With the development of titanium alloy wire processing technology, in recent years, titanium alloy has been widely used in the manufacture of aircraft engine parts such as compressor segment, engine hood, exhaust device and structural frame parts such as aircraft girders. Tapping in titanium alloys, especially small holes below M6mm, is very difficult. Mainly because the chips are small, easy to bond with the blade and workpiece, resulting in large machining surface roughness and torque.
Improper tap selection and operation during tapping can easily lead to work hardening, low processing efficiency and tap breaking phenomenon. The solutions are as follows:
Priority to choose a bit in place of the jump tap, the number of teeth should be less than the standard tap, generally 2 ~ 3 teeth. Cutting cone Angle should be large, taper part is generally 3-4 buckle thread length. To facilitate chip removal, it can also grind negative inclination Angle in the cutting cone part. Use short taps to increase the rigidity of taps. The inverted cone part of the tap should be larger than the standard part to reduce the friction between the tap and the workpiece.
In order to reduce the working hardening of the bottom hole, rough drilling should be carried out before reaming. For threads with a screw pitch of 0.7 ~ 1.5mm, the bottom hole size can be processed to the upper difference of the standard thread bottom hole specified in the national standard and another 0.1mm is allowed.
If not limited by the position of the screw hole and the shape of the workpiece, try to use machine attack, to avoid manual tapping feed uneven, halfway stop and caused by the work hardening.
Titanium alloy is an ideal material for aircraft and engine because of its high specific strength, good mechanical properties and corrosion resistance.