Abstract:
A machine tool bit holder providing a stable connection between a machine and a tool bit being used to perform machining operations on a work piece. The holder for the tool bit is of simple construction and has a large contact area relative to a tool bit size and a holder size between the holder and the tool bit, and the holder is configured so that the tool bit can be easily mounted into and dismounted from the holder. The holder allows different shapes or configurations of tool bits, such as an angle between the holder and the tool bit, and tool bits that are substantially rectangular as well as substantially round in cross-section.

Description:
CROSS-REFERENCE TO RELATED PUBLICATIONS 
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                 Patent Number 
                 Title 
                 Issue date 
               
               
                   
               
             
             
               
                 EP1488876 
                 Shrink fit holder and methods of 
                 Dec. 22, 2004 
               
               
                   
                 drilling and reaming 
               
               
                 7077608 
                 System for mounting a machine tool 
                 Jul. 18, 2006 
               
               
                   
                 in a holder 
               
               
                   
               
             
          
         
       
     
       BACKGROUND OF THE INVENTION 
       [0002]    Machine tools, such as lathes, screw cutters, boring devices, and the like, as they are commonly known in the art, provide for a rigidly held work piece which is rotated or otherwise manipulated around or along some axis, while a fixed tool such as a holder with a tool bit therein is introduced to the work piece for removing unwanted material from said work piece. It is imperative that both the tool and the work piece be rigidly held with respect to each other, except for the motion introduced to allow the tool to operate on the work piece. 
         [0003]    Alternatively, the work piece is fixed as the tool is rotated or manipulated for the above purpose. 
         [0004]    A tool bit, which is the part of the tool effecting said removal of material, is both expensive and difficult to form properly. The tool bit is normally made of a special hardened material to allow removal of material without excessive wear or damage to the tool bit or damage to the work piece due to excessive vibration of the tool bit. 
         [0005]    Consequently, the tool bit is made as small as is practical to minimize both material and preparation expense. However, the tool bit must not be unduly fragile, due to the possibility of breakage with high stresses, and the need to suppress vibration in the bit to avoid damage to the work piece. As disclosed above, the tool bit is normally held in a tool bit holder, which helps to minimize the material required for the bit, and allows for easier mounting and use. The size of the tool bit is determined in large part by the ability of the holder to contain the bit properly. 
         [0006]    One type of tool bit holder useful to those in the art is the so-called chuck. The chuck is designed to hold a bit axially within the chuck, normally by means of “fingers”, or multiple extensions from within the chuck along the long axis of the bit, with the fingers being urged against the bit to secure the bit firmly. The chuck does not readily allow for any other angle than axial with the chuck for the deployment of the bit. 
         [0007]    A simple holder, as opposed to a chuck, rigidly holds a work piece, such as other than axially with the holder, and when the work piece is rotated or otherwise manipulated around or along some axis, the tool bit in the holder is introduced to the work piece for removing unwanted material from said work piece. 
         [0008]    Alternatively, the work piece is fixed and the holder with a tool bit is rotated or otherwise manipulated for the above purpose. 
         [0009]    A primary purpose of the holder is to provide both a secure connection to the machine tool and a secure connection to the tool bit. Normally, the bit is inserted into the holder, such as in a groove or other type of receptacle for the bit, and is secured there by some stable means. The securing means is normally a set of set screws which thread through the holder and force the bit against an edge of the holder, the edge being formed for that purpose. Since the areas of the set screw ends are comparatively small, holding the bit securely requires substantial force on the screws, both for clamping the bit in place and for minimizing vibration of the bit. These requirements often determine a minimum size of bit that can be used without an unacceptable risk of damage to the bit or vibration of the bit. A larger bit is more expensive and may require a larger holder, which is disadvantageous, both for the expense involved and for the limitations in operating in confined spaces which are introduced thereby. 
         [0010]    An alternative holder of the current art is the “shrink fit” holder. With the shrink fit holder, the recess in the holder is too small to allow the bit to be inserted, until the holder is heated with respect to the bit or the bit is cooled with respect to the holder, or both. The differences in the thermal expansion of the holder and the tool bit, when the holder is heated relative to the bit, allows the bit to be inserted. When the holder and bit are allowed to stabilize at the same temperature the bit is securely held in the holder. 
         [0011]    With the shrink fit holder, a smaller bit may be used, with corresponding savings in both material cost and bit preparation expense. The smaller bit is made practical because the securing force is spread over a larger area and less force is applied to any one point on the bit. Also, the larger area of contact, relative to the size of the holder and the size of the bit, minimizes vibration. 
