Abstract:
A cutting tool assembly ( 10 ) having a body portion ( 12 ) and at least one cutting portion ( 14 ), the at least one cutting portion ( 14 ) having a clamping portion ( 16 ), an insert retaining member ( 18 ), a precisely located cutting insert ( 20 ) and a securing member ( 22 ) for ensuring that precise location of the cutting insert is maintained. If the insert-retaining member becomes damaged due to contact with a workpiece it can be removed from the cutting tool assembly and replaced.

Description:
FIELD OF THE INVENTION 
     This invention relates to a cutting tool assembly having a resilient clamping mechanism and a replaceable insert retention member. 
     BACKGROUND OF THE INVENTION 
     Cutting tools employing a resilient clamping mechanism for clamping cutting inserts are generally of relatively narrow thickness. For example, cutting operations such as grooving and parting off can be performed by a cutting insert retained in an insert pocket located between the clamping surfaces of upper and lower jaws of a relatively narrow holder blade. The holder blade is, in turn, generally clamped in a blade-retaining block. The holder blade is generally provided with a suitably designed opening, in the vicinity of the insert pocket whereby a relatively narrow bridging portion is formed enabling a limited degree of resilient displacement of one of the holder blade&#39;s jaws relative to the other. Generally, the lower jaw is rigid and the upper jaw is resiliently displaceable. The opening can be of the form of an aperture,or a slot, or a slot terminating in an aperture. Examples of such cutting tools are disclosed in U.S. Pat. No 3,785,021 and U.S. Pat. No 4,580,930. A rotary slot-cutting tool employing a resilient insert clamping mechanism is disclosed in U.S. Pat. No 5,059,068. The cutter body is disc-shaped and of relatively narrow thickness, with cutting insert pockets located around its periphery. As with the holder blade, an insert pocket of a rotary slot-cutting tool has two jaws between which an insert is clamped by means of the resilient force resulting from the bending of the clamping jaw. 
     Whether the cutting tool is a holder blade or a rotary slot cutting tool, the bending of the clamping jaw is obtained by manufacturing the insert pocket such that the distance between the clamping surfaces of the jaws is smaller than the height of the portion of the insert located between the clamping surfaces. Consequently, when an insert is located in the insert pocket, the clamping jaw is held in a bent position creating an elastic force by means of which the insert is clamped in position. 
     An example of a well-known problem with cutting tools of the type described above is that a forward region of the insert pocket can come into contact with the workpiece and consequently become damaged. This can be particularly problematic with rotary slot cutting tools, where the damaging of one or two insert pockets requires the replacing of the whole cutting tool. A solution to this problem is proposed in U.S. Pat. No. 4,604,004 in which there is disclosed a cutting tool assembly having a hard, wear resistant insert, a shim and a blade body. The shim has a recess that tapers towards its open end to springingly hold the insert. The blade body has a downwardly and rearwardly extending recess that tapers toward the blade body to wedgingly hold the shim and insert. Assembly of the cutting tool assembly is accomplished by first inserting the insert into the shim recess, after which the shim, with the insert mounted therein, is inserted into the blade body recess. As the cutting tool assembly is contacted with a workpiece, the insert and the shim are wedged further into the blade body recess, thereby increasing the positive retention of the insert and the shim. After a period of use, the insert and shim are removed from the body so that the insert can be replaced. The shim is removed from the blade body by inserting a screwdriver in a gap between the blade body and the shim and applying a prying action to the screwdriver. The insert is removed from the shim by inserting a screwdriver into a notch of the shim and then twisting the screwdriver. 
     A disadvantage of the cutting tool assembly disclosed in the &#39;004 patent is that after assembling the cutting tool assembly, the cutting edge of the cutting insert is not precisely located. As pointed out in the &#39;004 patent, the insert and the shim are further wedged into the blade body recess as the cutting tool assembly is contacted with a workpiece. This situation is particularly disadvantageous for rotary slot cutting tools where there are a plurality of cutting inserts spaced about the periphery of the tool and imprecise location of the cutting edges of the cutting inserts results in inefficient cutting operations in which some of the inserts participate more in the cutting operation than others. 
