Prevailing torque nut

A method and apparatus is provided for making a prevailing torque nut from a regular nut. The regular nut is placed between two anvil members, and a gap between the anvil members is first decreased so that they contact the nut on opposite sides. Then, the gap between the anvil members is further decreased by a preset amount, in order to permanently inwardly deform the nut. By making the preset amount a constant quantity, a plurality of nuts having slightly different outside and inside dimensions can be consistently deformed. A feature of this invention is the provision of a deformation apparatus which smoothly, progressively and consistently deforms a nut from one end to another. To accomplish this, the anvil members which cause the deformation have oblique working surfaces which taper toward each other, and which are adapted to bear against the nut over substantially the whole of the length of the nut, with the exception of an integral washer if such is present.

This invention relates generally to prevailing torque nuts, particularly of 
the kind used in the automotive industry, and in other areas such as 
appliances, agriculture and lawn mowers, where vibration and loss of 
fastening is significant. 
BACKGROUND OF THIS INVENTION 
Prevailing torque nuts are (usually) a deformed version of a hexagonal nut, 
often with an integral flange washer, and the intention is for the binding 
and prevailing torque to take place between the threads of the nut and the 
bolt (screw, stud or other externally threaded element), as the nut is 
threaded onto the bolt. Normally, the nut is applied with a power wrench 
or other method, and the person carrying out this operation will preset 
the wrench to a specified value, in accordance with a tightening 
specification. If the assembly subsequently loosens, the nut will remain 
in place and will strongly resist being shaken loose through vibration 
because of the prevailing torque. 
Although there are numeous methods available, many of which are patented, 
for applying a deformation to a hexagonal nut in order to deform it or at 
least a portion of it, so that binding will take place between the nut and 
the bolt on which it is threaded, to date a satisfactory degree of 
consistency of deformation has been lacking. This has meant that many of 
the produced nuts were rejects, as being either too greatly deformed or 
too little. 
GENERAL DESCRIPTION OF THIS INVENTION 
In view of the foregoing disadvantage of known methods for deforming 
hexagonal nuts, it is an aspect of this invention to provide a method and 
apparatus for carrying out such deformation, which is capable of carrying 
out a very uniform deformation of standard and special undeformed 
hexagonal nuts, thus resulting in an output with few or no rejects. 
It is a further aspect of this invention to provide a deformed nut, 
exhibiting superior characteristics as a prevailing torque nut and capable 
of specified prevailing torque when maximum material nut is applied to 
maximum material bolt and minimum material bolt. 
"More particularly, this invention provides a method of making a prevailing 
torque nut from a regular nut, that includes at least one pair of opposed 
external facets, the method including the steps of first placing the 
regular nut between two anvil members which have oblique working faces, 
the nut being oriented so that the opposed facets face the anvil members, 
then decreasing the spacing between the anvil members so that they contact 
the facets over substantially the full axial height of the nut, and 
finally further decreasing the spacing between the anvil members by a 
preset amount, to permanently inwardly deform the nut in a graduated 
manner. 
According to another aspect of this invention, there is provided a method 
of feeding a hexagonal nut to a location between two parallel anvil 
members in such a way that the nut is oriented with two opposed flats 
parallel with the anvil members. The method includes first passing the nut 
along a first track defined between first and second edges spaced apart a 
distance greater than the corner-to-corner diametral dimension of the nut, 
then providing a second track continuous with the first track and defined 
between third and fourth edges spaced apart by a distance greater than the 
flat-to-flat diametral dimension of the nut but less than the 
corner-to-corner diametral dimension thereof, and then, laterally adjacent 
the junction between the two tracks, reciprocating a contact element 
longitudinally of the tracks while allowing the element some lateral 
freedom of movement, whereby if the nut tries to enter the second track, 
the contact element rotates the nut so that its flat dimension is across 
the track. 
According to another aspect, this invention provides apparatus for 
converting regular nuts into prevailing torque nuts. The apparatus 
includes two anvil members having oblique working surfaces, delivery means 
for placing the regular nuts sequentially between the anvil members, and 
power means for controlling the spacing between the anvil members such 
that (a) the anvil members first come into contact with opposite sides of 
a nut located between them over substantially the full axial height of the 
nut, and then (b) the spacing between the anvil members decreases by a 
predetermined amount which is the same for all nuts within a given size 
range, whereby to permanently inwardly deform each nut in a smooth and 
progressive manner from one end of the nut to the other. 
