Method for manufacturing part for floating nut assembly

An attaching sleeve for a floating nut assembly is formed from rod or wire stock by successive cold heading or cold forming operations. The steps involve cutting off a longitudinal segment from the stock, forming a flange on the front end of the segment, forming a centrally disposed opening through the segment, and forming longitudinally extending ridges projecting outwardly around the periphery of the segment. The attaching sleeves made by the method of the present invention have accurately positioned ridges or knurls which will consistently mate with a similarly configured opening in panels to which the floating nut assembly is to be secured.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method for manufacturing an attaching sleeve 
for a floating nut assembly. Further provided are the attaching sleeves 
formed by the method of the present invention. 
2. Description of Related Art 
Nut plates have been used extensively on panels and other parts for holding 
a nut to a panel so that the nut is always available with limited floating 
movement of the nut being permitted so that it can be more easily engaged 
by a bolt. Such a fastening device includes a receptacle which is provided 
by a flat plate from which portions are bent to engage and retain flanges 
projecting from the nut. This holds the nut to the receptacle while 
allowing movement of the nut. 
Nut plates typically were installed on a panel or other workpiece by 
drilling accurately spaced openings for rivets through the panel. Several 
of these openings were used to secure the receptacle to the panel with the 
rivets. This is a time-consuming and relatively expensive operation. 
Efforts have been made to provide a floating nut plate which avoided the 
use of the rivets for attachment to the panel. This was done by providing 
a knurled sleeve to fit in the opening in the panel. The knurled sleeve 
would become embedded in the panel and resist rotation. Tubular portions 
were provided on such sleeves having straight knurls on the periphery of 
the tube to dig into the wall of the opening in the panel. This operated 
to prevent rotation of the nut plate. However, this design had the 
disadvantage that the knurl didn't fit the wall of the opening tightly 
enough. It didn't embed itself securely in the wall of the opening, 
gripping with low torque resistance. When a bolt was subsequently engaged 
by the nut plate, the entire nut plate turned with the bolt, which 
prevented the bolt from being threaded into the nut, and sometimes the 
bolt fell out of the nut. 
U.S. Pat. No. 3,695,324 is included in such floating nut assemblies, which 
provides a lightweight floating nut arrangement having a sleeve member 
with a tubular section that extends through a hole in the panel. 
Attachment of the assembly to the workpiece was accomplished by extending 
a tubular section through the single opening in the workpiece. A straight 
knurl was provided on the tubular portion and became embedded in the 
periphery of the opening in the panel which thereby prevented rotation of 
the assembly. 
One disadvantage of that design, as well as previous designs, results from 
the method for manufacturing the attaching sleeve. Those methods produce 
sleeves with knurls that do not securely embed in the wall of the opening 
of the workpiece. This is due to an imprecise and inaccurate method for 
forming knurls on the tubular section. Knurls or ridges are typically 
formed by a rolling knurl tool rolled around the tubular sleeve, forming a 
plurality of knurls or ridges. The placement of these ridges, however, is 
difficult to precisely control. As a result, difficulties are encountered 
in placing the knurls or ridges on the tubular sections precisely in line 
with recesses formed in the wall of the opening of the workpiece or panel, 
particularly when the panel or workpiece is formed of very hard material 
where such mating recesses in the panel are employed. As a result, 
slippage may occur between the tubular section and the workpiece when a 
bolt is subsequently engaged by the nut assembly. 
One obvious disadvantage of these nut assemblies is that they may lead to 
inefficiencies in bolt installation caused by nut slippage, or loosening 
of the entire assembly prior to bolt installation. It would be desirable 
to have a floating nut assembly in which this slippage between the nut 
assembly and the wall of the opening of the workpiece was eliminated by a 
method of manufacture which accurately and precisely places ridges or ribs 
on the tubular section that securely fit into and mate with recesses 
placed on the wall of the opening of the workpiece. 
