Machine for forming a head on a shank, such as a nail or a screw

A machine for forming heads on shanks, in particular nail heads, where the shanks are temporarily secured in a preferably rotary tool defining wholly or partially the shape of the heads and co-operating with a rotary roll. According to the invention at least one roll is adapted for internal rolling with respect to one or more of rings serving as tools, the shanks being located substantially radially in said rings.

The invention relates to a machine for forming a head on a shank, in 
particular for forming heads on nails or screws in a single process of 
working by combined forging and rolling, said machine comprising at least 
one driven roll for acting on one end of a shank secured in an annular, 
preferably rotating tool, the shank being driven at a speed different from 
that of the surface of the roll. 
The U.S. Pat. No. 2,917,756 discloses an apparatus for forming nail heads, 
where the nail shank is placed axially in an annular tool and extends 
beyond one, plane side face thereof, said face being provided with a mould 
cavity defining the shape of the nail head. The nail head is formed in 
that rotation of said tool about its axis causes the nail shank to 
co-operate with a plurality of rolls mounted for rotation about respective 
axes, each of which being perpendicular to the axis of the tool, at a 
peripheral speed somewhat greater than the nail shank peripheral speed 
about the axis of the tool. In this known machine the nail head is formed 
in a manner, whose principles are known, it being formed by several 
successive strokes by means of a plurality of rolls. 
Said known machine has its drawbacks, however. Firstly, it is necessary to 
mount idler rolls, serving as backstop means, in a number corresponding to 
that of the rolls mentioned above, on the opposite side of the plane side 
face of the tool. As mentioned, the peripheral speed of the heading rolls 
exceeds the speed of the nail shank to prevent the protruding end of the 
shank from being bent rearwardly with respect to the tool rotating 
direction when the shank end hits a roll. Thus, in order for a roll to 
urge forwardly the shank end there must be a sufficiently large frictional 
force between the roll and the shank end. The frictional force obtained 
will be sufficient only if rolls with a relatively large diameter are 
employed, which makes the known machine large and expensive to 
manufacture. Moreover, the finished nails are ejected from the known 
machine by means which are not simple and reliable. 
The object of the invention is to provide a machine of the subject type, 
which obviates said drawbacks. 
This object is achieved in that the annular tool is adapted to secure a 
plurality of shanks so that they are located substantially radially in 
said tool, and in that the roll is mounted for acting on the end of the 
shanks which faces towards the centre of the tool. 
The invention is based on the new recognition that the angle between the 
tangents for the tool and the roll respectively at the point where the 
shank contacts the roll, should be as acute as possible, and in practice 
it may be as acute as 3.degree. when forming a conventional nail head. To 
achieve this by the prior art using external rolling, the number of the 
rolls and/or their diameters must be larger than is feasible in practice 
at reasonable costs. However, since the invention is based on internal 
rolling, it permits arbitrarily small angles between said tangents at roll 
diameters which are easily realized. Internal rolling involves another 
advantage since the production rate may be increased because several 
shanks may be placed side by side in axial planes of the annular tool, 
allowing the heads to be formed by a single roll. Such increase in 
production rate cannot be achieved by the prior art because the nail shank 
speed depends upon the respective distances of the shanks from the axis of 
rotation of the annular tool. Further, the prior art can only be used for 
making nails of a specific length, whereas the machine according to the 
invention is capable of making nails whose length is not limited by the 
tools as the nail points may protrude freely beyond the outer periphery of 
the tool. 
To obtain the best possible spreading of material in the mould cavity, the 
peripheral speed of the roll is advantageously somewhat greater than the 
speed of the shanks. This permits the achievement of a completely 
symmetrical head seen from the end face, but in some cases said head is 
not exactly perpendicular to the shank. A symmetrical head perpendicular 
to the shank may be obtained by making each shank form an acute angle with 
a line through the centre of the tool and through the end of the shank 
facing the centre, such that the shank is located in front of said line 
with respect to its direction of rotation. 
A preferred embodiment of the annular tool is characterized in that the 
tool comprises two or more rings of a uniform construction and positioned 
side by side, said rings having a plurality of mould halves adapted in 
pairs to receive a shank, and in that means are provided for retaining the 
shanks against longitudinal movement when the respective mould cavities 
are located within a working area where the roll co-operates with the 
shanks. The annular tool is preferably provided with mould jaws preferably 
replaceably mounted in the ring side faces directed towards each other. As 
a result of this the machine may easily be adapted for forming heads of 
other dimensions. 
