Abstract:
A separable rotary cutting tool is disclosed. The tool comprises a shank and a head. The shank has a receiver comprised of a shank guide at a trailing end of the receiver, opposing shank drive keys at a leading end of the receiver, and a shank locator located axially between the shank guide and the shank drive keys. The shank drive keys each comprises an axially extending shank drive key radial stop surface that is disposed at an angle relative to a plane extending through a central axis of the receiver. The head has a connector comprised of a head guide at a trailing end of the connector, opposing head drive keys at a leading end of the connector, and a head locator located axially between the head guide and the head drive keys. The head drive keys each comprises an axially extending head drive key radial stop surface that is disposed at an angle relative to a plane extending through a central axis of the connector. Each shank drive key radial stop surface is adapted to angularly align with a corresponding head drive key radial stop surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a cutting tool and is specifically concerned with a separable end working or rotary cutting tool that is adapted to rotate to cut a stationary workpiece or that may cut a rotating work piece when stationary. 
     2. Description of the Related Art 
     Separable rotary cutting tools are known in the prior art. One such tool is described in U.S. Pat. No. 5,904,455, to Krenzer et al. This tool is described as a drill comprising an insert and body. The drill has a locating feature comprised of a groove in the body defined by two groove flanks and mating side faces on the head. The groove is slightly smaller than the insert. This results in a positive location and an interference fit between the insert and body. In operation, the insert is forced in an axial direction in the groove or drawn into the groove with a screw. In absence of a screw, the insert is predisposed to be axially displaced and thus can become axially dislodged from the groove. On the other hand, the use of a screw would require the physical size of the tool to be large enough to accompany the screw. 
     Other separable rotary cutting tools are described in U.S. Pat. Nos. 6,059,492 and 5,957,631, to Hecht. Both patents describe an insert and body joint. One embodiment includes two base surfaces, two torque transmission walls, and two fixation walls. The transmission and fixation walls are located between the base surfaces and adjacent to one another. The transmission walls are spaced 180 degrees apart as are the fixation walls. The fixation walls are conical or dovetail in shape and expand in a direction away from the cutting tip of the insert. The base surfaces are transverse or perpendicular from the axis of the body. A front base surface is used as the axial stop. The torque transmission walls are defined as extending in radial directions. The fixation walls are defined as having radial dimensions substantially less than the cutting diameter. Hecht also describes an embodiment comprised of a pair of base surfaces, one of which acts as an axial stop. Torque transmission walls and fixation walls are located between these base surfaces. The torque transmission walls are transverse to the axis of the fixation walls. The length of the fixation and transmission walls is about the same. The fixation walls are located further away from the tool tip than the torque transmission walls. Both of these embodiments described by Hecht have a reduced risk of becoming axially dislodged because each includes conical or dovetail shaped fixation walls. However, such walls are difficult to machine because the walls expand in a direction away from the cutting tip of the insert and into the body. 
     Clearly, there is a need for a separable rotary cutting tool that is not prone to inadvertent axial separation. Ideally, such a tool would be easier to manufacture and thus minimize the cost of the tool. Finally, it would be desirable if such a tool could be easily assembled. 
