Patent Publication Number: US-7217070-B2

Title: Deburring tool and cutting insert therefor

Description:
FIELD OF THE INVENTION 
   The present invention relates to a tool comprising a spring-loaded cutting insert for the deburring of bores. 
   BACKGROUND OF THE INVENTION 
   An example of such a deburring tool is disclosed in U.S. Pat., No. 5,755,538 in accordance with which a cutting insert with a cutting portion, loaded by a spring engaged in a rear groove of the insert, is held in a radially, outwardly sealed window in a tool holder. In the first embodiment, the insert is guided slidable in the tool holder and can, accordingly, be moved in or out by a radial sliding or swinging out of the window of the tool holder. The insert is designed with a lateral groove which is located perpendicular to its longitudinal axis. In the area of this groove, a tension pin is engaged perpendicular to the cutting portion-longitudinal axis and flush in the tool holder and is fixed by the size of the groove in the insert-sliding direction of the insert-sliding path in the window-sliding direction. The insert has only one cutting portion comprising two cutting edges. One cutting edge being operative in the forward direction and the other in the reverse direction. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention there is provided an indexable cutting insert, comprising: 
   a top surface, a bottom surface and peripheral surface therebetween; and 
   two identical opposing cutting portions, each cutting portion comprising two identical cutting edges, each cutting edge being located between a rake surface and a relief surface, the two cutting portions being reflection symmetric with respect to a major median plane of the cutting insert, the two identical cutting edges of each cutting portion being reflection symmetric with respect to a minor median plane P 2  of the cutting insert; 
   the bottom surface comprising two bottom surface sections and a single guide member therebetween, the guide member comprising at least one ridge protruding beyond the bottom surface sections in a direction away from the top surface, the guide member having a longitudinal axis directed perpendicular to the major median plane. 
   If desired, the cutting insert is provided with a through hole, passing between the top and bottom surfaces, the through hole dividing the guide member into two guide member portions, located on either side of the major median plane 
   In accordance with the present invention, the rake surface is located in the top surface and the relief surface is located in the peripheral surface of the cutting insert. 
   Preferably, the two bottom surface sections are flat and coplanar. 
   Further if desired, the cutting insert is provided with a recess in the top surface. 
   Preferably, the cutting insert is octagonally shaped in a top view of the cutting insert. 
   There is also provided in accordance with the present invention, a deburring tool comprising: 
   at one least cutting insert in accordance with the present invention; and 
   a tool body having at least one insert pocket in which the at least one cutting insert is slidably retained, the at least one insert pocket opening out to a peripheral surface of the tool body via an aperture, the at least one insert pocket comprising a slot and a guide groove with the guide member engaging the guide groove and the cutting insert located at least partially in the slot; 
   the cutting insert being slidable between a retracted position and an extended position by means of a spring which biases the cutting insert towards the extended position, wherein in the extended position a given cutting portion protrudes from the aperture beyond the peripheral surface. 
   In accordance with the present invention, the spring is a compression spring. 
   Typically, the cutting insert is held in the extended position by a holding member. 
   Preferably, in the extended position the holding member abuts a holding surface of the cutting insert. 
   If desired, the holding surface is a portion of a hole-surface of an insert through hole formed in the cutting insert. 
   Further if desired, the holding surface is a portion of a recess in the top surface. 
   In accordance with one application of the present invention, the tool body of the deburring tool comprises a shank portion of a drill. 