The means for securing the shanks comprise a stop means for co-operating 
with the shanks at the working area, said stop means being mounted closely 
adjacent the outer periphery of the rings. 
The shanks may also be secured in that at least a portion of each mould jaw 
extends substantially axially with respect to the rotation axes of the 
rings out through an associated recess in the associated ring a distance 
beyond its outwardly facing side face for co-operating with stop means at 
the working area, said stop means being mounted on opposite sides of the 
rings. 
The rings are mounted for rotation such that their respective ring planes 
which are disposed perpendicularly to the associated ring rotation axes, 
diverge seen from the working area. This means that the shanks may be 
secured in a very simple manner in the working area, and that the blanks 
may very easily be inserted and removed over a large part of the periphery 
outside the working area. 
The roll is normally mounted such that its axis of rotation defines the 
mean direction of the rotation axes of the rings. 
Said difference in speed between roll and shank can be achieved in a very 
simple manner for example by providing each ring with a roll path facing 
the associated axis of rotation and adapted to abut on a corresponding 
roll path on the roll, the diameter of the roll path on the roll being 
smaller than the diameter of the roll surface which co-operates with the 
shanks, said roll surface clearing said mould jaws. This also makes it 
possible to bias the roll by pressing it against the internal periphery of 
the tool, the roll being supported by said roll paths such that the roll 
surface just clears the mould jaws. Furthermore, it is possible to drive 
either the roll or the tool alone, the driving power being transferred via 
the roll paths. If sufficient driving power cannot be transferred in this 
manner, the rolls paths may be toothed. 
The mould jaws are much simpler to manufacture, for example with a conical 
opening, when each mould cavity includes a channel-shaped cavity serving 
to receive a portion of the shank and merging into an evenly increasing 
opening at the end facing the centre of the annular tool. The parameters 
of the machine, such as the relative difference in speed between the roll 
and the tool, the angle of entry between the shank and roll as well as 
other parameters, may be adapted so as to obtain a head where only its 
under side is defined by the mould cavity, while its rim is produced by a 
free spreading of the material. It is also possible to produce a head with 
a D-shaped end face by free forming, for example by providing one mould 
jaw with a face directed towards the other mould jaw, the plane of said 
face touching the channel wall in the first-mentioned mould jaw and 
extending inwardly and towards the centre of the annular tool for abutting 
on one of the side faces plane of the roll. Hereby it is achieved that the 
straight edge of the head is exactly flush with the nail shank, which is 
important if the nails are to be stacked for being inserted into the 
magazine of a nail gun where the nails must be positioned closely adjacent 
each other. The same may be obtained by providing the roll with an annular 
flange extending from the roll surface so as to define a radial face whose 
plane touches the channel wall in one mould jaw which is recessed so as to 
clear the outer circumference of the flange. Other advantageous effects of 
this are that no burrs can be formed along the straight edge of the head, 
and that the diameter of the flange need not be large because the 
deformation of the end of the nail shank do not spread far down into the 
shank. 
As mentioned above the free forming entails that the upper side of the head 
is located outside the mould jaws, permitting such a large roll clearance 
with respect to the mould jaws that small foreign bodies cannot get jammed 
between the roll and the mould jaws. The roll paths mentioned above may be 
omitted by securing a gear wheel, at one or either side of the roll, to 
the shaft for co-operating with an internal toothing in a respective one 
of the said rings, the pitch diameter of the gear wheels being smaller 
than the diameter of the roll surface directed towards the shanks. This 
makes the working area of the machine insensitive to small foreign bodies. 
The power transmission of the machine may be completely confined in one 
side, while the other side is free and permits ejection of the finished 
blanks and inspection of the working area without any risk of foreign 
bodies getting jammed, by providing a single gear wheel for co-operating 
with an internal toothing in one of the rings, said toothing being in 
engagement with a toothed drive driven by a drive motor, there being 
provided a guardplate between the roll and said ring, which plate is 
located substantially closely adjacent the internal periphery of the ring. 
Further control facility may be obtained by providing a friction-increasing 
pattern on the surface of the roll, which co-operates with the shanks. 
By providing the periphery of the roll co-operating with the shanks, with 
an annular bead, it is possible to make both a screw head and a slot 
therein in one and the same operation, the dimensions of said slot being 
defined by the bead.

