Thread milling represents a modern and efficient approach to creating threads. In this article, you'll discover why you should opt for thread milling instead of a thread tap.

Thread Tap vs. thread milling

We tell you the characteristics and benefits of each tool so that you can choose one or the other according to your needs.
Among the distinctive characteristics of a thread milling cutter, it stands out that:

– Can cover a range of hole diameters rather than a single size. The CNC tool path determines the measurement, not the tool itself, which means the diameter can change. In this way, the same tool can produce threads in different diameters as long as they have the same pitch.
– You can bring the thread closer to the bottom of a blind hole and machine threads in large holes with ease. The conical tip of the male, for its part, will stop when it reaches the bottom, leaving incomplete threads.
– Leave a space where the chips come out. Additionally, the chips are usually short and split. This prevents the hole from clogging and the tool from breaking.
– It can combine several hole threading operations in a single tool.
– While a thread taps only threads, a thread mill can perform other hole operations such as drilling, chamfering, machining the thread, and convolving the thread, i.e., cutting the incomplete portion of the thread at the end.
– Unlike the thread tap, the thread milling cutter can produce a left or right thread, making a simple change in the CNC programming. In addition, it can be removed from the hole with a rapid advance without needing to be "unscrewed" or moved in reverse at the end of the operation.

But then why does thread tap continue to be so popular?

The answer may be that it is a less demanding operation, which can be performed on a wide variety of machines at conventional speeds without helically interpolated tool paths.

Thread tap can also be performed on lathes with rotary tool capability. A long tap is capable of effectively machining threads in very deep holes. This does not happen with thread milling: the tool is more prone to bending because the cutting forces are not balanced. Generally, a milling cutter is limited to a depth of about 2.5 times the diameter of the tool. The type of material to be threaded is also a key factor when deciding what type of operation to perform.

While thread tap can be used on most materials with hardnesses up to 50 Rc, milling can be used on materials up to 60 Rc. On the other hand, when dealing with exotic metals, milling is recommended. Another aspect to consider is speed. Thread milling typically requires faster cutting and feed speeds since the winding path is longer.

A safe machining operation

There is minimal risk of machining interruptions due to low cutting forces and short chips. If an accident occurs, the work piece will not be damaged since the tool will not become trapped since the diameter of the thread cutter is smaller than that of the thread. Tap breakage quickly destroys expensive work pieces since thread tap usually represents the last operation on the part.

Materials that are difficult to machine

Excellent cutting conditions allow milling threads in challenging materials, such as hardened steel up to HRC 65, titanium, and other difficult-to-machine materials. Laser-cut holes are becoming more common. Threading with a tap is difficult because the surface becomes complicated, but with thread milling, it is easily done.

Different tolerances

Very tight tolerances can be achieved using radius correction in the CNC program. With thread taps, different tools are required for different tolerances. Once worn, the male is no longer useful. However, you can continue threading with a thread mill after adjusting the radius compensation.

Higher thread quality

Cutting conditions are optimal when thread milling. Chip evacuation is excellent as the tool diameter is smaller than the thread diameter. The thread will obtain a perfect surface finish and outstanding quality

Flexible tool

The same cutter can be used for both right and left-hand threads. This versatile tool allows you to create threads of different diameters and tolerances if the pitch is the same. In addition, it is possible to use the thread mill in blind and through holes. W, BSPT, PG, NPT, NPTF, and NPSF are thread profiles where you can use the same tool for external and internal threads.

Threading in blind holes

When milling threads, you will obtain a complete thread profile to the bottom of the hole. This allows you to make a thread where it is not normally possible.
When thread tapping tools, it is necessary to drill much deeper since, until the third thread, the tap will not form a complete thread profile.

Threading without burrs

By using Thread burr, the thread entry will be free of burrs. This allows threading and deburring to be performed in a single process, thus eliminating additional time associated with deburring.

Faster machining time

Thread tap is typically considered a faster method than milling. That is correct on small and coarse threads if deburring time is not considered.

Less wear on the machine spindle

Thread milling extends the life of the machine tool spindle compared to tapping because it is not necessary to stop and reverse spindle rotation for each thread.

Thread milling on lathes with rotating tools

Thread milling decreases machining time compared to turning, and excellent chip control minimizes the risk of tool failure.