   In another aspect, the present invention is directed to an indexable cutting insert comprising a top surface, a bottom surface and a peripheral surface therebetween. The peripheral surface comprises two opposing end surfaces and two opposing side surfaces. The bottom surface comprises two bottom surface sections and a single, centrally located guide member therebetween, the guide member protruding from the bottom surface sections in a direction away from the top surface, the guide member having a longitudinal axis that intersects the two opposing end surfaces, in a bottom view of the cutting insert. The cutting insert also includes a first cutting portion comprising two identical cutting edges, one on either side of a first of said end surfaces; and a second cutting portion comprising two identical cutting edges, one on either side of a second of said end surfaces. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
       FIG. 1  is a side view of a deburring tool in accordance with the present invention; 
       FIG. 2  is an exploded perspective view of the deburring tool shown in  FIG. 1 ; 
       FIG. 3  is top perspective view of one embodiment of a cutting insert in accordance with the present invention; 
       FIG. 4  is bottom perspective view of the cutting insert shown in  FIG. 3 ; 
       FIG. 5  is top view of the cutting insert shown in  FIG. 3 ; 
       FIG. 6  is bottom view of the cutting insert shown in  FIG. 3 ; 
       FIG. 7  is top perspective view of an alternative embodiment of a cutting insert in accordance with the present invention; 
       FIG. 8  is bottom perspective view of the cutting insert shown in  FIG. 7 ; 
       FIG. 9  is a partial side view of the deburring tool shown in  FIG. 1  rotated through 90° with the cutting insert removed; 
       FIG. 10  is a cross-sectional view of the deburring tool shown in  FIG. 9  taken along the line X–X; 
       FIG. 11  is the view of the deburring tool shown in  FIG. 9  with the cutting insert retained in the insert pocket; 
       FIG. 12  is a cross-sectional view of the deburring tool shown in  FIG. 11  taken along the line XII–XII; and 
       FIG. 13  is a drill combined with a deburring tool in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Attention is first drawn to  FIGS. 1 and 2 , showing a deburring tool  20  in accordance with the present invention. The deburring tool  20  has a longitudinal axis of rotation A, defining a forward to rear direction, and comprises a generally cylindrical tool body  22  having an insert pocket  24  at the forward end  26  of the tool body  22  in which an indexable cutting insert  28  is slidably retained. The cutting insert  28  is shown in greater detail in  FIGS. 3 to 6  and comprises a top surface  30 , a bottom surface  32  and peripheral surface  34  extending between the top and bottom surfaces  30 ,  32 . It should be noted that directional terms appearing throughout the specification and claims, e.g. “top”, “bottom”, “upper”, “lower”, etc., are used as terms of convenience to distinguish various surfaces relative to each other. Although these terms may be meaningful with reference to particular component orientations, they are used for illustrative purposes only, and are not intended to limit the scope of the appended claims. The cutting insert  28  is octagonally shaped in top and bottom views and has two identical opposing cutting portions  36 , each cutting portion  36  comprising two identical cutting edges  38 , each cutting edge  38  being located between a rake surface  40  and a relief surface  42 . Therefore, the cutting insert  28  has a total of four cutting edges  38 , all associated with the top surface  30  of the cutting insert  28 . Each relief surface  42  is located in the peripheral surface  34  and each rake surface  40  is located in the top surface  30  and forms part of a chip groove  44  in the top surface  30 . Each chip groove  44  merges with a major top surface section  46  of the top surface  30 . The major top surface section  46  is typically flat. The two cutting portions  36  are reflection symmetric with respect to a major median plane P 1  of the cutting insert  28 , and the two identical cutting edges  38  of each cutting portion  36  are reflection symmetric about a minor median plane P 2  of the cutting insert  28 . 
   The peripheral surface  34  comprises two opposing end surfaces  48  that are reflection symmetric about the major median plane P 1 , each end surface  48  belonging to a given cutting portion  36 , and two opposing side surfaces  50  that are reflection symmetric about the minor median plane P 2 , the side surfaces  50  being located between the cutting portions  36 . 
   The bottom surface  32  of the cutting insert  28  comprises two bottom surface sections  52  and a centrally located guide member  54  therebetween. The two bottom surface sections  52  are typically flat and coplanar and parallel to the major top surface section  46  and are located on either side of the minor median plane P 2 . The guide member  54  protrudes outwardly forming a ridge, protruding beyond the bottom surface sections  52  in a direction away from the major top surface section  46  and runs parallel to the minor median plane P 2  and has a longitudinal axis B lying in the minor median plane P 2 . As seen in  FIG. 6 , the longitudinal axis B intersects the opposing end surfaces  48 , in a bottom view of the cutting insert. 
