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Analysis on the fracture of tapping taps

2018/5/27 12:12:15 Viewers:
The tapping machine is a machine tool for machining internal threads, screws, or tooth buckles on the inner surface of the holes of various holes or blind holes with different specifications, such as the shell of the machine parts, the end face of the equipment, the nut, the flange plate and so on. It has the advantages of simple operation, low cost and so on. It is widely used in hardware production, machinery manufacturing and other industries. However, the taps caused by various factors seriously affect the processing efficiency.


First, the quality of the taps is not good
It includes main materials, NC tool design, heat treatment, machining accuracy, coating quality and so on.
(1) the size difference between the transition areas of taps and the design of transition fillets lead to stress concentration, which is prone to fracture at the stress concentration.
(2) the cross section of the cross section of the handle and edge is too close to the weld, which leads to the superposition of the complex stress and the stress concentration in the cross section of the cross section, resulting in a larger stress concentration, which causes the taps to break in the use.
(3) improper heat treatment process. If the taps are heat treated without quenching, quenching, overheating or overburning before heating, premature tempering and cleaning can lead to cracks in the tap.
Countermeasures: choose a reliable and reliable taps brand and a more suitable taps.


Two. Unsuitable selection of taps
For high hardness parts, high quality taps should be used, such as cobalt high speed wire cones, carbide taps, coated taps, etc. In addition, different tap designs are applied to different workplaces, such as the number, size and angle of the chip removal slot, which affect the chip removal performance.
(1) for the refractory materials with high hardness and high hardness, such as precipitated stainless steel and high temperature alloy, it may be broken that the taps are not strong enough to resist the cutting resistance of tapping.
(2) the mismatch between the taps and the processed materials has been paid more and more attention in recent years, and the variety of tool materials is increasing continuously. It is necessary to choose the suitable taps before the tapping.
Countermeasures: the taps of high strength materials such as high temperature steel, such as powder high temperature steel, are used to improve the strength of the taps, and to improve the surface coating of the taps to improve the surface hardness of the silk screen; in extreme cases, even manual tapping may be a feasible method.


Three. Overwear of taps
The overwear of the taps is a very common case. After the taps are machined, the cutting resistance of the taps becomes larger because of the overwear of the taps, which leads to the disassembly of the taps.
Countermeasures: it is recommended to use a special taper, which will obviously delay the taper wear and thus improve the service life of the taps; at the same time, the use of high quality tapping oil can also effectively delay the taper wear.


Four, axial synchronization error
In the process of tapping, a large number of broken taps are due to the error of the synchronism of the spindle rotation and the axial feed, which makes the tap of the taps increase and cause the taps to break.
Countermeasures: using special tap handle to solve the problem of axial synchronous error compensation for rigid tapping.


Five. It is difficult to break chip and chip
For the blind hole tapping, the screw taps are usually used for the tapping of the back of the spiral groove. If the iron chips are entangled on the taps, the taps will not be discharged smoothly, and a large number of processed materials are usually difficult to break the chips.
Countermeasures: first, change the spiral angle of the taps to make the iron chip removed smoothly; at the same time, the cutting parameters are properly adjusted to ensure that the iron chips can be eliminated smoothly; when necessary, the variable spiral angle taps can be selected to ensure the smooth discharge of the iron chips.


Six. The aperture of the bottom hole is small
When the tap hole is selected, the diameter of the bottom hole will be increased by using the unreasonable bottom hole diameter, so that the tap can be broken.
Countermeasures: it is suggested that the correct bottom hole diameter should be selected according to the variety of taps and the different material of the tapping. If the bit is not fully conformed, the larger one can be selected.


Seven. The problem of material quality
The impure parts are impure, and there are some excellent points or blowholes, causing the tap to lose balance and break instantly.
Countermeasures: before the processing, the performance and quality of all raw materials should be tested and verified completely, and the unqualified raw materials should be prohibited.


Eight. The precision requirement of the machine tool has not reached the taps
Machine tools and clamping bodies are also very important, especially for high quality taps, as long as a certain accuracy of machine tools and clamping body can play the taps performance. The common thing is that the concentricity is not enough. When the tapping begins, the taps are not located correctly, that is, the main axis of the spindle is not concentric on the center line of the bottom hole, and the torsional torque is too large during the tapping process, which is the main reason for the taps broken.
Countermeasures: comprehensive calibration of machine tool equipment, reduce accuracy error.


Nine. The quality of the cutting oil or tapping oil is not good
The use of oil, vegetable oil and other non special oil products as cutting fluid, the quality of the products processed is easy to appear burr and other bad conditions, and the taps will also have a great reduction in life.
Countermeasures: using the special tapping oil instead of non exclusive oil products can significantly improve the processing effect.


Ten, the cutting speed and feed are not reasonable
When the cutting speed and feed rate decrease hours, the propelling force of the taps will be reduced, and the thread precision of the production is reduced greatly, so the roughness of the thread surface is increased, the screw aperture and the thread precision are not controlled, and the burr is certainly more unavoidable. But too much torque is too fast to cause too much torque.