Method and apparatus for fabricating one piece all metal prevailing torque locknut fasteners

Method and apparatus for modifying conventional internally threaded nut blanks to form one piece all metal prevailing torque locknut fasteners having uniform, repeatable torque characteristics when engaged with conventional bolt threads. This is accomplished by positioning the conventional internally threaded nut blanks in a single file in an orientation with their base facing downward and their arcuate crown portion facing upward and feeding these conventional internally threaded nut blanks one at a time between a first rotating deforming wheel having a substantially "v-shaped" groove on an end surface thereof, the substantially "v-shaped" groove corresponding to the arcuate crown portion of the conventional internally threaded nut blanks, the rotating deforming wheel rotating at a predetermined rotational speed and in a first rotational direction, and a rotating backing wheel positioned a predetermined distance from the rotating deforming wheel, the rotating backing wheel including a flat surface on its end surface corresponding to the base of the conventional internally threaded nut blanks, the rotating deforming wheel rotating at the same predetermined rotational speed as the rotating backing wheel, but in a second rotational direction opposite to that of said wheel.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates generally to a new and novel method and 
apparatus for fabricating internally threaded fasteners which provide 
interfering engagement with conventional bolt threads. More particularly, 
the present invention relates to a new and novel method and apparatus for 
modifying conventional internally threaded nut blanks to form one piece 
all metal prevailing torque locknut fasteners having uniform, repeatable 
torque characteristics when engaged with conventional bolt threads. 
Two types of locknut fasteners have traditionally been used in conjunction 
with conventional bolt threads to provide a fastener which requires 
additional torque for disassembly as compared with a conventional 
fastener. The first type of locknut fasteners, prevailing torque locknut 
fasteners, rely on some form of mismatch in the locknut thread form in 
relation to the conventional threaded bolt body when assembled together. 
The other type of locknut fasteners, free spinning or free running locknut 
fasteners, utilize an axial load applied to the base of the nut to "lock" 
or restrict movement between the locknut fastener and the conventional 
threaded bolt body. The first type of locknut fasteners, prevailing torque 
locknut fasteners, have become widely accepted due to their economical 
fabrication cost, ease of use and reliability in a wide variety of 
applications. Prevailing torque locknut fasteners can be divided into two 
general categories, insert type prevailing torque locknut fasteners, which 
depend upon an insert, such as a compression collar, in the interior 
threads of the locknut fastener, and one piece all metal prevailing torque 
locknut fasteners. Insert type prevailing locknut fasteners are self 
locking due to plastic deformation of the insert regardless of the amount 
of bolt tension, however, such insert type prevailing locknut fasteners 
are generally relatively expensive to fabricate as compared to one piece 
all metal prevailing torque locknut fasteners. Accordingly, one piece all 
metal prevailing torque locknut fasteners have found wide acceptance due 
to their economical cost and applicability to a wide variety of products 
and applications. 
Many varieties of one piece all metal prevailing torque locknut fasteners 
are currently available. However, all of these known prior art one piece 
all metal prevailing torque locknut fasteners induce their locking 
characteristics through either pitch distortion of the internal nut 
threads, nut ovalization or some combination of these two. One piece all 
metal prevailing torque locknut fasteners which utilize thread pitch 
distortion to provide prevailing torque tend to experience a relatively 
rapid decline in prevailing torque capability through subsequent reuse. On 
the other hand, one piece all metal prevailing torque locknut fasteners 
utilizing nut ovalization generally experience a reduced rate of decrease 
in prevailing torque capability through subsequent reuse. 
Ovalized one piece all metal prevailing torque locknut fasteners have 
traditionally been fabricated using one of two methods. The first method 
generally utilities a press having a vertical stroke with a plate or die 
which corresponds to the shape of the crown portion of the conventional 
internally threaded nut blanks which are to be fabricated into one piece 
all metal prevailing torque locknut fasteners. Using this method, a 
conventional internally threaded nut blank is positioned on a table with 
its crown portion facing upward and the plate or die engages and deforms, 
in most cases, three sides of the crown portion and sides of the 
conventional internally threaded nut blank to deform or ovalize the 
internal thread configuration of the conventional internally threaded nut 
blank into an internal thread configuration having three (3) "flats" or 
distorted sections which approach the configuration of an equilateral 
triangle. 
One significant drawback of using a press to fabricate one piece all metal 
prevailing torque locknut fasteners is that, when utilizing a press, it is 
generally necessary to go through the steps of loading a conventional 
internally threaded nut blank in position on a table, going through the 
press stroke cycle and then removing the formed one piece all metal 
prevailing torque locknut fastener from the table. These steps can be time 
consuming and often result in a slower locknut production rate. 