     SUMMARY OF THE INVENTION 
     Generally speaking, the invention is directed to a rotary cutting tool that overcomes the aforementioned shortcomings associated with the prior art. To this end, the tool of the invention comprises a shank and a head. The shank has a receiver comprised of a shank guide at a trailing end of the receiver, opposing shank drive keys at a leading end of the receiver, and a shank locator located axially between the shank guide and the shank drive keys. The shank drive keys each comprises an axially extending shank drive key radial stop surface that is disposed at an angle relative to a plane extending through a central axis of the receiver. The head has a connector comprised of a head guide at a trailing end of the connector, opposing head drive keys at a leading end of the connector, and a head locator located axially between the head guide and the head drive keys. The head drive keys each comprises an axially extending head drive key radial stop surface that is disposed at an angle relative to a plane extending through a central axis of the connector. Each shank drive key radial stop surface is adapted to angularly align with a corresponding head drive key radial stop surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the present invention, as well as the advantages derived therefrom, will become clear from the following detailed description made with reference to the drawings in which: 
     FIG. 1 is an exploded perspective view of a rotary cutting tool of the invention; 
     FIG. 2 is a perspective view of the rotary cutting tool shown in FIG. 1 partially assembled; 
     FIG. 3 is a perspective view of the rotary cutting tool shown in FIGS. 1 and 2 completely assembled; 
     FIG. 4 is an exploded side elevational view of the rotary cutting tool shown in FIGS. 1-3; 
     FIG. 5 is a sectional view in elevation of a rotary cutting tool of the invention; 
     FIG. 6 is a cross-sectional view of the rotary cutting tool taken along the line  6 — 6  in FIG. 5; 
     FIG. 7 is a sectional view in elevation of another rotary cutting tool of the invention; 
     FIG. 8 is a cross-sectional view of the rotary cutting tool taken along the line  8 — 8  in FIG. 7; 
     FIG. 9 is a sectional view in elevation of another rotary cutting tool of the invention; 
     FIG. 10 is a cross-sectional view of the rotary cutting tool taken along the line  10 — 10  in FIG. 9; 
     FIG. 11 is a sectional view in elevation of another rotary cutting tool of the invention; 
     FIG. 12 is a cross-sectional view of the rotary cutting tool taken along the line  12 — 12  in FIG. 11; 
     FIG. 13 is a sectional view in elevation of another rotary cutting tool of the invention; 
     FIG. 14 is a cross-sectional view of the rotary cutting tool taken along the line  14 — 14  in FIG. 13; 
     FIG. 15 is a sectional view in elevation of another rotary cutting tool of the invention; and 
     FIG. 16 is a cross-sectional view of the rotary cutting tool taken along the line  16 — 16  in FIG. 15; and 
     FIG. 17 is a sectional view of the taken along the line  17 — 17  in FIG.  16 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference now to FIGS. 1-6, wherein like numerals designate like components throughout all of the several Figures, there is illustrated a rotary drill or tool  10  having a leading end, generally indicated at  12 , and the trailing end, generally indicated at  14 . The tool  10  is comprised of a body or shank  16  and an insert or head  18 . The shank  16  has a receiver or receiving portion  20  at its leading end and a shank  22  at its trailing end. The head  18  has a cutting tip  24  at its leading end and a connector or mounting portion  26  at its trailing end. The mounting portion  26  cooperates with the receiving portion  20  to couple the head  18  to the shank  16 . 
     The receiving portion  20  is comprised of a guide or shank guide portion  28 , a locator or shank locating portion  30  at the leading end of the shank guide portion  28 , and diametrically disposed torque or drive keys  32  (also referred to as shank drive keys) at the leading end of the shank locating portion  30 . The mounting portion  26  is comprised of diametrically disposed torque or drive keys  34  (also referred to as head drive keys), a locator or head locating portion  36  at the trailing end of the head drive keys  34 , and a guide or head guide portion  38  at the trailing end of the head locating portion  36 . 
     The mounting portion  26  is adapted to be axially inserted into the receiving portion  20  until the head guide portion  38  engages the shank guide portion  28 . Upon twisting the head  18 , the locating portions  30  and  36  engage one another to provide an interference fit. The drive keys  32  and  34  radially engage one another to function as cooperating radial stop surfaces and drive surfaces during the operation of the tool  10 . 
     The shank guide portion  28  is preferably defined in part by an inner cylindrical surface, such as the inner guide surface  40  shown. The inner guide surface  40  is preferably a generally straight cylindrical surface having a shank guide diameter D 1  (shown in FIG.  4 ). The shank guide portion  28  may also be provided with a generally spherical radial inner radial surface  42  adjacent its trailing end, as shown in FIGS. 1-6, or a conical inner radial surface  44 , as shown in FIG.  6 . In a preferred embodiment of the invention, the diameter of a conical inner radial surface  44  increases toward the leading end of the shank guide portion  28 . The trailing end of the shank guide portion  28  may be defined by a first radially extending surface, which may also be referred to a radially extending shank guide surface. The first radially extending surface may be an arcuate or spherical surface  46 , which may coexist with the spherical inner radial surface  42 , or a generally flat surface  48 , as shown in FIGS. 7,  9 ,  11 ,  13 , and  15 , which extends generally perpendicular to the axis A 1  of the shank  16 . The spherical and conical inner radial surfaces  42  and  44  may function as axial stop surfaces, as shown in FIGS. 5 and 7. This holds true even if the radially extending surface is perpendicular to the shank axis A 1 , as shown in FIGS. 9,  11 ,  13 , and  15 . 
