EP0949977A1

EP0949977A1 - Method for the crosswise shrinking of a cylindrical part in a tubular part, tool kit for its implementation, and assembly of two corresponding parts

Info

Publication number: EP0949977A1
Application number: EP97952995A
Authority: EP
Inventors: Daniel Valin
Original assignee: Vallourec Composants Automobiles Vitry SA
Current assignee: ArcelorMittal Tubular Products Vitry SAS
Priority date: 1996-12-31
Filing date: 1997-12-23
Publication date: 1999-10-20
Anticipated expiration: 2017-12-23
Also published as: PL334556A1; NO993248L; CA2276718A1; FR2757788B1; DE69711696D1; NO312658B1; NO993248D0; EP0949977B1; US6186696B1; JP2000506787A; ES2172828T3; FR2757788A1; DE69711696T2; AR009851A1; WO1998029207A1; BR9714128A

Abstract

The invention concerns the production of an assembly (10) formed of two parts shrunk crosswise, viz. a cylindrical part (11) and a tubular part (12) with a transverse hole (14), which is bordered by cut-off edges (18) and in which the cylindrical part (11) is forcefully fitted. The invention is characterised in that a bracing block (16) internally stays the tubular part (12) around the hole (14). The invention is applicable in particular to the assembly of two parts.

Description

"Method for the cross fitting of a cylindrical part in a tubular part, tools suitable for its implementation, and set of two corresponding parts"

The present invention relates generally to the fitting of a cross piece at least locally cylindrical in a tubular piece, that is to say the fitting of this piece at least locally cylindrical in the tubular piece generally transversely relative to the direction of elongation thereof.

By at least locally cylindrical part is meant here a part whose external surface is, at least locally, at its fitting with the tubular part, a cylindrical surface, that is to say a surface which, whatever the nature, circular or otherwise, of the outline of its cross section, is formed of parallel generatrices.

This at least locally cylindrical part, which, for convenience, will be referred to hereinafter more simply as a cylindrical part, may be solid, hollow or tubular.

In the case of a hollow or tubular part, it can serve as a housing for at least any other component.

As a corollary, one understands here, by tubular part, a part, which, while being generally elongated in the form of tube, by being open at at least one of its ends, can be more or less conformed, being for example more or less curved or curved, and which, transversely, has any section.

The assemblies formed of a cylindrical part fitted crosswise in such a tubular part can find their own application by themselves, due in particular to the particular assembly of the parts which constitute them, but they can also find their application in the assembly of other components linked to one or other of these parts, for example in automobile construction. For their fitting, a hole is made through the tubular part, perpendicular to the direction of elongation thereof, capable of enveloping the overall outline of the cylindrical part, and, for example with the press, it is subjected jointly this cylindrical part and this tubular part having a relative movement from which it follows that the cylindrical part engages under stress in the hole of the tubular part on one side of the latter however that the tubular part is buttressed externally on the side opposite to the previous.

Various difficulties are to be overcome during such a fitting. First of all, to avoid untimely deformation of the tubular part during the formation in the latter of the hole necessary for this fitting, it is normally necessary to proceed by machining, at the cost of implementing a relatively complex tool and expensive.

Then, this tubular part forming, overall, around its hole, by the very fact of its tubular structure, two partitions, that of these partitions which, during the fitting of the cylindrical part, is located on the engagement side of this cylindrical piece primarily collects the corresponding fitting force and is therefore itself liable to be subject to a certain deformation. If this is the case, the cross section of the tubular part around its hole is modified, which can be detrimental to the quality of the mechanical connection normally provided between the cylindrical part and it, and, therefore, to the holding of all.

In any event, the deformation, thus apparent, of the tubular part cannot fail to cast some discredit on this outfit, and the assembly concerned must therefore normally be discarded.

Furthermore, even in the absence of any deformation of one or other of the partitions of the tubular part, the contact surface between this tubular part and the cylindrical part is reduced to that of the edge of the partitions of this part. tubular around its hole. However, it is on this contact surface that the quality of the desired mechanical connection depends.

It turns out, in practice, that, at least for certain applications, in which the parts in question are subjected to a tearing force and / or to vibrations, this contact surface may prove to be insufficient to ensure the good overall performance.

