Abstract:
An apparatus for repairing steering knuckle (kingpin) bearings includes a table having multiple, adjustable slides for receiving and securing the steering knuckle to the table, a boring bar and cutter, two adjustable bearing supports for receiving and positioning the boring bar along an axis coincident with the axis of the kingpin bearings, a first drive assembly for advancing the boring bar and a second drive assembly for rotating the boring bar. A method of repairing a steering knuckle comprises securing the knuckle to the slides and the slides to the table, utilizing cylindrical centering rings to align the boring bar with the axis of the kingpin bearings, supporting and securing the boring bar on the previously established axis in a pair of bearing supports and rotating and feeding the boring bar and cutter to create new surfaces in the steering knuckle adapted to receive bearing sleeves. Upon installation of both bearing sleeves, the boring bar and drive unit are reinstalled and the inside diameter of the sleeve is bored to the proper size to receive the kingpin.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a specialized boring apparatus and method and particularly to an apparatus and method for repairing worn and oversized kingpin bores in motor vehicle steering knuckles.  
       BACKGROUND OF THE INVENTION  
       [0002]     The most common geometric arrangement for front wheels of trucks and heavy duty motor vehicles comprehends defining left and right converging oblique axes about which the front wheels pivot to steer the vehicle. These axes are defined by a component denominated the kingpin. The kingpin extends between two spaced apart bearing structures extending from a steering knuckle and pivotally couples it to an end of the front axle. The steering knuckle includes a spindle upon which a front tire and wheel are rotatably supported and secured and a flange to which a front brake assembly is mounted. Each end of the front axle includes an eye which receives the kingpin and defines the pivot axis of the steering knuckle. Thrust bearings are disposed between each of the bearing structures and the end of the axle. The steering knuckle also includes an attachment feature to which a component of the steering mechanism, such as the Pittman arm or a tie rod, is attached.  
         [0003]     Given the portion of the vehicle weight carried by the front tires, the expected and often exceeded service life of the vehicle and various road hazards, it is not surprising that the kingpin bearings deteriorate, allowing excessive play in the front wheel suspension which slowly renders the steering unsafe and causes excessive tire wear.  
         [0004]     Given the direct cost of replacing the steering knuckle wherein frequently only the kingpin bearing surfaces have deteriorated, and the indirect cost related to the vehicle downtime, it is understandable that various repair methods have been proposed. For example, in U.S. Pat. No. 4,969,246, repair of the bearing portion within the axle is described. The axle end or eye is tightly engaged by a fixture which facilitates on-site repair of the axle eye. While this method and apparatus offered a simplified repair process and reduced the cost of repairing axle bearing failures, primarily due to its on-site capability, it did not address how repair of the more frequently worn or damaged bearings in the steering knuckle could be achieved. The present invention is so directed.  
       SUMMARY OF THE INVENTION  
       [0005]     An apparatus for repairing steering knuckle (kingpin) bearings includes a table having multiple, adjustable slides for receiving and securing the steering knuckle to the table, a boring bar and cutter, two adjustable bearing supports for receiving and positioning the boring bar along an axis coincident with the axis of the kingpin bearings, a first drive assembly for advancing the boring bar and a second drive assembly for rotating the boring bar. A method of repairing a steering knuckle comprises securing the knuckle to the slides and the slides to the table, utilizing cylindrical centering rings to align the boring bar with the axis of the kingpin bearings, supporting and securing the boring bar on the previously established axis in a pair of bearing supports and rotating and feeding the boring bar and cutter to create new surfaces in the steering knuckle adapted to receive bearing sleeves. Upon installation of both bearing sleeves, the boring bar and drive unit are reinstalled and the inside diameter of the sleeve is bored to the proper size to receive the kingpin.  
