A cylinder with spiral groove on its outer surface or a cone with conical spiral groove. The screw has different heads, such as the head in the picture is called external hexagon screw. There are others, such as large flat screw, hexagon screw and so on.

It can be seen from the extrusion process that the screw works under high temperature, certain corrosion, strong wear and large torque. Therefore, the screw must be resistant to high temperature without deformation under high temperature; wear resistance, long service life; corrosion resistance, material is corrosive; high strength, can withstand large torque and high speed; has good cutting performance; small residual stress and small thermal deformation after heat treatment.

HCVAC has 20 years of experience in coating parts, providing high-performance hard carbon based coatings that reduce friction and wear and improve power and reliability. The greatly improved wear resistance extends the service life and durability of components and provides emergency operation reserve. Reduced friction loss increases power output and reduces engine heat load. The use of lighter materials and a more compact design can reduce overall weight and cost, can coat the original parts without any design changes, lower coating temperature avoids changes in shape or size, and avoids the need for finishing.