Thread processing tools that can automatically open or shrink the cutting part at the end of the working stroke, including automatic open die heads for processing external threads and automatic shrink taps for processing internal threads. When the self-opening, self-closing string trimmer head retracts quickly, there is no need to invert the workpiece or tool.
Auto open/close string trimmer heads typically have 4 comb-shaped trimmer heads (see picture). According to the shape of the comb, the automatic opening head is divided into two types: circular comb type and flat comb type. The latter is divided into two types: radial and tangential depending on the forward direction of the comb (see machine tool).
The ordinary circular comb type self-opening die head can process external threads with a diameter of 4-60mm. There is only one type of auto shrink tap, which is a radial flat comb type, which is generally used to process screw holes with a diameter of 36mm or more. Depending on the mode of use, there are two types of self-opening and self-closing thread trimmer heads, rotating and non-rotating, which are respectively used in automatic lathes, turret lathes, drilling and tapping machines. The self-opening and self-closing thread trimming head is driven by the spindle or tool rest of the machine tool to complete the working stroke when trimming the thread.
At the end of the working stroke, the stopper fixed on the machine tool toggles the shift fork or thread trimmer head clamp to trigger. The trimmer head action mechanism causes all four trimmer heads to open or retract at the same time, and the position of the cutter head can be precisely adjusted according to the size of the yarn to be processed. The comb blade that automatically opens and closes the thread trimmer head is usually made of high speed steel by grinding with high precision.
The comb can automatically open or shrink, so the productivity is high. Although the structure is complex, it is still widely used. Similar to the self-opening die head, there is the self-opening and self-closing thread rolling head, which uses the plastic deformation of metal to unwind the thread.