Finally, according to another aspect of this invention, there is provided a 
delivery apparatus for feeding a hexagonal nut to a location between two 
parallel anvil members in such a way that the nut is oriented with two 
opposed flats parallel with the anvil members, the apparatus comprising: 
a first track defined between first and second edges spaced apart a 
distance greater than the corner-to-corner dimension of the nut, 
a second track continuous with the first track and defined between third 
and fourth edges spaced apart by a distance greater than the flat-to-flat 
dimension of the nut but less than the corner-to-corner dimension thereof, 
the second track leading to the location between the anvil members, 
and a contact element located at the junction between the two tracks, and 
means for reciprocating the contact element longitudinally of the tracks 
while allowing the element some lateral freedom of movement, whereby if a 
nut tries to enter the second track with its corner-to-corner dimension 
across the track, the contact element rotates the nut so that its 
flat-to-flat dimension is across the track.

DETAILED DECRIPTION OF THE DRAWINGS 
Attention is first directed to FIG. 1, which shows the main components of 
an apparatus designed to deform nuts into prevailing torque nuts. 
In FIG. 1, a hopper 10 is designed to feed nuts into a guideway 12 shown in 
broken lines. The hopper is of standard construction, and does not require 
detailed discussion herein. The guideway 12 is shown in solid lines in 
FIG. 2, where it can be seen that the guideway 12 has an upper, wider 
portion 13 and a lower, narrower portion 14. A nut 15 is shown in the 
upper portion 13 of the guideway 12, and the sectional view shown in FIG. 
3 illustrates that the guideway at this location is wide enough to accept 
the nut if it is oriented with the corners horizontal, i.e. its widest 
dimension. 
However, the lower portion 14 is too narrow to accept a nut across the 
corners, and the nut must be arranged across the flats in order to pass 
into the lower portion 14. FIG. 4 shows the relative narrowness of the 
lower portion 14 with respect to the upper portion 13. 
Means is provided to "roll" the nuts from a corner-horizontal position such 
as that shown for the nut 15, to a corner-vertical position such as that 
shown for the nut 17 in the lower part of FIG. 2. In the corner-vertical 
position shown by nut 17, the width of the nut across the flats is that 
which determines its narrowness, and its width is adapted to be received 
in the lower portion 14 of the guideway 12, as aforesaid. 
The means for rolling the nuts consists essentially of the plate 18 which 
has a lower elongated slot 19, and an upper elongated slot 21. The upper 
elongated slot 21 is wider than the lower elongated slot 19, for a reason 
which will be explained below. A leaf spring 22 is also provided, the leaf 
spring 22 being firmly affixed at 24 to the right-hand side of the 
guideway 12, through an auxiliary plate 25 and bolts 26, and has its free 
end 28 pressing leftwardly or inwardly against the upper part of the plate 
18. Due to the relative narrowness of the elongated slot 19, the lower 
part of the plate 18 is constrained laterally, and can move essentially 
only in a vertical sense. However, the relatively greater width of the 
upper elongated slot 21 allows a certain degree of lateral motion for the 
upper part of the plate 18, and this is useful when the plate is "rolling" 
a nut, such as the nut 15, through a sufficient angle to bring the flats 
parallel with the guidway 12. The plate 18 is moved up and down by a link 
29, which has its forward end projecting through a slot 30 in the plate 
18, is pivoted at an intermediate location identified in FIG. 1 by the 
numeral 32, and has its other end pivotally connected to a further link 
33, the lower end 34 of which (see FIG. 6) is pivotally connected to an 
eccentric location on a boss 35 which is adapted to oscillate about a 
point 37, in a manner and for a reason which will be explained below. 
FIG. 6, where the last-mentioned components are shown in side view, it will 
be seen that oscillation of the boss 35 through approximately 45.degree. 
will move the link 33 between its solid-line and broken-line positions, 
which correspondingly will move the plate 18 between its broken-line and 
solid-line positions seen in FIG. 2. Passing through the slots 19 and 21 
are shouldered guide bolts 40, which are not tightened but which hold the 
plate 18 snugly and slidably against the rightward half of the guideway 
12, identified in FIGS. 3-5 as a component 41. 