         [0006]     These and other aspects and advantages of the present invention will become apparent upon study of the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a perspective view of a first embodiment of a steering knuckle boring apparatus according to the present invention with a steering knuckle in place thereupon;  
         [0008]      FIG. 2  is a top, plan view of a steering knuckle boring apparatus according to the present invention with a steering knuckle in place thereupon;  
         [0009]      FIG. 3  is an exploded perspective view of the boring bar feed assembly in a steering knuckle boring apparatus according to the present invention;  
         [0010]      FIG. 4  is an exploded perspective view of the boring bar drive assembly of a steering knuckle boring apparatus according to the present invention;  
         [0011]      FIG. 5  is a front elevational view with portions broken away of the steering knuckle boring apparatus according to the present invention illustrating the first step of the repair method;  
         [0012]      FIG. 6  is a front elevational view with portions broken away of the steering knuckle boring apparatus according to the present invention illustrating the second step of the repair method;  
         [0013]      FIG. 7  is a side elevational view in partial section of the steering axle boring apparatus according to the present invention illustrating measurement and adjustment of the boring bar cutting tool;  
         [0014]      FIG. 8  is a top, plan view of a steering knuckle boring apparatus according to the present invention illustrating installation of a sleeve in one of the bearing structures of the steering knuckle;  
         [0015]      FIG. 9  is a side elevational view in partial section of a steering knuckle boring apparatus according to the present invention illustrating the boring to size of the installed sleeve;  
         [0016]      FIG. 10  is a perspective view of a portion of a second embodiment of a steering knuckle boring apparatus according to the present invention; and  
         [0017]      FIG. 11  is a full sectional view of a drive unit of a second embodiment of a steering knuckle boring apparatus according to the present invention taken along line  11 - 11  of  FIG. 10 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Referring now to  FIG. 1 , a first embodiment of an apparatus for repairing motor vehicle steering knuckles is illustrated and generally designated by the reference number  10 . The apparatus  10  cooperates with and repairs a motor vehicle, typically truck or industrial or heavy duty, steering knuckle assembly  12 . The steering knuckle assembly  12  includes a generally circular, flat body or brake flange  14  having a plurality of through apertures  16  which receive fasteners for securing, for example, brake components when the steering knuckle assembly  12  is installed in a vehicle. Extending perpendicularly to the brake flange  14  is a spindle  18  typically including a threaded terminal portion  20 . On the side of the brake flange  14  opposite the spindle  18  are a pair of relatively large ears or lugs  22  which both define oblique, aligned, kingpin receiving through bearing passageways  24 . At least one of the lugs or ears  22 , and often both, include a feature or circular passageway  26  to which components of the vehicle steering system such as a Pittman arm or a tie rod (both not illustrated) are secured.  
         [0019]     The steering knuckle repair apparatus  10  includes a rigid support assembly  30 , a boring bar feed assembly  40  and a boring bar drive assembly  50 . A hydraulic cylinder assembly  70 , illustrated in  FIG. 8 , is also a component of the apparatus  10  and is utilized during the repair procedure.  
         [0020]     Referring now to  FIGS. 1 and 2 , the rigid support assembly  30  includes a rigid, planar support table  302  which is preferably fabricated of steel having a thickness of at least one-half inch (12.7 millimeters) or thicker having a flat, smooth upper surface. The support table  302  is secured to and supported upon vertical legs  304  which preferably extend approximately three feet (0.95 meters) to raise the support table  302  to a convenient, working height. At a minimum, the legs  304  are long enough that the spindle  18  of a typical steering knuckle assembly  12  secured to the support table  302  will not contact or interfere with the leg supporting surface such as a bench or low table (not illustrated). Centrally disposed within the support table  302  is a circular opening  306  which receives the spindle  18  of the steering knuckle assembly  12 .  
         [0021]     Four pairs of arcuate slots  308  are arranged concentrically about the circular opening  306 . The arcuate slots  308  are preferably arranged into adjacent pairs defining an acute included angle of approximately 60°. The adjacent pairs of arcuate slots  308  are separated by, a wider angle of approximately 120° which provides clearance for other assemblies. Received upon each pair of the four pairs of slots  308  is a mounting finger  310 . The four mounting fingers  310  are both adjustable and securable to the support table  302  by virtue of a pair of threaded fasteners such as bolts  312  which extend through both a longitudinal slot  314  in the fingers  310  and one of each of the pair of slots  308  in the support table  302 . The threaded fasteners or bolts  312  are secured by nuts and washers  316  and include enlarged heads and regions of square cross sections (both not illustrated) similar to carriage bolts which prevent the threaded fasteners or bolts  312  from passing through the slots  308  and prevent rotation of the threaded fasteners or bolts  312  in the slots  308 , respectively, thereby simplifying and speeding tightening and release thereof.  
