Abstract:
A broaching tool for machining a workpiece formed of a parallelogram shaped insert which fits within a slot formed in a body member. The insert has two juxtaposed corners either of which may be oriented at the distal end of the body member to function as a cutting edge. Repositioning of the insert to place either cutting edge in place is provided by flipping it over in its engagement within the slot. The inserts may be provided in a kit of differently configured inserts to yield different cutting widths.

Description:
This application claims priority to U.S. Provisional Patent Application No. 61/130,427 filed on May 30, 2008 incorporated herein in it&#39;s entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     The disclosed invention relates to machine tooling. More particularly it relates to a broaching tool having a reversible indexable cutting insert which is configured to maintain a registration with the engaged tool body when the insert is reversed to expose a new cutting edge of the insert. 
     BACKGROUND OF THE INVENTION 
     In the metalworking industry of machine shops, a cutting tool is any tool that is employed to remove metal from the workpiece being machined. This removal is accomplished generally by means of a shear deformation. Essentially, with the workpiece or the tool in motion, the tool is placed in controlled contact with the workpiece to thereby remove material such as metal strategically, to thereby form the desired shape to the workpiece. 
     Tools generally employ a bit or insert, which is engaged to a holder. The bit or insert is formed of material sufficiently hard to cut the workpiece in the manner intended. Over time, the cutting formed by the bit or insert tends to dull from repeated contact with the workpiece to remove material. The insert must therefore be replaced to maintain the quality of the workpiece produced and the speed of the operation producing the parts formed by the fully machined workpiece. A dull tool insert will not only slow the process, it can easily yield inferior parts from chatter and other problems inherent to contact of a dull insert with the workpiece being machined. 
     Additionally, the cutting tool insert must employ a specific geometry so as to place the cutting edge of the tool insert in proper contact with the workpiece. Concurrently, the rest of the tool insert must be spaced from the workpiece to prevent dragging of non cutting surfaces upon workpiece. Other elements of tool insert geometry such as the angle of the cutting edge, the flute width, the tool margin and hardness of the cutting edge also must be maintained during use of the tool insert to work upon the workpiece. 
     Frequently employed in modern machining is the lathe, particularly a Computer Controlled (CNC) lathe. Such devices generally spin the workpiece against a plurality of sequentially positioned tool inserts to thereby yield a final component. One operation which can be employed with the lathe is the art of broaching. In broaching, instead of spinning the workpiece, the lathe&#39;s spindle is locked in place to hold the workpiece engaged in a fixed position. Thereafter a broaching tool insert is driven into and out of the workpiece being held by the spindle to thereby create keyways and slots within the workpiece. 
     This mode of operation of the lathe increases the number of operations which can be performed in a single chuck on a single lathe. Also, because the same machine is employed for two operations for a fixed in position workpiece, the accuracy of the dimensions of the final part formed by the fully machined workpiece is increased. This is because the workpiece need not be removed and remounted from machine to machine, which causes errors in the accuracy of sequential cuts to the workpiece. Shop labor time is also reduced since the workpiece need not be continually dismounted and remounted. Further, the need for specialized broaching machinery is reduced since the workpiece is held by the lathe for a plurality of cuts to the workpiece. 
     In the broaching operation, cutting tools are employed in a number of configurations. In one conventional configuration, carbide or similar tool inserts, have a cutting edge formed thereon which is a separate part that is brazed to a tool body portion. This creates a sturdy, yet permanently engaged cutting insert from the two individual parts. However, with only one cutting edge formed of two components, during each replacement of a dull tool insert, the set up must be re-registered to position the cutting edge of the tool insert to properly machine the workpiece. 
     A second configuration employs a tool insert which is replaceable and held in removable engagement with a tool body. This allows for replacement of the tool insert, when dull, by dismounting it from its holder, and engaging a new tool insert. However, the temporary engagement with the holder using screws or other means of engagement suffers from chatter during machining of the workpiece due to the minimal contact of set screws and the like with the tool insert to engage it to the holder. Additionally, such tool inserts generally require a new setup of the tool insert geometry each time the cutting tool insert is replaced. 
     Both conventional types of broaching tool configurations suffer from dulling of the single cutting edge of the cutting tool insert. Since they thus require frequent replacements machining time is significantly increased by the need to re-register the geometry of the cutting tool insert with the workpiece after each replacement. Accuracy of the parts formed by the machined workpiece suffers due to the numerous reconfigurations of the tool insert each time the single cutting edge wears past desired specifications. 
