Rigid tapping is also one of the important control modes of the milling machine spindle. In the tapping process, the spindle speed and the Z-axis feedrate fZ must be satisfied:
fZ = tap pitch x spindle speed
In the normal way to tapping processing, due to the spindle and Z axis feed acceleration and deceleration characteristics are inconsistent, tapping screw on the tap must be equipped with spring chuck, in order to compensate for the Z axis feed and spindle does not synchronize the pitch error.The handle with a spring chuck is shown in the figure. When the thread is tapped in this way, when the tap is rotated and the Z axis is stopped, the spindle does not stop immediately, the tapping spring chuck is compressed for a distance; when the tap is rotated in the reverse direction of the Z axis, the milling machine spindle accelerates, the spring chuck is stretched again. Common way to attack the thread cycle can only meet the general accuracy of the processing of screw holes. In addition, if the spindle speed is high when the thread is tapped, the telescopic range of the spring chuck must be large enough so that the spindle speed can only be limited to 600r/min or less when tapping the thread in this way.
Rigid tapping, also known as synchronous feed tapping. Rigid tapping does not require a spring chuck and a rigid taper shank as shown. Rigid tapping, the milling machine spindle speed and Z-axis feed speed to establish a synchronous relationship, so that the spindle speed and Z-axis feed speed to ensure a linear proportional relationship, as shown.
When the tapped thread is machined with a rigid tapping thread, the spindle rotates synchronously with the Z axis feed and decelerates simultaneously when the Z axis is tapped to the command position. The spindle reverse start acceleration is also synchronized with the Z axis reverse feed start acceleration. In addition, the rigid tapping in the tap strength allows the case, the milling machine spindle speed can be high, up to 4000r/min, processing efficiency significantly improved, and the thread accuracy is guaranteed.