The new recognition on which the invention is based, will be explained with 
reference to FIGS. 1 and 2 before the description of some embodiments of 
the machine according to the invention. The following description concerns 
the making of nails though the machine may also be used for forming heads 
on for example screws or bolts, as mentioned above. It has been found that 
a well-defined spreading of the nail material is obtained when the impact 
on the material is a combination of forging, which is well-known for 
making nails, and rolling. To obtain a complete filling of the mould 
cavity there may advantageously be provided a relative difference in speed 
between the roll and the tool securing the nail. FIG. 1 shows a roll 1 
which revolves in the direction of the arrow P1 and is adapted to 
co-operate with nail blanks 3,4 secured in a tool 2 moved translatorily in 
the direction of the arrow P2. Thus, the peripheral speed of the roll 1 is 
somewhat greater than the translatory speed of the tool 2. 
Moreover, it has been found that the relatively acute angle of entry of the 
nail blank is important for an efficient and well-defined spreading of the 
nail material in the mould cavity 5 which wholly or partially defines the 
shape of the nail head. The angle of entry is defined as the angle U in 
FIG. 1 and is equal to the angle between the tangent to the roll 1 at the 
point where it initially hits the nail blank 3 and the tangent to the tool 
2 at the point where the nails 3 are secured in the tool. In the example 
shown the tangent to the tool 2 is parallel with the tool itself, but the 
definition of the angle U in dependency of the tangent to the tool is 
advantageous where the tool is curved. In some cases the angle of entry 
must be so acute that it is impossible in practice in the manner shown in 
FIG. 1, it being necessary for the roll 1 to have a very large diameter. 
According to the invention the tool consists of one or more rings in which 
the roll 1 revolves, permitting very small values for the angle U. 
The embodiment of the invention which will be described first, is adapted 
to make for example nails with a reduced head. Such nails are mainly used 
for nail guns where the nails must be stacked before they are inserted 
into the nail gun. The stacking consists in placing the nails in one plane 
closely adjacent each other, and they can therefore be brought closer to 
one another if the head is reduced so that the nail shanks may abut on one 
another over the entire length of the nail. When the nail head is viewed 
from above, this is tantamount to there being removed a segment of a 
circle from said head. FIG. 2 shows analogously with FIG. 1 a roll 6 and a 
tool 7 with a mould cavity 8 for a reduced head. When nails with a reduced 
head are to be made, the angle of entry U must be made somewhat larger 
than is required in respect of nails with a full head, but the increased 
angle of entry is still not feasible by means of the prior art. When the 
nail blank hits the roll 6 under the increased angle of entry, the nail 
blank 9 will be bent rearwardly as shown in FIG. 2 and downwardly towards 
the mould cavity 8. Later on the tangent angle V becomes so acute that 
friction between the roll 6 and the nail blank 9 results in an initial 
rolling, and the combined process of rolling and forging produces a nail 
without burrs and with well-defined tolerances so that the finished nail 
may be stacked direct without any intermediate working. Up to now it has 
been necessary to subject the nails to a finishing treatment of about 20 
minutes to deburr them, and the known tools have till now required 
continuous and careful maintenance in order for the tolerances of nails 
for nail guns to be observed. In the machine according to the invention 
the tools are not worn noticeably, firstly because the material is 
subjected to an even impact which is not in the nature of a stroke, and 
secondly because the rearward bending of the nail blank relieves the nail 
shank of axial pressure, obviating burrs from tools for retaining the nail 
shank against a large axial force. 
FIG. 3 shows a vertical longitudinal section of an embodiment of the 
machine according to the invention where the roll 10 corresponds to the 
roll 6 in FIG. 2, while the ring 11 corresponds to the tool 7 in FIG. 2. 
The ring 11 has an internal toothing 12 axially clearing the sides of the 
roll 10 and being engaged with a toothed drive 13 driven by a motor M. The 
roll 10 may be driven separately by a motor or by the ring 11 by means 
which will be described later, it being recalled that the peripheral speed 
of the roll 10 is somewhat greater than the internal peripheral speed of 
the ring 11. 
When this difference in speed is optimum for achieving a completely 
symmetrical head, as viewed from the end, it may be expedient, depending 
upon inter alia the dimension of the head, that the extension of the 
shank, represented by the line L in FIG. 3, is disposed somewhat laterally 
of the centre C of the tool rings, ensuring that the surface of the 
finished head is exactly perpendicular to the shank. With the direction of 
rotation shown in FIG. 3, the shank must point to the left of the centre 
C, and forms thus an angle of the order of a couple of degrees with a 
radius for the ring 11. 
