Tap improvement ( 1) Optimization of tap chip pockets. In the blind hole tapping of the crankshaft, the tapping often occurs when the tap retracts, which causes the problem of the inner hole rotten. In this case, it is often caused by poor chip removal of the taps, and the use of spiral groove taps is more conducive to chip removal. There are many things to be aware of when selecting a spiral groove tap. If the failure mode of the spiral groove tap is the blade wear, the angle of the spiral groove can be appropriately lowered to increase the strength of the tap blade. For example, in a specific processing situation, through the test and verification, the life of the 20° spiral groove tap is 25% higher than the life of the 30° spiral groove tap. In addition, the shape of the chips that the taps discharge during the tapping process is also critical. We prefer to wind fine chips, which is good for the discharge of chips, and it is not easy to cause the chips to squeeze the taps in the closed cavity. There are many ways to change the state of the chip, the most straightforward is by modifying the groove shape of the spiral groove. The spiral groove of the tap is generally processed by grinding, and various groove shapes can be processed by the grinding wheel. Reducing the radius of the arc of the spiral groove can make the chip become fine and dense, which is good for chip removal. In deep hole machining, the use of an internal cooling tap can effectively reduce the cutting heat and reduce the early failure of the taper blade. Due to the complicated process of the inner cooling tap, the price is often high. In practice, the same effect can be achieved by lengthening the flutes, and the cost of the taps will not change much. ( 2) Tap cutting edge optimization. In the case where the depth of the bottom hole is sufficient, the number of cutting edges can be increased to increase the life of the tap. The inverted cone of the cutting edge of the leading end of the tap determines several cutting edges on one blade. The more cutting edges on each blade, the less the amount of cutting per cutting edge and the less wear on the cutting edge. Generally, there are 2 to 3 cutting edges on each blade of the tap. If the space of the bottom hole is large enough, it will not interfere with the bottom of the tap and the bottom of the bottom hole, and at the same time, the effective tapping depth can be ensured to meet the product requirements. It is possible to reduce the angle of the cutting edge of the cutting edge and increase the number of cutting edges. This method can greatly improve the service life of the tap. ( 3) Optimization of tap material. Most of the machine taps are made of ordinary high-speed steel. The advantages of ordinary high-speed steel materials are that they are cheap and have low manufacturing costs, and have certain advantages in processing products with low hardness. However, with the advent of new materials such as cobalt high-speed steel and powder metallurgy high-speed steel, the advantages of ordinary high-speed steel have become less obvious. Under normal circumstances, the price of cobalt high-speed steel wire cone is about 4 times that of ordinary high-speed steel wire cone . Under the same conditions, the life of the cobalt high-speed steel wire cone is about 4 times higher than that of the ordinary high-speed steel wire cone, and this is increasing. The cobalt high-speed steel is equivalent to the ordinary high-speed steel. The price of using powder metallurgy cobalt high-speed steel is twice that of ordinary cobalt high-speed steel, and the service life is improved, and the cost performance will be higher in the use of difficult-to-process products. Due to the material upgrade, the purchase cost of single-piece taps is greatly improved. If the processing conditions are not good, the high-performance taps accidentally break one piece will cause the cost performance of the taps under the condition that the tapping, vibration and cooling conditions of the tapping shank are not ideal. reduce. However, if the processing conditions are good, the taps do not need to be replaced frequently, and the processing quality will not be degraded due to improper replacement. Therefore, when conditions permit, the use of high-performance taps is an improvement in efficiency and improvement in processing quality. Surface treatment is also a way to improve the life of the tap without changing the material of the tap. Steam tempering, which generally improves the chip removal performance, and various coatings that increase the surface hardness of the tap can improve the life of the tap to a certain extent. However, after using the surface treatment, the price/performance ratio has improved and needs to be carefully accounted for. 2. Machine reliability improvement As the mother machine tap tapping, the reliability of the machine tool is also a key factor affecting the life of the tap. More commonly used tapping equipment has a machining center or a special plane. This type of machine is equipped with a special tapping shank. The most important factor affecting the life of the tap is the tapping shank. There are currently two types of tapped shank, one is a rigid tapping shank and the other is a flexible tapping shank. The advantage of rigid tapping is that the product processing quality is high. The disadvantage is that there are strict requirements on the clearance and inertia of the spindle drive mechanism, otherwise the tap will be broken. The flexible tapping tool holder can be selected for torque overload protection. Generally, the tapping life of the flexible tapping thread is longer than that of the rigid tapping thread. From the perspective of the life of the tap, a flexible tapped shank is preferred. The rigid tapping rotation and feed are strictly matched with the pitch set by our programming, but from the tap manufacturing, the pitch error of the tap is unavoidable, so the actual feed rate of the rigid tapping is always much larger than the tap. The actual pitch is slightly larger or smaller, so that a force due to the inconsistent pitch of the two is added to the axial direction of the tap. This force causes the flank of the tap to be particularly stressed, which exacerbates wear. Flexible tapped shank with over-torque protection. Once the tap is sluggish and the torque is too large, a signal is sent from the high-frequency transmitter inside the chuck, which can stop the machine in time, replace the tap to eliminate the problem, and avoid the scrapping of the workpiece. At the same time, the elastic structure in the flexible tapping shank can automatically compensate the error between the actual feed rate of the tapping thread and the actual pitch of the tap to ensure the balance of the tap force. The quick-change chuck is often provided on the tapping shank to facilitate quick replacement of the tap. The daily inspection and replacement of the quick change chuck is just as important. The quick change chuck ensures that the tap is centered by contacting several beads attached to the elastic mechanism with the tap. If one or more of the steel balls in the quick change chuck lose elasticity, the tap is offset from the center of the handle, which is easy. Causes the tap to break. Generally, the damage of the quick change chuck is caused by a violent collision, such as a machine tool collision. Therefore, after the collision of the machine tool, it is necessary to check whether the quick change chuck has been damaged, otherwise it is easy to break the tap again in the subsequent tapping. 3. Conclusion The life of taps in blind hole tapping is related to many factors. For different products, different types of taps need to be selected, and the improvement of processing conditions is crucial. Only when a suitable tap is selected can the life of the tap be improved if the machine is in good condition.
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Blind hole tapping, lifting tap life is critical
Taps are one of the most complex and toughest tools in the machining environment, especially in the fully enclosed environment of blind hole tapping. The selection of taps and machine reliability are very important. In the process of processing, premature wear, chipping, and breakage of the tap will cause the life of the tap to decrease, and the quality of the processed product is greatly affected. Therefore, it is very important to improve the life of the tap in the blind hole tapping thread, mainly from the aspects of tap structure, material and machine reliability.