There are many ways for thread drilling in metalworking. As for external thread, both thread rolling and thread dies are most common used. As for inner thread machining, we generally use taper/second/bottoming three steps thread tapping or fluteless tapping.
Frankly speaking, to drill a deep and small inner thread on high hardness or malleability raw material is a difficult mission. Thread machining is all about factors. Such as hole diameter, the forming speed and types of drill bet on the responses: torque, hardness, feeding rate, and thrust force of the form tapping process. Fluteless tap is the one of the best tooling for machining inner thread on CNC turning machines.
What is the Advantages of Fluteless Tap?
Fluteless tapping, so called form tapping. The screw thread is formed by plastic deformation of a working metal under high level of torque. And, well monitored operation processing to avoid tool bit breakage when thread machining.
Fluteless tapping can form a perfect screw thread with no waste material in a pre-drilled hole. Besides, it is kind of opposite style of external thread rolling method. The inner screw thread machined by fluteless tap is with higher strength and less error of pitch diameter. So, we mainly use fluteless tap machining inner thread on aluminum part, brass part and zinc part when in CNC precision manufacturing.
Thread Machining in Industrial Application
Let’s consider automobile industrial application as an example. Mechanical components need to have threaded parts allowing quick and precise assemblies and dis-assemblies. The engine heads manufactured with non-ferrous metals have a excellent capacity to deform and maintain an acceptable mechanical strength. As a result, thread formed by fluteless tapping can guarantee perfect full threading and high tensile strength.
However, inner thread machined by fluteless taps have some peculiarities. For example, the appearance of a split crest on the top of the thread. Above phenomenon is directly rely on the initial pre-drill hole diameter. In addition, the smaller the inner diameters, the slighter the split crest on the top of the screw thread after flutless tap forming.
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