Turning more particularly to the FIGS. 3-5, it will be seen that the 
component 41 has an undercut 42, and that the component 41 is matched on 
the other side of the guideway 12 by a component 44, also having an 
undercut 45. The component 44 is greater in height than the component 41, 
and has affixed to its upper surface a retention plate 47, for the purpose 
of keeping the nuts in place. As will be appreciated from FIG. 3, the 
purpose of the undercuts 42 and 45 is to allow for the integral washer 48 
of each nut. 
It will also be seen that the undercut 42 shown in FIG. 3 appears to be 
smaller than the same undercut in FIG. 4. The explanation of this relates 
to the narrowing of the guideway 12 at about the location where the 
section lines 3--3 are shown. However, the distance between the outside 
walls of the undercuts 42 and 45 do not change, and thus only the extent 
of the "overhang" of one of the undercuts needs to be altered in order to 
accomplish this transition. 
Following the progress of a nut through the portion of the apparatus shown 
in FIG. 2, it can be seen that the nut, after first falling into the 
guideway 12 from the hopper 10, may or may not become stalled through 
contact with the plate 18, depending upon the nut's orientation when it 
reaches that level. If the flats are parallel with the guideway 12, then 
the nut will slip easily into the lower portion 14 of the guideway 12, 
whereas if the corners are across the guideway 12, the nut will become 
stuck until the plate 18 moves upwardly and "rolls" the nut into the other 
orientation, whereupon it will slip into the lower portion 14 of the 
guideway 12. The plate 18 oscillates in a regular pattern, as will be 
explained subsequently, and therefore there is a constant tendency to roll 
any stuck nuts into the proper orientation to allow them to fall into the 
lower portion 14 o the guideway 12. 
Once in the lower portion 14, the nuts will pass to the lower end, and at 
the bottom end of the stack seen in FIG. 2 the lowermost nut 17' has 
become lodged against a stack support latch 50, which is slidable 
horizontally as seen in FIG. 2, and which is urged rightwardly (i.e., 
toward the guideway 12) into a blocking position by a leaf spring 51, 
which is secured against component 44 by an auxiliary plate 53 and 
suitable machine bolts 54. 
As can be seen in FIG. 2, the latch 50 has an oblique camming surface 56, 
which is such that it will allow a nut to pass downwardly along the 
guideway 12, thus camming the latch 50 leftwardly out of the way, provided 
sufficient pressure is brought to bear in a downward direction against the 
nut attempting to pass the latch 50. The camming surface 56 has 
substantially the same slope as the mating one of the hexagonal flats of 
the nut, as can be seen in FIG. 2. 
Attention is now directed to FIG. 6 and to FIG. 1, for description of the 
mechanism whih urges each nut sequentially downwardly past the latch 50. 
In FIG. 6, there is shown an arm 57 which is one of two arms aligned in 
FIG. 6, both of these arms bearing the number 57 in FIG. 1. The two arms 
pass centrally through two aligned bosses 35, these being located on 
either side of a support block 58, which is secured to a base plate 60. 
The two bosses 35 rotate with each other, through a shaft (not seen) which 
is journalled in the block 58. One of the arms 57 extends diametrically 
through its respective boss 35, and projects out the other end as a 
shorter arm 57', the rearward end of which is pivotally connected at 61 to 
the upper end 62 of the piston 63 of an air or hydrulic cylinder 64, the 
lower end 65 of which is pivotally mounted at 66 to a bracket 67 secured 
to the base plate 126. 
As the double acting cylinder 64 moves the piston 63 upwardly and then 
downwardly repeatedly, the connection at 61 will move between the 
solid-line position and the broken-line position of FIG. 6, thus moving 
the arms 57 between the solid-line and the broken-line positions. At the 
leftward or forward ends of the arms 57 is a shaft 69, on which is mounted 
a member 70 which is journalled for rotation thereabout. Fixed to member 
70 is a push arm 71 which is somewhat S-shaped in configuration, as seen 
in FIG. 6, and which has an indented configuration at its lower end 72. 
The indented configuration at the lower end 72 defines a V-shaped notch 
which is adapted to rest against the top face of a nut caught in the 
lowermost position of the stack shown in FIG. 2, i.e. resting against the 
latch 50. As can seen in FIG. 6, this V-shaped notch is adapted to grasp 
the nut and to push it downwardly, as the push arm 71 moves fom its 
solid-line to its broken-line position in FIG. 6. Spring 72' biases the 
arm 71 inwardly in FIG. 2. 