A further disadvantage encountered in the manufacture of prior floating nut 
assemblies, and in particular with attaching sleeves involved in floating 
nut assemblies, is the large number of steps required to manufacture these 
pieces. They are manufactured as piece work, requiring drilling, stamping, 
knurling, and other machining steps. These multiple manufacturing steps 
are expensive. Furthermore, the resulting parts are not identical. Large 
variations from piece to piece are seen in the critically fitting areas of 
the piece, such as the knurls or ridges. In addition, the drilling and 
other steps result in much unnecessary scrap metal. 
It would be desirable to provide a method of manufacture which reduces the 
number of steps in forming such attaching sleeves. It would be further 
desirable for such a method to provide accurate, precise, and consistent 
placement of ridges or knurls. Further desired would be a manufacturing 
method which produces attaching sleeves which consistently fit the 
workpiece opening snugly with sufficient torque resistance to make bolt 
installation efficient in workpieces requiring floating nut assemblies. 
Also desirable would be a manufacturing method which operated 
automatically with rate of production much higher than piece-work 
manufacture. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a method is provided for forming 
an attaching sleeve for a floating nut assembly which overcomes the 
above-mentioned difficulties and provides the advantages of high-speed, 
cost-efficient, precision manufacture of attaching sleeves, which tightly 
fit previously formed holes in a work piece or panel. The steps of the 
method of the present invention are substantially achieved by cold heading 
operations. 
The method involves the discovery that cold heading forging operations, 
typically used in manufacturing solidcored bolts and screws, could be used 
in manufacturing hollow-bodied parts by means of appropriate dies and 
mating dies. 
The method of the invention involves cutting off a longitudinal segment 
from an input bar or wire. This segment has a first portion located toward 
a front end of the segment, and a second portion located toward a rear end 
of the segment. On the front end of the longitudinal segment, a cold 
heading operation forms a first flange. A second successive cold heading 
operation may complete the formation of the first flange, and may form a 
first centrally disposed hole in the front end of the segment. The hole 
extends rearward from the flange toward the second portion of the segment. 
By a further cold heading operation, the method of the invention forms 
longitudinally extending ridges or knurls projecting outwardly around the 
periphery of the first portion of the longitudinal segment. The ridges are 
adjacent the first flange. A second centrally disposed hole is achieved in 
the course of the cold heading operations. This second hole is formed in 
the rear end of the longitudinal segment. The second hole extends forward 
from the rear end toward the first portion. Following a final cold heading 
type operation, the second hole is extended to communicate with the first 
hole to form a substantially uniform diameter opening through the 
longitudinal segment. The invention further provides a step for trimming 
the generally circular flange to form outwardly extending tabs. 
As an additional feature of the invention, the rear end of the attaching 
sleeve is relatively malleable so that the rear end can be bent outwardly 
to form a rear flange used in holding the attaching sleeve to a workpiece. 
The ridges provided by the cold heading operation of the present invention 
are located inwardly from the rear end of the segment. The ridges are 
straight knurls. 
The attaching sleeve formed by the method of the present invention includes 
a hollow cylindrical body portion, a plurality of tabs extending outwardly 
from one end of the cylindrical body, and longitudinally extending ridges 
or knurls disposed around the body portion. The knurls are located 
adjacent the tabs. 
The invention further provides the attaching sleeves produced by the method 
of the present invention. The attaching sleeves accomplish attachment of 
the floating nut assembly to a workpiece by extending the cylindrical body 
through a single opening in the workpiece. The straight ridges or knurls 
provided by the method of the invention on the periphery of the 
cylindrical body become embedded in the periphery of the opening of the 
workpiece or panel, which thereby prevents rotation of the assembly. As 
noted above, for panels formed of hard materials, the holes in the panels 
may be provided with an accurately formed set of grooves or recesses which 
mate precisely with the accurately formed ridges on the attaching sleeve. 