To overcome, at least in part, this latter drawback, it has been proposed, in Swiss patent No 383 303, to form an edge fallen around the hole of the tubular part, on at least one of the partitions of this tubular part , and, in practice, on both of them.

In practice, in this Swiss patent, the tool used to do this is a punch whose end is blunt in the shape of a blade, so that, when the fallen edge is formed, the partition concerned is simply pushed back laterally , on either side of this blade. It follows, on the one hand, that the fallen edge obtained does not extend over the entire perimeter of the hole which it borders, and, on the other hand, that of zero height at both ends with a diameter of this hole, its height varies from one to the other of these ends, to the detriment of the homogeneity of the reinforcement obtained for holding the cylindrical part in the tubular part, and, therefore, ultimately, to the detriment of this reinforcement.

In addition, and above all, the risk of untimely deformation of one or other of the partitions of the tubular part during the fitting of the cylindrical part into the hole thereof remains almost unchanged.

The present invention generally relates to a provision making it possible to avoid such deformation and also leading to other advantages.

More specifically, it firstly relates to a process for the force fitting of an at least iocally cylindrical part, here called for simple convenience cylindrical part, in a tubular part, generally transversely to that this, this process being of the kind according to which, a hole envelopes the overall outline of the cylindrical part having to pass right through the tubular part by affecting one and the other of the two partitions that this tubular part forms generally transversely around it, we form, on at least a portion of the perimeter of this hole, for at least one of the partitions of the tubular part, a fallen edge which, integral with this partition, extends in the direction of the other partition of the tubular part, and jointly subjects the cylindrical part and the tubular part to a relative movement from which it follows that the cylindrical part engages under stress in the hole of the tubular part on one side thereof, however this tubular part is buttressed externally on the side opposite to the previous one, and being generally characterized in that, prior to the formation of the fallen edge on the tubular part, there is inserted in the latter a spacer wedge suitable to butt it internally in the vicinity of its hole on at least a portion of the perimeter thereof. Thanks to this spacer wedge, any deformation is avoided for that of the partitions of the tubular part which would be susceptible to such deformation, that is to say for that of these partitions located on the side on which the engagement of the cylindrical part.

As a corollary, thanks to the fallen edge bordering the hole of the tubular part, the contact surface between this tubular part and the cylindrical part is significantly increased, to the benefit of the holding of the assembly, and, preferably, such a edge fallen on one and the other of the partitions of the tubular part, over the entire perimeter of the corresponding hole, and of substantially constant height all around the latter. The fallen edge (s) thus used can be formed by stamping, the spacer wedge present inside the tubular part forming therein a matrix suitable for allowing such stamping, without deformation of the partition concerned. According to the invention, it can if desired be advantageously taken advantage of this spacer wedge for the very formation of the hole initially required therein.

According to this possibility, the spacer wedge is put in place in the tubular part before the formation of this hole, and a hole, in this case a pilot hole, is formed in this tubular part by simple die-cutting. of it.

Unlike the tooling to be used for machining, the tooling to be used for such a die-cutting is advantageously very simple and inexpensive.

It also advantageously does not cause a chip problem, and it is not very subject to wear.

Finally, this tool is advantageously capable of being used on a standard machine, in this case a simple press, and, more particularly, on a simple hydraulic press, without any specific arrangement.

The result, overall, is a great saving in implementation and construction.

The present invention also relates, on the one hand, to a tool particularly suitable for implementing the method according to the invention, and, on the other hand, to any assembly, which, formed of two parts fitted in a cross, to know a piece at least locally cylindrical and a tubular piece having transversely a hole in which is engaged by force this piece at least locally cylindrical, results from such an implementation. According to the invention, such an assembly is normally advantageously free from any deformation, the spacer wedge implemented effectively counterbalances, from the inside, during the engagement of the part at least locally cylindrical in the hole of the part. tubular, that of the partitions of this tubular part which is located on the side of this engagement. The objects of the invention, their characteristics and their advantages will become apparent from the description which follows, by way of example, with reference to the appended schematic drawings in which: FIG. 1 is a perspective view of a set formed by two pieces fitted crosswise according to the invention; Figure 2 is, on a larger scale, a partial view in longitudinal section of this assembly, along the plane II-II of Figure 1; Figure 3 is, on a different scale, a perspective view of the spacer block implemented in this assembly, shown in isolation; FIGS. 4A, 4B, 4C, 4D, 4E and 4F are partial views in longitudinal section, which, in correspondence with that of FIG. 2, illustrate various successive phases of the production of the assembly according to the invention; Figure 5 is a partial perspective view of one of the punches used for this embodiment; Figure 6 is a partial perspective view of another of the punches also used; Figure 7 is a partial view in longitudinal section, which, with reference to that of Figure 2, relates to an alternative embodiment of the invention. As illustrated in these figures, it is, overall, the production of a set 10, which, as is better visible in Figure 1, is formed of two parts fitted in a cross, namely a cylindrical part 1 1 and a tubular part 1 2.

