1. The twisted screw shall be considered according to the actual inner diameter of the barrel, and the outer diameter deviation of the new screw shall be given according to the normal clearance with the barrel for manufacturing;
2. The thread surface with the diameter of the wear screw reduced shall be treated, thermally sprayed with wear-resistant alloy, and then ground to the size. This method generally has a professional spray factory processing repair, the cost is relatively low;
3. The wear-resistant alloy is overlaid on the thread part of the worn screw. According to the wear degree of the screw, the thickness of overlay welding is 1-2mm, and then the screw is ground to the size. The wear-resistant alloy is composed of C, Cr, VI, Co, W and B materials, which increases the wear resistance and corrosion resistance of the screw. The cost of this kind of processing is very high in the professional hardfacing factory. Except for the screw with special requirements, it is seldom used;
4. Hard chromium plating can also be used to repair the screw. Chromium is also a wear-resistant and corrosion-resistant metal, but the hard chromium layer is easy to fall off.