Method for straightening out of true work pieces, especially crankshafts

A method for straightening a work piece having cross-sections along its length with fillets forming transition areas between neighboring cross-sections, said cross-sections having a work piece diameter (D1), said work piece having a rotational axis and a bend relative to said rotational axis, said bend being determined by three values, namely as to its location by an axial coordinate value, as to its direction by an angular coordinate value, and as to its size by an eccentricity magnitude value, comprising the following steps:

• (a) first introducing into said fillets of said work piece first residual compressive stresses in a complete circumferential surface layer for increasing a fatigue strength of said work piece,
• (b) determining from said three values a respective control signal which represents a circumferentially limited angular range (.beta.1) within about 5.degree. to about 160.degree. around a portion of at least one of said fillets requiring the introduction of further residual compressive stress for said straightening, and
• (c) second introducing additive second residual compressive stresses in response to said control signal, for adding said second residual compressive stresses to said first residual compressive stresses only in said range (.beta.1) of said surface layer zone, by a rolling tool having a diameter (D2) substantially smaller than said work piece diameter (D1) by applying to said rolling tool a straightening force only in said limited angular range (.beta.1) of said surface layer zone of said at least one fillet to introduce said second additive residual compressive stresses only to a radial depth (D3) short of a depth where said second residual compressive stresses tend to become subtractive, for increasing said first residual compressive stresses by said second residual compressive stresses only in said limited angular range (.beta.1) of said surface layer, thereby avoiding reducing said fatigue strength and simultaneously reducing or eliminating said bend.