     In the &#39;004 Patent the member in which the cutting insert is mounted is referred to as a “shim”. In the following description and claims the member in which the cutting insert is mounted will be referred to as an “insert retention member”. 
     It is an object of the present invention to provide a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that does not suffer from the above mentioned disadvantage. 
     A further disadvantage of the cutting tool assembly disclosed in the &#39;004 patent is that in order to remove a retained cutting insert, the shim has to be removed from the blade body recess. It is a further object of the present invention to provide an embodiment of a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that does not require the removal of the insert retention member in order to remove a retained cutting insert. 
     A yet further disadvantage of the cutting tool assembly disclosed in the &#39;004 patent is that, the shim is not secured to the blade body. This can be especially problematic if the shim is used in a rotary slot-cutting tool, since there is nothing to prevent the shim from becoming displaced during a slotting operation. It is yet a further object of the present invention to provide an embodiment of a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that is firmly secured to the body of the rotary slot cutting tool. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided a cutting tool assembly ( 10 ), comprising a body portion ( 12 ) and at least one cutting portion ( 14 ), the at least one cutting portion ( 14 ) comprising a clamping portion ( 16 ), an insert retaining member ( 18 ) and a cutting insert ( 20 ); the clamping portion ( 16 ) comprising: 
     a base jaw ( 26 ) having an upper side ( 28 ) constituting a first clamping surface; 
     a clamping jaw ( 30 ) having an upper side and a lower side ( 32 ), the lower side ( 32 ) constituting a second clamping surface, the base jaw ( 26 ) and the clamping jaw ( 30 ) having a gap ( 34 ) between them for receiving the insert retaining member ( 18 ); and 
     a first location surface ( 44 ) for fixing the location of the insert retaining member ( 18 ); the insert retaining member ( 18 ) comprising: 
     a base jaw ( 48 ) having a lower side ( 54 ) constituting a first clamping abutment surface and a clamping jaw ( 50 ) having an upper side ( 56 ) constituting a second clamping abutment surface, the base jaw ( 48 ) and the clamping jaw ( 50 ) defining therebetween an insert pocket ( 52 ) for resiliently receiving the cutting insert ( 20 ); and 
     a second location surface ( 60 ) capable of abutting the first location surface ( 44 ) for precisely locating the insert locating member ( 18 ) in the gap ( 34 ). 
     Preferably, the gap ( 34 ) is further provided with a slot ( 36 ) extending in a generally rearward direction from a rear section of the gap ( 34 ), the slot terminating in an aperture ( 38 ). 
     If desired, the first location surface ( 44 ) is located at a rear section of the gap ( 34 ) adjacent the slot ( 36 ) and oriented substantially perpendicular to the first ( 28 ) and second ( 32 ) clamping surfaces. 
     Further if desired, the second location surface ( 60 ) is located to the rear of the base jaw ( 48 ) of the insert retaining member ( 18 ). 
     In accordance with the present invention, the first location surface ( 44 ) abuts the second location surface ( 60 ) to precisely locate the insert retaining member ( 18 ) in the gap ( 34 ) between the clamping jaw ( 30 ) and the base jaw ( 26 ) of the clamping portion ( 16 ). 
     Further in accordance with the present invention, the insert retaining portion ( 18 ) further comprises a securing portion ( 58 ) to which a securing member ( 22 ) can be removably attached for securing the insert retaining member ( 18 ) in position in the gap ( 34 ) between the clamping jaw ( 30 ) and the base jaw ( 26 ) of the clamping portion ( 16 ). 
     In accordance with a preferred embodiment, the securing portion ( 58 ) is an elongated portion of the insert retaining member ( 18 ) extending in a generally rearward direction and capable of passing through the slot ( 36 ). 
