Tapping is a difficult process. Because the tapping feed rate is a function of tap pitch, so as to be artificially controlled. For example, the specifications for the 1/2-20 tap its feed rate is only 0.050ipr (1.27mm/r). Therefore, the processing is very difficult to control the chip load per tooth tapping is usually the final processing. Process parts, if the tap break in the workpiece hole, it may cause great economic losses.
Stainless steel tapping is a unique challenge. Stainless steel is difficult to machine materials, will produce long is not easy to break chips. In addition, stainless steel is prone to cold hardening stainless steel tapping. In order to improve the productivity and prolong tool life, must consider the machinability of the stainless steel, the cutting performance of tapping process and tap itself.
The machinability of the stainless steel and carbon steel or alloy steel are more difficult to be quite different, most stainless steel cutting.400 series of ferritic stainless steel although also can produce slender chips, but the process is relatively easy. While the 300 series austenitic stainless steel has great tendency of viscous and rapid cold hardening, the processing difficulty is great. Double phase stainless steel is a mixture of ferrite stainless steel and austenitic stainless steel, with good toughness and strength, but also prone to cold hardening.
The problem of stainless steel tapping is usually characterized by rough and broken threads, which kill the tap and cause it to break. The flaw in the tap itself may be the root cause. However, there are usually some other reasons
The need to use stainless steel tapping with high lubricity cooling liquid. Tapping is usually one of the processing methods of cutting load maximum, if insufficient lubrication of the cooling liquid and its adverse effects will be faster than most other processing to emerge.