Other objects, features and advantages of the invention will become 
apparent from a consideration of the following detailed description and 
from the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring more particularly to the drawings, FIG. 1 shows the attaching 
sleeve 10 for a floating nut assembly 12. The attaching sleeve 10 has a 
hollow cylindrical body portion 11, a plurality of tabs 34 extending 
outwardly from one end of the cylindrical body 11, and longitudinally 
extending ridges 28 or knurls disposed around the cylindrical body portion 
11. The knurls 28 are adjacent the tabs 34. 
FIG. 2 is an exploded perspective view of a floating nut assembly 12 and 
includes the attaching sleeve 10 formed by the method of the present 
invention. The floating nut assembly 12, as illustrated in FIG. 2, 
consists of three parts that include a nut 48, a basket 50 and an 
attaching sleeve 10. The basket 50 holds the nut 48, allowing limited 
floating movement while preventing substantial rotation of the nut 48. The 
attaching sleeve 10 secures the basket 50 to the workpiece 36. 
The method of the present invention for forming an attaching sleeve for a 
floating nut assembly is substantially achieved by cold heading operations 
in a cold heading machine 44. FIG. 10 shows the step of the method of the 
present invention in which an input bar or wire or rod stock (13) or other 
precursor material is inputted into the cold heading machine 44. Wire 
stock -3 typically used in the method of the present invention is may be a 
soft steel with a very thin coating of copper to facilitate forming 
operations. An exemplary cold heading machine 44 for use in the method of 
the present invention is that made by a Japanese company named 
Nakashimada, a known supplier of cold forming machines. 
Within the cold heading machine, the first step is to shear or cut off a 
longitudinal segment 14 from an input bar or wire stock 13. This 
longitudinal segment 14 has a first portion 16 located toward a front end 
18 of the longitudinal segment 14. The front end 18 of the longitudinal 
segment 14 enters the cold heading machine ahead of a second portion 20 of 
the longitudinal segment 14. The second portion 20 of the longitudinal 
segment 14 is located toward the rear end 22 of the segment 14. 
As shown in FIG. 5, a cold heading operation forms a first flange 24 on the 
front end 18 of the longitudinal segment 14. This first flange 24 is 
formed by striking the front end of the longitudinal segment with a 
recessed forming die. Typically, formation of the first flange is 
completed in a successive cold heading operation, which involves striking 
the front end 18 of the longitudinal segment 14 with a recessed die having 
a somewhat shallower recess of greater diameter than that involved in the 
first cold heading operation. 
A centrally disposed hole 26 is formed in the second cold heading operation 
concurrently with the expansion of the flange in the front end 18 of the 
longitudinal segment 14, and this first hole 26 extends rearward from the 
first flange 24 toward the second portion 20 of the segment 14. 
A further cold heading operation forms longitudinally extending ridges or 
knurls 28 which project outwardly around the periphery of the first 
portion 16 of the longitudinal segment 14. These longitudinal ridges 28 
are located adjacent the flange 24. A second hole 30 is formed in the rear 
end 22 of the longitudinal segment 14 in the course of the cold heading 
operations which form the ridges in a successive step indicated in FIG. 7. 
This second hole 30 is centrally disposed in the rear end 22 of the 
longitudinal segment 14. The second hole 30 extends forward from the rear 
end 22 toward the first portion 16 following the final cold trimming 
operation indicated by FIG. 8. The second hole 30 communicates with the 
first hole 26 to form a substantially uniform diameter opening 32 
extending all the way through the longitudinal segment 14 from the front 
end 18 to the rear end 22. All of the above operations are achieved by 
cold forming operations within the cold heading machine 44. 
The attaching sleeve 10, as shown in FIG. 8, is ejected from the cold 
heading machine 44. The method of the invention provides a further step 
for subsequently trimming the first flange 24 formed in the cold heading 
operation in the cold heading machine. This trimming step forms the first 
flange into a plurality of outwardly extending tabs. This trimming step is 
typically accomplished using a stamping machine. 
As a feature of the invention, the rear end 22 of the attaching sleeve 10 
is relatively malleable. This is advantageous because it permits the 
outward deformation of the rear end to provide a flange for use in holding 
the attaching sleeve 10 to a workpiece or panel 36. 