     The shank locating portion  30  is preferably defined by a cylindrical bore. The cylindrical bore may be a generally straight cylindrical bore defined by generally straight cylindrical inner locating surfaces  50 , as shown in FIGS. 7,  9 ,  11 ,  13 , and  15 , or a tapered bore defined by tapered inner locating surfaces  52 , as shown in FIG.  5 . The distance between the generally straight cylindrical inner locating surfaces  50 , or the smallest distance between the tapered inner locating surfaces  52 , is measured by a shank locator or locating diameter D 2  (shown in FIG.  4 ). 
     The surfaces defining the shank guide and locating portions  28  and  30  may be joined by a transitional surface  54 . In a preferred embodiment of the invention, the transitional surface  54  is inclined obliquely relative to the central axis A 1  of the shank  16  and faces generally longitudinally toward the leading end of the receiving portion  20 . The transitional surface  54  accommodates for the difference between the shank guide and locating diameters D 1  and D 2  (shown in FIG.  4 ). 
     The locating portion  30  terminates at a second radially extending surface located at the leading end of the locating portion  30 . The second radially extending surface may be defined by a pair of radially extending surfaces  56 , which extend perpendicularly to the central axis A 1  of the shank  16 , as shown in FIGS. 5,  7 ,  9 ,  13 , and  15 , or radially extending surfaces  58 , which are inclined obliquely relative to the central axis A 1  and face generally longitudinally toward the leading end of the shank  16 , as shown in FIG.  11 . The second radially extending surface may function as an axial stop surface in the place of the first radially extending surface described above. 
     The shank drive keys  32  are located at the leading end of the shank locating portion  30 . In a preferred embodiment of the invention, the shank drive keys  32  have an axial profile dimension D 3  (shown in FIG. 5) and a radial profile dimension D 4  (shown in FIG.  4 ). The radial profile dimension D 4  is preferably smaller than the axial profile dimension D 3  to enable the shank drive keys  32  to be closely aligned with the central axis A 1  of the shank  16 . The shank drive keys  32  are defined by an inner shank drive key surface  60 , an outer shank drive key surface  62 , a pair of circumferentially spaced, axially extending shank drive key surfaces  66  and  64 , and a radially extending shank drive key surface, which may also be referred to as a third radially extending surface  68 . The third radially extending surface  68  extends in a first direction between the inner and outer shank drive key surfaces  60  and  62  and in a second direction between the circumferentially spaced, axially extending shank drive key surfaces  66  and  64 , all shown in FIG.  1 . The inner shank drive key surface  60  may be coexistent with the inner shank locating surface. Similarly, the outer shank drive key surface  62  may be coexistent with an outer curved surface  70  of the shank  16 . One of the circumferentially spaced, axially extending shank drive key surfaces  66  may define a flute, or a flute portion, through which particles of a workpiece may be discharged when the tool  10  is in use. The other circumferentially spaced, axially extending shank drive key surface  64  functions as a shank drive key radial stop surface, which is preferably disposed at an angle α (shown in FIG. 5) relative to a plane extending through the axis A 1  of the shank  16  and facing generally longitudinally toward the trailing end of the shank  16 . In a preferred embodiment of the invention, the angle α is 15 degrees. The shank drive key radial stop surfaces  64  may be perpendicular relative to the inner and outer shank drive key surfaces  60  and  62 , as shown in FIGS. 5,  9 ,  11 ,  13 , and  15 . Alternatively, shank drive key radial stop surfaces  72  may be provided which are inclined relative to the inner and outer shank drive key surfaces  60  and  62 , as shown in FIG.  7 . The third radially extending surface  68  may be perpendicular relative to the central axis A 1  of the shank  16 , as shown in FIGS. 5,  7 ,  11 , and  13 . Alternatively, a third radially extending surface  74  may be provided which is inclined relative to the central axis A 1 , as shown in FIGS. 9 and 15. Inclined axially or radially extending surfaces may reduce the risk that the shank drive keys  32  will spread apart. It should be appreciated that the third radially extending surface  68  may function as an axial stop surface in the place of the first and second radially extending surfaces described above. 