     Further in accordance with a preferred embodiment, the upper side ( 28 ) of the base jaw ( 26 ) of the clamping portion ( 16 ) is substantially parallel to the lower side ( 32 ) of the clamping jaw ( 30 ) of the clamping portion ( 16 ). 
     Still further in accordance with a preferred embodiment, the first ( 54 ) and second ( 56 ) clamping abutment surfaces taper towards the rear of the insert retaining member ( 18 ) forming therebetween a taper angle. 
     In accordance with a specific application the taper angle is approximately 2°. 
     In accordance with the present invention the securing member ( 22 ) is located in the aperture ( 38 ) and is removably attached to the securing portion ( 58 ) of the insert retaining member ( 18 ). 
     In accordance with a preferred embodiment of the invention, the securing member ( 22 ) is of a general trapezoidal shape, having a forward face ( 64 ) and a rear face ( 66 ), and wherein when the insert retaining member ( 18 ) is retained in the gap ( 34 ) in the clamping portion ( 16 ), the securing member ( 22 ) is received in a recessed region ( 68 ) in the elongated portion ( 58 ) of the insert retaining member ( 18 ), the recessed region ( 68 ) having a shape generally similar to that of the securing member ( 22 ), the aperture ( 38 ) has two rearwardly facing spaced apart abutment surfaces ( 40 ,  42 ) adjacent the slot ( 36 ) and the elongated portion ( 58 ) of the insert retaining member ( 18 ) has a forwardly facing rear abutment surface ( 72 ), the securing member ( 22 ) being provided with a countersunk through bore ( 74 ) with a first longitudinal axis ( 76 ) and the recessed region ( 68 ) being provided with a screw threaded bore ( 78 ) having a second longitudinal axis ( 80 ), the first and second longitudinal axes ( 76 ,  80 ) being relatively displaced one with respect to the other in a manner so that when a countersunk head screw ( 24 ) is placed in the countersunk through bore ( 74 ) and is screwed into the screw threaded bore ( 78 ) the forward face ( 64 ) of the securing member ( 22 ) abuts the two rearwardly facing spaced apart abutment surfaces ( 40 ,  42 ) and the rear face ( 66 ) of the securing member ( 22 ) abuts the forwardly facing rear abutment surface ( 72 ) of the elongated portion ( 58 ), thereby ensuring that precise location of the insert retaining member ( 18 ) is maintained. 
     If desired, the insert pocket ( 52 ) is provided with an aperture ( 53 ) extending from a rear section of the insert pocket ( 52 ) in a generally rearward direction. 
     In accordance with one application, the cutting tool is a rotary slot cutting tool ( 96 ). 
    
    
     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 an exploded side view of a cutting portion of a cutting tool comprising a clamping portion, an insert retaining member, a cutting insert and a securing member; 
     FIG. 2 is a side view of the cutting portion of FIG. 1, showing the retaining member mounted in the clamping portion thereof and secured in position by means of the securing member; 
     FIG. 3 is a side view of the cutting portion of FIG. 1, showing the insert retaining member mounted in the clamping portion thereof and secured in position by means of the securing member with the cutting insert mounted in the insert pocket; 
     FIG. 4 is a partial cross sectional view of the cutting portion of FIG. 2 taken along the line IV—IV; 
     FIG. 5 is a partial cross sectional view of the cutting portion of FIG. 2 taken along the line V—V; and 
     FIG. 6 is a side view of a rotary slot cutting tool having a cutting portion in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Attention is first drawn to FIGS. 1 to  3 . A cutting tool assembly  10 , comprises a body portion  12  and a cutting portion  14 . In the following description and claims the directional terms are in accordance with the orientation of the portion of the cutting tool assembly shown in FIGS. 1 to  3 . Therefore, a portion of a member to the left in the figures will be referred to as a forward portion of the member, whereas a portion of a member to the right in the figures will be referred to as a rear portion of the member. Similarly, portions of a member to the top and bottom in the figures refer, respectively, to upper and lower portions of the member. The cutting portion  14  is a forward portion of the cutting tool assembly  10  comprising a clamping portion  16 , an insert retaining member  18 , a cutting insert  20  and a securing member  22 . The securing member  22  is fastened to the insert-retaining member  18  by means of a countersunk head screw  24 . As will be described in greater detail below, the securing member  22  is for securing the insert retaining member  18  in position thereby ensuring that the precise location of the insert retaining member and consequently of the cutting insert is maintained throughout a cutting operation. 