The complete nail machine comprises some stations known per se, and they 
will therefore not be described in detail. They are indicated in FIG. 3, 
the operations of straightening, cutting and pointing, and insertion of 
the nail blank into the ring 11 being performed at the station 14. The 
nail blank is inserted radially, which is permitted by the inclined sides 
15 in cavities 16 for receiving nails/nail blanks. For the sake of 
clarity, cavities 16 are only shown in the area around the roll 10, said 
area being called the working area in the following. However, 
corresponding cavities are present around the entire ring 11. The finished 
nails are removed at the station 17 from where they are taken to a 
location where they are packaged or stored. FIG. 4 shows a section taken 
along the line VI--VI in FIG. 3, and it will be seen that the ring 
includes two mutually inclined tool rings 11A and 11B secured to 
respective inner rings 18A and 18B of bearings that may be ball or roller 
bearings. The outer rings 19A and 19B, respectively, of said bearings are 
secured to associated supporting plates, 20A and 20B respectively. The 
plate 20A is shown in FIG. 3 and is rigidly attached to a base plate 21, 
while the plate 20B is pivotally secured to the base plate 21 so that the 
plates 20A and 20B with associated rings may be urged against each other 
by means of the bolt 22. The roll 10 is secured to a shaft 23 rotatably 
mounted to the plates 20A and 20B respectively by means of spherical 
bearings 23A and 23B. 
FIG. 5 shows a section of one of the tool rings 11A or 11B shown in FIG. 4. 
The ring is secured to the associated inner ring by means of screws, and 
its internal periphery is shaped as a roll path 24. Said roll path 24 
serves as supporting face for the roll 10 (see FIG. 4) having roll paths 
with surfaces 25A and 25B respectively for abutment on the respective roll 
paths on the rings 11A and 11B respectively. The diameter of the roll 
paths 25A and 25B is smaller than the diameter of the central part of the 
roll 10, whose surface 26 is adapted to co-operate with the nail blanks. 
The nail blanks are secured by means of split tools also called mould 
jaws, one half 27 of four mould jaws being shown in FIG. 5, the other, 
corresponding half of these tools being positioned in the other tool ring 
so as to be flush with the halves shown in FIG. 5. Each tool half 27 
defines half of a mould cavity with a cavity 16 for receiving nail blanks, 
as shown at 9 in the figure, and with an opening 28. The cavity 16 
comprises a passage 29 of a semi-channel cross section whose dimensions 
correspond to the nail shank dimension employed. It will therefore readily 
be understood that a nail blank may be retained against axial movement in 
a passage defined by a pair of tool halves within the working area 
previously mentioned, said area extending on both sides away from the roll 
10, a distance which depends upon the divergent angle formed by the tool 
rings 11A and 11B, see FIG. 4. Thus, it will be understood that the nail 
blanks may be inserted radially at the station 14 (FIG. 3), the tool 
halves 27 being mutually spaced in pairs at this location, while the nail 
blanks will be effectively secured between mating tool halves 27 in said 
working area. Similarly, it will be understood that the finished nails may 
be removed at the station 17 shown in FIG. 3, where there is a maximum 
distance between the tool halves 27 permitting easy removal of the blank. 
In FIG. 5 it will be seen that the upper side of the tool halves 27 are 
located somewhat (the distance "a" in FIG. 5) below the roll path 24, and 
as the roll paths 25A or 25B of the roll ride on the roll path 24 in 
constant touch therewith the difference in radius brings about a 
difference in the peripheral speed of the surface 26 of the roll 10 and 
the upper side of the tools 27 respectively, thus permitting in a simple 
manner the achievement of the said, desired difference in speed determined 
by the distance "a". The diameter of the surface 26 of the roll 10 is so 
determined that the surface 26 just clears the tools 27, and at the same 
time the force with which the roll 10 may be biassed towards the nail 
blanks, is taken up exclusively by the roll paths. FIG. 4 (and later FIG. 
7) does not show this clearance because it is very small. In FIG. 5 the 
tool half 27 is shown as one piece, but as the part comprising the opening 
28 and passage 29 must be cured, the tools are preferably divided as is 
shown in FIG. 6 illustrating another embodiment of the rings. 