As specified above, the cylindrical part 1 1 is, in general, defined as being a part whose external surface 1 3 is at least locally, at the level of its fitting with the tubular part 1 2, a cylindrical surface .

In the embodiment shown, the cross section of this outer surface 1 3 is assumed to have a circular contour and to be continuous. But it can just as easily have another outline and / or be more or less indented.

In the embodiment shown, the cylindrical part 1 1 is also assumed to be full, like a bar. But it could just as easily be a hollow part, and for example tubular, like a socket, to serve as a housing for any other component not shown.

The tubular part 1 2, meanwhile, has, overall, an elongation direction D, with respect to which the generatrices of the outer surface 1 3 of the cylindrical part 1 1 extend substantially orthogonally.

This direction of elongation D is shown diagrammatically in broken lines in FIGS. 1, 2, 4A, 4B, 4C, 4D, 4E and 4F.

The length L1 of the tubular part 1 2 along its direction of elongation D may be greater or less.

In the embodiment shown, the tubular part 1 2 is, by way of example, a slender part, insofar as this length L1 is relatively large, in particular with respect to its width L2.

The cross section of the tubular part 1 2 can be arbitrary.

In the embodiment shown, this cross section is, for example, largely flattened in a buttonhole, substantially perpendicular to the generatrices of the external surface 1 3 of the cylindrical part 1 1. Furthermore, in this embodiment, this cross section is uniform over the entire length L1 of the tubular part 12.

But this is not necessarily so, the cross section of the tubular part 1 2 may on the contrary be more or less modulated along its length L1. It suffices that, at the level of the cylindrical part 11, it has a width L2 sufficient to receive the latter.

Finally, in the embodiment shown, the tubular part 1 2 is, for example, straight or substantially straight. But it is not necessarily so either.

On the contrary, this tubular part 1 2 can just as easily be more or less shaped.

For example, it can be more or less curved or curved.

Anyway, the tubular part 1 2 has, generally transversely, and, more precisely, generally transversely with respect to its direction of elongation D, for the intervention of the cylindrical part 1 1, a hole 14, which , envelope of the overall outline of the cylindrical part 1 1, the cross from side to side, and in which, according to arrangements described in more detail later, the cylindrical part 1 1 is forcibly engaged.

This hole 14 therefore affects one and the other of the two partitions 1 5 that the tubular part 1 2 forms generally transversely around it, and, in the embodiment shown, it has a circular contour.

Let D1 be its diameter. In the embodiment shown, the hole 1 4 intervenes, for example, at a distance from one and from the other of the ends of the tubular part 1 2.

But this is not necessarily so.

Finally, in the embodiment shown, and having regard to the flattening of the cross section of the tubular part 1 2, the two partitions 1 5 of this tubular part 1 2 are substantially flat, at least in the vicinity of the hole 14.

But it is not necessarily so either. Let E be the internal thickness of the tubular part 1 2 at its hole 14, that is to say the distance internally separating one from the other its partitions 1 5 at this hole 14.

Prior to the engagement of the cylindrical part 1 1 in the hole 14 of the tubular part 1 2, and according to methods described in more detail later, one forms, on at least a portion of the perimeter of the hole 14, for one at least partitions 1 5 of the tubular part 1 2, a fallen edge 1 8, which, integral with this partition 1 5, extends in the direction of the other partition 1 5 of the tubular part 1 2, substantially perpendicular to this other partition 1 5.