   The minor median plane P 2  constitutes a longitudinal median plane of the guide member  54 , dividing it longitudinally. Therefore, the cutting insert  28  comprises a main body portion  56  having a protruding guide member  54 . The guide member  54  comprises opposing flat abutment surfaces  58  located on either side of the minor median plane P 2 , extending outwardly away from the bottom surface sections  52  and merging with a longitudinally extending convex surface  60  that bridges between the abutment surfaces  58 . For later discussion, it is noted that (see  FIG. 6 ) each side surface  50  has a first length, L 1 , and the guide member  54  has a second length, L 2 ; each length being measured in the direction of the longitudinal axis B of the guide member  54 , the first length, L 1 , being smaller than the second length, L 2 . 
   An insert through hole  62 , passing between the top and bottom surfaces  30 ,  32  divides the guide member  54  into two guide member portions  54 ′, that is, divides the ridge into two ridges, located on either side of the major median plane P 1 . The insert through hole  62  has a hole-surface  64  forming a holding surface  65  of the cutting insert  28 . In an alternative embodiment, shown in  FIGS. 7 and 8 , instead of a through hole  62 , the cutting insert  28  is provided with a recess  66  in the top surface  30 . The recess  66  comprises a recess side surface  68  extending inwardly from the top surface  30  of the cutting insert  28  to a bottom surface  70  of the recess  66 . In this embodiment, the recess side surface  68  forms the holding surface  65 . As can be seen in  FIG. 8 , in this embodiment, the guide member  54  comprises a single uninterrupted ridge. 
   Attention is now turned to  FIGS. 9 and 10 . The insert pocket  24  has the general form of a T-shaped slot comprising a generally rectangular slot  72  (the “arms” of the “T”) and a guide groove  74  (the “foot” of the “T”). The generally rectangular slot  72  has a first width, W 1 , and the guide groove  74  has a second width, W 2 , the two widths being measured in the direction of the longitudinal axis of rotation A of the deburring tool  20 ; where the first width, W 1 , is greater than the second width, W 2 . The insert pocket  24  opens out to a peripheral surface  76  of the tool body  22  via a first aperture  78 . The insert pocket  24  extends from the peripheral surface  76  of the tool body  22  inwardly in a generally radial direction relative to the axis of rotation A of the deburring tool  20 . In the cross section shown in  FIG. 10 , the peripheral surface  76  of the tool body  22  is generally circular, having a given radius, R, with the axis of rotation A being located at the origin, O, of the circle. The generally rectangular slot  72  comprises opposing upper and lower walls  80 ,  82  joined by sidewalls  84 . The lower wall  82  comprises two lower wall sections  86  that are parallel to the upper wall  80 . The guide groove  74  is located between the two lower wall sections  86  and comprises opposing flat groove support surfaces  88  extending from respective lower wall sections  86  in a direction away from the upper wall  80  and merging with a longitudinally extending concave surface  90  that defines a longitudinal axis C of the guide groove  74  and that bridges between the two groove support surfaces  88 . With reference to  FIG. 9 , the generally rectangular slot  72  has a first width, W 1 , and the guide groove  74  has a second width, W 2 ; each width being measured in the direction of the rotational axis A of the deburring tool  20 , the first width, W 1 , being greater than the second width, W 2 . 
   Two bores communicate with the insert pocket  24 . A major bore  92  extends from a second aperture  94  in the peripheral surface  76  of the tool body  22  to the insert pocket  24 . The second aperture  94  of the major bore  92  is substantially diametrically opposite the first aperture  78  of the insert pocket  24 . The major bore  92  has a longitudinal axis D that is perpendicular to the axis of rotation A of the deburring tool  20 . The axis of rotation A of the deburring tool  20  passes through the major bore  92  which communicates with insert pocket  24 . A threaded minor bore  96  extends from a third aperture  98  in the peripheral surface  76  of the tool body  22  to the insert pocket  24 . The minor bore  96  has a longitudinal axis E that makes an acute angle with the longitudinal axis D of the major bore  92 . 