     The clamping portion  16  comprises a base jaw  26  having an upper side  28 , constituting a first clamping surface and a clamping jaw  30  having lower side  32 , constituting a second clamping surface. The base jaw  26  and the clamping jaw  30  having a gap  34  between them for resiliently receiving the insert retaining member  18 , the first and second clamping surfaces constituting, respectively, lower and upper boundaries of the gap  34 . The first and second clamping surfaces  28  and  32 , respectively, are substantially parallel to each other and the distance between them is h 1 . An imaginary line parallel to the first and second clamping surfaces  28  and  32 , respectively, and passing approximately midway between them, defines a longitudinal axis of the cutting portion  14  of the cutting tool assembly  10 . 
     A slot  36  extends in a generally rearward direction from a rear section of the gap  34 . The slot  36  terminates in an aperture  38 , having two rearwardly facing spaced apart abutment surfaces, an upper abutment surface  40  and a lower abutment surface  42 , adjacent the slot  36 . The abutment surfaces  40  and  42  lie along a common imaginary line that is substantially perpendicular to the longitudinal axis of the cutting portion  14 . A forwardly facing first location surface  44  is located at a rear section of the gap  34  adjacent the slot  36  and is oriented substantially perpendicular to the longitudinal axis of the cutting portion  14 . The base jaw is provided with a throughgoing aperture  46  for receiving a prong of a key for the removal of an insert retained by the insert retaining member  18 . The insert retaining member  18  comprises a base jaw  48  and a clamping jaw  50  defining therebetween an insert pocket  52  for receiving the cutting insert  20 . The insert-receiving pocket  52  is provided with an aperture  53  for receiving an insert-removing device that can be used in conjunction with the throughgoing aperture  46 . The aperture  53  extends from a rear section of the insert-receiving pocket in a generally rearward direction. 
     The base jaw  48  has a lower side  54  constituting a first clamping abutment surface and the clamping jaw  50  has an upper side  56  constituting a second clamping abutment surface. The first and second clamping abutment surfaces  54  and  56 , respectively, taper towards the rear of the insert-retaining member  18  forming between them a taper angle. The taper angle is, preferably, approximately 2°. The distance, h 2 , between the first and second clamping abutment surfaces  54  and  56 , respectively, taken approximately at the mid point of the second clamping abutment surface  56 , is approximately equal to h 1 . Therefore, due to the tapering of the clamping abutment surfaces, when the insert-retaining member  18  is mounted in the gap  34  and urged towards the rear of the gap, it will, at first, slide in without resistance until it is approximately halfway into the gap. In order to complete the mounting of the insert-retaining member, so that it is fully retained in the gap, force has to be applied to the insert-retaining member. 
     The insert-retaining member  18  has an elongated portion  58  extending in a generally rearward direction. The elongated portion constituting a securing member. The dimensions of the elongated portion are such that it is capable of passing through the slot  36  when mounting the insert-retaining member  18  in the gap  34 . The insert-retaining member  18  is provided with a rearwardly facing second location surface  60  located to the rear of the lower jaw  48 . When the insert-retaining member  18  is fully retained in the gap  34 , the first location surface  44  abuts the second location surface  60  to ensure precise location of the insert-retaining member  18 . The insert-retaining member is provided with an insert-locating surface  62  for precise location of the cutting insert with respect to the insert-retaining member. Consequently, with both the insert retaining member precisely located with respect to the body portion and the insert precisely located with respect to the retaining member, the cutting edge of the cutting insert is precisely located with respect to the body portion. 