According to the invention, prior to the formation of this fallen edge 18, there is inserted into the tubular part 1 2, a spacer wedge 1 6, also described in more detail later, capable of internally abutting this tubular part 12 in the vicinity of the hole 14. Preferably, and this is the case in the embodiment shown, forming a fallen edge 1 8 over the entire perimeter of the hole 1 4.

Preferably, also, the spacer wedge 1 6 inserted in the tubular part 1 2 intervenes at least in the direction of elongation D thereof.

In other words, it intervenes at least in the median zone of the partitions 1 5 of the tubular part 1 2, on either side of the hole 14 of this tubular part 1 2.

In the embodiment shown, the spacer wedge 1 6 is circularly continuous and it therefore occurs without discontinuity all around the hole 14.

Having the general shape of a ring, it has, in plan, an overall outline generally similar to that of hole 1 4, and, of diameter greater than that of it, it extends coaxially around it . The spacer wedge 1 6 can, for example, have an axial section, a rectangle or square profile, and, in practice, this profile can be most commonly used, this spacer wedge 1 6 can for example be formed by a section of tube, preferably metallic, machined or not. However, in the embodiment shown, the spacer block 1 6 has, in axial section, an isosceles trapezoid profile.

More specifically, the spacer wedge 1 6 comprises, overall, in this embodiment, in addition to the flats 1 9, which truncate it transversely at its axial ends while being sufficiently wide so that its compressive strength is not compromised, d on the one hand, an interior surface 20, which is generally cylindrical, and, on the other hand, an exterior surface 21, which has a middle portion 22 which is itself generally cylindrical, and, each arranged respectively on either side, axially, from this middle part 22, two generally frustoconical facets 23.

It is essentially the interior surface 20 which has, in plan, an overall contour, in this case circular, generally similar to that of the hole 14 of the tubular part 12.

Axially, the spacer block 1 6 used preferably has good resistance to compression and good rigidity.

For example, it is made of metal or hard synthetic material.

According to the invention, a first advantage is taken of this spacer wedge 1 6 even during the formation of the hole 14 of the tubular part 1 2. Indeed, according to the invention, this spacer wedge 1 6 being placed in the tubular part 1 2 before the formation of this hole 14, a pilot hole 14 ′ is formed, in this tubular part 1 2, by simple die-cutting thereof, FIGS. 4B and 4C.

A second part is then drawn from the spacer block 1 6, for the formation of the fallen edge 1 8. In fact, according to the invention, this fallen edge 1 8 is preferably formed by stamping the partition 1 5 concerned.

In both cases, that is to say both during the formation of the pilot hole 14 ′ and during the formation of the dropped edge 1 8, the spacer wedge 1 6 serves as a matrix for the relevant wall 1 5 of the tubular part 1 2.

Preferably, and this is the case in the embodiment shown, a fallen edge 1 8 is formed on one and the other of the partitions 1 5 of the tubular piece 1 2, on at least part of the perimeter of the hole 14, and, in practice, over the whole of it. However, for the implementation of the invention, it can, for example, be carried out as follows.

Firstly, in FIG. 4A, the spacer block 1 6 is inserted into the tubular part 12, along the arrow F1 in this FIG. 4A, by being introduced into this tubular part 1 2 from one of the ends of this one ci, until it comes substantially to the right of the location provided for the hole 14 to be formed.

In practice, this insertion can advantageously be done without great precision, the spacer wedge 1 6 coming from itself to be centered relative to this location during the formation of the hole 14. Preferably, however, it is ensured that the the spacer wedge 1 6 in the tubular part 1 2.

For example, from one of its flats 1 9 to the other, the spacer wedge 1 6 has a height H substantially equal to the internal thickness E of the tubular part.

1 2, or even slightly greater than this thickness E, so that it is forcibly engaged between the two partitions 1 5 and that it is therefore duly wedged between them.

But, if desired, the maintenance in position of the spacer wedge 1 6 can be ensured, or strengthened, by other means, and, for example, by mechanical means, such as imprints obtained by local stamping of the part. tubular 1 2. In a second step, Figures 4B to 4E, we proceed to the formation of the hole 14 and that of the fallen edges 1 8.