Furthermore, presses are generally noisy and all deformation or 
ovalization of the conventional internally threaded nut blank threads is 
generally accomplished in a single press stroke, thus requiring a 
relatively large force to be exerted over a relatively short period of 
time to form one piece all metal prevailing torque locknut fasteners using 
a press. 
It is generally desirable to deform or ovalize the first two to five 
threads of a conventional internally threaded nut blank to provide a 
balance between maximizing the number of free running threads which are 
available before the deformed or ovalized threads engage the conventional 
bolt threads on one hand and not relying on only one deformed or ovalized 
thread to provide the prevailing torque to "lock" the locknut to the 
conventional bolt threads on the other hand. 
Many standards directed to one piece all metal prevailing locknut fasteners 
require a minimum number of free running threads before the deformed or 
ovalized threads are engaged, thus limiting the number of threads in a 
conventional internally threaded nut blank which can be deformed or 
ovalized. These same standards also require one piece all metal prevailing 
torque locknut fasteners to maintain a minimum prevailing torque 
capability when the one piece all metal prevailing torque locknut fastener 
has been engaged and disengaged from a conventional threaded bolt body a 
predetermined number of times, in many cases, five times. If only one or 
two threads are relied upon to provide the prevailing torque capability, 
this repeated assembly/disassembly minimum prevailing torque capability 
requirement can be difficult to meet. Thus, it is advantageous to have a 
one piece all metal prevailing torque locknut fastener fabrication process 
which is capable of uniformly deforming or ovalizing a predetermined 
number of threads in conventional internally threaded nut blanks. 
An example of a prior art method of making locknuts utilizing the rotation 
of indented teeth formed on wheels is described in U.S. Pat. No. 4,038,714 
to Werner. The use of wheels to modify conventional internally threaded 
nut blanks to form locknut fasteners generally increases the one piece all 
metal prevailing torque locknut fastener production rate. However, one 
piece all metal prevailing torque locknut fasteners produced utilizing the 
method described in U.S. Pat. No. 4,038,714 to Werner have a series of 
indentations on two opposed side walls. A drawback of one piece all metal 
prevailing torque locknut fasteners fabricated in accordance with the 
method described in the U.S. Pat. No. 4,038,714 to Werner is that since 
the series of indentations, and thus the deformation or ovalization of the 
threads, extend significantly into the opposed side walls, more than the 
desired number of threads are deformed or ovalized, and the industry 
standards requirement of a minimum number of free running threads before 
the deformed or ovalized threads are engaged is difficult to meet. One 
possible way of increasing the number of free running threads before the 
deformed or ovalized threads are engaged is to use conventional internally 
threaded nut blanks having oversized internal threads to form one piece 
all metal prevailing torque locknut fasteners using the method described 
in U.S. Pat. No. 4,038,714 to Werner. However, the use of conventional 
internally threaded nut blanks having oversize threads results in a looser 
or "sloppier" fit with the conventional bolt threads and thus, reduces the 
force or load carrying capacity of one piece all metal prevailing torque 
locknut fasteners formed from conventional internally threaded nut blanks 
having oversize threads. Furthermore, since special taps are generally 
necessary to fabricate conventional internally threaded nut blanks having 
oversize threads, such conventional internally threaded nut blanks having 
oversize threads can be more difficult and expensive to obtain as compared 
to conventional internally threaded nut blanks having standard threads. 
Another drawback of one piece all metal prevailing torque locknut fasteners 
fabricated in accordance with the method described in U.S. Pat. No. 
4,038,714 to Werner is that the conventional internally threaded nut 
blanks are positioned on their base or bottom surface when the series of 
indentations are formed and the base or bottom surface of the conventional 
internally threaded nut blanks are forced downwardly against a stationary 
base or support surface by the deforming wheels and, while being forced 
downwardly against the stationary base or support surface, the 
conventional internally threaded nut blanks are moved or slid across the 
stationary base or support surface by the deforming wheels. This moving or 
sliding of the base or bottom surface of the conventional internally 
threaded nut blanks along the stationary base or support surface, along 
with the downward force exerted on the conventional internally threaded 
nut blanks can result in one piece all metal prevailing torque locknut 
fasteners which are unsightly and, in some cases, can interfere with the 
assembly and/or function of the one piece all metal prevailing torque 
locknut fasteners. Furthermore, such moving or sliding of the base or 
bottom surface of the conventional internally threaded nut blanks along 
the stationary base or support surface, along with the downward force 
exerted on the conventional internally threaded nut blanks by the 
deforming wheels, can also result in excessive wear and tear on the 
stationary base or support surface. While a lubricating fluid may be used 
to minimize the score marks on the one piece all metal prevailing torque 
locknut fasteners, and minimize the extent of excessive wear and tear on 
the stationary base or support surface, the use of such a lubricating 
fluid is another operation which has to be monitored and controlled when 
fabricating one piece all metal prevailing torque locknut fasteners in 
accordance with the description in U.S. Pat. No. 4,038,714 to Werner. 
