The part is a non standard screw.
The tolerances on the bearing journals are extremely tight for turning operations. Ningbo Luteng developed processes and controls to allow these journals to be turned to specification without the need for grinding or secondary operations. When these parts are machined, careful attention to temperature control must be maintained, as fluctuations in temperature can cause parts to go out of tolerance. In addition, the heavy metal removal in the center of the part presented a challenge to maintain straightness.