Abstract: Method of cold forming a blank made of press sintered material which includes moving at least one tool towards the blank and subjecting the blank to rolling under a roughly constant load for a number of passes until the at least one tool reaches a chosen position. At least one of, the chosen position, the roughly constant load, and the corresponding number of passes, is determined so as to control a surface densification and at least one dimension of the rolled blank.

Abstract: Method of cold forming by rolling of a blank made of press sintered material, in which at least one tool of predetermined peripheral geometry is brought close to the blank, so that the tool can then be rolled over the blank, urging the one towards the other, characterized in that it comprises, after a phase (a) of approaching the blank, a penetration phase (b), with (bn) at least one phase of rolling under roughly constant load, as far as a chosen position, this load, the chosen position, and the corresponding number of passes being determined so as to control the surface densification and the dimensions of the rolled part.

Abstract: A device for the formation by rolling of helical fins on heat exchange tubes to increase the heat transfer capacity of the tubes. The device comprises four forming rolls (6, 7, 8, 9) which are arranged on two carriages (4, 5) which are moved together in translation fashion by a hydraulic jack which enables the four forming rolls to bear simultaneously on the wall of a tube (2). The four forming rolls operate around the tube and are rotatably driven at equal speed by a single motor (50). The forming rolls are oriented about an axis (X2, X4, X5) which is perpendicular to the fin shaping zone. The tube (2) is driven by the forming rolls along an axis of translation.

Abstract: The apparatus and process according to the invention relate to the cold forming by rolling of revolving parts (7).The apparatus comprises two identical milling wheels (9A, 9B) arranged symmetrically with respect to the part (7) to be formed and performing the same rotation movement at speed Vm and progressively moving towards the axis of the part to be formed (X1--X1). The part (7) performs a rotation movement at speed Vp such that Vp=Vm.multidot.N1/N2, N1 being the number of grooves on each wheel (9A, 9B), N2 the number of grooves to be formed on the part (7). An initial setting makes it possible to bring about coincidence between the grooves formed by each of the milling wheels on the part (7).The apparatus and process make it possible to obtain high precision parts.

Abstract: The process according to the invention relates to the production of grooves such as helical threads on the wall of tubes composed of ductile or plastic materials without removal of matter.It involves using a knurling tool (11) of radius (R.sub.1) which is freely rotatable about an axis (X.sub.3). This axis covers, in the direction indicated by the arrow F2, a determined closed curve (12) which, in the figure, is a circumference of radius (R2) and of axis (X.sub.4).The enveloping curve of the path of the shaping edge (15) of the knurling tool has a region of intersection (13) with the wall of revolution (10) of axis (X.sub.2). The diameter of the knurling tool is greater than the diameter of the circumference (12). A helical thread is obtained by moving the wall of revolution (10) in relative manner along its axis (X.sub.2) relative to the knurling tool (11).

Abstract: A process for forming a helical screw thread comprising a flank with negative inclination on the wall of a rotationally symmetrical body (19) such as a metal pipe or tube. A first phase involves producing a screw thread having flanks with a positive inclination and then a second phase involves modifying the inclination of one of the flanks (24) by plastic deformation to make it negative (32). For that purpose, use is made of a roller (26) mounted on an inclined axis (X2--X2), which rolls against the flank of the thread.