         [0022]     The support table  302  also includes a first pair of parallel, more widely spaced apart slots  320  disposed on one side of the circular opening  306  and a second pair of parallel, more closely spaced apart slots  322  on the opposite side of the circular opening  306 . Within the first pair of slots  320  are disposed a first pair of symmetrically arranged angle brackets  326  which support a first bearing assembly or headstock  330 . Each of the first pair of brackets  326  includes a through aperture (not illustrated) which receives one of a pair of bolts or threaded fasteners  332  extending through the support table  302 . Once again, the heads of the threaded fasteners  332  are enlarged and include a square cross-section portion that prevents them from passing through the slots  320  and inhibits rotation thereof such that a nut and washer  334  may be readily tightened and loosened to secure the first pair of angle brackets  326  to the support table  302 . The headstock assembly  330  is likewise secured to the first pair of angle brackets  326 , which each include an elongate vertical slot  336 , by a pair of bolts or threaded fasteners and washers  338 . The headstock assembly  330  includes a headstock ball bearing assembly  342 , illustrated in  FIG. 5 , which may be secured and released from a through passageway  344  formed in the headstock assembly  330  by at least one suitable set screw  346 .  
         [0023]     Similarly, the second pair of more closely spaced apart slots  322  are associated with a second pair of symmetrically arranged angle brackets  356 . Each of the second pair of angle brackets  356  includes a through passageway (not illustrated) which each receive a bolt or threaded fastener  358  having an enlarged head and square cross-section portion which renders the fasteners  358  non-rotatable when installed in the slots  322 . A nut and washer  362  on each of the threaded fasteners  358  rotatably releases or secures the second pair of angle brackets  356  to the support table  302  at a desired location along the second pair of slots  322 . The second pair of brackets  356  support a second bearing or tailstock assembly  360 . The second pair of brackets  356  each include elongate vertical slots  362  which receive bolts or threaded fasteners and washers  364  which extend through the slots  362  and are threadably received within the tailstock assembly  360 . The tailstock assembly  360  includes a through aperture  366  which receives tailstock ball bearing assembly  368  as illustrated in  FIG. 5 . The ball bearing assembly  368  is retained within the tailstock assembly  360  by at least one set screw  372 .  
         [0024]     Referring now to  FIGS. 2 and 3 , the boring bar feed assembly  40  includes a two-piece symmetrical housing  402  having an inverted Y-shape, having a first or front housing  404 A and identically configured second or rear housing  404 B. The first and second housings  404 A and  404 B are partially hollowed out and receive various drive components of the boring bar feed assembly  40 . Secured to the outside face of the first housing assembly  404 A is a variable speed, bidirectional electric motor and speed reducing assembly  406 . The electric motor and speed reducing assembly  406  receives electric power through a multiple conductor cable  408  from a suitable electronic controller (not illustrated) which contains switches and circuitry and is well known in the art. The electric motor assembly  406  includes an output shaft  410  which defines a keyway  412 . The electric motor assembly  406  includes a mounting plate  414 . A plurality of threaded fasteners  416  extend through a plurality of suitable apertures  418  in the mounting plate  414  and are received within threaded apertures  420  in the first housing  404 A. A chain drive sprocket  422  is coupled to the output shaft  410  by a key  424 . An idler sprocket  428  engages the drive chain  426  and is received upon a stub shaft  430  which is received within blind apertures  432  in the first and second housings  404 A and  404 B. Extending around and engaging the teeth of the chain drive sprocket  422  is a drive chain  426 . Similarly, the drive chain  426  engages and drives a first driven chain sprocket  434 A and a second driven chain sprocket  434 B. So configured, as the chain drive sprocket  422  rotates, the pair of driven chain sprockets  434 A and  434 B correspondingly rotate.  
