1. * GB780018 (A)
Description: GB780018 (A) ? 1957-07-31
Improvements relating to heading tools for use in cold forging
Description of GB780018 (A)
PATENT SPECIFICATION
Inventor: ALAN HERBERT LYNALL 780.018 Date of filing Complete
Specification Nov. 25, 1955.
Application Date Nov. 25,1954.
No. 34228154.
Complete Specification Published July 31,1957.
Index at acceptance -Class 83(4), H(2E1: 2T: 9C).
International Classification:-B23j, k.
COMPLETE SPECIFICATION
Improvements relating to Heading Tools for use in Cold Forging We,
LINREAD LIMITED, a British Company, of Sterling Works, Cox Street,
Birmingham 3, Warwickshire, do hereby declare the invention, for which
we pray that a patent may be granted to us, and the method by which it
is to be performed, to be particularly described in and by the
following statement:-
This invention relates to heading tools for use in the production by
cold forging of metal articles comprising a shank portion and an
integral enlarged end or head, such as screws with circular or
non-circular heads.
The invention has particular reference to the production of such
articles from wire or rod in a two-station or double-impact heading
machine, wherein a blank or length of wire or rod is partly upset by a
first blow at one station thereby to partly form the enlarged end or
head which is finish formed by a second blow at the other station.
It is well known that difficulties are experienced in the cold forging
of articles having substantially parallel sided enlarged ends, such as
screws with cheese and similar heads. For instance, air, oil and
foreign matter is apt to become trapped in the bottom of the die
recess by the metal being deformed, with the result that the sides of
the head often narrow toward the underside, which latter also

2. frequently become recessed.
In an attempt to minimise the falling away of the sides of the head
and to ensure a flat seating face therefor it is common practice to
form the floor of the die recess with a small re-entrant angle
(usually of about 30 to 50), and to form inclined vents leading to the
bottom edge of the die recess; these vents, however, usually give rise
to the formation of slight pips around the lower edge of the head due
to spewing thereinto of the metal being forged.
It is also normal practice with cold heading tools to make the die in
two portions, namely a central insert-which is sometimes made of
tungsten carbide-and a steel case which is shrunk over the insert so
as to produce compressive stresses at the bore of the insert to [Price
3s. 6d.] By rn ' U counteract the bursting effect of the heading blow.
This type of die is quite successful witn the majority of screws, for
example, round, 50 countersunk and hexagon head screws, but so far as
we are aware, it has not been found possible to make accurate cheese
heads in this way, owing to the fact that the front portion of the
insert either cracks or breaks away. 55 The object of the present
invention is to provide an improved heading tool for the cold forging
of articles of the kind referred to, and accordingly provides such a
tool comprising an outer sleeve encasing and reinforcing an 60
intermediate sleeve having a bore which defines the side wall of the
enlarged head of the article, and an inner member having its end set
in from one end of the intermediate sleeve to an extent sufficient to
provide a recess 65 which gives the required depth of head of said
article, and said recess having an annular vented chamber at the
junction between its floor and its side wall for the escape of air
and/or oil. 70 In the case of a die the inner member is also a sleeve,
the bore of which would confine the shank of the article.
In a preferred arrangement the forward end of the inner member, which
in the case of a 75 die constitutes the floor of the recess thereof,
is radiused or chamfered around its outer edge, thereby providing in
effect a small annulus along which air and/or oil trapped under tne
forming head can flow until it escapes through 80 suitable vents.
In order that the invention may be more W- adily understood the
accompanying drawings illustrate, by way of example, dies made in
accordance with the invention, Figure 1 being 85 a fragmentary
sectional view of the forging end of the die, and Figures 2 and 3
enlarged sectional and end views respectively showing the air vents,
Figures 4 to 7 illustrate modified forms of dies hereinafter
described. 90 In the construction of die illustrated in Figures 1 to 3
of the accompanying drawings the die comprises an inner sleeve 1
assembled within an intermediate sleeve 2, and the inter780,018
mediate sleeve 2 is assembled within an outer sleeve 3 by force fits

