Characteristics and application of the hottest str

2022-08-14
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Characteristics and application of straight groove drill

the traditional concept of "irreplaceable spiral groove drill" is now being overturned by the processing efficiency of straight groove drill. In some processing occasions, straight groove drill is becoming a better tool choice than fried dough twist drill

the "pioneer" of modern straight slot drills is die drills. This kind of drill has short size, good rigidity and solid drill tip. It is suitable for drilling and processing hard steel materials at low spindle speed and small feed rate. Its high strength and high rigidity enable it to process holes with good straightness and roundness. The reason why the die drill can achieve good processing effect is that the processing material for designing the drill is usually the metal that produces short chips. Chip control is still a key problem in the processing and application of straight groove drill. The straight groove drill can get the best effect only when processing materials that will not produce long curly shavings, such as cast iron, powder alloy (p/m), silicon aluminum alloy with medium high silicon content (6% or higher), etc

however, with the progress of machine tool technology, coolant delivery technology and tool geometry design, the processing and application scope of straight groove drill is expanding. The traditional way of thinking believes that the spiral groove of the drill bit is essential for chip removal, and the straight groove drill can only be used to drill shallow holes with a hole depth of 2D ~ 3D (D is the hole diameter) on aluminum and cast iron. However, the developed high-pressure cooling system and higher machine tool spindle speed have greatly improved the chip breaking and chip removal performance of the straight groove drill with internal cooling

in the processing occasions with appropriate conditions, the straight groove drill can show that the processing method is very simple, which is far better than the good processing performance of the spiral groove drill. The advantage of straight groove drill is that it can process holes with high roundness and straightness, and its cutting speed is faster than standard cobalt or high-speed steel drill. For example, use a diameter of 0.394 ″( φ When the guhring rt150gg straight groove drill of 10mm replaces the fried dough twist drill to process aluminum parts, the cutting speed of the fried dough twist drill is 50sfm (15m/min), and the feed rate is 0.005ipr (0.127mm/r); The cutting speed of the straight slot drill can reach 800sfm (245m/min) and the feed rate can reach 0.007ipr (0.178mm/r). The machinability, surface properties and mechanical properties of the cutting products used in the straight groove drill are better than those of similar imported materials, and the time is only 1/10 of that of fried dough twist drill

part of the reason why the straight groove drill can significantly improve the processing efficiency is based on the basic design of the drill - the straight groove provides a direct channel for the chip to discharge out of the hole. However, because the cutting edge of the straight groove drill lacks a positive rake angle, its chip curling and chip breaking ability is very poor, especially when processing materials with good ductility

cutting speed (especially high enough cutting speed) is another factor for the successful application of straight slot drills. The faster the cutting speed, the smaller the chips formed. Straight slot drill achieves high productivity through faster spindle speed rather than higher feed rate

many fried dough twist drills with high performance and high penetration rate have considerable chamfering on the cutting edge, which requires that the feed rate of the drill into the work should exceed the chamfering size of the cutting edge, so that the cutting edge can cut the workpiece material rather than just push it. For some processing applications and processed materials, the cutting edge chamfering of fried dough twist drills works well, and these fried dough twist drills are usually drilled at a feed rate higher than the straight slot drill and a cutting speed lower than the straight slot drill

take the drilling processing of Saturn, an automobile manufacturer, as an example. The drill bit used by the company used to be processed at a cutting speed of about 500sfm (150m/min). Later, they decided to do a cutting test to determine how high the speed of these drill bits can be processed. As a result, they found that when the rotating speed was increased, the tool life was prolonged, the machining cycle was shortened, and the chip removal efficiency was improved. When using uncoated solid carbide bits, the cutting speed can reach 1000sfm (300m/min), and the tool life and hole quality are significantly improved

by using a reasonable combination of coolant pressure and cutting speed, the straight grooved drill can also effectively process workpiece materials that do not necessarily produce short chips due to emergency hazards in the operation process. For example, the effect of machining 1144 stress-resistant steel with a straight groove drill is very good, the chip breaking is smooth, the chip is small, and no chip buildup is formed. The drill bit used for processing is the uncoated inner cooling straight groove drill bit (diameter) of h.a.m. precision company φ 5mm), the drilling depth is 48mm, the cutting speed is 185sfm (63m/min), the feed rate is 0.003ipr (0.076mm/r), and the coolant pressure is 1500psi. The content of manganese sulfide in 1144 alloy is high, which is conducive to chip breaking. However, to successfully process this material, a very high coolant pressure is required (experience shows that the coolant pressure should be above 600psi, preferably 1000PSI, 1200psi or higher)

for straight grooved drills, in addition to chip control, chip buildup may also become a problem. This is because the cut workpiece material will pass through the cutting edge and be pushed to the drill tip of the drill when it is discharged from the center of the straight groove drill. One of the ways to avoid chip buildup is to use a drill with smooth surface and high finish; The use of coated drill bits also helps to prevent chip buildup. For example, molybdenum disulfide (MoS2) coating, which is widely used in aluminum processing, has similar characteristics to Teflon and is not easy to bond with other substances. The effect of using this coated drill bit in processing occasions that need to prevent chip buildup is excellent

the drill tip structure of the straight groove drill enables it to grind out two blade belts at the outer edge of each straight groove. Because the drill bit has four contact points with the workpiece, the drill bit is more stable in processing, which can improve the processing accuracy

