A method of manufacturing a die forged crankshaft to be mounted in a two or more cylinder reciprocating apparatus includes: an upsetting step that includes upsetting a billet having a constant cross-sectional area along an entire length thereof to form a blank having an enlarged cross-sectional area at a region between a portion to be formed into a leading crank arm of the crankshaft and a portion to be formed into a trailing crank arm thereof; a die forging step that includes die forging the blank formed in the upsetting step to form a forged blank having a shape of the crankshaft with a flash; and a trimming step that includes trimming the flash from the forged blank formed in the die forging step. This makes it possible to improve the material utilization and to use a billet having a cross-sectional size as small as possible.

In a forming apparatus, journal dies hold and retain rough journal portions of a preform blank therebetween, and reference crank pin die and movable crank pin dies contact rough crank pin portions thereof. In this state, the journal dies and the movable crank pin dies are moved axially toward the reference crank pin die and the reference crank pin die and the movable crank pin dies are moved perpendicular to an axial direction. With this, rough crank arm portions are axially compressed to reduce their thickness to that of crank arms of a forged crankshaft, and the rough crank pin portions are pressed perpendicular to the axial direction to increase an amount of eccentricity to that of the forged crankshaft crank pins. Consequently, it is possible to form a blank for finish forging having a shape generally in agreement with a shape of the forged crankshaft for a three-cylinder engine.

This invention concerns a burnishing head for smooth rolling of the ring-shaped flat end faces (3, 4) at the thrust bearing of crankshafts by means of two cylindrical burnishing rollers (1, 2) which are arranged to be rotated and are side by side in parallel to each other within a burnishing head housing (12) that is pivotable about its longitudinal axis (20) to reach its the working position. Each burnishing roller (1, 2) is pivoted in a cage (10, 11) which is provided in the burnishing head housing (12) with low play (13) and lateral relocatability.

In a crankshaft 200, one hole 213L formed in a crankpin 213 has a bottom surface having a larger area and a depth from a surface of the crankpin less than those of another hole 213M. In forming the hole 213L and the hole 213M, a preformed product 200 of the crankshaft having a shape smaller than that of a cavity is disposed in a die set and punches are simultaneously inserted into the crankpin 213. By this operation, the hole 213L and the hole 213M are simultaneously formed in each crankpin 213 of the preformed product 200.

Master and slave pullrods are disclosed in which a master pullrod is coupled to a journal of a crankshaft. The slave pullrod indirectly couples to the crankshaft by coupling to the master pullrod. Such a configuration allows two connecting rods to be coupled to the journal of the crankshaft inline with each other.