As the most common tool in the treatment of holes, drilling bits are widely used in mechanical manufacturing, in particular for the treatment of room holes such as cooling devices, pipe plates and generators of Steam in electricity production equipment, and their application areas are particularly large and important.
1. Characteristics of the borehole
The forest generally has two main cutting edges. The entrance angle of the forest is increasingly large from the central axis on the outside edge. The cutting speed of the rotation center of the drill bit is zero. The horizontal blade of the forest is located near the central axis of the rotation. If the edge of the cross -blade is crushed in type A or type C in DIN1414 and the cutting edge near the central axis is a positive front angle, cutting resistance can be reduced and the performance of cut can be considerably improved.
Depending on the form, the material, the structure, the function of the part, etc., the bits of drilling can be divided into many types, such as high -speed steel drilling bits (torsion drilling, group drill , flat drill), integral carbide packages, indexable drill of shallow hole, deep holes forest, nesting exercises and replaceable head drills, etc.
2. Breakage of broken chips and suppression of fleas
The cup of the forest is made in a hole with a narrow space, and the chips must be discharged through the groove of the edge of the forest, so that the shape of the chip has a large impact on the driving of the forest. The forms of common fleas include leaf chips, tubular fleas, needle chips, conical spiral shavings, ribbon chips, fan fleas, powder shavings, etc.
The key to drilling – flea control
When the shape of the chip is not appropriate, the following problems will arise:
① fine shavings block the groove of the edge, affect the precision of the borehole, reduce the lifespan and even break the forest (such as powder chips, fan fleas, etc.).
② Long shavings wrapped around the forest, hampering the operation, damaging the forest or hampering the cutting liquid of the entrance into the hole (such as spiral chips, ribbon shavings, etc.).
How to solve the problem of the inappropriate chip form:
① The effect of breaking and eliminating fleas from flea can be improved separately or in combination by increasing the volume of power, intermittent power, grinding the horizontal blade, the installation of flea circuit breakers, etc. ., and eliminate the problems caused by the chip cut.
You can use a professional flea breaking forest to pierce holes. For example: the addition of a chip circuit breaker designed in the groove of the drill bit breaks the chip in easier debris. The debris are removed smoothly along the groove and will not be blocked in the groove. Consequently, the new flea breakup forest reaches a much smooth cutting effect than the traditional forest.
At the same time, short iron shavings allow cooling of the coolant towards the tip of drilling, further improving the thermal dissipation effect and cuts performance during the processing process. In addition, as the newly added chip circuit breaker penetrates the whole groove of the forest, it can always maintain its shape and function after the repeated grinding. In addition to the above functional improvements, it should be mentioned that the design strengthens the rigidity of the drilling body and considerably increases the number of drilled holes before a single grinding.
3. Drilling precision
The accuracy of the hole is mainly composed of factors such as the size of the opening, the precision of the position, the coaxiality, the roundness, the roughness of the surface and the orifice lands.
Factors that affect the accuracy of the hole treated during drilling:
①The tightening precision and cutting conditions of the forest, such as tool support, cutting speed, quantity of power, cutting fluid, etc.
Size and shape of the decidelier bit, such as the length of the drill bit, the shape of the blade, the shape of the drilling nucleus, etc.
③The shape of the part, such as the lateral shape of the orifice, the thickness, the state of the jamming, etc.
1 hole extension
The bore is caused by the oscillation of the forest during treatment. The tool holder’s swing has a great impact on the opening and precision of the hole positioning. When drilling small holes, it is difficult to measure and adjust the swing, so it is preferable to use a thick forest diameter of the blade with better coaxiality and better manipulation. When using a reassembly forest, the reason for reducing the accuracy of the holes is mainly due to the asymmetrical shape behind. Control of the difference in the blade height can actually remove the hole cutting expansion.
2 rounding holes
Due to the vibration of the forest, the pierced holes are easily polygonal and the lines appear on the walls of the hole. The current polygonal holes are mainly triangles or pentagons. The reason for the triangular hole is that the drilling bit has two rotation centers during drilling, which vibrate at a frequency exchanged 600 times per interval. Not round. When the drilling depth reaches a certain level, the friction between the surface of the edge of the boring blade belt and the wall of the hole increases, the vibration fade, the multiple lines disappear and the roundness improves. This type of hole seems in the shape of a funnel from the longitudinal section. For the same reason, pentagonal heptagonal holes, etc. may also appear during the cut. To eliminate this phenomenon, in addition to control factors such as mandrel vibrations, the difference in peak height, the rear and the blade shape asymmetry, etc., it must also be used to improve the rigidity of the Drilling bit, increase food by revolution, reduce the back angle and repair grinding.