         [0012]    A problem with the shrink fit holder is that it is very difficult to remove the bit from the holder when it is desired to use another bit, such as with bit wear or breakage. As a result, the shrink fit holder normally requires special equipment, or a holder must be dedicated to a specific bit. Another problem is that the process for inserting the tool bit into the holder is relatively time-consuming and expensive, since heating and cooling operations are required. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    In this invention, a holder having jaws on deformable arms is provided. The jaws of the holder are of a substantial enough nature to hold the tool bit securely with a relatively large area of contact, but the holder is small compared to prior art holders for the area of contact achieved. The jaws are arranged on the arms of the holder in an opposing manner, with the arms being relatively wide in a direction parallel to both of the arms. In this way, when a bit is held, the two holder arms form a triangular structure with good stability, even with relatively flexible arms. The width of the arms provide lateral support, whereby each arm stabilizes the other and the bit is held securely thereby. 
         [0014]    The jaws of the holder of this invention are at an extreme end of said holder, and in the initial state are so disposed as to hold the tool bit with a light touch, or “slip fit”. The two arms, or arm-like extensions, hold the jaws essentially on the end of cantilever levers, and the jaws can be slightly flexed by the user when it is desired to clamp the tool bit. The extensions so formed may be further thinned at the far end of the arms from the jaws for allowing preferential flexing at that point. The thinning at the far end of the arms is normally by removal of some of the holder material, allowing the thinning to be accomplished such as by drilling a hole through the holder parallel to said width of said arms at said far end of said arms from said jaws. 
         [0015]    As disclosed above, the jaws are flexed together when it is desired to clamp a tool bit, such as by applying pressure on the sides of the jaws or on the sides of the arms. In a preferred embodiment, this pressure is provided by tightening a set screw mounted on said arms between said ends of said arms, the set screw forming a slip fit with a first arm, and threaded into a second arm. A head of the set screw applies the desired pressure on an outside surface of the first arm when the screw is tightened into the second arm. 
         [0016]    While the tool bit is normally rectangular in cross-section, it will be clear that tool bits having other cross-sections can also be accommodated, such as by introducing a contour into the jaws where they meet the tool bit in order to hold, for example, a round bit. 
         [0017]    The preferential flexing so allowed provides advantages similar to a shrink fit holder by providing a relatively large area and secure contact with a tool bit, as compared to the bit size or holder size, but further allows the tool bit to be easily inserted into or released from the holder by simply relieving the flexure, such as by loosening a set screw. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE INVENTION 
         [0018]    An embodiment of the prior art shown in  FIG. 1  illustrates a tool bit holder of the prior art utilizing set screws in a machined groove for holding a tool bit. 
           [0019]    Another embodiment of the prior art shown in  FIG. 2  illustrates a shrink fit holder. 
           [0020]    Yet another embodiment of the prior art shown in  FIG. 3  illustrates a tool bit in a chuck. 
           [0021]    An embodiment of the invention shown in  FIG. 4  illustrates mounting a tool bit at an arbitrary angle with respect to a holder. 
           [0022]    Another embodiment of the invention shown in  FIG. 5  illustrates mounting a tool bit at an angle of substantially 90 degrees, or normal to, a holder. 
           [0023]    Yet another embodiment of the invention shown in  FIG. 6  illustrates configuring a tool bit along a long axis of a holder, by offsetting a set screw. 
           [0024]    A preferred embodiment of the invention shown in  FIG. 7  illustrates mounting a tool bit at an arbitrary angle to a long axis of a holder, such as normal to the holder, and the removal of material, such as by drilling through the holder parallel to arms of the holder, to increase flexure at a preferential point on the arms. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    In an embodiment  101  of the prior art shown in  FIG. 1 , a tool bit holder  103  having set screws  105 A and  105 B is configured to hold a tool bit  107 . Holder  103  is attached to a machine  109  (partially shown) with mounting bolt  111 . Machine  109  holds and rotates or otherwise manipulates a work piece (not shown) for tool bit  107  to operate on, or optionally rotates or otherwise manipulates tool bit  107  to operate on a work piece (not shown). The need for multiple set screws  105 A and  105 B and the small area of the contact between the screws and the tool bit results in a more complex and restrictive holder and larger tool bit than is often desired by those in the art. 
         [0026]    In another embodiment  201  of the prior art, shown in  FIG. 2 , a partial view of a tool bit holder  203  is shrink fitted around a tool bit  205 , and tool bit  205  is thereby tightly contained within holder  203 . Holder  203  is also attached to a machine (not shown) to allow tool bit  205  to operate on a work piece (not shown). The necessity for heating and cooling holder  203  to insert and remove tool bit  205  places restrictions on the shapes and sizes of tool bit  205  and holder  203 , resulting in a more complex and restrictive holder  203  than is often desired by those in the art. 
         [0027]    In yet another embodiment  301  of the prior art shown in  FIG. 3 , a partial view of a tool bit holder  303  comprising a chuck is fitted around a tool bit  305 , and tool bit  305  is thereby tightly contained within holder  303 . Holder  303  is also attached to a machine (not shown) to allow tool bit  305  to operate on a work piece (not shown). Because the chuck fingers  307  are forced inward onto the tool bit body, or shank, such as by tightening a knurl nut  309 , the tool bit  305  is normally constrained parallel to a long axis of the holder  303 , which results in a holder  303  that is more complex and restrictive than is often desired by those in the art. 
