The crankshaft is an eccentric shaft and converts the alternating linear motion from the piston to continuous circular motion and transmits it to the gearbox via flywheel and clutch.

The crankshaft is generally produced by casting method and the areas where the connecting rod will work are precisely machined by machining. The crankshaft material is low alloy steel. The crankshaft produced by casting is also produced with spherical garnetted cast iron. In order for the material to be resistant to abrasion, warping and torsion, the parts that are in the middle of the cross section are produced from a softer alloy, as in other shafts. The plain bearings (crankshaft bearings) that support the crankshaft are made of gray cast iron to prevent micro-boiling.

The lubrication of the crankshaft is made by the lubrication channels on it or the connecting rods hitting the oil in the crankcase and splashing the oil.