         [0025]     Each of the driven chain sprockets  434 A and  434 B include a keyway  436 A and  436 B which receives a key  438 A and  438 B, respectively, which positively couples the sprockets  434 A and  434 B to respective terminal portions of a pair of lead screws  440 A and  440 B having respective keyways  442 A and  442 B. Tightly seated within suitable circular bores  444 A of the first and second housings  404 A and  404 B are a first pair of ball bearing assemblies  446 A which each cooperatively support the terminal portion of the lead screw  440 A. Similarly, a second pair of ball bearing assemblies  446 B are seated within circular bores  444 B of the first and second housings  404 A and  404 B and cooperatively support the terminal portion of the lead screw  440 B. The lead screws  440 A and  440 B are retained within the housings  404 A and  404 B and the pairs of ball bearing assemblies  446 A and  446 B, respectively, by suitable washers  448 A and  448 B and threaded fasteners  452 A and  452 B which are received within suitable threaded openings  454 A and  454 B in the ends of the lead screws  440 A and  440 B. Each of the lead screws  440 A and  440 B include male threads  460 A and  460 B substantially along their full lengths.  
         [0026]     Referring now to  FIGS. 1 and 4 , the boring bar drive assembly  50  includes a bidirectional electric motor and gear reduction assembly  500 . The electric motor and gear reduction assembly  500  is secured to a mounting block  502  by any suitable means such as threaded fasteners (not illustrated). The electric motor and gear reduction assembly  500  is controlled by a conventional electric motor controller (not illustrated) which provides electrical energy through a multi-conductor cable  504 . The controller includes conventional switches and circuitry for energizing the assembly  500 , selecting the direction of rotation of the output of the assembly  500  and the speed of the output. The bi-directional electric motor and gear reduction assembly  500  drives an output shaft or member  506  which extends through the mounting block  502  and defines a female, keyed passageway  508 .  
         [0027]     A boring bar  510  includes a stub, projection, shaft or other feature  512  and key  514  which are complementary to the keyed passageway  508  in the output shaft  508  of the motor and gear reduction assembly  500  such that the boring bar  510  can be readily coupled and driven thereby as well as disassembled therefrom. A setscrew  516  disposed in a threaded, radial passageway in the output shaft or member  506  ensures a secure, positive coupling between the output shaft or member  506  and the boring bar  510 . The boring bar  510  includes a radially adjustable cutting tool  518 , illustrated in  FIG. 2 .  
         [0028]     The mounting block  502  also includes a pair of spaced apart, through apertures  520 A and  520 B having diameters just slightly larger than the diameter of the lead screws  440 A and  440 B arranged in diametric opposition adjacent the output shaft  506 . The spaced apart apertures  520 A and  520 B each receive a respective one of the lead screws  440 A and  440 B. Intersecting the through apertures  520 A and  520 B are larger diameter blind apertures  522 A and  522 B. Each of the blind apertures  522 A and  522 B extend into the mounting block  502 , perpendicularly intersect the through apertures  520 A and  520 B, respectively, and extend a short distance therebeyond. Disposed within each of the blind apertures  522 A and  522 B are one of a pair of compression springs  524 A and  524 B.  
         [0029]     Also received within the blind apertures  522 A and  522 B are a respective pair of releasable, thread engaging cylindrical nuts  530 A and  530 B. The releasable, cylindrical nuts  530 A and  530 B are slidably received within the respective blind apertures  522 A and  522 B and each includes a through radial passageway  532 A and  532 B, respectively. The lower portion of each of the through passageways  532 A and  532 B includes conventional female threads  534 A and  534 B which are complementary to the male threads  460 A and  460 B on the lead screws  440 A and  440 B. The apertures  532 A and  532 B are, however, neither circular nor do they include threads on the entire inner surface of each of the apertures  532 A and  532 B. Rather, the apertures  532 A and  532 B are oval or, more accurately, race track shaped, i.e., they define two semi-cylinders separated by two straight, tangent sides, and their upper portions are free of threads such that only when in an upper position, biased by the compression springs  524 A and  524 B, the female threads  534 A and  534 B on the lower portion of the apertures  532 A and  532 B of the cylindrical nuts  530 A and  530 B engage the threads  460 A and  460 B of the lead screws  440 A and  440 B. In this configuration, as the lead screws  440 A and  440 B rotate, the mounting block  502 , and in fact the entire boring bar assembly  50 , translates along the lead screws  440 A and  440 B.  