Another prior art one piece all metal prevailing torque locknut fastener 
design is described in Canadian Patent No. 1,119,440. This prior art one 
piece all metal prevailing torque locknut fastener design has many of the 
same drawbacks as one piece all metal prevailing torque locknut fasteners 
fabricated in accordance with the method described in U.S. Pat. No. 
4,038,714 to Werner as discussed above. These drawbacks include 
indentations on opposed side walls of the one piece all metal prevailing 
torque locknut fasteners, thus reducing the number of free running threads 
before the deformed or ovalized threads are engaged, as well as score 
marks on the base or bottom surface of the one piece all metal prevailing 
torque locknut fastener and excessive wear and tear to a stationary base 
or support surface due to moving or sliding of the base or bottom surface 
of the conventional internally threaded nut blanks along the stationary 
base or support surface, along with the downward force exerted on the 
conventional internally threaded nut blanks by the deforming wheel. 
Accordingly, an object of the present invention is the provision of a 
method and apparatus for fabricating one piece all metal prevailing torque 
locknut fasteners which is capable of modifying conventional internally 
threaded nut blanks to form one piece all metal prevailing torque locknut 
fasteners having uniform prevailing torque characteristics when assembled 
to conventional bolt threads. 
Another object of the present invention is to provide a method and 
apparatus for fabricating one piece all metal prevailing torque locknut 
fasteners from conventional internally threaded nut blanks at a relatively 
rapid one piece all metal prevailing torque locknut fastener production 
rate. 
Yet another object of the present invention is to provide a method and 
apparatus for fabricating one piece all metal prevailing torque locknut 
fasteners which is capable of modifying conventional internally threaded 
nut blanks without scoring the base or bottom surface of the one piece all 
metal prevailing torque locknut fasteners and without excessive wear and 
tear to a stationary base or support surface due to relative movement or 
sliding between the conventional internally threaded nut blank and the 
stationary base or support surface. 
These and other objects of the present invention are attained by the 
provision of a method and apparatus for modifying conventional internally 
threaded nut blanks to form one piece all metal prevailing torque locknut 
fasteners having uniform, repeatable torque characteristics when engaged 
with conventional bolt threads. This is accomplished by positioning the 
conventional internally threaded nut blanks in a single file in an 
orientation with their base facing downward and their arcuate crown 
portion facing upward and feeding these conventional internally threaded 
nut blanks one at a time between a first rotating deforming wheel having a 
substantially "v-shaped" groove on an end surface thereof, the 
substantially "v-shaped" groove corresponding to the arcuate crown portion 
of the conventional internally threaded nut blanks. The rotating deforming 
wheel rotates at a predetermined rotational speed in a first rotational 
direction and a rotating backing wheel is positioned a predetermined 
distance from the first rotating deforming wheel, the rotating backing 
wheel including a flat surface on its end surface corresponding to the 
base of the conventional internally threaded nut blanks, the rotating 
deforming wheel rotating at the same predetermined rotational speed as the 
rotating deforming wheel, but in a second rotational direction opposite to 
that of the rotating deforming wheel to form the one piece all metal 
prevailing torque locknut fasteners. 
Other advantages and novel features of the present invention will become 
apparent in the following detailed description of the invention when 
considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
In the following detailed description of preferred embodiments of the 
present invention, reference is made to the accompanying drawings which, 
in conjunction with this detailed description, illustrate and describe a 
preferred embodiment of a method and device for fabricating one piece all 
metal prevailing torque locknut fasteners in accordance with the present 
invention. Referring now to FIGS. 1 through 3, which illustrate a 
prospective view, a top view and a cross-sectional side view, 
respectively, of a one piece all metal prevailing torque locknut fastener, 
generally identified by reference numeral 10, in accordance with a 
preferred embodiment of the present invention, one piece all metal 
prevailing torque locknut fastener 10 has a generally hexagonally shaped 
body, indicated by reference numeral 12, in the form of a conventional 
internally threaded nut blank. It should be understood that although the 
present invention is depicted herein in connection with a single exemplary 
nut size, the concepts of the invention are applicable to the entire range 
of standard nut sizes. 