     The head guide portion  38  is preferably defined in part by an outer cylindrical surface, such as the outer guide surface  78  shown. The outer guide surface  78  is preferably a straight cylindrical surface having a head guide diameter D 5  (shown in FIGS.  4  and  6 ). The head guide portion  38  may also include a generally spherical outer radial surface  82 , as shown in FIG. 5, adjacent its trailing end, or a conical outer radial surface  84 , as shown in FIG.  7 . In a preferred embodiment of the invention, the diameter of the conical surface  84  increases toward the leading end of the head guide portion  38 . The trailing end of the head guide portion  38  may be defined by a first radially extending surface, which may also be referred to as a radially extending head guide surface. The first radially extending surface maybe an arcuate or spherical radial surface, which may coexist with the spherical outer radial surface  82 , or a generally flat surface  76 , as shown in FIGS. 7,  9 ,  11 ,  13 , and  15 , which extends generally perpendicularly to the axis A 2  of the head  18 . The head guide portion  38  is adapted to engage the shank guide portion  28  and functions to stabilize the shank  16  and head  18  in radial direction when coupling the head  18  to the shank  16 . 
     The head locating portion  36  is defined by an outer surface. The outer surface may be a generally straight cylindrical surface outer locating surface  86 , as shown in FIGS. 7,  9 ,  11 ,  13 , and  15 . Alternatively, the outer surface may be a tapered outer locating surface  88 , as shown in FIG.  5 . The largest diameter of the outer surface is defined by the head locator or locating diameter D 6  (shown in FIGS. 4 and 6) and is slightly larger than the shank locating diameter D 2  (shown in FIG.  4 ). Consequently, the head locating portion  36  must be forced into the shank locating portion  30 , causing the shank locating portion  30  to deflect outward, resulting in an interference fit between the two locating portions  30  and  36 . It should be appreciated that a tapered outer locating surface  88  having a larger diameter at its leading end insures contact substantially with the entire shank locating portion  30 , even when the shank locating portion  30  deflects outward. The increase in diameter D 6  is preferably measured by an angle of inclination β (shown in FIG. 5) in the tapered outer locating surface  88  of less than one degree relative to a plane P 1  extending generally parallel to the central axis A 1 . 
     The head locating portion  36  preferably has an axially extending angular lead surface  90  which provides clearance for an approaching portion of the head location portion  36  upon rotating the head  18  to couple the head  18  to the shank  16 . The angle of the axially extending or angular lead surface  90  may vary. The angle is preferably in a range between 2 degrees and 20 degrees. For example, the angle θ 1  of the lead surface  90  shown in FIG. 14 is 15 degrees relative to a line tangent to the outer locating surface at the intersection of the outer locating surface and the lead surface  90 . The angle θ 2  of the lead surface  90  shown in FIG. 6,  8 ,  10 ,  12 , and  16  is 20 degrees. 
     In the preferred embodiment of the invention, the head locating portion  36  has a larger diameter D 6  (shown in FIGS. 4 and 6) that is more than half the cutting diameter D 7  of the tool  10  (shown in FIGS.  4  and  5 ). This is to establish a relationship between the locating diameter and the depth of the flute to insure proper assembly of the shank  16  and head  18 . Moreover, the length of the head locating portion  36  is slightly less or more than the head locating diameter D 6  (shown in FIGS.  4  and  6 ). For example, a range for the length of the head locating portion  36  may be ¾ to 2 times the head locating diameter D 6 . The length of the head locating portion  36  would be determined by the size of the tool  10 . Larger tools would be in the ¾ to 1 ¼ range while smaller diameters could be up to 2 times the diameter. 
     Similar to the receiving portion  20  set forth above, the mounting portion  26  may be provided with a transitional surface  92 . In a preferred embodiment of the invention, the transitional surface  92  is inclined obliquely relative to the central axis A 2  of the head  18  and faces generally longitudinally toward the trailing end of the mounting portion  26 . The transitional surface  92  accommodates for the difference between the head guide and locating diameters D 5  and D 6  (shown in FIGS.  4  and  6 ). 
