THREAD FORMER HAVING FLARING RIDGES

Abstract

A tool and related method for the non-cutting production or reworking of a thread in/on a workpiece comprises a forming area which is rotatable about a tool axis (A), the forming area having a plurality of pressing lobes protruding or projecting radially outwards away from the tool axis (A) for producing or post-reworking the thread by pressing the pressing lobes into the workpiece surface. The pressing lobes are arranged in succession along a shaping curve which substantially spirally encircles the tool axis (A), and the pitch of the shaping curve corresponds substantially to the pitch of the thread to be produced or reworked. The pressing lobes form at least one pressing ridge, wherein adjacent to the at least one pressing ridge a flaring ridge with a lower height H.sub.B than the height of the pressing ridge H.sub.D is formed.

Claims

1. A tool for the non-cutting production or reworking of a thread in or on a workpiece, in particular a cold-forming tap or thread former, comprising: at least one forming area which is rotatable or rotates about a tool axis (A) for the non-cutting production or reworking of the thread, in particular an internal thread; wherein: the forming area has a plurality of pressing lobes protruding or projecting radially outwards away from the tool axis (A) for producing or reworking the thread by pressing the pressing lobes into the workpiece surface; the pressing lobes being arranged in succession along a shaping curve which substantially spirally encircles the tool axis (A); the pitch of the shaping curve corresponds substantially to the pitch of the thread to be produced or reworked; and the pressing lobes form at least one pressing ridge; wherein, adjacent to the at least one pressing ridge, a flaring ridge with a lower height H.sub.B than the height of the pressing ridge H.sub.D is formed.

2. The tool according to claim 1, wherein: the pressing lobes are arranged in at least two pressing ridges; and the tool has at least two flaring ridges, which are each arranged between two pressing ridges.

3. The tool according to claim 1, wherein the flaring ridge has a height H.sub.B which lies between half a core diameter of the tool H.sub.K and the height of the pressing ridge H.sub.D.

4. The tool according to claim 1, wherein the at least one pressing ridge and the at least one flaring ridge extend parallel to the tool axis (A).

5. The tool according to claim 1, wherein the at least two flaring ridges are arranged symmetrically with respect to the tool axis (A).

6. The tool according to claim 1, wherein a plurality of pressing ridges is arranged between two flaring ridges.

7. The tool according to claim 1, wherein a pitch angle between a pressing ridge and/or flaring ridge and the following pressing ridge and/or flaring ridge in the circumferential direction is substantially the same.

8. The tool according to claim 1, wherein one or more pressing lobes in one or more pressing ridges are reduced in size or removed.

9. The tool according to claim 1, wherein: the flaring ridge extends along the entire length of the at least one pressing ridge and/or the flaring ridge is formed from two or more partial flaring ridges, each partial flaring ridge being arranged on the shaping curve and preferably having a greater length in the direction of the tool axis (A) than the preceding pressing ridge on the shaping curve.

10. A method for producing an internal thread, having the following iteratively repeating steps: pressing in a thread by means of one or more pressing lobes with a rotating tool, the rotating tool being in particular a tool for the non-cutting production or reworking of a thread in or on a workpiece, in particular a cold-forming tap or thread former, comprising: at least one forming area which is rotatable or rotates about a tool axis (A) for the non-cutting production or reworking of the thread, in particular an internal thread; wherein: the forming area has a plurality of pressing lobes protruding or projecting radially outwards away from the tool axis (A) for producing or reworking the thread by pressing the pressing lobes into the workpiece surface; the pressing lobes being arranged in succession along a shaping curve which substantially spirally encircles the tool axis (A); the pitch of the shaping curve corresponds substantially to the pitch of the thread to be produced or reworked; and the pressing lobes form at least one pressing ridge; wherein, adjacent to the at least one pressing ridge, a flaring ridge with a lower height H.sub.B than the height of the pressing ridge H.sub.D is formed; and subsequently forming the interspace between the threads with a flaring ridge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The invention will be explained in more detail below with regard to further features and advantages by means of the description of exemplary embodiments and with reference to the appended drawings, in which

[0034] FIG. 1 shows a perspective view of an exemplary embodiment of a cold-forming tap according to the invention

[0035] FIG. 2 shows another view of the exemplary embodiment from FIG. 1 of the cold-forming tap and

[0036] FIG. 3 shows a projection of the exemplary embodiment from FIG. 1 of a tool according to the invention in a plane perpendicular to the tool axis, in a direction of view counter to a feed direction of the tool.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Parts and parameters that correspond to each other are indicated in the figures with the same reference signs.

