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Drilling technology Daquan, collected! _ Drill

Started Feb-2 by ylors; 60 views.

From: ylors


Original Title: Drilling Technology Encyclopedia, Collected! Tips: Click [Window Fastener] on the top, click [..] in the upper right corner, and click [Set as Star], so that we can meet every day. Drill, as the most common tool in hole processing, is widely used in mechanical manufacturing, especially in the processing of holes in cooling devices, tubesheets of power generation equipment and steam generators. I. Characteristics of drilling Drills usually have two main cutting edges, and when machining, the drill cuts while rotating. The rake angle of the drill is getting larger and larger from the central axis to the outer edge, the cutting speed of the drill is getting higher and higher when it is closer to the outer circle, and the cutting speed decreases to the center, and the cutting speed of the rotary center is zero. The chisel edge of the drill is located near the central axis of rotation. The chisel edge has a large secondary rake angle, no chip space and low cutting speed, so it will produce a large axial resistance. If the chisel edge is ground to Type A or Type C in DIN1414 and the cutting edge near the central axis has a positive rake angle, the cutting resistance can be reduced and the cutting performance can be significantly improved. According to the shape, material, structure and function of the workpiece, the drill bit can be divided into many types, such as high-speed steel drill bit (twist drill, group drill, flat drill), solid carbide drill bit, indexable shallow hole drill, deep hole drill, trepanning drill and interchangeable head drill bit. 2. Chip breaking and chip removal The cutting of the drill is carried out in a narrow hole, and the chips must be discharged through the drill edge groove, so the chip shape has a great influence on the cutting performance of the drill. Common chip shapes include flaky chips, tubular chips, acicular chips, conical spiral chips, ribbon chips, fan-shaped chips and powdery chips. The Key of Drilling Machining: Chip Control When the chip shape is not appropriate, the following problems will arise: ? Fine chips block the cutting edge groove, affecting the drilling accuracy, reducing the life of the drill bit, and even breaking the drill bit (such as powdery chips, fan-shaped chips, etc.); ? Long chips entangle the drill bit, which hinders the operation, causing the drill bit to break or preventing the cutting fluid from entering the hole (such as spiral chips, ribbon chips, etc.). Expand the full text How to Solve the Problem of Inappropriate Chip Shape ? The chip breaking and chip removal effects can be improved by increasing the feed rate, intermittent feed, grinding the chisel edge, installing the chip breaker and other methods respectively or in combination, so as to eliminate the problems caused by chips. ? Professional chip-breaking drill can be used for drilling. For example, the addition of a designed chip breaker in the groove of the drill breaks the chips into more easily removed chips. The debris is smoothly discharged along the groove, and the phenomenon of blockage in the groove does not occur. Therefore, the new chip-breaking drill obtains a much smoother cutting effect than the traditional drill. At the same time, the short scrap iron makes the coolant flow to the drill tip more easily, which further improves the heat dissipation effect and cutting performance in the processing process. Moreover,Tapered Rock Bit, because the new chip-breaking edge penetrates the whole groove of the drill bit, it can still maintain its shape and function after many times of grinding. In addition to the above functional improvements, it is worth mentioning that the design strengthens the rigidity of the drill body and significantly increases the number of holes drilled before a single grinding. III. Drilling accuracy The accuracy of the hole is mainly composed of the hole size, position accuracy, coaxiality, roundness, surface roughness and hole burr. Factors affecting the accuracy of the hole to be machined during drilling ? Bit clamping accuracy and cutting conditions, such as tool holder, cutting speed, feed rate, cutting fluid, etc.; ? Drill size and shape, such as drill length, blade shape, drill core shape, etc.; ? Workpiece shape, such as orifice side shape, orifice shape,DHD Drill bit, thickness, clamping state, etc. Reaming Reaming is caused by the oscillation of the drill during machining. The swing of the tool holder has a great influence on the hole diameter and the positioning accuracy of the hole, so when the tool holder is worn seriously, it should be replaced with a new one in time. When drilling a small hole, it is difficult to measure and adjust the swing, so it is better to use a drill with a thick shank and a small edge diameter with a good coaxiality between the blade and the shank. When the regrinding drill is used for machining, the reason for the decrease of hole accuracy is mostly due to the asymmetry of the back shape. Controlling the height difference of the cutting edge can effectively restrain the amount of hole expansion. Roundness of the hole Because of the vibration of the drill bit, the drilled hole shape is easy to be polygonal, and the lines like rifling appear on the hole wall. Common polygonal holes are mostly triangular or pentagonal. The reason for the triangular hole is that the drill bit has two rotary centers during drilling, and they vibrate at the frequency of exchanging once every 600. The main reason for the vibration is that the cutting resistance is unbalanced. When the drill bit rotates for one turn, the resistance is unbalanced during the second turn of cutting due to the poor roundness of the processed hole. The last vibration is repeated again, but the vibration phase has a certain deviation. Cause rifling pattern to appear on that walls of the hole. When the drilling depth reaches a certain degree, the friction between the drill edge and the hole wall increases, the vibration decreases, the rifling disappears, and the roundness becomes better. The orifice of this pass is funnel-shaped when viewed in longitudinal section. For the same reason, pentagonal and heptagonal holes may also appear in cutting. In order to eliminate this phenomenon, in addition to controlling the factors such as Chuck vibration, cutting edge height difference, back and edge shape asymmetry, measures such as improving drill rigidity, increasing feed per revolution, reducing clearance angle and grinding chisel edge should be taken. Drill holes on sloped and curved surfaces When the cutting surface or penetration surface of the drill is inclined, curved or stepped, the positioning accuracy is poor, and the tool life is reduced because the drill has a radial single-sided cutting surface. To improve the positioning accuracy, the following measures can be taken: 1. Drill the center hole first ; 2. Milling hole seat with end mill ; 3. And that selection cut-in property is good Drill bit with good rigidity; 4. Reduce the feed speed ? Treatment of burrs During drilling, bur
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