     During replacement of brazed cutting tool inserts the dismounting of the cutting tool insert and subsequent brazing of a new cutting edge portion to the body, is tedious at best. The process then requires the entire cutting tool insert to be registered in engagement relative to the machine and the workpiece position to yield the desired material cuts to the workpiece. 
     Replacement of an insertable and screw-held cutting tool inserts, while somewhat easier, still suffer from chatter and other problems due to the nature of the engagement of the cutting tool insert to the body of the tool holding it. Further, due to the variance in dimensions of each different cutting tool insert, re-registration of the geometry of the insert to the workpiece is virtually assured. 
     Accordingly, there exists an unmet need for a method for a broaching cutting tool device which provides the convenience of a replaceable cutting tool insert with a tool body. Such a device should however be free of the problems inherent with conventional tool inserts of chatter due to poor engagement with the holder, and the need to re-setup the tool geometry each time, due to varying engagement with the body holding it. 
     With respect to the above, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components or steps set forth in the following description or illustrated in the drawings. The various apparatus and methods of the invention are capable of other embodiments and of being practiced and carried out in various ways which will be obvious to those skilled in the art once they review this disclosure. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based, wherein a cutting tool insert is shaped to engage with the cutting tool body holding it, in a manner to yield a stronger and more accurate mount, may readily be utilized as a basis for designing of other devices, and methods and systems for carrying out the several purposes of the present disclosed device and method. It is important, therefore, that the objects and claims be regarded as including such equivalent construction and methodology, insofar as they do not depart from the spirit and scope of the present cutting tool invention. 
     SUMMARY OF THE INVENTION 
     The device and method herein described and disclosed is a cutting tool employed for broaching. The device is formed of a body portion and a removable cutting insert which has a plurality of cutting edges adapted for cutting a workpiece. 
     The body portion is adapted at a first end, for engagement to a machine tool mount which is well known to those skilled in the art such as those employed on a lathe or CNC machine. Also, at the first end of this body portion is a means for communication of a stream of cooling fluid to the distal end of the body portion, which may be employed for lubricating and cooling the workpiece and cutting insert during use. 
     On the distal end of the device, a slot provides means for registered engagement of a cutting tool insert therein. The shape of the insert and the shape of the slot, provide for exceptional repeatable accuracy in the positioning of the cutting edge of any such tool insert, relative to the workpiece. Thus registration of the cutting tool geometry to the workpiece is substantially eliminated or minimized. 
     The current preferred shape of the tool insert is a parallelogram. The tool insert has an as-used position mounted within the slot formed within the tool body which is configured similarly in shape. In the as-used position, a leading corner of the insert is formed at the intersection of a first endwall and the first side edge of the insert, which when mounted, is positioned just above the distal end of the tool. From a center section of the first side surface, the first side surface of the tool insert is formed at a declining angle relative to a declining angle of the second side surface of the insert from the center section of the second side surface. This declining or narrowing angle is toward the top side of the tool body in which the slot is formed. 
     A second corner of the insert, at the intersection of the second side edge and the second endwall of the insert, is positioned within and in contact with, the slot of the tool body. The second side edge is of a length to extend past the center axis of the elongated body portion of the tool when in the as-used position. 
     The cutting insert is dimensioned in the preferred mode, as a parallelogram with both the top or first side edge surface and the second side edge surface parallel to each other as are the first endwall and second endwall. This shape has been found to be especially preferred in that it places the first corner of the tool insert, used for cutting the workpiece, above the tool body. More importantly, this configuration concurrently engages the entire second sidewall of the tool insert in contact with a rear wall of the slot formed in the tool body. This engagement directs the force caused by the first corner engaging the workpiece in a translation of the tool in a jig, directly to the tool body along its strongest point at the central axis of the body. 
     The shape of the insert places the entire surface of the trailing or second endwall in contact with a parallel surface of the slot in the body and thereby allows for maximum transmission of force from cutting the workpiece, directly to the body to relieve chatter of the insert. Further, both the first and second endwalls of the insert are angled such that in the as-used position, they are substantially perpendicular to the center axis of the tool body. This positioning of the endwalls substantially normal to the body axis provides additional means to transmit a maximum amount of force exerted on the insert during cutting to the tool body. Consequently, it is preferred that the angles of the endwalls and opposing side edge surfaces of the insert are dimensioned to yield this engagement with the body when in the as-used position. 
