There are several reasons for the broken taps
1, the speed of feeding is too fast and the torque is too big. It is suggested that the speed of the tapping machine should not exceed 100 RPM when the thread is processed with a common taps.
2, bottom outlet aperture and the tap does not match. For example, the processing of ferrous metal materials M5 * 0.5 threads, with cutting tap should choose 4.5mm diameter drill hit bottom, if used to play 4.2mm drill hole, tapping tap required cutting part must be increased so that the tap break. Suggestions according to the different types and selection of tap material of the correct hole size, if not fully comply with the drill bit can choose a big level.
3. Improper operation. When processing blind hole thread, when the tap is about to touch the bottom of the hole, the operator does not realize that the tap is still forced to enter when it does not go to the bottom of the hole, or when the chip is not smooth, it will cause the tap to break. It is suggested that the operators strengthen their sense of responsibility.
4. No use of cutting fluid or improper selection. In the process of tapping, a large amount of heat will be produced, especially for some nonferrous metals, which have a strong ductility. It is necessary to select a good cutting fluid.
5. The concentricity is not enough. Start tapping, tap start positioning is not correct, namely the center line axis and tap the heart, in the process of tapping torque is too large, this is the main reason for the tap break.
6, the problem of the material of the attack. The material of the attack is not pure, and the part has a strong point or air hole, which causes the taps to lose balance and break at the moment.
7, improperly tapping steps. The high hardness of the attack or hole tapping, tapping should be graded, avoid one.
8, the taps are not well welded. In particular, large size taps, many manufacturers to save expensive high speed steel, taper shank, blade with 45 steel and high speed steel by friction welding. A large number of taps are broken because of the poor welding. The quality of the taps is mainly determined by the friction pressure, the time of friction, the pressure of the forging and the time of the forging. During the friction stage, the harmful impurities such as low melting point compounds on the contact surface between the 45 steel and high-speed steel are extruded, and finally extruded together under proper forging pressure. When welding, because the strength of 45 steel under high temperature is low in friction pressure will produce big deformation, the formation of large and high speed steel flange; because there is enough strength of the flanging is small, low melting point compounds which makes the welding surface of high speed steel side was not completely out, easy to crack after welding. In the process of using tap crack cause fracture. In addition, if the taps are welded, it is easy to break up in the heat affected zone if the stress is eliminated in time.
9, the effective cutting area of the taps is too small, which leads to the oversize of the unit area bearing capacity, which exceeds the fracture of the taps.
10, the size of the cross section of the taps is too large or the transition angle is not designed to lead to the stress concentration, and it is easy to break at the stress concentration. The transition area between the cross section of the handle and the blade is too close to the welding port, which leads to the complex welding stress and the stress concentration at the transition section, resulting in a larger stress concentration, resulting in the fracture of the tap.
11. The heat treatment process is improper. When the taps are heat-treated, the taps are likely to cause cracks without preheating, quenching overheating or overheating, untimely tempering and prematurely cleaning.
12, the taps are not chosen properly. High quality taps should be selected for hard parts with too much hardness, such as cobalt taps, hard alloy taps, coated taps, etc.
