In qualitative to different capable person whorl Kong Jia is versed in can discover in the process, qualitative to material compact, have relatively the material of high strenth (like steel) the whorl opening that attend, because its surface roughness, tigidity and intensity are higher, uses bolt can come back for many times into come back piece, screw damages not easily also; And to aluminium alloy the whorl opening that attend, its surface roughness and intensity are inferior, classics bolt comes back repeatedly into come back after going out, screw damages very easily, affect the use of workpiece thereby. The screw that uses extruding tap to machine aluminium alloy workpiece to go up criterion but better prevent screw damage. As a result of aluminium alloy Die Casting exterior 1mm appears easily below stomatic, use the convention such as bore, tap to machine craft to arise easily to buckle so, and the whorl aperture strength that uses extrusion craft treatment to go out is higher. Extrusion is treatment of cutting of a kind of blame, theoretic inside quantity of qualitative obligate of aperture surface ability and the whorl that form are inside unit length bulk is equal, accordingly can the measure of whorl bottom outlet that tap of cipher out extruding machines is as follows: Whorl norms - M3 of bottom outlet diameter - 2.
71mmM4 - 3.
74mmM5, 4.
64mmM6 - 5.
55mm (go up deviation + 0.
05mm, next deviation - 0.
08mm) M8 - 7.
45mmM10 - 9.
35mmM12 - 11.
25mm (go up deviation + 0.
06mm, next deviation - 0.
12mm) the characteristic in view of whorl extrusion, its cutting parameter also differs somewhat with common tap. According to practical use experience, raising efficiency and the premise that make sure cutting tool is used normally to fall, relatively ideal cutting dosage is as follows (it is with tap of M5, M6 exemple) : M5 tap: Rotate speed 400r/min, feed 320mm/minM6 tap: Rotate speed 400r/min, feed 400mm/min in addition, the proposal uses corresponding bottom outlet broach to arrange whole bottom outlet before attacking whorl, eliminate bottom outlet flaw, prevent extruding tap to rupture. CNC Milling