         [0030]     The cylindrical nuts  530 A and  530 B are retained within the blind apertures  522 A and  522 B by a respective pair of retaining and actuating pins  540 A and  540 B. The retaining and actuating pins  540 A and  540 B are received within blind passageways  542 A and  542 B which perpendicularly intersect the passageways  522 A and  522 B, respectively. The pins  540 A and  540 B each include a cutaway region or flat  544 A and  544 B which engages the upper surface of a respective one of the cylindrical nuts  530 A and  530 B. When the pins  540 A and  540 B are in the positions illustrated in  FIG. 4 , with the flats  544 A and  544 B opposite or above the cylindrical nuts  530 A and  530 B, the cylindrical nuts  530 A and  530 B are driven down into a lower position such that the threads  534 A and  534 B no longer engage the threads  460 A and  460 B, respectively, on the lead screws  440 A and  440 B. Thus, the lead screws  440 A and  440 B may be removed or installed into the mounting block  502  as desired. When the pins  540 A and  540 B are rotated 180°, the compression springs  524 A and  524 B translate the cylindrical nuts  530 A and  530 B up, causing engagement of the threads  534 A and  534 B with the threads  460 A and  460 B, respectively, of the lead screws  440 A and  44 B as described directly above.  
         [0031]     Referring now to  FIGS. 1 and 5 , the operation of the steering knuckle repair apparatus  10  as it relates to the boring and resleeving of the kingpin bearings of a steering knuckle  12  will be described. The first step involves adjusting the four fingers  310  which have been previously loosely secured to the support table  302  by the threaded fasteners  312  such that four apertures  16  in the brake flange  14  of the steering knuckle  12  align with end openings in the fingers  312 . Bolts and nuts  602  are then installed loosely within the openings of the brake flange  14 . Attention must be paid to ensuring that the bearing passageways  24  align with the pairs of slots  320  and  322  in the support table  302 .  
         [0032]     Next, centering rings  604  are installed within the bearing passageways  24  of the steering knuckle assembly  12 . The centering rings  604  have an inside diameter just slightly larger than the outside diameter of the boring bar  510  such that they snuggly receive it and an outside diameter just slightly less than the inside diameter of the bearing passageways  24  in the steering knuckle  12 . As illustrated in  FIG. 5 , the boring bar  510  is thus aligned with the axis of the bearing passageways  24  in the steering knuckle  12 . At this time, the bearing  342  and the headstock assembly  330  and the bearing  368  and the tailstock assembly  360  are installed and moved as necessary within the supporting brackets  326  and  356 , respectively, such that the bearings  342  and  368  support the boring bar  510  on an axis coincident with and defined by the bearing passageways  24  of the steering knuckle assembly  12 .  
         [0033]     At this time, the appropriate bolts are installed and tightened to secure the headstock assembly  330  and the tailstock assembly  360  securely to the support table  302 . It should be noted that the inside faces of the bearing  342  of the headstock assembly  330  and the bearing  368  of the tailstock assembly  360  adjacent the steering knuckle assembly  12  are preferably moved to within approximately one half inch (12.7 mm.) separation from the steering knuckle assembly  12  in order to achieve a minimum unsupported length of the boring bar  510  which, as will be readily appreciated, improves the quality of all subsequent boring operations. Also, it should be stated that while the various bolts of the headstock and tailstock assemblies  330  and  360  are being tightened, it is important that none of the associated components move out of position or cause the boring bar  510  to bind as it is rotated. Next, the boring bar  510  is removed and the centering rings  604  are likewise both removed.  
