The thread turning pitch smaller, generally using direct feed cutting method (in the direction perpendicular to the workpiece axis line feed); thread turning pitch larger, in order to reduce the cutting force, often using about sword cutting method (left and right cutting edge were used to move through the small skateboard for thread cutter).
When turning the thread, the movement of the bed saddle is realized by the movement of the opening and closing nut by the rotation of the long screw. There is an axial clearance in the bearing of the filament bar, and there is also an axial gap between the filament bar and the opening and closing nut. When using the sword cutting method about strong turning with the right main right-hand worm cutting edge, cutter workpiece to force P (ignoring the chip and the rake face friction, as shown in Figure 1), the P is decomposed into axial force Px and radial force which coincidentally, the feed direction and the cutter axial force Px the same tool to the axial force Px to the saddle, so as to promote the saddle to the gap side to do fast violent movement back and forth, the result is that the tool back and forth movement, and the processing of the ripple on the surface, or even broken. But with the left main cutting edge when there is no such phenomenon, when the left main cutting edge, axial force Px and the feed direction of the cutter to bear the opposite, to eliminate the gap in the direction of movement, when the saddle do uniform motion.
