Patent ID: 6857190

Claim:
A method of forming an annular collar ( 11 ) that is essentially radial on a hollow annular end portion ( 12 ) of a part ( 7 ), said method comprising the following steps: radially deforming the end portion ( 12 ) by means of a first tool ( 16 ), the first tool ( 16 ) being in local contact with said end portion ( 12 ), the axis ( 18 ) of the tool ( 16 ) and the axis ( 5 ) of the end portion ( 12 ) forming a non-zero angle α between them, the first tool ( 16 ) comprising a contact projection ( 19 ) formed in two frustoconical portions ( 19 a, 19 b ) which are mutually superimposed along the axis ( 18 ) of the tool ( 16 ) while tapering in the direction of the projection ( 19 ), so as to have a transverse surface of revolution ( 16 a ) that slopes at an angle γ relative to the axis ( 18 ) of the tool ( 16 ), a lateral surface of revolution ( 16 b ) that slopes at an angle β relative to the perpendicular to the axis ( 18 ) of the tool ( 16 ), the angle β being substantially equal to the angle α, and an interconnection transition ( 16 c ) between the two surfaces, the tool ( 16 ) and the end portion ( 12 ) being moved relative to each other first in rotation about the axis ( 5 ) of the end portion ( 12 ) and, second, linearly along the axis ( 5 ) of the end portion ( 12 ), so as to obtain a collar preform ( 17 ) that is essentially radial; and deforming said preform ( 17 ) by means of a second tool ( 23 ), said second tool ( 23 ) and said preform ( 17 ) being moved relative to each other linearly along the axis ( 5 ) of the preform ( 17 ) so as to obtain final shaping of the collar ( 11 ) by pressing.