         [0034]     Referring now to  FIG. 6 , the boring bar  510  is reinstalled in the headstock assembly  330  and the tailstock assembly  360 . Next, the boring bar feed assembly  40  is secured to the headstock assembly  330  utilizing two mounting bolts (not illustrated). Next, the boring bar drive assembly  50  is mounted on the lead screws  440 A and  440 B and the retaining and actuating pins  540 A and  540 B are appropriately manipulated to cause engagement of the threads  534 A and  534 B in the cylindrical nuts  530 A and  530 B with the threads  460 A and  460 B on the lead screws  440 A and  440 B. At this time the boring bar  510  is secured to the collar  508  and the output of the bidirectional electric drive motor  500  by tightening the setscrew  516 .  
         [0035]     As illustrated in  FIG. 7 , the cutter  518  of the boring bar  510  is then set to achieve the appropriate diameter cut within both bearing passageways  24  of the steering knuckle assembly  12 . This setting is achieved through the use of a micrometer  620  which is secured to a jig or fixture  622  having a triangular throat  624  which engages the wall of the boring bar  510 . Then, as illustrated in  FIG. 6 , boring of each bearing passageway  24  in the bearing structures  22  of the steering knuckle assembly  12  commences. Such boring is undertaken in accordance with conventional practice, the rotational speed and the feed rate of the boring bar  510  being adjusted to achieve a satisfactory cut, surface finish and cutting time. Upon completion of the boring of both bearing passageways  24 , the electric motors  406  and  500 , are turned off and the boring bar feed assembly  40  and boring bar drive assembly  50  removed from the headstock assembly  330 . The boring bar  510  is then removed. Of course, to remove the boring bar  510  through the bearing  342  or  368 , the cutting tool  518  must be released and retracted into the boring bar  510 .  
         [0036]     Turning then to  FIG. 8 , a pair of sleeves  630 , one of which is illustrated in  FIG. 8 , are now installed into the just completed, enlarged bores  606 . To accomplish this, a bushing installing hydraulic cylinder assembly  70  is positioned in the headstock assembly  330 . The hydraulic cylinder assembly  70  includes a housing  702  which defines a cylinder having a hollow (rodless) piston  706  disposed therein. The hollow piston  706  defines a through aperture  708  which receives an elongate shaft  710 . The shaft  710  includes an enlarged collar  712  and suitable fasteners  714  at both ends which retain the piston  706  and the collar  712  upon the elongate shaft  710 . The housing  702  includes a necked down or smaller diameter region  720  which is received within the bearing opening  344  of the headstock assembly  330  such that the elongate rod  710  generally conforms to the axis previously defined by the bearings  342  and  368  and upon which the boring bar  510  resides when in use. A sleeve or bushing  730  is placed adjacent the collar  712  on the elongate rod  710  and the hydraulic cylinder assembly  70  is actuated such that the piston  706  moves to the left, as illustrated in  FIG. 8 , drawing the sleeve or bushing  730  into the aperture  606  of the bearing structure  22  of the steering knuckle  12 . A second sleeve (not illustrated) is similarly installed in the other bearing aperture  606  by removal and reinstallation of the hydraulic cylinder assembly  70  in the tailstock assembly  360 .  
         [0037]     Referring now to  FIG. 9 , the boring bar feed assembly  40 , the boring bar drive assembly  50  and the boring bar  510  are once again installed in the headstock and tailstock assemblies  330  and  360  as illustrated. Again, the radial position of the cutter or cutting tool  518  is adjusted by use of a micrometer such as illustrated in  FIG. 7  and the just installed bearing sleeves  730  are bored out to the exact desired diameter to receive a kingpin (not illustrated). Upon completion of the boring of the inside diameters of both of the sleeves  730 , the boring bar feed assembly  40 , the boring bar drive assembly  50  and the boring bar  510  are all removed from the headstock and tailstock assemblies  330  and  360 . Next, the bolts and nuts  602  are loosened and removed and the steering knuckle assembly  12  is removed from the support table  302 . The steering knuckle assembly  12  is now ready for reassembly with the motor vehicle.  
         [0038]     In order to facilitate compact storage, the headstock and tailstock assemblies  330  and  360  as well as the fingers  310 , if desired, may be removed from the support table  302 .  