In FIG. 6 the lower part 16 of the tool is formed continuously with the 
ring 30, which has secured thereto, for example by means of screws, pieces 
31 of hard metal shaped with the mould cavity shown in FIG. 5 with an 
associated passage in which the nail blank is secured within the working 
area. In FIG. 6 the ring 30 is also provided with a toothing 32 on the 
roll path adapted to be engaged with a corresponding toothing (not shown) 
on the roll paths of the roll. The toothing is necessary where the torque 
to be transmitted between the roll and the ring is of such a size that the 
said frictional force between the smooth roll paths is not sufficient. 
The embodiment of the machine according to the invention which has been 
described above includes only two rings for receiving nail or screw shanks 
in a single radial plane. However, the production rate may be stepped up 
by placing three or more rings side by side, so that a single roll 
extending through all the rings may form heads on a plurality of shanks 
located in axial planes for the rings. It will still be possible for the 
shanks to be secured by inclining the rings with respect to one another, 
but in the event of a large number of rings it may be expedient to employ 
other means for securing the shanks in the working area, which will be 
explained below with reference to FIG. 7. 
FIG. 7 shows three rings 33, 34, 35 which like in the embodiment described 
above are secured to respective inner rings of bearings which are not 
shown in the figure for the sake of clarity, it being easy for a skilled 
person to add such machine parts. The machine parts not shown also secure 
a roll 36 having two roll paths 37, 38 for co-operating with shanks 39, 40 
secured in their respective split tools, 41, 42 and 43, 44 respectively. 
The roll paths 37, 38 are provided with an annular bead 45, 46 level with 
the shanks 39, 40, said bead clearing a cut-out 45A, 46A in the tools and 
forming a slot in the head of the shanks 39, 40 which may thus be screw 
shanks. The roll 36 is furthermore provided with roll paths 47, 48, 49 
abutting on associated roll paths on the rings 33, 34, 35 as was explained 
in connection with FIG. 4, and it will be understood that the roll paths 
may either be formed as shown in FIG. 5 or as shown in FIG. 6. It is not 
necessary for the intermediate ring 34 to be driven by the roll, it being 
rotated by the associated tools partially surrounding the screw shanks in 
the working area which thus serve as carriers. Alternatively, all rings in 
the described embodiment may be provided with carrier studs (not shown) 
which are circumferentially spaced and extend axially through the rings 
for transferring torque between these. 
FIG. 7 shows that the tool halves 41 and 44 extend through associated holes 
in the respective rings 33 and 35 and protrude from the outer plane sides 
of these. The projection on said tool halves is adapted to co-operate with 
respective means 50 and 51 respectively, which are of uniform 
construction, and therefore only the means 51 will be explained more fully 
in connection with FIG. 8. Said means are adapted to exert a powerful 
pressure on the tool halves 41 and 44 within the previously defined 
working area, whereby the shanks 39 and 40 as well as the other shanks 
present within the working area are retained against axial movement during 
the co-operation with the roll. 
As mentioned, FIG. 8 shows one clamping means 51, seen from above in FIG. 
7. The clamping means comprises two, preferably driven chain wheels 52, 53 
around which a chain runs which comprises a plurality of rotatable rolls 
54 interconnected by sectional plates 55, as is shown in FIG. 7, and 
located in parallel with the axis of rotation of the wheels 52 and 53. A 
guide block 56 is provided between the chain wheels 52 and 53, which is 
biassed by a predetermined force towards the chain, and for co-operation 
with the chain said guide block has a guide path 57 preferably inclined at 
the ends, said guide path defining the extent of the working area. Since 
the clamping means 50 is shaped in the same manner as the clamping means 
51 it will be understood that within the working area there can be 
obtained a pressure against the tools sufficient for securing the shanks, 
while outside the working area they are so loose in the tools that they 
may be inserted into and removed from these. 
The shanks may alternatively be retained against axial movement away from 
the roll by means of a crawler mechanism of the same type as the one shown 
in FIG. 8, by positioning such a mechanism in the working area at the end 
of the shanks which is opposite the head. In that case, the tools should 
be adapted only to control the shanks and to define the shape of the head. 