The tools used for this purpose operate in practice on a standard machine, in this case a simple hydraulic press. According to the invention, this tool 25 comprises, successively, from bottom to top, a first punch 26 stage having a first section 27, by the free end 28 of which it is capable of cutting a pilot hole 14 'to the punch -piece, a second section 29, with a progressive transverse profile, by which it is capable of ensuring stamping, and a third section 30, by which it is capable of perfecting this stamping.

The diameter D2 of the first section 27 is much smaller than that D1 of the hole 14 to be formed, while the diameter D3 of the third section 30 is substantially equal to this diameter D1, while being slightly smaller than this. Preferably, the free end 28 of the first section 27 of the punch 26 is circularly divided into at least two lips 31, the edges of which are connected in continuity with one another and thus form the wire or cutting edge of the assembly.

In the embodiment shown, only two lips 31 are provided.

They form, internally, a dihedral 32, which is concave, and whose edge extends substantially transversely relative to the axis of the punch 26.

The first section 27 of the punch 26 therefore generally has an inverted V configuration.

In the embodiment shown, the end of each of its lips 31 is cut transversely by a flat 33.

The tool 25 also includes, for counterbalancing the tubular part 1 2 to be worked, a die 34 hollowed out of a hole 35 whose diameter D4 is substantially equal to the diameter D2 of the first section 27 of the punch 26 while being slightly greater than this diameter D2.

Once the tubular part 1 2 applied, by one of its partitions 1 5, hereinafter called second partition 1 5, on the matrix 34, being duly held thereon by clamping means of the usual type not shown, the punch 26, which extends directly above the hole 35 of the die 34, is controlled to move in the direction of the latter, according to arrow F2 in FIG. 4B.

By its first section 27, the punch 26 successively ensures, first of all, the cutting of the other partition 1 5 of the tubular part 1 2, hereinafter called first partition 1 5, FIG. 4B, with a slight fold back towards inside the edge 1 8 ′ thereof intended to form a fallen edge 1 8, then the cutting of the second partition 1 5, FIG. 4C.

As will be noted, thanks to the inverted V configuration of this first section 27, the waste 36 coming from the first partition 1 5 of the tubular part 1 2 remains temporarily attached thereto, so that it is not likely to interfere with the path of this first section 27 before it attacks the second partition 1 5 of the tubular part 1 2, which prevents it from inadvertently disturbing the cutting of this last. After detaching from the first partition 1 5, the waste 36 is discharged through the hole 35 of the matrix 34, together with the waste 37 from the second partition 1 5, Figure 4C.

By its second section 29, the punch 26 completes the folding inwards of the fallen edge 1 8 coming from the first partition 1 5, and, as shown in FIG. 4C, this folding is then confirmed by the third section 30 .

The tool 25 includes a second punch 38 capable of then successively stamping and calibrating the tubular part 12. For the intervention of this second punch 38, and, as shown in FIGS. 4D and 4E, the tubular part 12 is placed on a new matrix 39 perforated with a hole 40 whose diameter D5 is substantially equal to that of D1 of the hole 14 to be formed while being slightly greater than this.

Like the first punch 26, the second punch 38 is a step punch.

In addition to a first section 41, generally frustoconical, and a second section 42, generally cylindrical, capable of ensuring the folding of the fallen edge 1 8 coming from the second partition 1 5 of the tubular part 1 2, it has, successively, from the top at the bottom, alternating with connecting sections 43, 43 '... etc., at least one other section 44, 44' ... etc., generally cylindrical, of diameter greater than that of the second section 42, for a calibration, successive, in several passes, of the hole 14 then obtained.

For example, and as shown, there are provided several sections 44, 44 '... etc., whose respective diameters are increasing.

For its action, the second punch 38, which extends plumb with the hole 40 of the matrix 39, is controlled to move in the direction of the latter, along arrow F3 in FIGS. 4D and 4E.

It then suffices, also with the press, to jointly submit the cylindrical part 1 1 and the tubular part 1 2 to a relative movement from which it follows that the cylindrical part 1 1 engages under stress in the hole 14 of the tubular part 1 2, along arrow F4 of Figure 4F, intervening, to do this, on a first side of this tubular piece 1 2, while externally abutting this tubular piece 1 2, on the side opposite to the previous one, by a matrix 45 perforated with a hole 46 whose diameter D6 is slightly greater than that D1 of the hole 14 of the tubular part 1 2.

