Method for producing a polygonal shaft

A method for producing a shaft, which is partially polygonal on the outer periphery, by radial forging, the method comprising the steps of:

• providing a cylindrical blank, wherein the blank includes a passage opening at least partially penetrating the blank and forming a central cavity of the blank;
• clamping the blank in a clamping head of a radial forging device, wherein an opening of the central cavity of the blank is disposed on an end face of the blank facing away from the clamping head;
• axially moving the clamping head with the clamped blank relative to forging hammers and positioning the forging hammers axially at a first portion of the blank;
• axially advancing a counterhold relative to the clamped blank, wherein the counterhold includes a counterhold base and a counterhold mandrel, wherein the counterhold mandrel includes an inner part and an outer part, wherein the counter mandrel penetrates the central cavity of the blank up to a defined stop and supports the clamed blank;
• radially advancing the forging hammers into contact with the blank along the first portion of the blank;
• rotating the blank and round forging the first portion of the blank in a first round forging step into a first shaft portion with a first inner diameter and a first outer diameter via the radially advanced forging hammers;
• radially releasing the first shaft portion from the forging hammers;
• axially moving the outer part of the counterhold mandrel in a direction toward the counterhold base and away from the clamping head out of the central cavity of the blank;
• axially moving the clamping head with the clamped blank relative to the forging hammers and positioning the forging hammers axially at a second portion of the blank, wherein the inner part of the counterhold mandrel lies along the second portion;
• radially advancing the forging hammers into contact with the second portion of the blank;
• rotating the blank and round forging the second portion of the blank in a second round forging process into a second shaft portion with a second inner diameter and a second outer diameter;
• radially releasing the second shaft portion from the forging hammers,
• axially moving the inner part of the counterhold mandrel in the direction away from the clamping head and out of the central cavity of the blank;
• axially moving the counterhold and the clamping head with the clamped blank relative to the forging hammers and aligning the forging hammers at the first shaft portion;
• radially advancing the forging hammers into contact with the first shaft portion,
• rotationally fixing the blank and performing polygonal forging on the first shaft potion, wherein the blank does not rotate during the polygonal forging;
• and
• radially releasing the first shaft the first shaft portion form the forging hammers.