     In addition to FIGS. 1 to  3 , attention is now also drawn to FIG.  4 . The securing member  22  is of a general trapezoidal shape, having a forward face  64  and a rear face  66 , and is received in a recessed region  68  in the elongated portion  58  of the insert retaining member  18 . The recessed region  68  has a forward face  70  and a rear face  72 , and has a shape generally similar to that of the securing member  22 . The rear face  72  constitutes a forwardly facing abutment surface. The securing member is provided with a countersunk through bore  74  having a first longitudinal axis  76 , and the recessed region  68  is provided with a screw threaded bore  78  having a second longitudinal axis  80 . 
     When the retaining member is fully retained in the gap  34  and the securing member  22  is positioned in the recessed region  68 , the first and second longitudinal axes are relatively displaced with respect to each other, in a manner such that when the countersunk head screw  24  is placed in the countersunk through bore  74  and is screwed into the screw threaded bore  78 , the forward face  64 , of the securing member  22 , abuts the two rearwardly facing spaced apart abutment surfaces  40  and  42 , and the rear face  66 , of the securing member, abuts the rear face  72  of the recessed region  68  in the insert retaining member. This creates a three-point contact arrangement between the securing member  22 , the insert retaining member  18  and the body portion  12 . As the countersunk head screw  24  is tightened its conical head  82  abuts an upper portion of the matching countersunk through bore  74  of the securing member  22 , and the securing member is forced to move in an upward direction as the first longitudinal axis  76  moves towards the second longitudinal axis  80 . Due to the three-point contact arrangement and the trapezoidal shape of the securing member, the more the countersunk head screw  24  is tightened, the greater the securing force applied by the securing member on the insert retaining member via the rear face  66  of the securing member as it abuts the rear face  72  of the recessed region  68 . As seen in FIG. 4, the thickness of the securing member  22  is such that its outwardly facing surface  84  is substantially flush with a side surface  86  of the body portion  12 . 
     Attention is now drawn to FIG. 5, showing the mechanism for preventing lateral movement of the insert retaining member  18  with respect to the clamping portion  16  of the body portion  12 . In accordance with a preferred embodiment of the present invention, the first and second clamping surfaces  28  and  32 , respectively, of the base jaw  26  and clamping jaw  30 , respectively, have convex V-shaped cross-sections, and the first and second clamping abutment surfaces  54  and  56 , respectively, of the base jaw  48  and clamping jaw  50 , respectively, of the insert retaining member  18 , have mating concave V-shaped cross-sectional surfaces. As is well known in the art (see, for example, U.S. Pat. No. 4,580,930 and U.S. Pat. No. 4,887,945) lateral stability of a cutting insert can be achieved in a similar way. The clamping surfaces  88  and  90  of the base jaw  48  and clamping jaw  50 , respectively, have convex V-shaped cross-sections, and the lower and upper abutment surfaces  94  and  92 , respectively, of the cutting insert  20  have mating concave V-shaped cross-sectional surfaces (shown by broken lines in FIG.  2 ). 
     FIG. 6 shows a rotary slot-cutting tool  96  with a plurality of cutting portions  14 , arranged around the periphery of the tool, each cutting portion comprising a clamping portion  16 , an insert retaining member  18 , a cutting insert  20  and a securing member  22  in accordance with the present invention. 
     The preferred embodiment of the cutting tool assembly described herein has attributed to it three main properties: (i) it provides precise location of the cutting insert; (ii) it enables the insertion and removal of the cutting insert without necessitating the removal of the insert retaining member; and (iii) it provides means for firmly securing the insert retaining member to the cutting tool body. Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications can be made without departing from the spirit or scope of the invention as hereinafter claimed. Therefore, a cutting tool assembly having only the first property is also within the scope of the present invention. Similarly, cutting tool assemblies having property (i) together with either of properties (ii) or (iii) are also within the scope of the present invention.