     The head locating portion  36  terminates at a second radially extending surface located at the leading end of the head locating portion  36 . The second radially extending surface may be defined by a pair of radially extending surfaces  94 , which extend perpendicularly to the central axis A 2  of the head  18 , as shown in FIGS. 5,  7 ,  9 ,  13 , and  15 , or radially extending surfaces  96 , which are inclined obliquely relative to the central axis A 2  and face generally longitudinally toward the trailing end of the head  18 , as shown in FIG.  11 . 
     The head drive keys  34  are located at the leading end of the head locating portion  36 . In a preferred embodiment of the invention, the head drive keys  34  have an axial profile dimension D 8  and a radial profile dimension D 9  (shown in FIG.  4 ). The radial profile dimension D 9  is preferably less than the head locating diameter D 6  (shown in FIGS.  4  and  6 ). Longer head drive keys  34  may result in a weaker connection between the shank  16  and the head  18 . Moreover, the radial profile dimension D 9  is preferably smaller than the axial profile dimension D 8  to enable the head drive keys  34  to be closely aligned with central axis A 2  of the head  18 . The head drive keys  34  are defined by an outer head drive key surface  100 , circumferentially spaced, axially extending head drive key surfaces  102  and  104 , and a radially extending head drive key surface, which may be referred to as a third radially extending surface  106  (all shown in FIG.  1 ). One of the axially extending head drive key surfaces  102  may define a portion of a flute. The other axially extending head drive key surface  104  functions as a head drive key radial stop surface, which is preferably disposed at an angle a relative to a plane P 1  extending through a central axis A 2  of the head  18  and facing generally longitudinally toward the leading end of the head  18 , as shown in FIG.  5 . In a preferred embodiment of the invention, the angle α is 15 degrees. The head drive key radial stop surfaces  104  may be perpendicular relative to the outer surface  100 , as shown in FIGS. 5,  9 ,  11 ,  13 , and  15 . Alternatively, head drive key radial stop surfaces  108  may be provided which are inclined relative to the outer surface  100 , as shown in FIG.  7 . The head drive key radial stop surfaces  102  and  108  are adapted to fit in angular alignment with the shank drive key radial stop surfaces  64  and  72 . The third radial surface  106  may be perpendicular relative to the central axis A 2 . Alternatively, a third radially extending surface  106  may be provided which is inclined relative to the central axis A 2 , as shown in FIGS. 9,  15 , and  17 . 
     In operation, the mounting portion  26  is adapted to be inserted axially into the receiving portion  20 . Subsequently, the head  18  is twisted into a final radial location determined by the engagement of the shank drive keys  32  and  34 . 
     It should be noted that the locating diameters D 2  and D 6  (shown in FIG. 4) must be larger than the guide diameters D 1  and D 5  (also shown in FIG.  4 ). Moreover, the guide diameters D 1  and D 5  should be sufficiently small enough to require the head guide portion  38  to be inserted axially into the shank guide portion  28 . In this way, the guide portions  38  and  28  cooperatively act as a guide during rotation of the head  18 . The drill flutes should be dimensioned so that the head guide portion  38  does not escape in the radial direction from the shank guide portion  28 . By providing locating diameters D 2  and D 6  that are larger than guide diameters D 1  and D 5 , the drill flutes may be dimensioned large enough to allow the mounting portion  26  to be inserted into the receiving portion  20  within the flutes. The head  18  may then be rotated 90 degrees with an assembly tool (not shown) that serves as a radial guide for the leading end of the shank  16  and the head  18 . 
     The angular alignment of the drive key radial stop surfaces  64  and  72  provides retention of the head  18  during removal of the tool  10  from a work piece (not shown). Rotary cutting tools tend to drag during retraction. This drag creates a torsional moment on the head  18  as well as a force to separate the head  18  from the shank  16 . The torsional moment, combined with the angular alignment of the drive keys  32  and  34 , make it difficult for the head  18  to separate from the shank  16 . 
     It should be appreciated that the shank  16  may include a mounting portion, such as that shown and described above, and the head  18  may include a receiving portion. 
     While this invention has been described with respect to several preferred embodiments, various modifications and additions will become apparent to persons of ordinary skill in the art. All such variations, modifications, and variations are intended to be encompassed within the scope of this patent, which is limited only by the claims appended hereto.