Preferably, the fitting force developed is controlled by strain gauges. As will be noted, there is used, according to the invention, only one and the same punch, in this case the first punch 26, for cutting with a punch a front -hole 14 'in the tubular part 1 2 and for the stamping of one of the partitions 1 5 thereof. It goes without saying, however, that, if desired, these two operations can also be provided by different punches.

Anyway, it follows from the above that the assembly 10 according to the invention comprises, between the two partitions 1 5 that its tubular part 1 2 forms around its hole 14, a spacer wedge 1 6 which, in general, extends over at least a portion of the perimeter of this hole 14, and that, for at least one of the partitions 1 5, this hole 14 is, in general, bordered on at least a portion of its perimeter, by a fallen edge 1 8, which, integral with this partition 1 5, extends in the direction of the other partition 1 5 of the tubular part 1 2, substantially perpendicular thereto. In the embodiments shown, the dropped edge 18 extends over the entire perimeter of the hole 14 of the tubular piece 1 2, in one piece with the partition 1 5 concerned thereof, and there is thus a fallen edge 1 8 for one and the other of the partitions 1 5 of this tubular part 1 2.

In addition, this fallen edge 1 8 has, from the internal surface of the partitions 1 5, a constant height h, all around the hole 14.

As will be noted, this hole 14 is defined by the fallen edges 1 8 of the partitions 1 5, and, more precisely, by the external, free surface, of these fallen edges 1 8.

Thus formed by these fallen edges 1 8, the contact surface by which the cylindrical part 1 1 and the tubular part 1 2 are engaged with each other is therefore significantly greater than that of the only edges of the partitions 1 5 of this tubular part 1 2.

In the embodiment shown in Figures 1 to 6, the fallen edges 1 8 extend as close as possible to the spacer wedge 1 6, being substantially in contact with the latter. Preferably, even, they are supported radially on the spacer block 1 6.

In the embodiment shown in Figures 1 to 6, the free edges of the fallen edges 1 8 extend at a distance from each other, the height h of these fallen edges 1 8, which is the same for l 'one and the other of them, being less than half the height H of the spacer wedge 1 6.

But this is not necessarily so.

For example, in Figure 7, the free edges of the fallen edges 1 8 can at least locally be in place in place in contact with each other, to strengthen the resistance to sinking when engaging the cylindrical part 1 1, parallel to the action also exerted in this regard by the spacer wedge 1 6.

In all cases, it is desired, for the spacer block 1 6, a maximum compressive strength, both axially and radially. The present invention is moreover not limited to the embodiments and embodiments described and shown, but encompasses any variant.

Claims

CLAIMS 1. Method for the press fit of an at least locally cylindrical part (1 1), called here simply for convenience cylindrical part, in a tubular part (1 2), generally transversely with respect thereto, of the kind according to which , a hole (14) wraps the overall outline of the cylindrical part (1 1) to pass right through the tubular part (1 2) by affecting one and the other of the two partitions (1 5) that this tubular part (1 2) forms generally transversely around it, one forms, on at least a portion of the perimeter of this hole (14), for at least one of the partitions (1 5) of the tubular part (1 2) , a fallen edge (1 8), which, integral with this partition (1 5), extends in the direction of the other partition (1 5) of the tubular part (1 2), and the cylindrical part is jointly subjected (1 1) and the tubular part (1 2) to a relative movement from which it follows that the cylindrical part (1 1) engages under stress in the hole ( 14) of the tubular part (1 2) on one side thereof, however this tubular part (1 2) is buttressed outwardly on the side opposite to the previous one, characterized in that, prior to the formation of the fallen edge (1 8) on the tubular part (1 2), there is inserted therein a spacer wedge (1 6) adapted to butt against it internally in the vicinity of the hole (14) on at least a portion of the perimeter thereof.

2. Method according to claim 1, characterized in that the fallen edge (1 8) is formed by stamping the partition (1 5) concerned of the tubular part (1 2).

3. Method according to any one of claims 1, 2, characterized in that, the spacer wedge (1 6) being placed in the tubular part (1 2) before the formation of the hole (14) therein , a pilot hole (14 ′) is formed in this tubular part (1 2) by simple die-cutting thereof.