It should also be noted that the longitudinal ridges 28 formed by the cold 
heading operation of the present invention are located inwardly of the 
rear end 22. A preferred form of the ridges produced by the method of the 
present invention is straight knurls. 
Certain advantages are provided by the method of the present invention for 
manufacturing the attaching sleeve. These advantages include faster 
manufacture of the attaching sleeves in automated cold heading operations 
relative to manufacture by piece work. A further advantage of the method 
is cost-efficiency, that is, the cost of making an attaching sleeve by the 
method of the present invention is much less than that for an attaching 
sleeve produce by piece work, which includes the successive steps of 
machining, boring, knurling, and other manufacturing steps as mentioned 
above The method of the invention also provides the advantage of forming 
attaching sleeves with precision-placed longitudinal ridges or knurls. 
This results in better-fitting attaching sleeves, less slippage in the 
workpiece when a bolt is installed, and more efficient manufacturing 
techniques. 
In accordance with the present invention, an attaching sleeve 10 for a 
floating nut assembly 12 is provided, which is produced by the method of 
the present invention. The attaching sleeve 10 includes a hollow, 
cylindrical body portion 11, a plurality of tabs 34 extending outwardly 
from the front end 18 of the cylindrical body 11, and longitudinally 
extending ridges or knurls 28 accurately and precisely disposed around 
said body portion adjacent said tabs 34. 
For attaching a floating nut assembly to a workpiece, as illustrated in 
FIG. 2, the cylindrical body portion 11 of the attaching sleeve 10 is 
extended through the opening 38 of the workpiece 36. The straight knurl 28 
provided on the cylindrical body 11 embeds in the recesses 42 of the wall 
of the opening 38 of the workpiece 36. Rotation of the floating nut 
assembly 12 in the workpiece when a bolt is installed is prevented by the 
straight knurls 28 gripping the recesses 42 in the wall 40 with sufficient 
torque resistance. 
As indicated schematically in FIG. 11, the method of the invention forms 
the attaching sleeve 10 by cold heading operations that include striking 
the longitudinal segment 14 with dies 60, 62. FIG. 11 shows the formation 
of the flange 24 of FIG. 5 and FIG. 6 and the formation of the first hole 
26 in the front 18 of the longitudinal segment 14 by successive cold 
forming operations. The top portion of FIG. 11 corresponds to the cold 
forming operation that achieves formation of the flange 24 by an initial 
striking of the front end 18 of the longitudinal segment 14 with a 
recessed forming dye 60. The bottom portion of FIG. 11 corresponds to the 
cold forming operation that completes the formation of the flange 24 by 
the successive striking of the flange 24 formed in the initial striking. 
The successive striking typically completes formation of the flange by 
striking with a recessed die having a somewhat shallower recess of greater 
diameter than that involved in the initial striking. The successive 
striking also involves the initial formation of the first hole 26 in the 
front end 18. In a similar manner as well known in the art, successive 
cold forming operations achieve the method of the invention, completing 
the formation of the attaching sleeve. 
It is to be understood that the dimensions of the attaching sleeve may vary 
in accordance with the application. However, in one illustrative example 
of a part formed in accordance with the invention, the sleeve was about 
3/8 inch long, the wall thickness was about 0.020 inch, and the diameter 
of the sleeve was about 1/4 inch. The overall extent of the flanges or 
tabs was slightly less than 1/2 inch, and the ridges extended from the 
flange a distance of about 3/32 inch. There were approximately 20 ridges 
or knurls around the periphery of the sleeve and they extended outwardly 
from the sleeve by about the thickness of the sleeve wall, or about 0.020 
inch. Also, the wire or rod input stock was formed of a relatively soft 
steel, plated with a very thin plating of copper to facilitate the forming 
operations. 
The present invention is not limited precisely to the embodiments shown in 
the drawing and as described in detail herein above. Thus, by way of 
example and not by limitation, the length and diameter of the sleeve may 
vary and it may be formed by different materials. Further, the outwardly 
extending flanges or tabs may be dimensioned to fit the complete assembly.