   Attention is now turned to  FIGS. 11 and 12 . The cutting insert  28  is slidably retained in the insert pocket  24  with the guide member  54  engaging the guide groove  74  and the main body portion  56  of the cutting insert  28  located in the generally rectangular slot  72 . At the rear end of the major bore  92 , in the vicinity of the second aperture  94 , the major bore  92  has a threaded portion  100  in which a first screw  102  is threaded. A spring  104 , such as a helical compression spring, is located in the major bore  92  between the first screw  102  and the cutting insert  28  for urging the cutting insert  28  radially outwardly through the first aperture  78  at a predetermined pressure. The spring  104  abuts the inner end surface  48 ′ of the cutting insert  28 . The inner end surface  48 ′ being the end surface  48  facing inwards into the insert pocket  24 , as opposed to the outer end surface  48 ″ that faces outwards in a direction away from the insert pocket  24 . The pressure applied by the spring  104  can be adjusted by adjusting the location of the first screw  102 , which also acts as a plug to prevent the spring  104  from exiting the major bore  92  through the second aperture  94 . 
   As can be seen in  FIG. 10 , the major bore  92  and the insert pocket  24  are not fully aligned so that the forward end of the major bore  92 , adjacent the insert pocket  24 , is partially closed forming a spring retaining surface  106 . Therefore, even when the cutting insert  28  is removed from the insert pocket  24 , the spring  104  is held in position between the spring retaining surface  106  and the first screw  102 . The cutting insert  28  is held in an extended position, as shown in  FIG. 1 , with one of the cutting portions  36  protruding from the first aperture  78 , by means of a holding member  108  which prevents the cutting insert  28  from being completely pushed out of the insert pocket  24  by the spring  104 . In the embodiment shown, the holding member  108  is a second screw threaded in the minor bore  96 . 
   To retain the cutting insert  28  in the extended position, the second screw  108  is set in a first position with its forward end protruding beyond the forward end  114  of the minor bore  96  and located partially within the insert through hole  62  (or within the recess  66 , for the cutting insert  28  shown in  FIGS. 7 and 8 ) so that it engages the holding surface  65  of the cutting insert  28 . The cutting insert  28  can be urged radially inwardly into the insert pocket  24  to a retracted position by applying a radially inwardly directed force to the outer end surface  48 ″ of the cutting insert  28 . To remove the cutting insert  28  from the insert pocket  24 , in order to index or replace it, the second screw  108  is set in a second position by unscrewing it until its forward end  112  is withdrawn from the insert through hole  62  (or the recess  66 ), thereby enabling the cutting insert  28  to slide freely out of the insert pocket  24 . During deburring operations in which the cutting insert  28  slides between the retracted and extended positions, the second screw  108  is maintained in the first position. 
   In accordance with the present invention, the sliding movement of the cutting insert  28  between the retracted and extended positions is performed mainly by the sliding of the guide member  54  in the guide groove  74 . This arrangement has a number of advantages. It enables a compact cutting insert design without compromising free sliding movement of the cutting insert  28 . In other words the first length, L 1 , of the side surfaces  50  of the cutting insert  28  can be made relatively small in relation to the first width, W 1 , of the generally rectangular slot  72 . 
   If the cutting insert  28  were to comprise only the main body portion  56  without the protruding guide member  54 , then the sliding movement of the cutting insert  28  would take place through sliding abutment of the side surfaces  50  of the cutting insert  28  with the sidewalls  84  of the generally rectangular slot  72 . In accordance with the present invention, the first length, L 1 , of the side surfaces  50  of the cutting insert  28  is less than the first width, W 1 , of the generally rectangular slot  72 . In accordance with a non-binding example, the first width, W 1 , is five to six times greater than the first length, L 1 . This being the case, the cutting insert  28  can easily get wedged in the generally rectangular slot  72 . To avoid wedging, the first length, L 1 , would have to be larger than the first width, W 1 . Due to requirement of four cutting edges  38  and due to the constraint of reflection symmetry with respect to the major median plane P 1  of the cutting insert  28  (i.e., the cutting insert  28  is a “double ended” cutting insert with a cutting portion  36  at each end, each cutting portion  36  having two cutting edges  38 ), the cutting insert  28  is constrained to have the octagonal form shown in  FIGS. 5 and 6 , and any attempt to design the first length, L 1 , to be larger than the first width, W 1 , would create an impractically large cutting insert. 