         [0028]    In an embodiment  401  of the invention shown in  FIG. 4 , a tool bit holder  403  has two jaws  405 A and  405 B cut into arms  407 A and  407 B at an arbitrary angle at first ends of arms  407 A and  407 B of the holder  403 . Holder  403 , having minimal adjustment requirements for holding a tool bit  409  (shown with dashed lines for clarity), optimally provides a relatively large area of contact to tool bit  409  compared to a size of bit  409  and holder  403 , and is thereby made compact for use in a wide variety of machine tools. It will be clear to those in the art that otherwise shaping the arms  407 A and  407 B will allow greater or lesser flexure of the arms  407 A and  407 B for greater or lesser pressure on the tool bit  409  with a given operation of a set screw  411 . It will be also be apparent to those in the art that a variety of shapes and configurations of tool bit  409  may be accommodated, such as substantially rectangular or substantially round. Jaws  405 A and  405 B are readily shaped to hold tool bit  409  at some arbitrary angle when jaws  405 A and  405 B are flexed inwardly, such as by tightening set screw  411 . Other methods of providing flexure to the arms  407 A and  407 B for holding tool bit  409  firmly while providing an arbitrary angle for tool bit  409  will be clear to those in the art. Replacement of bit  409  is readily accomplished by loosening set screw  411 , allowing holder  403  to be easily reused. The holder  403 , though simpler than most prior art holders, is easily configured for use in a wide variety of machines (not shown) and for machining a variety of work pieces (not shown). 
         [0029]    In another embodiment  501  of the invention shown in  FIG. 5 , a tool bit holder  503  has jaws  505 A and  505 B. Jaws  505 A and  505 B are on first ends of arms  507 A and  507 B of the holder  503 . Holder  503 , having minimal adjustment requirements for a tool bit  509  (shown with dashed lines for clarity), optimally provides a relatively large area of contact to tool bit  509  and is thereby made compact for use in a wide variety of machine tools (not shown). It will be apparent to those in the art that arms  507 A and  507 B may be shaped for greater flexibility. It will be also be apparent to those in the art that a variety of shapes and configurations for tool bit  509  are accommodated, such as substantially rectangular or substantially round. Jaws  505 A and  505 B firmly hold tool bit  509  when jaws  505 A and  505 B are flexed inwardly such as by tightening a set screw  511  Replacement of bit  509  is easily accomplished by loosening set screw  511 , allowing holder  503  to be easily reused. The holder  503 , being simpler than prior art holders, is easily configured for use in a wide variety of machines (not shown). 
         [0030]    In yet another embodiment  601  of the invention shown in  FIG. 6 , a tool bit holder  603  has jaws  605 A and  605 B configured to accept a tool bit  609  with the long axis of the tool bit  609  parallel to the long axis of the holder  603 . Jaws  605 A and  605 B are on ends of arms  607 A and  607 B of the holder  603 . Holder  603  having minimal adjustment requirements, optimally provides a relatively large area of contact to a tool bit  609  (shown with dashed lines for clarity) by a flexure means such as a set screw  611 , and is thereby made compact for use in a wide variety of machine tools (not shown). It will be apparent to those in the art that a variety of shapes and configurations of tool bit  609  are accommodated, such as substantially rectangular, or substantially round as shown in embodiment  601 . The jaws  605 A and  605 B securely hold tool bit  609  when jaws  605 A and  605 B are flexed inwardly such as by tightening set screw  611 . In this embodiment, to accommodate set screw  611  without interference with tool bit  609 , holder  603  is made wider to provide wider arms  607 A and  607 B, and flexibility of arms  607 A and  607 B is maintained in the correspondingly wider arms  607 A and  607 B by preferentially further thinning arms  607 A and  607 B, such as by removing material from a second end  613  of arms  607 A and  607 B. Other methods of providing additional flexure to the arms will be clear to those in the art. Replacement of bit  609  is accomplished by loosening set screw  611 , allowing holder  603  to be easily reused. Holder  603 , being simpler than prior art holders, is easily configured for use in a wide variety of machines (not shown) and for machining diverse work pieces (not shown). 
         [0031]    In a preferred embodiment  701  of the invention shown in  FIG. 7 , a tool bit holder  703  having two jaws  705 A and  705 B on first ends of arms  707 A and  707 B is shown. Holder  703 , having minimal adjustment requirements, mounts tool bit  709  at an arbitrary angle with respect to the long axis of the holder, and provides a relatively large, secure contact to a tool bit  709  (shown with dashed lines for clarity) by a flexure means such as set screw  711 . Holder  703  is thereby made optimally compact for use in a wide variety of machine tools (not shown). It will be apparent to those in the art that a variety of shapes and configurations of tool bit  709  are accommodated, such as substantially rectangular or substantially round. Jaws  705 A and  705 B hold tool bit  709  securely when jaws  705 A and  705 B are flexed inwardly such as by tightening set screw  711 . Additional flexure of the arms  707 A and  707 B is provided, such as by removing material from holder  703  at second end  713  of arms  707 A and  707 B. Replacement of bit  709  is readily accomplished by loosening set screw  711 , allowing holder  703  to be easily reused. Holder  703 , being simpler than prior art holders, is readily configured for use in a wide variety of machines (not shown) and for machining diverse work pieces (not shown).