1. taper teeth, the main reason for teeth
In the daily tapping thread, the taper teeth, teeth, the main reason is summarized as follows: ① reverse, the cutting root high point of the cutting edge squeeze the "teeth". ② reverse, the cutting of particles squeeze in the tap and the workpiece between the cutting edge of the squeeze called "teeth". ③ As the workpiece material is too hard, if the lubrication is not good, the cutting edge sticky, called "teeth". ④ because the workpiece material is too hard, the top of the tooth, called "teeth". ⑤ case of incessors, material uneven lumps, the top of the tooth, called "teeth". ⑥ unreasonable operation caused by the collision, such as intermittent cutting speed, entry and exit collision, resulting in the teeth called "teeth".
The reason is that most people do not find the seriousness of their destructive power. For example, Weihai Vocational and Technical College of the internship factory - Tin Connaught CNC Machinery Co., Ltd., the production of CNC Arbor, knife rod tail has a silk hole, respectively: Model 40 series corresponds to M16, model 45 series corresponding M20, model 50 series Corresponding to M24, there is a long life of the tap is not long, mostly due to the collapse of the teeth caused by the scrapped. This problem is also prevalent among other fraternal units, even in the national machinery manufacturing industry. Because the problem in the manual tapping, general machine tool tapping, CNC machine tool tapping are present, the destruction of the taps great, should cause everyone's attention. The following analysis of the causes and countermeasures.
2. Solution
First, as shown in Fig. 1, the workpiece is fixed in Fig. 1, the tap is rotated, the main cutting edge is marked as E, and the chip breaker is marked as F. Figure 1 is the tap back frying edge F, cutting the cutting, leaving the high point G, the height of the taper angle difference (EF arc length), the tap is cut, the tap is inverted, the cutting broken, in order to facilitate the discharge; Rear angle difference height); Figure 1d is due to the high point G caused by the taper teeth.
Most of the material of the workpiece, when the back to the cutting edge F back to the cutting root near, you can cut the top off (see Figure 1b), but will leave a high point, if you continue to back, (See Figure 1c), and then continue to retreat, that is, forced the back of the interference, because the tap is followed by a 6 ° ~ 8 ° angle after the slope to the main cutting edge E near the largest interference, The most prone to interference squeeze, so that the main cutting edge teeth (see Figure 1d). Now the machine with a tapered cutting edge is shorter, mainly to the two buckle half wire around the cutting, especially the larger diameter tap, single blade cutting allowance, encountered the workpiece material slightly stick hard, high point G resistance increased Large, this time the taps are most likely to dislocate, because the high point of the top of the force and the force when cutting, the cutting edge is a two-way fatigue alternately destroyed, greatly reducing the tap edge of the lasting limit, Figure 2 shows Cut open the M12 tap (did not break through), reverse the main cutting edge when the high point of the photo. The protrusion is the high point G, the main cutting edge is too high, the high point there is a clear signs of friction, but the convex is still very obvious, easily lead to taper teeth.
A large number of practical operations and found that when the tap reversal is less than the number of cutting edge, that is, three-blade tap reverse less than 1/3, four-blade tap less than 1/4, the probability of taper The minimum, as long as the tap inversion, the cutting broken, easy to chip can be, you can achieve the purpose of retreat, do not let the main cutting edge is too high G, which can effectively avoid the tap due to high G squeeze lead to teeth. Especially the manual operation, the use of the main cutting edge, but the high point is very feel, it is easy to achieve the purpose, not easy to break the tap. Motor attack thread, regardless of fitter or car workers also try to control the back trip, and strive to avoid the main cutting edge retreated high point, which can greatly improve the life of the tap. For example, we did not control the back trip before, in the Z512 drill upside down M12 thread (the production of about 100 F214 boring head slider, each 6 M12 thread, thread depth 18mm, through hole, material 40G) generally need to use 2 More than 6 tap, since the high point of the tap to understand the dangers, try to control the back trip, try not to let the main cutting edge of the high point G (foot switch control), for two consecutive months Production of the three batches (the first batch of 105, the second batch of 105, the third installment of 103), the results of taps life greatly improved, of which the first batch with two taps, the second batch only 1 (due to When the production of more than 70, the tapered blade in front of gently grinding about), the third batch with two tap, but the first tap dry 81, the second tap only 22, this process The middle taps are intact.
On the CNC machine tool because the program is fixed, the general operator can not change the use of procedures, it can not solve the problem, in this to the CNC machine manufacturer suggested that the NC machine program to adjust the machine operator to set the tap before and after the rotation. Motor attack thread, but also try to control the back trip, and strive to avoid the main cutting edge retreat high, so that can greatly improve the life of the tap Through research found that CNC machine tool tapping on the tap damage most of the teeth, if not teeth, blunt can simply grinding the tap front, so that the sharp reuse, if the teeth are not worth grinding.
3. Conclusion
The reason why the previous did not pay attention to the above problems, because the books generally tell us a certain amount of tap after the forward, reverse 1/4 ~ 1/2, so that cutting broken, easy to discharge. By looking at some books, it is found that the description of the tapping is the same. Therefore, through practice, the proposed teaching materials should be based on the actual situation changes: four-tap tap should be less than 1/4, three-blade tap should be less than 1/3, so that cutting broken, easy to discharge can be. Therefore, the mechanical colleagues should be used to tap the factory more research to understand the CNC machine tool tapping when the taps too much damage to the reasons, efforts to adjust the existing process to improve the service life of the tap, to contribute to a conservation-oriented society.