Generally hexagonally shaped body 12 includes six side surfaces or flats 
14, 16, 18, 20, 22 and 24 forming three pairs of opposed flats 14, 20; 16, 
22; and 18, 24; each pair of flats lying in substantially parallel planes. 
The spaced pairs of flats 16, 22 and 18, 24 are preferably in accordance 
with conventional standard internally threaded nut design, except that a 
portion of the remaining pair of flats 14, 20 are modified over a portion 
thereof as hereinafter described. 
The lower extremity of hexagonally shaped body 12 of one piece all metal 
prevailing torque locknut fastener 10 is defined by base or bearing face 
26 which is preferably of an annular configuration in accordance with 
industry standards for conventional internally threaded nut blanks. Base 
or bearing face 26 is joined to each of the side surfaces or flats 14, 16, 
18, 20, 22 and 24 by chamfered surfaces, again in accordance with industry 
standards for conventional internally threaded nut blanks. Base or bearing 
surface 26, which is substantially perpendicular to the axis of generally 
hexagonally shaped body 12, has a central opening or through bore 28 which 
is also in accordance with industry standards for conventional internally 
threaded nut blanks. 
Central opening or through bore 28 extends from base or bearing surface 26 
to top surface 30 which lies substantially in a plane perpendicular to the 
axis of generally hexagonally shaped body 12 and therefore lies in a plane 
substantially parallel to the plane of base or bearing surface 26. Top 
surface 30 is joined to side surfaces or flats 14, 16, 18, 20, 22, 24 and 
26 by arcuate crown portion 32 which preferably has the configuration of a 
frustrum of a cone having an angle of approximately 45.degree. with 
respect to the plane of side surfaces or flats 14, 16, 18, 20, 22 and 24 
which parallel the axis of generally hexagonally shaped body 12. Arcuate 
crown portion 32 varies from the preferred conical configuration in the 
areas of side surfaces or flats 14 and 20 in a manner hereinafter 
described. 
One piece all metal prevailing torque locknut fastener 10 includes 
substantially flat surfaces 34 and 36 on arcuate crown portion 32 
corresponding to side surfaces or flats 14 and 20. As seen in FIG. 2, 
substantially flat surfaces 34 and 36 are preferably shaped substantially 
as a parallelogram including substantially parallel top surfaces 38 and 40 
which extend substantially to top portion 42 of arcuate crown portion 32, 
substantially parallel bottom surfaces 44 and 46 which extend 
substantially to the intersection between side surfaces or flats 14 and 20 
and arcuate crown portion 32 and angled side surfaces 48, 50, 52 and 54 
which preferably angle inwardly from substantially parallel top surfaces 
38 and 40 to substantially parallel bottom surfaces 44 and 46. 
Substantially flat surfaces 34 and 36 are formed by compressing arcuate 
crown portion 32 above side surfaces or flats 14 and 20 as will be 
described hereinafter. 
Referring now to FIGS. 4 through 6, a one piece all metal prevailing torque 
locknut fastener fabricating apparatus for fabricating one piece all metal 
prevailing torque locknut fastener 10 in accordance with a preferred 
embodiment of the present invention is shown, indicated generally by 
reference numeral 56. One piece all metal prevailing torque locknut 
fastener fabricating apparatus 56 generally includes a vibratory nut 
feeder bowl 58, which can be of conventional design, including provisions 
for orienting conventional internally threaded nut blanks in an 
orientation with arcuate crown portion 32 facing upward and transporting 
the conventional internally threaded nut blanks so oriented onto feed 
track 60. Feed track 60 positions a plurality of properly oriented 
conventional internally threaded nut blanks in a single file to be fed 
between rotating deforming wheel 62 and rotating backing wheel 64 one at a 
time. As will be described hereinafter, rotating deforming wheel 62 
deforms arcuate crown portion 32 of the conventional internally threaded 
nut blanks above side surfaces or flats 14 and 20 to form substantially 
flat surfaces 34 and 36 while base or bearing face 26 of the conventional 
internally threaded nut blanks are supported on rotating backing wheel 64. 
Referring to FIGS. 5 and 6, which illustrate an end view and a side view, 
respectively, of rotating deforming wheel 62, rotating deforming wheel 62 
includes a central cylindrical aperture or opening 66 which engages with a 
first rotating shaft (not shown) extending from a source of rotational 
power, such as an electrical motor (not shown), to locate or centrally 
position rotating deforming wheel 62 in relation to the first rotating 
shaft (not shown). Rotating deforming wheel 62 also preferably includes a 
plurality of bolt holes 68 through which a plurality of conventional 
fasteners, such as machine bolts 70, extend to rotationally couple 
rotating deforming wheel 62 with a cylindrical plate (not shown) extending 
outwardly from the first rotating shaft (not shown). If desired, an 
interior portion of rotating deforming wheel 62 can include counterbore 72 
which corresponds to the cylindrical plate (not shown) extending outwardly 
from the rotating shaft (not shown) to assist in maintaining the position 
of rotating deforming wheel 62 in relation to the first rotating shaft 
(not shown). Thus, rotating deforming wheel 62 is located concentric with 
first rotating shaft (not shown) extending from the source of rotational 
power and is rotationally coupled to rotate at the same rotational speed 
and in the same rotational direction as first rotating shaft (not shown). 
