5 Questions about metric thread taps you always wanted to ask

Often it is seen that, people new to the world of taps and dies find it quite difficult to figure out the correct equipment required for specific threading purposes. Moreover when working with metric thread taps, a myriad of questions loom their minds in search for the right threading instrument. If you can relate to these dilemmas then the following questions to answer your problems in the most subtle way! So, read on.

1. Why does the size of a tap vary as compared to its internal thread design?

The process of cutting threads into a hole by inserting a rotating tap is known as tapping. This rotating tap is bored beforehand to the specific size. In most cases, the internal thread size becomes larger than its tap. A tap’s pitch diameter should be closer to its minimal range because of this tapping tendency. This should also be within the range of its thread size.
2. Why are tap ends of threads grounded off at a specific angle?

The primary motive is to avoid the cutting edges from getting chipped. This is protected by the inclined ground off threads at tap ends. For example, Trapezoidal thread taps have comparatively low tensile strength towards its edges.

If you start cutting threads using trapezoidal thread taps from beginning, it might cause damage to the cutting edges due to high load on the tap edge. These grounded off inclined mechanism cuts threads slowly decreasing the load of cutting considerably.
3. What is the necessity of flutes of tap?

Flutes serve as a space to accommodate chips. One cannot have a cutting edge if he uses a tap without a flute. One should maintain caution not to use flutes that are too small. This is because a tap might be damaged by chips packed in its flutes.
4. Specify the kind of materials used for metric thread taps?

Normal materials used for casting taps are light alloys, titanium alloys, iron or even plastic depending on the purpose. Other versatile tapping materials are also used which is purpose specific. These include vanadium, chromium, Molybdenum, Tungsten, Cobalt and some other dependable alloy steels.

5. Explain surface treatment?

Chromium clad was the primary material used for surface treatment. It is a process of extending a tool’s life by placing that hard layer over the tool surface. This kind of surface treatment has gained popularity over these years and is used in almost all cutting tools.

6. Why are no chips produced in thread forming taps?

When normal taps cut threads, chips are produced. But thread forming taps carve out threads by inserting themselves into its surface. Thus no chips are formed. They do not include cutting edges or flutes. In this case, relatively soft materials are used as the process involves inserting the thread forming tap into the surface of the material.

Therefore, to conclude:-

It can be seen that the choice of taps in very crucial in order to get that perfect thread. Moreover, taps which are not grounded off at a certain angle may cause the thread edges to break off. So, one needs to judge with care your choice of metric thread taps and make sure you select the correct apparatus.

Frank Xu is the author of this article on metric thread taps.
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