When the nut is shoved downwardly by the push arm 71, it passes into the 
second major portion of the apparatus, namely the compensating portion 
constituted in FIG. 1 by the various components located between a frame 73 
and a bracket 74. 
Before describing in detail all of the components just mentioned, attention 
is directed to FIGS. 9, 10 and 11, in order to allow an understanding of 
the three-step procedure by which a nut is firstly positioned, then 
compensated and then deformed. In FIG. 9, a permanently fixed frame member 
is shown at 75. Slidable against the frame member 75 is a slide block 76, 
seen in exploded position in FIG. 1. The slide block 76 has affixed to it 
a hardened anvil 77. A cover plate 79 is provided, to stabilize the slide 
block 76, and to sandwich the latter between itself and frame member 75. 
Opposite from the slide block is located a movable block 80 consisting of 
portions 81 and 82. Slidably connected with the block 80 is a wedge 81' 
which will be described more fully below. In the fully opened position 
shown in FIG. 9, it can be seen that the wedge 81' is situated in such a 
way that there is a gap 82' between the wedge 81' and the frame member 75. 
This adjustable gap 82' represents the total permissible rightward 
movement of the movable block 80 with its components 81 and 82. Supported 
at the rightward edge of the component 82 is a hardened anvil 84, secured 
in place by member 86 and 87. It is to be noted that the anvils 77 and 84 
(interchangeable to provide varying angles) have sloping contact faces 77' 
and 84', respectively. 
Member 87 supports a pivot connection 88 for a hold-down arm 90 seen in 
FIG. 6. The hold-down arm 90 is slightly bent, and has a nut-contacting 
end 91 at its lower end, and an upper end 92 which is biased leftwardly 
through engagement by a spring 93 (i.e. the hold-down arm 90 is biased in 
the counter-clockwise direction as seen in FIG. 6, about the pivot 
connection 88). Integral with the upper part of the hold-down arm 90 is a 
stop arm 96 (FIG. 7) which is bent to overlie the member 87, and 
terminates in a convered end 96 adapted to contact the outer (lower in 
FIG. 9) surface of the member 87 when no nut is in the position shown in 
FIG. 9. This prevents contact between the lower end 91 of the hold-down 
arm 90 and the frame member 75. It will be recalled that the nut is in a 
position in which the flats are parallel with the guideway 12, and since 
the guideway 12 is also parallel with the working surfaces of components 
77 and 84, the nut will appear as seen in FIG. 9, looking downwardly along 
the space between the components 77 and 84. 
FIG. 10 shows the completion of the compensation phase for the nut, in 
which the slide plate 76 has moved leftwardly to bring the nut 17' over 
and between anvils 77 and 84. When the nut contacts the anvil 84, a 
resistance is felt to further leftward movement of the slide plate 76, and 
this causes an increase in the hydraulic or air pressure moving the slide 
plate 76 leftwardly, which in turn opens a pressure relief valve to stop 
the slide plate 76 from moving further. Thus, the nut 17' is merely being 
held between the two components 77 and 84 in the direction shown in FIG. 
10, and has not yet been deformed. 
The third phase is shown in completion in FIG. 11, in which the component 
82 has moved rightwardly to bring the wedge 81' against the frame member 
75, thus causing the pre-determined gap 82' to disappear. The gap 82' has 
thus precisely determined the extent of deformation of the nut 17', and 
when contact occurs between the wedge 81' and the frame member 75, no 
further deformation of the nut 17' can take place. 
Attention is now directed simultaneously to FIGS. 1, and 8-11. The 
component referred to as slide plate 76 is seen in FIG. 1 in exploded 
position in front of the main apparatus, and is also identified by the 
same number in FIG. 8. Also in FIG. 8 are shown the stationary cover plate 
79, the frame member 75, and both components 81 and 82 of the movable 
block 80. The gap 82' is also visible in FIG. 8, and the remainder of the 
smaller components shown in FIG. 9 are seen in FIG. 8 to a smaller scale. 
These have not been identified by numerals in FIG. 8 in order to avoid 
cluttering the drawing. 
The means by which the slide plate 76 and the anvil 77 are moved leftwardly 
in the first phase described above with reference to FIGS. 9 and 10 
involves a wedge member 97. This is visible in both FIGS. 1 and 8. 
