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酚醛塑料零件上孔径较小、精度较高的螺纹孔,直接压制成型是困难的,一般要用丝锥加工。若是用加工钢件的标准丝锥来攻丝是比较困难的。因为,塑料的线膨胀系数比金属大,加工出来的零件螺纹中径略小于丝锥的实际中径,既是用新的标准丝锥加工酚醛塑料的螺纹孔,螺纹中径也是偏下差;另外,酚醛塑料中有各种填料,如木粉、玻璃纤维等,这些填料一方面降低了塑料的导热系数,另一方面增加了工件与丝锥的摩擦。
Phenolic plastic parts on the smaller aperture, high precision threaded holes, direct compression molding is difficult, generally use tap processing. It is more difficult to tap with the standard tap of machined steel. Because the linear expansion coefficient of plastic than the metal, the thread diameter of the machined parts slightly smaller than the actual diameter of the tap, both with a new standard tap processing phenolic plastic screw holes, the thread diameter is also the partial difference; In addition, the phenolic Plastic in a variety of fillers, such as wood flour, glass fiber, these fillers on the one hand to reduce the plastic thermal conductivity, on the other hand increased friction between the workpiece and the tap.