[0038] FIG. 1 shows a cold-forming tap 1 according to the invention, comprising a tool shank 2 and a working area, the forming area 5. A tool axis A, which also represents a rotation axis of the cold-forming tap 1, runs parallel to the longitudinal extension of the cold-forming tap 1 through the centre of the cold-forming tap 1. A feed direction V of the cold-forming tap 1 runs parallel to the tool axis A and is indicated by the direction of the arrow in FIG. 1. The cold-forming tap 1 is used for non-cutting internal thread production.

[0039] The tool shank 2 can be for example cylindrical and usually has a square 3 on the side inserted in the chuck in order to transfer the cutting torque. The tool shank 2 is in this case firmly connected to the adjacent forming area 5, in particular the tool shank 2 and the forming area 5 are embodied in one piece.

[0040] In the forming area 5, numerous pressing lobes 7 along a shaping curve 6 are formed on a tool core as shaping thread. The shaping curve 6 runs spirally or helically, i.e. with a pitch, around the tool axis A. The pressing lobes 7 each have a tip 8 (also referred to as the head) at their free outer end. The pressing lobes 7 are arranged axially offset along the tool axis A along the shaping curve 6 and thus an account of the pitch of the shaping curve 6.

[0041] In the embodiment shown, the pressing lobes 7 are arranged in six pressing ridges 9. This means that six pressing lobes are arranged in one revolution along the shaping curve 6. The pressing ridges 9 are arranged parallel to the tool axis A. FIG. 1 also shows two flaring ridges 10, which are also arranged parallel to the tool axis A on opposite sides of the shank.

[0042] FIG. 2 shows a projection of the embodiment shown in FIG. 1. The pressing ridges 9a, 9b, 9c are arranged next to each other. The flaring ridges 10 are illustrated in each case next to the pressing ridge 9a and next to the pressing ridge 9c in the projection shown at the upper and lower edge of the cold-forming tap 1 shown.

[0043] FIG. 3 shows a projection of the exemplary embodiment of a tool according to the invention in a plane perpendicular to the tool axis, in the direction of view counter to a feed direction of the tool. In the projection, three pressing lobes 7 are arranged next to each other respectively. The pressing lobes 7 are arranged in pressing ridges 9. The flaring ridges 10 are arranged between the groups of three pressing ridges 7 each. The flaring ridges 10 have a height H.sub.B which is lower than the height H.sub.D of the pressing ridges 9 but greater than half the core diameter H.sub.K of the tool. When the cold-forming tap rotates, first of all a thread is pressed with the pressing lobes. The following flaring ridge 10 in the direction of rotation U has such a height that it does not reach the already formed thread, but the area between the thread turns. The material located between the thread turns is pressed radially outwards and, if necessary, partially into the thread turns, so that the formation of forming claws located between the thread turns is reversed. Continuing in rotation, the thread turn is further formed with the three following pressing lobes 7. The area between the thread turns is again contacted with the following flaring ridge 10. As a result of the iterative processing of the thread turns and of the area between the thread turns, a thread can be produced in which no reworking is necessary by subsequent cutting or drilling of an inner area for the removal of forming claws. In a configuration individual pressing lobes may be missing or be smaller in size in order to prevent jamming.

REFERENCE NUMBER LIST

[0044] 1 Tool for material processing, cold-forming tap [0045] 2 Tool shank [0046] 3 Square [0047] 5 Shaping area [0048] 6 Shaping curve [0049] 7, 7a, 7b, 7c Pressing lobes [0050] 8 Tip of the pressing lobe [0051] 9, 9a, 9b, 9c Pressing ridge [0052] 10 Flaring ridge [0053] A Tool axis [0054] V Feed direction [0055] H.sub.B Height of flaring ridge [0056] H.sub.D Height of pressing ridges [0057] H.sub.K Half core diameter of the tool