Referring to FIG. 1, it can be seen that the wedge member 97 tapers 
upwardly, and is attached to a cylinder 98, the bottom end 99 of which is 
fixed to a bracket 100 which is secured with respect to an immovable 
component 101 of the frame of the apparatus. When the cylinder extends its 
piston upwardly, thus moving the wedge member 97 upwardly (the wedge being 
shown in ghost outline in FIG. 1), the slide plate 76 is caused to move 
leftwardly. As can be seen in FIG. 1, the mating edges of the slide plate 
76 and the wedge 97 are vertical (i.e. aligned with the guideway 12), 
whereas the other or rightward side of the wedge member 97 is oblique. 
This means that the mating portion 103 (FIG. 8) of the frame member 75 
must also be oblique, and this is the case as seen in FIG. 1. 
It can also be seen in FIG. 1 that the slide plate 76 has rectangular 
registration portions 104 at both the top and the bottom thereof, and 
extending both rearwardly and forwardly. There are thus four portions 104 
in all, each containing a spring 104a and a return plunger 104b. These 
portions 104 register pair-wise in recesses 105 of the cover plate 79, and 
recesses 106 in the frame member 75. These recesses are wider laterally 
than the portions 104, to allow for sliding motion of the slide plates 76. 
Thus, it will be understood that, in order to bring the slide plate 76 
leftwardly from the position of FIG. 9 to the position of FIG. 10, the 
wedge member 97 accomplishes this motion by moving upwardly, under the 
urging of the cylinder 98. It should be noted that wedge 97 and the urging 
cylinder 98 can be substituted by a number of mechanical devices. A 
partial list includes cam means, an eccentric screw urged by an electric 
motor or air motor, an air cylinder, a hydraulic cylinder, a hydralic 
motor or lever or any combination thereof. When the slide plate 76 has 
moved far enough to grip the nut 17' between the components 77 and 84, the 
back pressure in the feed for the cylinder 98 causes a pressure valve to 
open, and upward movement of the wedge member 97 is halted. The opening of 
the pressure valve (not shown) also passes a signal to the logic of the 
machine (not forming a part of this invention), which thereupon initiates 
movement of the movable block 80, including its two components 81 and 82. 
The prime mover for this motion is a single-acting cylinder 108, which is 
located in a recess 109 in a frame 73. The cover 110 for the recess 109 
has been shown in exploded position, to reveal the cylinder 108, and the 
mechanisms with which it is connected. Reference should be had at this 
point simultaneously to FIGS. 1 and 8. 
A threaded shaft 112 is the member which actually pulls the movable block 
80 to the right, in order to accomplish the deformation of the nut. The 
shaft 112 is threaded through block 80 to provide adjustment for various 
nut sizes. The shaft 112 is also shouldered into a block 114 having two 
pivotal connections 116, to each of which a rocker arm 118 is pivoted. 
Each rocker arm 118 bears pivotally against pins 119, and has a 
rightwardly extending portion terminating in supported rollers 120. The 
rollers are adapted to bear against a wedge block 122, which has two 
differently sloped portions that can be thrust leftwardly between the 
rollers, through the action of the cylinder 108. It will thus be 
understood that, when the cylinder 108 moves its piston leftwardly, the 
wedge block 122 is thrust between the rollers 120, thus urging the rockers 
arms 118 outwardly away from each other, thus rocking each one of them in 
the opposite sense about its respective pin 119, thus pulling the block 
114 rightwardly, and also pulling the threaded shaft 112 rightwardly (as 
seen in FIG. 1 and 8). The rightward motion continues until contact is 
made between the wedge 81 and the frame member 75, as described above with 
respect to FIG. 11. By this point in time, the respective nut has been 
deformed to precisely the right degree, as explained earlier. A 
microswitch 124 secured to a table 126 is adapted to be activated by an 
adjustable contact 127 secured through a bracket 129 to the movable block 
80. Thus, upon completion of the deformation of a nut, the microswitch 124 
is activated, to tell the logic of the machine to complete the cycle by 
withdrawing the wedge 97 downwardly, allowing block 76 to move rightwardly 
(as seen in FIG. 8) and urging the block 82 leftwardly by the action of 
spring 138. Prior to the beginning of a new cycle, the push arm 71 has 
returned to its uppermost position to grasp another nut, and then a new 
cycle starts with the downward thrust of the push arm 71 to bring that new 
nut into a position in which it can subsequently be deformed, thereby 
ejecting the deformed nut. The logic receives a signal from the push arm 
connections to tell it that the nut is in position for deformation, due to 
a contact post 131 attached to the arm 57 (see FIG. 6). This post 131 is 
adjusted to contact another microswitch 133, which is affixed to the base 
plate 60. The bracket 74 is intended to be secured where shown by the 
broken line at the left in FIG. 1 (and where shown in place in FIG. 8), 
and has an adjustable stop 135 by which to establish a limit to the 
leftward motion of the movable block 80. A slidable shaft 136 is in a 
suitable bore axially of the threaded shaft 112, and a compression coil 
spring 138 (see FIG. 8) leftwardly of the shaft 136 tends to push the 
shaft 112 and the wedge block 122 away from each other, in order to return 
the single-acting piston 108 to its position prior to being activated 
(with its piston rightwardly), and to return the movable block 80 
leftwardly to the position established by the adjustable stop 135. 
