With the development of processing technology, in recent years, titanium alloys have been widely used in the manufacture of aircraft engine compressor sections, hoods, exhaust devices and other structural components such as aircraft frame frames. Titanium tapping, especially tapping of small holes below M6mm is quite difficult. Mainly because the chip is small, it is easy to bond with the blade and the workpiece, resulting in a large surface roughness value and a large torque.
Improper tapping and improper operation during tapping can easily cause work hardening, and the processing efficiency is extremely low and the tap is broken. The solution is as follows:
1. It is preferred to use a wire jumper in place, the number of teeth should be less than the standard tap, generally 2 to 3 teeth. The cutting cone angle should be large, and the taper portion is generally 3 to 4 thread length. In order to facilitate chip evacuation, a negative inclination angle can also be ground in the cutting cone portion. Try to use a short tap to increase the rigidity of the tap. The inverted cone portion of the tap should be appropriately enlarged compared to the standard to reduce the friction between the tap and the workpiece.
2. When machining the bottom hole of the thread, first rough drill and then ream the hole with a reaming drill to reduce the work hardening of the bottom hole. For threads with a pitch of 0.7 to 1.5 mm, the bottom hole size can be machined to the upper limit of the standard threaded bottom hole specified by the national standard and allowed to increase by 0.1 mm.
3. If it is not limited by the position of the screw hole and the shape of the workpiece, the machine attack should be adopted as much as possible to avoid the work hardening caused by the uneven feeding of the manual tapping and the pause in the middle.