     In addition to the maximum transfer of force from the insert to the body for a more stable cutting edge, the dimensioning of the insert as a parallelogram yields an additional benefit to the device. The insert may be formed with cutting edges on two opposing corners which allows for the insert to be flipped in its engagement in the slot of the body to thereby expose a fresh cutting edge during use if replacement is needed. Because of the dimensional characteristics of the insert noted above, when flipped to position the opposite corner in the cutting position in the body, the newly positioned corner is placed perfectly in position to cut the workpiece. This eliminates the need to re-setup the tool as is required with conventional broach cutting tools. 
     Secure mounting of the cutting insert in the slot of the body is provided by a plurality of allen or other bolts threadably engaged to the body to communicate with one side wall surface of the insert. Both sidewall surfaces have a central portion which is substantially planar and extends parallel to the center axis of the body of the tool when the insert is in the as-used position. Consequently, when the insert is mounted or flipped and remounted, the two planar surfaces provide an excellent mount of the insert with the sidewalls of the slot. A tightening of the set screws hold the insert in the slot in the as-used position. 
     From the planar center section of both sidewalls, a relief is formed in the sidewall surface, to angle it toward the first and second side surfaces. This relief is substantially triangular in shape to thereby keep the planar center sections of both sidewalls running parallel to the center axis of the body when in the as-used position. 
     It is thus an object of the invention to provide a machine tool for broaching which provides a cutting insert engaged to a body portion which may be flipped to yield a new cutting edge without the need to re-setup the geometry of the tooling. 
     It is a further object to provide a device wherein a new insert may be engaged to the body of the tool without the need to re-setup the tooling. 
     It is yet an additional object of this invention, to provide such an insert that is dimensioned to minimize chatter by transmitting a maximum amount of force to the body holding the insert while cutting. 
     These together with other objects and advantages which will become subsequently apparent, reside in the details of the method and device for proximate communication between authorizing users as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  depicts the device showing the cutting insert held by set screws in the as-used position in the body portion. 
         FIG. 2  depicts the opposite side from  FIG. 1 . 
         FIG. 3  depicts a top plan view of the device of  FIG. 1 . 
         FIG. 4  shows the parallelogram-shaped insert inside a similarly dimensioned slot in the as-used position. 
         FIG. 5  depicts the slot in the distal end of the body running along the center axis of the elongated body and the angled sides of the tool insert. 
         FIG. 6  depicts a slice through  FIG. 4  along lines  6 - 6  showing the slot in contact with the endwall and side edge of the insert. 
         FIG. 7  is an enlarged view of a side surface of the tool insert showing the triangular relief sections extending toward the first and second side edges, from the planar center section. 
         FIG. 8  is an end view of the insert of  FIG. 7  showing the angled portions of the sidewalls extending from the planar center section. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings in  FIGS. 1-8  individually or as a group, wherein similar parts are identified by like reference numerals, the device  10  is depicted in figures as a broaching tool for cutting a workpiece. 
     A body  12  portion is adapted at a first end  14 , for engagement to a machine tool mount on a lathe which would hold the workpiece. Also shown at the first end,  14  in  FIG. 3  is a relief  15  which provides means for engagement of a cooling fluid for lubricating and cooling the workpiece and the insert  20  engaged in the slot  18  at the distal end  16  of the body  12 . 
     At the distal end  16  opposite the first end  14 , the slot  18  is formed to provide means for registered engagement of a cutting insert  20  therein and contacting surfaces of the slot  18 . The current preferred shape of the insert  20  is that of a parallelogram and the shape of the slot  18  is a conforming parallelogram. 
     The insert  20  has an as-used position shown in  FIGS. 1 , and  4 - 6  which depict it removably engaged within the slot  18  on the tool body  12  with a leading corner or leading cutting edge, shown as the first corner  22 , providing a leading cutting edge positioned at the intersection of a first endwall  23  and a top or first side surface  24  of the insert  20 . The first side surface  24  of the insert  20  declines at an angle toward the central portion  41  and the second endwall  28  of the insert  20 . When in the as used position, the angle declines toward the center axis  33  or top side  31  of the tool body  12 . 
     At the intersection of the second side surface  30  and the second endwall  28  of the insert  20 , a second cutting edge  43  is provided at the trailing corner  22  or second corner  32  positioned opposite to the first corner  22 . When flipped, the insert  20  positions the second corner  32  as the leading corner or cutting edge, and the first corner  22  in a trailing corner  25  position. 
