Reasons for the instability of thread size in CNC turning

Reasons for the instability of thread size in CNC turning

After CNC turning the thread, the phenomenon of the "GO" of the external thread can`t go through or degree of tightness inconsistencies in front and back and can through the [ NOT GO" parts when measuring by thread ring gauge occurs sometimes.

The causes of these malpractices:

1. Screw thread type is wrong. Even if the effective diameter of the thread has reached the specified size, the thread ring gauge, male gauge may be still can`t unscrew.

2. The problem of direction restriction often occurs when measuring with a thread gauge, that is to say that it is through tighter from one end, and through looser from the other end, there is even appears a phenomenon that the [NOT GO" side can pass but the [GO" side can`t pass.

3. The bottom diameter of the inner thread is too small or the bottom of the outer thread is large also will course the thread gauge can`t go through.

4. In the thread turning smaller diameter, due to the restrictions of the knife rod by the size of the car, resulting in less rigid tool, it is easy to produce "cutter relieving" in the process of turning, so as to cause partial exceed tolerance.

5. When turning slender screw, due to the poor rigidity of the workpiece, the deformation of the CNC turning process causes the size error on the thread.

6. When CNC turning the internal and external thread of the thin wall parts, the effect of the workpiece due to the force and the cutting temperature, produce local deformation, and that also cause partial exceed tolerance.

Therefore, in order to solve the problem of "screw gauge can`t through", we must take corresponding measures for the above reasons, mainly from the correct installation and the proper clamping of workpieces.