Apparatus and method for forming a front toothing on an inner ring of a wheel hub and associated front toothing

A method for forming by plastic deformation a front toothing on an inner ring of a wheel hub, comprising:

• forming on one end of the inner ring of the wheel hub an upset annular collar;
• plastically deforming the collar in order to realize, frontally on the same, the frontal toothing impressing axially and sequentially on the collar a plurality of pressing elements;
• providing first pressing elements carried axially sliding by a first plate and second pressing elements carried axially sliding by a second plate coupled frontally to the first plate, respective first ends of the first pressing elements cooperating in contact and head to head with second ends of the second pressing elements arranged on the side opposite to the collar;
• obtaining on each second pressing element an engraving head provided on the side opposite to the second end with a respective wedge-shaped knife, circumferentially presenting a profile complementary to that of the front toothing to be obtained;
• pressing by means of a rotating head in orbital motion respective hammer heads of the first pressing elements to push the first pressing elements against the second pressing elements and consequently, selectively and in sequence, each knife against the collar;
• each knife being configured to form, when pushed against the collar, the flank profile of two adjacent teeth of the front toothing to be obtained;
• during pressing by means of a rotating head, guiding the first and second pressing elements so that the first pressing elements are angularly spaced while the hammer heads of the same are always kept in circumferential contact with each other, substantially without play, and so that the second pressing elements are angularly spaced while the engraving heads of the same are always kept in circumferential contact with each other, substantially without play.