Crank Pin is a high precision item, having Crank Pinround cylindrical shape. It can be of hole or solid type, but must have a high surface finish, to serve as running surface for needle bearings. The surface must be free from nick marks and must be hard, to bear the normal wear and tear of the vehicle. It is firmly connected to the connecting rod and as such the geometry of the outer diameter as well as side faces plays a vital role in fitment and running. It is a vital part of kinematics of the transmission of a two / three wheeler assembly, where a direct transfer of power, without slip, is sought from the Piston to the wheel / gear box. A similar situation prevails in single cylinder engines for agriculture, industrial and other uses.