     The positioning of the second endwall  28 , or the first endwall  23  when the insert  20  is flipped, against a rear wall  36  of the slot  18 . This positioning directs the force caused by the first corner  22  or second corner  32  depending on which way the insert  20  is engaged in the slot  18 , in a cutting of the workpiece, along the center axis  33  of the tool body  12  where it is strongest. The parallelogram shape maximizes the area of contact area of the rear wall  36  of the slot  18 , and the first or second endwall  23  or  28 . This contact area is substantially perpendicular to the center axis  33  of the body  12  to maximize transmission of force from the insert  20  to the body. 
     The insert  20  is dimensioned for engagement into the slot  18  such that it may be secured by set screws  40  against the thicker central portion  41  which is substantially the same in width as the short side width or rear wall  36  width of the slot  18 . The parallelogram shape of the insert  20 , the substantially equal width of the central portion  31  to the width  36  allow the insert  20  to be flipped in its engagement in the slot  18 , without the need to re-setup the insert  20  and body  12 , relative to the workpiece. Both sidewall surfaces of the insert  20  have a central portion  41  which is substantially planar on both sides and extends parallel to the center axis  33  of the body  12  of the tool when the insert  20  is in the as-used position. 
     Thus, the shape of the insert  20  and contact of the trailing corner  22  or  32 , with the rear wall  36 , and a contact of the central portion  31 , with the sides of the slot  18 , provide means to maintain the relative geometry of the insert  20  with the workpiece when the insert  20  and flipped in its engagement to the body  12  and to eliminate the need to readjust the insert  20  to the workpiece upon such a change in position. This secure mount configuration also reduced chatter from which conventional tools suffer. 
     From the planar center section  41 , a pair of triangular reliefs  42  is formed in the sidewall surfaces on both sides of the insert  20 . The triangular reliefs  42 , provides clearance on both sides of the insert  20  in the as used position and from the top surface  31  of the body  12 . The depth of the triangular reliefs  32  determine a width  29  of the leading cutting edge as shown in  FIG. 5 . This can vary depending on the depth of the reliefs  42  in their angle from the central section  41  to the first or second side surfaces  24  and  30 . When engaged in either orientation, the triangular reliefs  42  positions the hypotenuse of that triangular shape, which depending insert  20  orientation is the first side surface  24  or second side surface  30 , at a declining angle toward the top surface  31  of the body  12 . The shortest side of the triangular shaped reliefs  42  will always lead with the leading cutting edge of the insert  20  when in the as used condition. 
     In broaching, contact of the leading edge of the insert  20 , with the workpiece, will generally impart a downward and rearward force on the insert  20 . The large area of contact of the trailing surfaces of the insert  20 , with the slot  18  eliminates chatter and positioning of the trailing corner position  25  below the center axis  33  of the body  12 , has been found to resist the rotational force on the insert by the contact of the leading edge with the workpiece, further reducing chatter. Therefor it is important to configure the slot  18  to mirror the shape of the insert  20 , with a width substantially equal to or slightly larger than the width across the central section  41 , and to position the trailing corner position  25  below the center axis  33  of the body  12  to be engaged therewith. 
     The device  10  may be provided as a kit form where a body  12  has a slot  18  configured for multiple inserts  20  all of which would seat into the slot  18 , and be replaceable with other inserts  20  from the kit, without having to reorient the geometry of the insert  20  and body  12  to the workpiece. Further, all of the inserts  20  could be flipped in the slot  18  to provide a new and sharp cutting edge without the need for a new insert  20 . Finally, the triangular reliefs  42  can be provided at varying angles toward each other, and thus reliefs toward each other, to form the first and second side surfaces  24  and  30  in a manner yielding a leading cutting edge width  29  that can be wider or narrower depending on the width of the broach intended. In a kit form, a plurality of different inserts  20  may therefor be provided, all with different cutting edge widths  29 , all of which will securely mount in the body  12 . All such inserts  20  would also be capable of changing orientation by flipping to reveal a second cutting edge in the correct position to function as the leading cutting edge without the need to reposition the insert  20  or body  12  to continue broaching workpieces. 
     While all of the fundamental characteristics and features of the improved disclosed and described broaching tool have been described, a latitude of modification, various changes and substitutions are intended in the foregoing disclosure and it will be apparent that in some instances, some features of the invention will be employed without a corresponding use of other features without departing from the scope of the invention as set forth. It should be understood that such substitutions, modifications, and variations may be made by those skilled in the art without departing from the spirit or scope of the invention. Consequently, all such modifications and variations are included within the scope of the invention as defined herein.