Thread Milling for Efficient and Flexible Thread Machining Solutions
01. Machining Stability
When machining difficult-to-machine materials such as titanium alloys, high-temperature alloys, and high-hardness materials, the excessive cutting forces often cause the tap to twist or even break off inside the workpiece. When machining materials that produce long chips, if chip evacuation is inadequate, the chips may wrap around the tap or block the hole opening, frequently leading to tap chipping or breaking off inside the workpiece. Removing a broken tap is not only time-consuming and labor-intensive but may also damage the part. To address this issue, we can use a thread milling cutter. Since the thread milling cutter gradually cuts into the material, it generates smaller cutting forces and rarely breaks. The chips produced are powder-like. Even if a break occurs, you can easily remove the broken section from the part without causing damage, since the milling cutter’s diameter is much smaller than the thread hole.
02. Diverse Range of Machining Materials
The excellent cutting conditions enable thread milling cutters to machine a wide range of materials, including high-hardness steels such as HRC65°, titanium alloys, and nickel-based alloys. When machining difficult-to-machine materials, thread milling provides a convenient method for thread processing, whereas tapping would be impractical.
03. High Thread Machining Accuracy
Thread milling typically operates at high speed and efficiently produces powder-like chips without causing tangling. Therefore, both machining accuracy and surface finish are significantly higher than other thread processing methods. Since the tool rotates at high speed and the spindle interpolates the motion, thread milling allows for convenient chip removal. Thread milling is a chip-breaking cutting process, producing short chips.
Additionally, thread milling uses a smaller tool diameter than tapping, which helps avoid forming spiral lines caused by tap rotation—an issue not allowed in applications requiring high sealing. Since the original milling cutter does not produce spiral lines, whereas taps cannot avoid them, chip adhesion is less likely to occur. For softer materials, chip adhesion may occur during machining, but thread requirements demand lower machine power. Since thread milling is chip-breaking machining with localized tool contact, the cutting force is small, and tool wear is easier to manage.
04. Wide Application
The same tool handles both right-hand and left-hand thread machining. As long as the pitch matches, it produces threads of different diameters. You can use the same thread milling cutter for both blind and through holes. For thread types like W, BSPT, PG, NPT, NPTF, and NPSF, the cutter also machines both external and internal threads.
PS: In daily work, we encounter various thread specifications. We will summarize the corresponding taps for different threads in the future. Please stay tuned.
05. Advantages of Processing Blind Holes
When machining blind holes, thread milling produces a complete thread profile all the way to the bottom of the hole. In contrast, when tapping with a tap, the hole must be drilled deeper because the tap does not form a complete thread profile until the third thread. Therefore, when using a thread milling cutter, there is no need to modify the structure to deepen the hole.
06. Reduced Spindle Wear
Compared to thread tapping with a tap, thread milling does not require the spindle to stop abruptly or reverse at the bottom, significantly extending the spindle’s service life.
07. High Processing Efficiency
In high-volume thread processing, improving efficiency is challenging due to the low cutting speed of taps and the need to reverse and retract after completing the thread. However, when you use a thread milling cutter with high milling speed and a multi-flute design that increases cutting edges, you can easily boost feed rates and significantly improve processing efficiency. In long thread machining, you can select longer-edge inserts to reduce the axial feed distance and effectively shorten the thread length, further enhancing efficiency.
08. Deburring Functionality
Some brands of thread milling cutters can complete both thread machining and deburring in a single pass. This eliminates the need to spend additional time on deburring, thereby saving labor costs.
09. Low Processing Costs
Thread milling cutters offer versatility and perform well in various conditions. For example, you can use the same thread milling cutter to machine both left-hand and right-hand threads, as well as external and internal threads. You simply adjust the interpolation program to achieve this. In contrast, when using taps for machining, you must prepare different-diameter taps if the part has multiple thread holes with the same pitch but different diameters. This not only requires a large number of taps but also increases tool change time.
When using a thread milling cutter, since it employs spiral interpolation for machining, only the machining program needs to be modified to process threads of all diameters, significantly reducing tooling costs and tool change time. To ensure thread accuracy, different types of taps are required when machining various materials with taps. However, there are no such restrictions when using a thread milling cutter. The same thread milling cutter can process most materials and achieve high-precision threads. This also significantly reduces tooling costs. When machining threads near the bottom of a blind hole, using a tap to cut threads makes it difficult to achieve complete threads at the bottom.
Conclusion
Additionally, there is a risk of tool breakage during the brief period when the tap stops at the bottom and prepares to reverse and retract, as the tool may continue to move forward slightly (floating tapping). Using a thread milling cutter eliminates this issue—the thread milling cutter is smaller than the hole and does not require reversing to retract, and the tool tip maintains a complete thread shape. This allows us to achieve a complete and precise thread depth! In some machining operations, thread milling can help solve many issues.
For example, in the thread machining of large, non-circular parts, if machined on a lathe, complex clamping and balancing are required to avoid vibration. In such cases, machining on a machining center can be adopted, where the part remains stationary while the thread milling cutter rotates, avoiding balancing issues. Another example is when machining interrupted threads, where vibration and impact significantly affect the tool, potentially causing cracks. Using a thread milling cutter, however, allows the tool to gradually enter the discontinuous sections of the material, thereby avoiding large impacts and extending tool life.