3. providing interference calculated to set up compressive stresses at
the respective inner diameters so as tc counteract S the bursting
stresses produced by the upsetting of the blank.
A recess 4 defining the shape of the head of the article is provided
by setting in the forward end 5 of the inner sleeve 1, said end 5
constituting the floor of the recess. At the junction between the
floor and the side wall of the recess 4 a small annulus is provided by
radiusing or chamfering the outer edges of the inner sleeve 1, and
from this annulus extend vents constituted by longitudinal grooves 6
made in the outer surface of the inner sleeve 1. The bore 7 of the
inner sleeve 1 defines the shank of the article being forged in the
die.
Since metal flowing under pressure during a cold forging operation
does not form an absolutely sharp corner we have found that by
suitably determining the radius or chamfer at the edge of the inner
sleeve the metai flows to provide a flat underside and a squave side
of the head.
The venting eliminates back pressure in the tool, which results in the
formation of an accurately shaped head with much greater ease than
hitherto, together with a much longer life than with known dies
whether made in one piece or as inserts.
Various modifications of the above described die construction may be
employed. For instance, the front face 5 of the inner sleeve 1 is not
necessarily flat, and by way of example, Figure 4 illustrates a
construction for making a blank such as that indicated by reference 8
which requires provision of a conical mouth 9 at the front end of the
inner sleeve 1.
In the constructions already described the intermediate sleeve 2 is
shown with a plain cylindrical bore of uniform diameter throughout,
but in the production of some articles, such as a bolt having a
hexagonal head fine bore 10 of intermediate sleeve 2 which is exposed
by the set-back inner sleeve 1 may be appropriately shaped, as
indicated in Figure 5. Similarly in the case of an article having
beneath its head a chamfer or conical neck which does not extend to
the shank of tae article (as determined by the bore 7 of inner sleeve
1) the intermediate sleeve 2 may be formed with a recess 11 having a
wall adapted to give the required circular (or non-circular, shape to
the head and a chamfer 12 at the inner end of recess 11 to form a
chamfer or conical neck as shown in Figure 6.
Figure 7 illustrates, by way of example, another variant, that is, a
die for making an article. such as a bolt or screw, having a stepped
underface or spigoted base. The stepped portion or spigot could be
made by counterboring the outer end of inner sleeve 1, but a more
suitable arrangement is shown in Figure 7 where the inner sleeve 1 is

4. made of interfitting parts lA and IB, with part lA set-back within
part lB so that the outer end of the bore of part lB defines the
diameter of the step or spigot. Venting channels 6 are shown 71 on the
exterior ot part lB but may also be provided on part IA.
Alternatively or additionally the intermediate sleeve 2 may be
constituted by two or more interfitting parts.
Tne improved construction of heading tool according to the invention
also readily lends itself to the production of headed articles having
part of the shank of non-circular form, for instance, square-necked
screws, and the g& required necx form may be made entirely within a
single inner sleeve or a two part inner sleeve may be used.
Although the invention has been described above with particular
reference to a die, it is us to be understood that a punching tool
constructed on similar lines could be employed.
For instance, the punch may comprise outer and intermediate sleeves
and an inner plug (instead of inner sleeve), the plug being 90
retracted within the intermediate sleeve to provide a head rorming
cavity. Tne inner sieeve of tne corresponding die would still, by its
bore, control the shank form, but would not be inset within the
intermediate die sleeve. 95 WAhat we ciaim is: 1. A heading tool for
the cold forging of articles of the kind referred to, said tool
comprising an outer sleeve encasing and reinforcing an intermediate
sleeve having a bore which loc dennes the side wail of the enlarged
head of the article, and an inner member having its end set in from
one end of the intermediate sleeve to an extent sufficient to provide
a recess giving the required depth of head of said 105 article, and
the recess having an annular vented clamber at the junction between
its floor and its side wall for the escape of air and/or oil.
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