Many processing methods 1. Introduction <br> <br> nut, a method using metal cutting processing, a method can also be used metal forming method, i.e. extrusion processing. At present, the domestic method of processing nuts mainly adopts cutting processing, that is, tapping the internal thread with a tap.
In the fastener industry, the nut tap is the only tool for machining the internal threads of the nut, and it can also machine the internal threads of other through holes. It is basically a single-piece cutting process, which can perform continuous cutting on the nut automatic tapping machine, and has high production efficiency.
The tap is a semi-closed multi-blade thin cutting process in the tapping process. Compared with the turning thread, the cutting conditions are bad, the chip discharge is not smooth, the cooling and lubrication are difficult, the friction between the tap and the workpiece and the chip is large, and a large amount of cutting heat cannot be generated in time. Dissipated, so the tap is more likely to wear and break, and it is easy to cause defects such as excessive thread size, high surface roughness, "bad teeth", "folding" and other defects, affecting product quality.
The extrusion method uses the plastic deformation of the metal material to tap the internal thread of the nut. An extrusion tap is a tool that extrudes a thread through plastic deformation of the material. Compared with the ordinary nut tap, the cutting portion is a tapered thread having a complete tooth shape, and the end portion of the working portion has a polygonal shape. The extrusion tap rotates while moving relative to the axial direction, and is squeezed into the hole of the nut blank to extrude the internal thread under a certain pressure. Squeeze nut taps are shown in the attached drawing.
2. Characteristics of extrusion taps (1) High thread precision and surface quality can be obtained. Due to cold extrusion, the metal fibers of the threads are not cut and the work hardens, so the surface of the thread is dense, strong, hard and wear resistant. The quality is improved, and because of its good orientation, the thread surface can be squeezed, so the quality of the processed thread is good. The accuracy is usually up to 6H, and the surface roughness value is up to R a = 6. 3 to 1. 6 μm, even R a = 0.8 μm.
(2) The long life of the tap is due to the use of metal plastic forming to process the thread. The extrusion tap does not need to open the chip flute. The cross section is made of multi-prism mainly to reduce the pressing contact surface, reduce the tapping torque, and have a large tap section and high strength. It can withstand large torque and is not easy to break. At the same time, the crest is an arc that is not easy to wear, so the tap has a long life. Its tap life is 5 to 10 times higher than that of the general tap.
(3) High productivity The extrusion tap internal thread is a chipless processing, so there are no problems such as chip removal, chip blocking and tapping, and the extrusion processing is suitable for high-speed forming, which is favorable for high-speed production and high productivity. .
(4) Tap manufacturing is difficult. Extrusion taps are difficult to manufacture and have high lubrication requirements. Therefore, the extrusion tap is suitable for processing high-precision internal threads and metal materials with low strength and good plasticity. For example, copper, aluminum, stainless steel, low carbon steel and other materials with low hardness and plasticity can also be used for thread processing of difficult-to-cut materials such as titanium alloys with high toughness and plasticity. Especially for machining non-through-hole threads, threading below M6 with high strength and precision requirements and low surface roughness values, and through-hole or through-hole threading of thin-plate workpieces, the effect of extrusion taps is more significant.
(5) The extrusion tap requires a relatively large screw hole for the screw hole, and the amount of the base metal is small, resulting in an excessively small internal thread diameter and insufficient strength. The screw hole is too small, and the closed extruded metal has nowhere to go, causing the tap to break.
3. nut tapping machine works <br> <br> fastener industry mostly a horizontal tapping machine, into a cam and a spring-fed feed two. During operation, the operator pours a certain number of blanks into the hopper, and the automatic arrangement can be performed by the reciprocating motion of the sliders in the feeding member. In operation, the tap rotates and moves axially and moves the blank in the V-groove to machine the thread.
4. extrusion tap and other relevant parameters to determine <br> <br> pressing portion pressing tap multiple prism cross section, M6 tap using the following three prism, M6 made more or six quadrangular prism. The use of even numbers makes the force symmetrical and easy to manufacture. The parameters such as the tap diameter and pitch are required to be manufactured with high precision, and the tolerance is 2/3 to 4/5 of the ordinary tap.
(1) The large diameter of the tap is considered to be the retraction of the hole after the squeezing, and the wear of the tap and the manufacturing tolerance, etc., the large diameter of the squeezing tap should be slightly larger than the diameter of the ordinary tap, generally about 0.11 P (P For the pitch).
d =( D+0. 8T hD2 ) ei sd / 3
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