   By transferring the sliding movement of the cutting insert  28  to the sliding of the guide member  54  within the guide groove  74 , the dimensions that determine the possibility of wedging are the second length, L 2 , of the guide member  54  and the second width, W 2 , of the guide groove  74 . In accordance with a non-binding example, the second length, L 2 , is about three times greater than the second width, W 2 . Choosing the second length, L 2 , to be greater than the second width, W 2 , prevents wedging of the guide member  54  in the guide groove  74  and therefore prevents wedging of the cutting insert  28  in the insert pocket  24 . 
   Clearly, by transferring the sliding movement of the cutting insert  28  from the sliding contact between the main body portion  56  of the cutting insert  28  and the generally rectangular slot  72  portion of the insert pocket  24  to the sliding contact of the guide member  54  within the guide groove  74 , the wedging constraint is decoupled from the geometry of the main body portion  56  of the cutting insert  28 , thus enabling the design of a compact “double-ended” cutting insert. Moreover, by transferring the sliding movement of the cutting insert  28  to the sliding of the guide member  54  within the guide groove  74 , neither the sidewalls  84  of the insert pocket  24  nor the side surfaces  50  of the cutting insert  28  have to be manufactured with high accuracy, since they do not play an essential role in the sliding movement of the cutting insert  28 . 
   Since sliding movement of the cutting insert  28  is carried out by the sliding of the guide member  54  within the guide groove  74 , there is a designed clearance between the insert pocket sidewalls  84  and the cutting insert side surfaces  50  ensuring that there will be no contact between these surfaces. Any contact between these surfaces could lead to wedging of the insert in the rectangular slot  72 . There is also a designed clearance between the lower wall sections  86  of the insert pocket  24  and the bottom surface sections  52  of the cutting insert  28  and between the upper wall  80  of the insert pocket  24  and the major top surface section  46  of the cutting insert  28 . There is also a designed clearance between the concave surface  90  of the guide groove  74  and the convex surface  60  of the guide member  54 . The only designed contact during sliding movement is between the groove support surfaces  88  of the guide groove  74  and the abutment surfaces  58  of the guide member  54 . However, due to cutting forces acting on the cutting edges  38  during the deburring of bores, or due to forces acting on the cutting insert  28  as the forward end  26  of the deburring tool  20  rotates and passes through a bore, there will be a certain amount of uncontrollable contact between the lower wall sections  86  of the insert pocket  24  and the bottom surface sections  52  of the cutting insert  28  and also between the upper wall  80  of the insert pocket  24  and the major top surface section  46  of the cutting insert  28 . However, these forms of uncontrollable contact cannot give rise to wedging of the cutting insert  28  due to the favorable relative dimensions of the members involved in the above-described uncontrollable contact. 
   It will be appreciated from  FIGS. 2 ,  11  and  12  that the “deburring mechanism”, of the deburring tool  20  of the present invention, that is, the cutting insert  28 , spring  104  and first and second screws  102 ,  108  described hereinabove, is localized in a small region of the tool body  22 . It will be clear to the skilled person that it is a simple matter of design to locate the “deburring mechanism” in any required tool body by forming the insert pocket  24 , and minor and major bores  96 ,  92  in the tool body, in much the manner as in the deburring tool  20  described herein above.  FIG. 13  shows a drill  116  in which the “deburring mechanism” of the present invention has been incorporated, showing the cutting insert  28  in the extended position. 
   Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the invention as hereinafter claimed.