4. Method according to claims 2, 3, taken together, characterized in that only one and the same punch is used (26) for punching out a pilot hole (14 ') in the tubular part (1 2) and for stamping one of the partitions (1 5) thereof.

5. Method according to any one of claims 1 to 4, characterized in that one introduces the spacer wedge (1 6) in the tubular part (1 2) from one of the ends thereof.

6. Method according to any one of claims 1 to 5, characterized in that one forms a fallen edge (1 8) over the entire perimeter of the hole (1 4).

7. Method according to any one of claims 1 to 6, characterized in that one forms a fallen edge (1 8) on one and the other of the partitions (1 5) of the tubular part (1 2 ).

8. Tools for implementing the method according to claim 4, characterized in that it comprises a punch (26), stage, having a first section (27), by the free end (28) of which it is suitable cutting a pilot hole (14 ') with a punch, a second section (29), with a progressive transverse profile, by which it is capable of ensuring stamping, and a third section (30), by which it is suitable for perfecting a stamping.

9. Tool according to claim 8, characterized in that the free end (28) of the first section (27) of the punch (26) is circularly divided into at least two lips (31).

10. Tool according to claim 9, characterized in that the edges of the two lips (31) of the free end (28) of the first section (27) of the punch (26) are connected in continuity with each other and thus form the thread or cutting edge of the whole.

1 1. Tool according to any one of Claims 8 to 10, characterized in that, for implementing a method according to Claim 7, it comprises a second punch (38), stage, capable of ensuring successively a stamping and a calibration .

1 2. Tools for the implementation of a method according to claim 7, characterized in that it comprises a punch (38), stage, capable of ensuring successively a stamping and a calibration.

1 3. Tool according to any one of claims 1 1, 1 2, characterized in that the punch (38) has a first section (41) generally frustoconical, a second section (42) generally cylindrical, and, alternately with connecting sections (43, 43 '... etc.), at least one other section (44, 44' ... etc.), generally cylindrical, of diameter greater than that of the second section (42), for a successive calibration, in several passes, of the hole (14) then obtained.

14. Assembly formed by two parts (1 1, 1 2) fitted in a cross, namely a part (1 1) at least locally cylindrical, here called for simple convenience cylindrical part, and a tubular part (1 2) having a hole (14) in which the cylindrical part (1 1) is forcibly engaged, said hole (14) being bordered, on at least a portion of its perimeter, and for at least one of the partitions (1 5) that the tubular part (1 2) forms around it, by a fallen edge (1 8) which, integral with this partition (1 5), extends in the direction of the other partition (1 5) of the tubular part (1 2), characterized in that it comprises, between the two partitions (1 5) of the tubular part (1 2), a spacer wedge (1 6) which extends over at least a portion of the perimeter of the hole (14 ).

1 5. An assembly according to claim 14, characterized in that the fallen edge (1 8) extends over the entire perimeter of the hole (1 4) of the tubular part (1 2).

1 6. An assembly according to any one of claims 14, 1 5, characterized in that the fallen edge (1 8) has a height (h) substantially constant around the hole (14).

1 7. An assembly according to any one of claims 14 to 1 6, characterized in that the fallen edge (1 8) is in one piece with the partition (1 5) concerned of the tubular part (1 2).

1 8. An assembly according to any one of claims 14 to 17, characterized in that the fallen edge (1 8) extends closest to the spacer wedge (1 6).

1 9. An assembly according to any one of claims 14 to 18, characterized in that it comprises a dropped edge (18) for one and the other of the partitions (1 5) of the tubular part (1 2) .

20. The assembly of claim 1 9, characterized in that the free edges of the two fallen edges (1 8) extend at a distance from each other.

21. Assembly according to any one of claims 14 to 20, characterized in that the spacer wedge (1 6) intervenes at least in the direction of elongation (D) of the tubular part (1 2).

22. An assembly according to any one of claims 14 to 21, characterized in that the spacer wedge (1 6) is circularly continuous.

23. An assembly according to any one of claims 14 to 22, characterized in that the inner surface (20) of the spacer block (1 6) has, in plan, an overall outline generally similar to that of the hole (14) of the tubular part (1 2).