Traditional thread processing methods mainly include turning threads with thread turning tools or manual tapping with taps, plate teeth and sockets. With the development of NC machining technology, NC milling of threads has been realized. Compared with traditional thread processing, thread milling has great advantages in processing accuracy and efficiency, and it is not restricted by thread structure and thread rotation direction. For example, a thread milling cutter can process various internal and external threads with different rotation directions. The following is a brief introduction of how to choose the milling cutter for the thread milling process.
I. advantages of thread milling
(1) For threads with no transition buckle or withdrawal groove structure, it is difficult to machine by traditional turning method or tap or plate teeth, but it is very easy to realize by CNC milling.
(2) The durability of threaded milling cutter is more than ten times or even tens of times that of tap, and in the process of NC milling threads, it is very convenient to adjust the diameter and size of threads, which is difficult to achieve by using taps and plate teeth.
Two. Thread milling process
(1) thread milling cutter runs quickly to the safety plane of the workpiece, and the thread drill is drilled to the hole depth.
(2) the thread milling cutter is rapidly raised to the thread depth dimension, and the thread milling cutter enters the starting point of the thread by circular arc.
(3) The threaded milling cutter interpolates around the threaded axis, and simultaneously moves parallel to the axis and raises a pitch along the direction. The three-axis linkage trajectory is a helix.
(4) the thread milling cutter withdraws from the starting point with the circular arc, and the thread drilling and milling cutter returns to the safety plane of the workpiece quickly.
Three. Types of thread milling cutters
(1) cylindrical thread milling cutter
The shape of cylindrical thread milling cutter is very similar to the combination of cylindrical end milling cutter and thread tap, but its thread cutting edge is different from the tap. There is no spiral lift on the cutter. The spiral lift in processing is realized by the movement of the machine tool. Because of this special structure, the tool can process both right and left threads, but it is not suitable for processing larger pitch threads.
(2) thread milling cutter and blade
Thread milling cutter is suitable for machining large diameter thread. Its characteristic is that the blade is easy to manufacture and the price is low. Some threaded blades can be cut on both sides, but the impact resistance is slightly worse than that of the whole threaded milling cutter. Therefore, the cutter is often recommended for machining aluminum alloy materials.
(3) combined multi station special thread boring and milling cutter
The combined multi-position thread boring and milling cutter is characterized by multi-edge cutter. Completing multi-position processing at one time can save auxiliary time such as tool changing and significantly improve productivity.
Four. Selection of thread cutting oil
(1) Because of the toughness of stainless steel, cutting is not easy to be separated, so cutting oil is required to have a higher cooling performance to take away a lot of heat.
(2) Because of its high viscous and melting property, it is easy to produce chip tumors in the process of cutting threads, so the cutting oil should have high lubricity.
(3) It is required that the cutting oil has good permeability, which can penetrate into the micro-gap lines in the metal area in the cutting process, so that the chips are easy to break off.
(4) Cutting oil should contain sulfide extreme pressure and anti-wear additives, which can effectively protect cutting tools and improve process accuracy.
(5) Compared with rapeseed oil, mechanical oil and regenerated oil, the special cutting oil has good stability and does not harm equipment, human body and environment.
(6) The cutting oil has passed strict tests in viscosity, flash point, dip point and thermal conductivity to meet various cutting process requirements.
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