3 -discovered holes in tilted and curved surfaces
When the forest is a bevel surface or step, the positioning accuracy is bad.
To improve the accuracy of positioning, the following measures can be taken:
① First pierce the central hole.
②.
③ Choose drills with good cutting capacity and good rigidity.
④ Reduce the power speed.
4 Burning treatment
During the borehole, Burrs will appear at the entrance and exit of the hole, in particular during the treatment of thin materials and plates with high tenacity. The reason is that when the forest is about to unravel, the treated material will undergo a plastic deformation. Folded on the outside, then on the outer edge of the forest, the rooms and the edges are also rooted under the action of the edges of the blade, forming curly edges or burrows.
4. Drilling treatment conditions
The general catalog of the drilling product sample contains the “basic cutting volume reference board” organized by treatment materials. The question of whether the cutting conditions are appropriate should be selected by the test cut and the full judgment according to factors such as processing accuracy, processing efficiency and life of the bit.
1 LIFE and PROCESSING EFFECTIVE drilling
Regarding the treatment of the technical requirements of the part to be processed, if the forest is used correctly must be measured exhaustively according to the lifespan and the machining efficiency of the forest. The cutting distance can be used for the assessment index of the life of the drilling bit; The power speed can be used for the evaluation index of the processing of processing efficiency. For high -speed steel bits, the forest of the forest is greatly affected by the speed of rotation and the quantity of food per revolution is less affected. A longer life of the forest. However, it should be noted that if the quantity of food per revolution is too large, the shavings thicken, causing difficulties in breaking fleas. For cemented carbide bits, there is a large chamfer in the direction of the negative forehead angle of the tip edge. Range during treatment, the use of drilling bits will be reduced. Given that the heat resistance of the breading bits in cement carbide is higher than that of steel drilling bits at high speed, the speed of rotation has little impact on the lifespan of drilling bits. Treatment The efficiency of cemented carbide drilling bits while guaranteeing the lifespan of forests.
2 Rational use of cutting fluid
The cup of the forest is made in holes with a narrow space, so that the type of cutting fluid and the injection method have a large impact on the lifespan and the precision of machining of the hole. The cutting fluid can be divided into two categories: soluble in water and insoluble in water. The insoluble cutting liquid in water has good lubricity, resistance to anchoring and adhesive, and also has an anti -ist effect. The water -soluble cutting liquid has good cooling properties, is smoked and non -flammable. For environmental protection, the water -soluble cutting liquid has been used in recent years. However, if the dilution ratio of the soluble cutting fluid in water is inappropriate or the cutting fluid deteriorates, the lifespan of the tool will be considerably shortened, so that attention must be paid during the ‘use. Whether it is a cut -soluble cutting fluid or insoluble in water, the cutting fluid must be fully reached the cutting point during use. cutting fluid must be strictly controlled.
5. Re-Blade of Drill Bit
Diagnosis of a drill again
The criteria to determine if the drilling bit should be noted is:
① The amount of slice wear, horizontal blade and the surface of the edge edge;
② Dimensional precision and surface roughness of the hole to be treated;
③The color and shape of chips;
④ Cup resistance (indirect values such as spindle current, noise, vibrations, etc.);
⑤ Quantity of treatment, etc.
In real use, precise and practical judgment criteria must be determined from the above indicators on the basis of specific circumstances. When using the amount of wear as a criterion, the best period of economic re-repair must be found. Since the main needle parts are at the back of the head and the horizontal edge, if the drilling bit is doing too much, the wear time is too much and the quantity of grinding is important, the number time to retreat can be reduced (total the lifespan of the tool = the lifespan of the tool after the recovery × the number of reproach times) will shorten the total lifespan of the forest; or the limit gauge checks the quantity of cutting, non-standard, etc. of the hole. To automatically stop after exceeding the defined limit value (such as spindle current);
How to refine the forest
When reproducing the forest, it is preferable to use a special machine-tool for crushing the forest or a grinding machine of universal tools, which is very important to ensure the life and the precision of machining of the forest. If the original drilling shape is in good condition, it can be enriched according to the primary drilling shape; of use.
The following points should be paid to attention during the sharpening:
①.
② All damage to the forest (in particular damage by the blade belt) must be removed.
③The type of drilling must be symmetrical.
④ Be sure not to damage the edge during sharpening and remove the terrifying after sharpening.
⑤ For cemented carbide bits, the form of sharpness has a great impact on forest performance. maintained during reintegration.
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