the large vertex angle used in the straight groove drill also helps to improve its machining performance. For example, the standard straight groove drill bit of h.a.m. precision adopts a 140 ° vertex angle, which is similar to a separate top drill. This structure can drill into the hole with a very small pushing force. In addition, the large vertex angle can also ensure that the entire diameter of the drill bit can be quickly connected with the workpiece material, minimizing the possibility of "Deviation" of the drill bit

in many processing cases, it is best to use a guide drill (center drill) whose top angle is greater than the top angle of the cemented carbide straight groove drill to process a starting hole (pre hole), so as to ensure that the center (transverse edge) of the drill tip of the straight groove drill first enters the pre hole during formal processing, so as to avoid edge collapse caused by the brittle cemented carbide cutting edge first contacting the workpiece. Another strategy of using straight slot drilling is to simply determine the hole position before drilling, because even the machined workpiece surface may have defects, and the operator only needs the drill to contact the pre hole to determine its position. As long as the horizontal edge of the drill bit contacts the workpiece first, the drill bit will not "deviate", and the positioning hole can play a role similar to the drill sleeve

machining on cast iron materials with three different drills φ The straightness of the hole measured when the hole is 10mm shows that the cutting speed of the high-speed steel spiral groove drill is 98sfm (30m/min), the feed rate is 7.66ipm (195mm/min), and the processing quality of the hole reaches it12 level by using external cooling mode; The cutting speed of the solid carbide spiral groove drill is 295sfm (90m/min), the feed rate is 34.5ipm (876mm/min), and the internal cooling mode with the coolant pressure of 440psi/2.4-gpm is adopted. The machining quality of the hole reaches it9 level; The cutting speed of the straight groove drill is 425sfm (130m/min), the feed rate is 33.3ipm (845mm/min), and the internal cooling method with the coolant pressure of 735psi/3.2-gpm is adopted. The machining quality of the hole reaches it8

many people call all straight groove drills "g drill", but this is not accurate. In fact, "g drill" is only the trademark name of a certain kind of straight groove drill produced by accuroma USA int. the outer edge of the tail of this kind of drill can play a role in crowding the hole wall

compare the hole wall finish that can be achieved by various hole processing tools. Generally speaking, the high-speed steel drill bit is about 125 RMS, the carbide spiral groove high-efficiency drill bit is about 63 RMS, the three groove reamer is about 32 RMS, and the G drill can reach 16 RMS or less, which has reached the level of finish machining cleanliness

in order to process holes of different quality levels, accuromm company has designed different drills. The company's g-drill can generally meet the hole processing requirements of H9 tolerance standard, while the company's G-7 drill integrates drilling and reaming functions, which can meet the processing requirements of H7 tolerance. For example, accuromm company listed an example of drilling on aluminum material with straight groove g drill instead of fried dough twist drill. The diameter of G drill is 0.394 ″( φ 10mm), with a cutting speed of 330ft/Min (100m/min), and the feed rate is 0.008ipr (0.20mm/r). The results show that the hole machining accuracy is significantly improved, and the hole diameter error is reduced from the original ± 0.0032 "(0.08mm) to ± 0.0012" (0.03mm). Under the same cutting parameters, if G-7 drill is used for machining, the aperture error can also be reduced to ± 0.0008 "(0.02mm)

due to the high drilling quality of the straight slot drill, it is also of great benefit to other hole processing procedures. Accuromm pointed out that if the hole processed by the straight groove drill needs to be tapped, its excellent dimensional accuracy can increase the tap life by about 50%

the improvement of cutting tool performance almost always requires a narrower range of machining objects. Although the straight slot drill is far from being a general-purpose tool, its scope of use is expanding. The promotion and application of straight slot drills can achieve very significant results in improving processing efficiency and workpiece quality, which is not commensurate with the economic aggregate of our province in the country

h.a.m. precision's "muilt drill", an integral carbide straight groove stepped drill, adopts TiAlN coating and internal cooling channel design, which is suitable for drilling, stepped hole and chamfering on short chip aluminum alloy materials

competitive carbide int.'s "insitable G-spot" special composite tool combines the company's G-spot straight slot drill with the inner cavity milling cutter, and a variety of machining of workpiece geometry can be completed with one tool. The tool can complete a total of 9 machining operations, including drilling, outer diameter (OD) chamfer and spot facer, inner diameter (ID) chamfer and spot facer, outer diameter turning (pre machining of threaded workpiece), etc. Because the contact area between the tool and the workpiece is large, and the outer diameter of the drill bit is in 4-point contact with the workpiece, this two-piece set of tools helps to maintain the stability of the workpiece position, which can play an additional clamping role on the workpiece. Because the straight groove drill has two blade belts, the tool can not only drill holes, but also squeeze the holes. This means that the machined hole has higher smoothness and better straightness, which can better meet the specific size requirements of the hole than the traditional drill with only one cutting edge. At least 3 ~ 4 kinds of tools can be replaced by using the instable G-spot composite tool, that is, if the original tool is used for processing, it needs 3 tool changes to complete 4 kinds of processing operations. Therefore, the use of this multi-functional composite tool is of great benefit to improve machining efficiency and shorten machining time

from tool Outlook (end)

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