1. Choose the optimal hole bottom size
This is the most important reminder. Tapping the bottom hole with a tap requires matching the size of the bottom hole. Generally, the corresponding range of bottom hole sizes is provided in the sample. Please note that this is the range. It is important to recognize that there is no single tap and drill size. Different drill bit sizes result in different thread percentages.
The key is that 100% thread strength is only 5% higher than 75% thread strength, but requires three times the torque. Therefore, for slightly smaller threaded holes, if the torque is too large, it is easy to break the tap, so it is not recommended to purchase a second-hand tap.
Because the used tap has already withstood uncertain torque, it is difficult to ensure machining accuracy due to different quality control measures. It is not only recommended to consider the cost of using a single tool, but also to consider the comprehensive cost.
The recommended drill bit size is almost always 75% thread. This provides a lot of power, but also enters areas with excessive torque.
2. Use Forming tap as much as possible
They will not produce iron filings, but will be processed into materials and extruded into shapes. The most common reason for taps is that they are blocked by their own chips, which is impossible to occur in the form of extrusion taps. The extrusion tap also has a larger cross-sectional area, so the tap itself is stronger than the cutting tap.
Forming Taps has two drawbacks. Firstly, tap extrusion cannot be used for hard materials. Your processed material can achieve a hardness of 36 HRC. This is much more than you imagine, but there must be some materials that are extruded. Secondly, some industries do not allow the extrusion of taps, as this process may create voids and trap pollutants on the threads. Squeeze tapping can also cause an increase in stress on the thread.
3. Thread milling cutter can be considered
For certain difficult to machine materials or high value-added parts, always consider thread milling instead of tapping.
The service life of thread mills is longer than that of taps, although the cutting speed of thread milling cutters is slower. You can thread closer to the bottom of the blind hole, and a single thread milling cutter can process various sizes of threads. In addition, thread milling cutters can be used with materials harder than taps.
For materials exceeding 50 HRC, thread milling cutters may be the only option. Finally, if you accidentally break a thread milling cutter, it will have a smaller hole than the machined part, so it will not break in the part like a tap, even if it is cut with good handling.
4. Consider using special tapping lubricants
Most machine coolants, especially water-soluble coolants, are not suitable for tapping because the lubricity of oil is relatively better than that of water.
If you encounter processing problems, please try using a special tapping lubricant. Put it beside the machine tool, take a container to fill it in, and program the G-code to make the tap automatically immersed in the cup. Alternatively, you can try coating taps to increase lubrication through coating.
5. Use the correct tapping tool handle (recommended only)
Firstly, use a lock to lock the square handle inside the tapping tool handle, so that it does not rotate in the tool handle. Because tapping requires a lot of torque, having a correct lock on the tool handle is helpful for tapping oil. You can use a tap chuck or a special ER tap chuck to achieve this.
Secondly, even if your device supports rigid tapping, consider floating tool handles. Floating tool handles are necessary in the absence of rigid tapping, but even in most rigid tapping situations, they can extend the tapping life. This is because the machine tool is limited by the acceleration of the spindle and shaft, and cannot synchronize the tap with the thread being processed. There is always some axial force pushing or pulling. Floating tool handles can alleviate stress caused by a lack of synchronization.
6. Use Spiral Fluted Taps in appropriate scenarios
If you are processing blind holes, the inability to remove chips may be the most common cause of tap breakage. That’s why we use Spiral Fluted Taps. They discharged the iron filings upwards. Please note that spiral groove taps are not as impact-resistant as more common tip taps and are recommended for blind hole machining.
Post time: Jun-17-2023