FIG. 9 shows some expedient details of another embodiment of the machine 
according to the invention. FIG. 9 shows a section of the machine, said 
section corresponding to the one shown in FIG. 4 of the embodiment 
previously described. The outer rings 60, 61 of the two large bearings 
are, as described above, secured to the respective side members 62, 63 of 
the machine, for example by means of the screws (not shown). The inner 
rings 64, 65 of the bearings clear the side members 62, 63, and the inner 
ring 64 is provided with an internal toothing in engagement with a toothed 
drive 67 driven by a drive motor (not shown). The inner rings carry their 
respective halves 68 and 69 of a plurality of split tools which will be 
described in connection with FIGS. 10-12. A shaft 70 is rigidly connected 
to a roll 71 rotated by means of a gear wheel 72 which is likewise rigidly 
connected to the shaft 70 and which is engaged with the toothing 66. The 
pitch diameter of the gear wheel 72 is smaller than the diameter of the 
roll 71, making the peripheral speed of the roll 71 somewhat greater than 
the speed of the end of a nail blank 73 co-operating with the roll 71. 
The embodiment shown in FIG. 9 is also provided with a guard plate 74 which 
is mounted substantially closely adjacent the internal periphery of the 
ring 64 and which may be attached by means of support legs to the side 
plate 62 as shown at 75. Thus, it will be seen that the entire power 
transmission of the machine is located behind the guard plate 74, 
preventing any foreign bodies from getting jammed between the toothings. 
But then the machine is also accessible without any danger from the other 
side through an opening 76 in the side plate 63 so that the machine may be 
inspected and so that the finished nails may be ejected by the ejection 
station 77 shown schematically. 
The tool halves or mould jaws 68, 69 are shown on a larger scale in FIG. 
10, where they are designated 68a and 69a. The mould jaws have between 
them a nail with a round head 78 formed by co-operation with the roll of 
which a section 71a is shown. In relation to the mould jaws previously 
described the mould jaws 68a and 69a are characteristic in that besides 
comprising a passage for securing the nail the mould cavity between the 
jaws define an opening with conical side faces directed towards the roll 
71a. In other words the mould jaws 68a and 69a do not define the rim of 
the nail head; it is brought about by free forming partly at a level 
outside the mould jaws, permitting a greater clearance between the mould 
jaws and the roll. In connection with the guard plate 74 in FIG. 9 this 
feature ensures that no foreign bodies will get jammed in the machine. 
The opening in the mould jaws 68a, 69a, defining the inclined under side of 
the head 78, does not have to be conical, but may assume other shapes 
which fit for example the under side of a nail with a square head. What is 
important is, as mentioned, that the rim of the nail head is made by free 
forming, which is feasible by correct adjustment of the various parameters 
of the machine, as for example the frictional coefficient between the roll 
71a and the nail head. This parameter may be varied by providing the 
surface of the roll with pattern promoting the friction as is indicated at 
the top of the roll 71 in FIG. 9. Preferably, the mould jaws are so 
arranged that the position of the nail shank indicated by the line L in 
FIG. 3 may be obtained. 
The free forming described above is also applicable for forming reduced 
nail heads, for example by means of the mould jaws 78, 79 shown in FIG. 
11. The opening in the mould jaw 79 defines only the under side of the 
nail head 80 so that the curved rim of the nail head is provided by free 
forming. The straight rim of the nail head is defined by a plane face 82 
which is provided on the mould jaw 78 and extends at least from the under 
rim of the nail head and a distance upwardly on the plane side face of the 
roll, of which a section 81 is shown. It is observed that the nail head 
will be turned 90.degree. with respect to the location of the nail heads 
in the tools shown in FIGS. 5 and 6. 
It has already been explained that a burr along the straight edge of the 
reduced nail head is not desirable. Such a burr might occur in the tools 
shown in FIG. 11 when they are worn, but is totally avoided by means of 
the tools shown in FIG. 12. The mould jaw 79a is formed in the same manner 
as the mould jaw 79, but the mould jaw 78a is recessed so that it just 
clears a flange 83 on the roll 81a. The annular, radial face 84 located 
between the surface of the roll 81a and the flange 80 is thus part of the 
forming tool, thereby obviating any risk of such burr being formed. It has 
been found that the deformation of the nail material in the forming of the 
head does not spread far down into the nail shank, and in practice there 
may thus be a small clearance between the flange 83 and the mould jaw 78a 
without any risk of a burr being formed at this location. 
Conclusively, the machine according to the invention offers may advantages 
of which several have already been mentioned. Moreover, the machine 
consumes less power as no accelleration power is lost as is the case in 
known, commercially available machines due to the translatory movements. 
This circumstance results in a low level of noise, little wear and long 
life. The production rate may be increased considerably in relation to the 
prior art, it being stressed that owing to the internal rolling optimum 
working conditions may be obtained which permit not only a great 
production rate, but also narrow tolerances and minimize formation of 
burrs.