Rotating backing wheel 64 is rotationally attached and coupled to a second 
rotating shaft (not shown) in a manner similar to that of rotating 
deforming wheel 62 and the second rotating shaft (not shaft) rotates at 
the same rotational speed, but in the opposite rotational direction, as 
first rotating shaft (not shown). 
As seen in FIG. 6, rotating deforming wheel 62 includes substantially 
"v-shaped" groove 73 located intermediate first side surface 74 and second 
side surface 76 of rotating deforming wheel 62. Substantially "v-shaped" 
groove 73 preferably has an included angle .varies. in the range of 
90.degree. to 120.degree., more preferably in the range of 100.degree. to 
110.degree. and most preferably 106.degree.. The width and depth of 
included angle .varies. corresponds to the width and height of arcuate 
crown portion 32 of the conventional internally threaded nuts, and thus 
rotating deforming wheels 62 designed for larger conventional internally 
threaded nut blanks will have a wider and deeper substantially "v-shaped" 
groove 73 than will rotating deforming wheels 62 designed for smaller 
conventional internally threaded nut blanks. Alternatively, the same 
rotating deforming wheel 62 could be utilized to deform or ovalize smaller 
or larger conventional internally threaded nut blanks by, respectively, 
decreasing or increasingly the distance between rotating deforming wheel 
62 and rotating backing wheel 64. The distance between rotating deforming 
wheel 62 and rotating backing wheel 64 can also be increased or decreased 
to increase or decrease the extent of deformation or ovalization of the 
conventional internally threaded nut blanks. Furthermore, base portion 78 
of substantially "v-shaped" groove 73 can be filled in or flat as shown in 
FIG. 6 since this portion of substantially "v-shaped" groove 73 is above 
central opening or through bore 28 of the conventional internally threaded 
nut blanks and is not used to deform arcuate crown portion 32. 
Rotating backing wheel 64 is preferably identical in configuration and size 
to rotating deforming wheel 62, except rotating backing wheel 64 has a 
flat surface extending between its first side surface (not shown) and its 
second side surface 80. Thus, rotating backing wheel 64 rotates at the 
same rotational speed, but in the opposite rotational direction, as 
rotating deforming wheel 62, and rotating backing wheel 64 supports base 
or bearing face 26 of the conventional internally threaded nut blanks 
while rotating deforming wheel 62 deforms arcuate crown portion 32 of the 
conventional internally threaded nuts. Since rotating deforming wheel 62 
and rotating backing wheel 64 rotate at the same rotational speed, but in 
opposite rotational directions, both rotating deforming wheel 62 and 
rotating backing wheel 64 assist in transporting the conventional 
internally threaded nuts from feed track 60 through the arcuate crown 
portion 32 deforming operating and away from feed track 60 once arcuate 
crown portion 32 is deformed to form one piece all metal prevailing torque 
locknut 10. This deforming or ovalization process is a progressive 
operation and requires less force exerted over a longer period of time 
when compared to, for example, a press which requires more force exerted 
over a shorter period of time. Furthermore, since there is no relative 
movement between base or bearing face 26 of the conventional internally 
threaded nut blanks and rotating backing wheel 64, no score marks are 
formed in base or bearing in face 26 and wear and tear to rotating backing 
wheel 64 is minimized. In addition, since base or bearing face 26 is flat 
and rotating backing wheel 64 is curved, some relative movement or 
"rocking" occurs as the conventional internally threaded nut blanks pass 
between rotating deforming wheel 62 and rotating backing wheel 64. 
Although the present invention has been described above in detail, the same 
is by way of illustration and example only and is not to be taken as a 
limitation on the present invention. For example, a rotating deforming 
wheel and rotating backing wheel arrangement in accordance with the 
present invention could be utilized to deform or ovalize conventional hex 
nuts not having arcuate crown portion 32 i.e., a flat top surface. In this 
case, the included angle of substantially "v-shaped" groove in rotating 
deforming wheel 62 would preferably be less than 90.degree.. Accordingly, 
the scope and content of the present invention are to be defined only by 
the terms of the appended claims.