Appropriate portions in FIG. 7 have been numbered, but these do not need to 
be discussed in detail with the exception of a stop 140, which is built 
into the block 76, and which acts to prevent the nut from moving upwardly 
after it has been positioned. The push arm 71 returns before squeezing 
takes place, and may exert a certain degree of upward pull on the deformed 
nut in so doing. The detent or stop 140 acts to prevent displacement of 
the nut under the influence of this upward pull. The stop 140 is part of 
an elongated arm 142, which is spring biased by spring 143 in a clockwise 
sense about a pivot 144, as seen in FIG. 7, This tends to bring the "nose" 
146 of the stop 140 out into an interfering position with respect to the 
nut 17'. As can be seen the arm 142 is located in a recess 148 in the 
anvil. 
As can be seen in FIG. 6, a fixed frame member 150 is shaped to define a 
slideway in which the movable block 80 can slide. 
A further aspect of this invention lies in the finished configuration of 
the squeezed nut, owing to the angulated faces 77' and 84', as seen in 
FIG. 9. To explain this advantage fully, attention is directed to FIGS. 
14-16. FIG. 14 shows one of the methods utilized in the prior art for 
deforming a nut. In this prior art method, the top of the nut 155 is 
passed through two rolls, 152, 153 set at a fixed spacing, which deforms 
the nut 155. The resulting deformation utilizing this prior art method is 
such that the magnitude of deformation varies, depending on the size 
across the flats of the nut to be squeezed. If the nut 155 is at the 
bottom of tolerance the squeeze is slight, and if the nut is at the top of 
the tolerance the squeeze is too much (causes socket interference). The 
undersqueezed nut 155 will often have insufficient contact 158 with an 
undersized bolt, i.e. a bolt which is at the lower end of the tolerance 
range. 
This prior art procedure results in a sudden shoulder region 158 and may 
cause sockets to partially engage or to slide on to the nut 155 in a very 
jerky manner. 
FIG. 15 illustrates another method known in the prior art, in which three 
distortion members 160 (one of these being hidden behind the illustrated 
member to the left) descend to the cone or top flat of the nut and through 
a pressing action distort the cone or the top of the nut. The 
disadvantages of this system are that (a) the nut distortion area is not 
oval and consequently not as flexible, (b) binding only extends down a few 
threads and (c) testing on maximum and minimum bolts shows some inability 
to perform to specified torques. 
The distortion system of the present invention is illustrated in FIG. 16, 
in which distortion members 162 (corresponding to the anvil faces 77' and 
84' in FIG. 9) move inwardly against opposing flats of a nut 164, and have 
a slight slope upwardly and inwardly with respect to the nut 164. This 
results in a smooth and graduated transition from a circular entry opening 
166 at the bottom to an oval top opening 167. By thus providing a nut in 
which the full height and width of two opposing nut flats is angularly 
side-squeezed, there is permitted a graduated interference with a bolt 
from top to bottom, without functional distortion of the entrance thread 
of the nut. Further, the squeeze is such that no sharp ridges or damage 
occurs to the flat in such a way as to interfere with wrenches or sockets. 
For each size of nut, the amount and angle of squeeze can be predetermined 
so that the bolt and nut assembly will not only meet prevailing torque 
specifications but will also do so for maximum and minimum bolt size 
tolerances. Since squeeze takes place while the nut is not in motion, no 
damage is occasioned to the washer face. 
While a preferred embodiment of this invention has been described above and 
illustrated in the accompanying drawings, it will be apparent to those 
skilled in the art that changes and modifications may be made therein 
without departing from the essence of this invention, as set forth in the 
appended claims.