chemical components include: carbon (0.56% ~ 0.68%), manganese (1.35% ~ 1.65%), silicon (0.2% ~ 0.35%), etc.; material tensile strength ≥ 882N / mm2, Both hardness and wear resistance are high. The drill is used to machine 30+0.5mm through holes on a 17mm thick material, portable drill power <1000W, drill life >30min, and drill material W6Mo5Gr4V2. In the process of developing the hollow drill bit, by repeatedly adjusting the design parameters of the drill bit and conducting the drilling test, the geometric parameters of the drill bit are determined as follows: the rake angle g=12°, the back angle a=9°, and the sub-back angle a1=3°. . A brief analysis of the influence of the design of the hollow drill bit on the cutting performance is given below. 1, the influence of the change of the rake angle on the cutting performance of the drill Effect of rake angle on cutting force The change in the rake angle affects the degree of deformation of the chip material, which causes the cutting force to change. The larger the chip deformation, the greater the cutting force; the smaller the chip deformation, the smaller the cutting force. When the current angle is changed from 0° to 15°, the cutting force correction coefficient varies from 1.18 to 1. The influence of the rake angle on the durability of the drill bit Increasing the front angle of the drill will reduce the strength of the tool tip and the heat dissipation volume, and will affect the force of the tool tip. When the current angle is positive, the tool tip is subjected to tensile stress; when the current angle is negative, the tool tip is subjected to compressive stress. If the front angle is too large, although the sharpness of the drill bit can be increased and the cutting force can be reduced, the tensile stress of the cutting edge is large, the strength of the cutting edge is lowered, and it is easy to break. Many drill bits were damaged by excessive rake angles during the cutting test. However, due to the high hardness and strength of the material to be processed, and the rigidity of the spindle and the whole machine of the portable drilling machine are low, if the front angle is too small, the increase of the cutting force during the drilling will cause the spindle to vibrate and the surface of the machine will be obviously vibrated. The durability of the drill bit will also be reduced. 2, the influence of the change of the back angle on the cutting performance of the drill Increasing the relief angle reduces the friction between the flank and the cutting material and reduces 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 durability of the drill bit. During the drilling process, the main wear forms of the drill bit are mechanical abrasion and phase change wear. Considering mechanical abrasion and wear, when the cutting life is constant, the larger the back angle, the longer the available cutting time; considering the phase change wear, the increase of the back angle will reduce the heat dissipation capability of the drill bit. After the bit is worn, as the wear band of the flank is gradually widened, the cutting power is gradually increased, the heat generated by the friction is gradually increased, and the temperature of the bit is increased. When the temperature rises to the phase change temperature of the bit, the bit will appear. Fast wear and tear. 3, the impact of bit design on sharpening processing The hollow drill bit is used in a small amount and the processing batch is small. Therefore, the design process should be considered when designing the drill bit, and the machining and sharpening should be realized by using common machining equipment and common tools. The chips flow out through the rake face, so the shape of the rake face directly affects the chip shape and chip removal performance. The chips are pressed and rubbed by the rake face during the outflow process, further deforming. The underlying metal of the chip is most deformed and slips along the rake face, so that the length of the chip bottom layer is long, thereby forming various curl shapes. When drilling with a hollow drill bit, it is desirable to make the chips into chips or ribbons to facilitate chip removal. For ease of machining and sharpening, the rake face must be designed to be flat and does not open chipbreakers. The rake face does not need to be reground in use. The flank is the most re-grinding surface of the hollow drill bit and the fastest wear surface. Therefore, the sharpening of the hollow drill bit is achieved by sharpening the flank. The secondary flank face is divided into an inner secondary flank face and an outer secondary flank face. From the perspective of regrind, it is not easy to re-grind the inner and outer minor flank faces, so the secondary flank face should be designed in a non-reground form. 4, the use of cutting fluid and the impact on the cutting performance of the drill The main feature of the hollow drill bit is that the inner core of the hole is not cut during machining, so the cutting amount of the hollow drill bit is significantly reduced compared to the twist drill, and the power required for the drill and the heat generated during the cutting are also small. When drilling with high-speed steel hollow drill bits, the temperature of the processing zone has a great influence on the hardness of the drill bit. Therefore, the coolant must be cooled during the drilling process. (If the coolant is not used, the wear of the drill will be based on phase change wear at the beginning. Wear). At the beginning, we used the external spray cooling method, but because the bit position is processed in the horizontal axis direction, the coolant is not easy to enter the blade edge portion, the coolant consumption is large, and the cooling effect is not ideal. After redesigning and changing the spindle structure of the rig, the external spray cooling is changed into internal spray cooling, and the coolant is added by the core of the hollow drill bit, so that the coolant can smoothly reach the cutting part of the drill, thereby significantly reducing the consumption of the coolant and improving the Cooling effect. 5, the use of hollow drill bit effect The well-designed hollow drill bit should meet the following requirements at the same time: 1 It is easy to manufacture, can be processed by ordinary machine tools and general tools; 2 It is easy to re-sharp, and can be sharpened by ordinary grinder; 3 High production efficiency and long service life; 4 low prices. The hollow drill bit we developed basically meets the above requirements. In actual use, the drill durability can be stabilized for up to 50 minutes, and the hole tolerance and surface roughness meet the design requirements. Since it is only necessary to re-grind the flank, the back angle of the drill bit is easier to control, and the sharpening can be easily performed on a conventional grinder. Oem Service,Obm Service,Stamping Parts Simple Shower Room Co., Ltd. , http://www.chinaatvpart.com