Method of manufacturing a blind threaded insert

1. A method of manufacturing a blind threaded insert from metal comprising a first zone and a second zone, the second zone including a nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, a single deformable section, a first transition section between the deformable section and the head, and a second transition section between the deformable section and the second zone, the deformable section having a higher relative ductility than the remainder of the insert; and extending over a greater length of the first zone than the length over which each of the transition sections extend;

which method comprises the steps of:

(a) at least partially forming the insert, by a cold-forming process, other than an internal thread;

(b) forming the internal thread in the nut portion; and

(c) annealing the first zone of the insert to produce a ductility in the deformable section which is higher than the ductility of the remainder of the insert and so that the deformable section has a hardness value which is lower than the hardness of the nut portion and which is of a substantially constant value along its length in order to promote later deformation in the deformable section during installation of the insert.

2. A process as in claim 1 , in which the annealing step is carried out by band annealing the first zone.

3. A method as claimed in claim 1 , in which the metal is low carbon steel.

4. A method as claimed in claim 2 , which is modified by the interchange in position of the steps of forming the internal thread and of band-annealing the first zone.

5. A method of manufacturing a blind threaded insert from metal comprising a first zone and a second zone, the second zone including a nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, and a single deformable section, a first transition section between the deformable section and the head, and a second transition section between the deformable section and the second zone, the deformable section having a higher relative ductility than the remainder of the insert, such that, during installation of the insert, the deformable section will deform in preference to the remainder of the insert, wherein the deformable section extends over a greater length of the first zone than the length over which each of the transition sections extend;

which method comprises the steps of:

(a) at least partially forming the fastener, by a cold-forming process, other than an internal thread;

(b) annealing the first zone of the insert to produce a ductility in the deformable section which is higher than the ductility of the remainder of the insert, such that the hardness of the deformable section is so that the deformable section has a hardness value which is lower than the hardness of the nut portion and which is of a substantially constant value along a its length;

(c) forming the internal thread in the nut portion; and

(d) induction hardening at least part of the nut portion.

6. A method as claimed in claim 5 , which is modified by the interchange of the positions of the steps of forming the internal thread and of annealing the first zone.

7. A method as claimed in claim 5 in which the metal is medium carbon steel.

8. A method as claimed in claim 1 , which includes a subsequent surface-treatment step.

9. A method as claimed in claim 8 , in which the surface-treatment step comprises electroplating.

10. A blind threaded insert comprising a first zone and a second zone, the second zone including a nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, a single deformable section, a first transition section between the deformable section and the head, and a second transition section between the deformable section and the second zone, the deformable section having a higher relative ductility than the remainder of the insert, such that the deformable section will deform in preference to the remainder of the insert, wherein the deformable section extends over a greater length of the length over which each of the transition sections extend; the insert manufactured by:

(a) at least partially forming the insert, by a cold-forming process, other than an internal thread;

(b) forming the internal thread in the nut portion; and

(c) annealing the first zone,

the insert having a hardness value in the deformable section which is lower than the hardness of the nut portion and which is of a substantially constant value along its length in order to promote deformation in the deformable section during installation of the insert.

11. A blind threaded metal insert comprising a first zone and a second zone, the second zone including an internally threaded nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, a single deformable section having a higher relative ductility than the remainder of the insert, the nut portion having an internal thread and a hardness of substantially constant value extending radially from the internal thread to the outer surface of the nut portion, the deformable section having a hardness of a substantially constant value which is lower than the hardness of the nut portion, such that deformation will occur in the deformable section in preference to the remainder of the insert.

12. An insert according to claim 11 wherein the hardness of the nut portion is in excess of Hv200.

13. A blind threaded insert comprising a first zone and a second zone, the second zone including an internally threaded nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, and a single deformable section, a first transition section between the deformable section and the head, and a second transition section between the deformable section and the second zone, the deformable section having a hardness value which is lower than the hardness of the nut portion and which is of a substantially constant low value along its length in order to promote deformation of the deformable section during installation, and wherein the deformable section extends over a greater length of the length over which each of the transition sections extend.

14. A method of manufacturing a blind threaded insert from metal comprising a first zone and a second zone, the second zone including a nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, and a single deformable section, a first transition section between the deformable section and the head, and a second transition section between the deformable section and the second zone, the deformable section having a higher relative ductility than the remainder of the insert and extending over a greater length than the length over which each of the transition sections extend; which method comprises the steps of:

(a) partially forming the insert, by a cold-forming process, other than an internal thread;

(b) annealing the first zone of the insert so that the deformable section has a hardness value which is lower than the hardness of the nut portion and which is of a substantially constant low value along its length in order to promote later deformation of the deformable section during installation of the insert; and

(c) forming the internal thread.

15. A method according to claim 14 , further comprising the step of completing the forming process of step (a) before forming the internal thread.

16. A method of manufacturing a blind threaded insert from metal comprising a first zone and a second zone, the second zone including a nut portion, and the first zone including a radially enlarged head at one end remote from the second zone, and a single deformable section, a first transition section between the deformable section and the head, and a second transition section between the deformable section and the second zone, the deformable section having a higher ductility relative to the remainder of the insert and extending over a greater length than the length over which each of the transition sections extend; which method comprises the steps of:

(a) partially forming the fastener, by a cold-forming process, other than an internal thread;

(b) annealing the insert;

(c) completing the forming process of step (a); and

(d) forming the internal thread in the nut portion.