Commonly used thread processing method in CNC machining center - tap processing method

1. Classification and characteristics of tap processing

Using taps to process threaded holes is the most common processing method, which is mainly suitable for small diameters (D

In the 1980s, flexible tapping methods were adopted for threaded holes, that is, a flexible tapping chuck was used to hold the tap, and the tapping chuck could be used for axial compensation to compensate for the feed caused by the asynchronous feed of the machine tool and the rotational speed of the spindle. Give the error to ensure the correct pitch. The flexible tapping chuck has a complex structure, high cost, easy damage and low processing efficiency. In recent years, the performance of CNC machining centers has gradually improved, and the rigid tapping function has become the basic configuration of CNC machining centers.

Therefore, rigid tapping has become the main method of thread processing at present.

That is, the tap is clamped with a rigid collet, and the spindle feed and spindle speed are controlled by the machine tool.

Compared with the flexible tapping chuck, the spring collet has a simple structure, low price, and a wide range of uses. In addition to holding the tap, it can also hold tools such as end mills and drills, which can reduce the cost of tools. At the same time, the rigid tapping can be used for high-speed cutting, which improves the efficiency of the machining center and reduces the manufacturing cost.

2. Determination of threaded bottom hole before tapping

The processing of the bottom hole of the thread has a great influence on the life of the tap and the quality of the thread processing. Usually, the diameter of the threaded bottom hole drill is selected close to the upper limit of the threaded bottom hole diameter tolerance,

For example, the bottom hole diameter of the M8 threaded hole is Ф6.7+0.27mm, and the diameter of the selected drill bit is Ф6.9mm. In this way, the machining allowance of the tap can be reduced, the load of the tap can be reduced, and the service life of the tap can be improved.

3. Selection of taps

When choosing a tap, first of all, the corresponding tap must be selected according to the material to be processed. The tool company produces different types of taps according to the different materials to be processed, and special attention should be paid to the selection.

Because taps are very sensitive to the material to be processed compared to milling cutters and boring tools. For example, using taps for processing cast iron to process aluminum parts is easy to cause thread loss, random buckles or even tap breakage, resulting in scrapped workpieces. Secondly, attention should be paid to the difference between through-hole taps and blind-hole taps. The front-end guide of through-hole taps is longer, and the chip removal is front chip removal. The front end of the blind hole guide is short, and the chip evacuation is rear chip evacuation. Blind holes are processed with through-hole taps, and the depth of threading cannot be guaranteed. Furthermore, if a flexible tapping chuck is used, it should also be noted that the diameter of the tap shank and the width of the square should be the same as that of the tapping chuck; the diameter of the tap shank for rigid tapping should be the same as the diameter of the spring jacket. In short, only a reasonable selection of taps can ensure the smooth progress of processing.

4. NC programming for tap machining

Programming for tap machining is relatively simple. Now the machining center generally solidifies the tapping subroutine, just assign each parameter value. However, it should be noted that different numerical control systems have different subprogram formats, and the meanings of some parameters are different.