         [0039]     As illustrated in  FIGS. 1, 3  and  4 , the first embodiment repair apparatus  10  includes separable and independent assemblies for feeding and rotating the boring bar  510 , namely, the boring bar feed assembly  40  and the boring bar drive assembly  50 . In a second embodiment repair apparatus  800 , partially illustrated in  FIGS. 10 and 11 , the two boring bar feed and drive assemblies  40  and  50  are combined into a single unit, a boring bar power assembly  810 .  
         [0040]     Referring now to  FIGS. 10 and 11 , the second embodiment repair apparatus  800  includes a common or unified boring bar power assembly  810  which includes a housing  812  to which is mounted a first bi-directional electric motor and gear reduction assembly  814  for rotating the boring bar  510 . The housing  812  is preferably fabricated of aluminum and includes a plate or cover (not illustrated) which closes and protects components within the housing  812 . The electric motor and gear reduction assembly  814  may be identical to the electric motor and gear reduction assembly  500  of the first embodiment repair apparatus  10 . As such, it includes a multiple conductor cable  816  which connects the electric motor and gear reduction assembly  814  to a conventional electronic variable speed, bidirectional motor controller (not illustrated) which contains switches and circuitry and is well known in the art. As illustrated in  FIG. 11 , the electric motor and gear reduction assembly  814  includes an output shaft  818  having an output pinion  822  which is engaged by and drives a complementary chain or timing belt  824  which in turn engages and drives a driven pinion  826  coupled to the boring bar  510  by a key and threaded fastener  828 .  
         [0041]     Also mounted upon the housing  812  is a second, bi-directional electric motor and gear reduction assembly  834 . The second electric motor and gear reduction assembly  834  receives electrical energy through a multiple conductor cable  836  from a suitable bi-directional, variable speed electronic controller (not illustrated) which contains switches and circuitry and is well known in the art. The electric motor and gear reduction assembly  834  includes an output shaft  838  which is secured to and drives an output pinion  842  which is engaged by and drives a complementary chain or timing belt  844  which, in turn, engages and drives a pair of driven pinions  846 . Each of the driven pinions  846  is secured to and rotates a threaded lead screw  440 A or  440 B extending from the housing  812 .  
         [0042]     The second embodiment repair apparatus  800  also includes a headstock assembly  850  which includes a removable ball bearing assembly  852  which rotatably receives and supports the boring bar  510 . The headstock assembly  850  also includes a pair of retaining and actuating pins  854 A and  854 B which actuate a respective pair of spring biased, releasable, thread engaging cylindrical nuts (not illustrated). These components are the same as and function in a manner identical to the components illustrated in  FIG. 4  to engage and release the lead screws  440 A and  440 B, so that the boring bar drive assembly  810  may be assembled with or removed from the headstock assembly  850 .  
         [0043]     When the actuating pins  854 A and  854 B are in their released positions, the leadscrews  440 A and  440 B may be installed, along with the boring bar power assembly  810 , in the headstock  850 . When the actuating pins  854 A and  854 B are in their actuated positions, the leadscrews  440 A and  440 B are engaged by the cylindrical bits and rotation of the leadscrews  440 A and  440 B advances or retracts the boring bar power assembly  810  and the boring bar  510  attached thereto.  
         [0044]     The headstock assembly  850  is supported on a first pair of angle brackets  326  having vertical elongate slots  336  and secured thereto by threaded fasteners  338 . The brackets  326  are secured to the support table  302  by threaded fasteners  332  which pass through slots  320  and are secured by nuts and washers  334 . The other components of the second embodiment repair apparatus  800  not illustrated in  FIG. 10  are the same and function the same as those of the first embodiment repair apparatus  10 .  
         [0045]     Although the foregoing apparatus and method have been described within the context of repair to a motor vehicle steering knuckle, it should be understood that the disclosure relates more broadly to similar repair of an article of manufacture having one or more aligned bores, sleeves or bearing openings oriented at an oblique angle to a planar and/or circular reference plate, component or surface. That is, the apparatus and method may be utilized and adapted to bore or true any bore or aligned bores disposed at an oblique angle to a reference feature or component of an assembly.  
         [0046]     As any person skilled in the art of specialized boring apparatus and method and particularly to an apparatus and method for repairing worn and oversized bearing openings in motor vehicle steering knuckle assemblies will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of this invention defined in the following claims.