Patent Publication Number: US-2019176244-A1

Title: Insert adaptor for parting off

Description:
RELATED APPLICATIONS 
     This is a Bypass Continuation of International Patent Application No. PCT/IL2017/050975 filed 31 Aug. 2017, which published as WO 2018/047162A1 and claims priority to U.S. Provisional Application No. 62/383,739, filed 6 Sep. 2016. The contents of the aforementioned applications are incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The subject matter of the present application relates to an insert adaptor for parting off operations, the insert adaptor comprising pockets for inserts. In particular, the subject matter of the present application relates to insert adaptors which are only rotated (i.e. indexed) about a central index axis to bring a single pocket, and hence the insert mounted in that pocket, into an operational position for machining a workpiece. 
     BACKGROUND OF THE INVENTION 
     EP 0 497 257 discloses a parting off device for rotating workpieces comprising an adaptor rotatably connected to a tool holder and comprising an insert in a pocket of the adaptor. As shown in  FIG. 4 , the insert pockets are positioned at diametrically opposed sides of the adaptor. This is done to maximize cutting depth, since the cutting edges of the inserts are wider than the adaptor, and to have them positioned closer to each other would reduce the cutting depth capability. 
     As understood by  FIG. 1 , the non-rotating tool is configured for the inserts to be used successively as opposed to concurrently. To elaborate, after an operative edge is, for example, worn, a successive edge can be selected to become an operative edge. This can be achieved by one of two ways, namely by replacing the worn insert in the pocket with a new insert or rotating (indexing) the adaptor so that a different insert in a different pocket is presented as a new operative edge. 
     It will be understood that the present application is directed only to adaptors of the type being configured for rotation (indexing) about a central index axis (hereinafter called adaptor index axis) which positions a different insert to be the active insert for a parting off application. Stated differently it relates to insert adaptors which position a single insert in an operational position and after use thereof position a different single insert in the operational position (i.e. successive insert use). 
     For such parting operations to work, a workpiece is rotated and the adaptor is moved in an operational direction into the workpiece. The operational direction is typically parallel, or substantially parallel, with an elongation direction of a tool holder&#39;s elongated shank. 
     It is an object of the present application to provide a new and improved insert adaptor and/or tool assembly comprising same. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the subject matter of the present application, there is provided an insert adaptor for parting off having an adaptor index axis and comprising: parallel adaptor first and second sides connected by an adaptor peripheral surface which extends peripherally around the adaptor; the adaptor index axis extending through the center of the first and second sides; wherein the adaptor peripheral surface is formed with at least three pockets. 
     Previously, only two pockets were known for such adaptors. Increasing the number of pockets around a peripheral surface of an insert adaptor was previously thought disadvantageous for reducing cutting depth compared to known adaptors with two diametrically opposed pockets (due to the limitation caused during usage by the cutting edge width of an insert inside the pocket), and will increase adaptor production costs due to manufacturing of additional pocket(s), it is believed that such disadvantages can be offset by an increased pocket life which thereby increases the overall lifetime of the adaptor. 
     Yet a further, separate advantage, is that even though production of an insert with three or more cutting edges circumferentially spaced therearound may be simpler than a separate adaptor and insert manufacturing construction (requiring production of the pockets etc.) it has been found that comparatively long cemented carbide inserts require a greater width than metal, particularly steel, thereby increasing the material wastage in parting off operations which require relatively deep cuts. While the cemented carbide is structurally stronger, nonetheless a slightly thinner adaptor can be achieved with metal than cemented carbide, which for certain operations can be advantageous. 
     It has further been found that when using such insert adaptor with only a single insert only, the previously considered disadvantageous effect of reduced cut length can be eliminated. 
     In accordance with a second aspect of the subject matter of the present application, there is provided an insert adaptor for parting off having an adaptor index axis and comprising: parallel adaptor first and second sides connected by an adaptor peripheral surface which extends peripherally around the adaptor; the adaptor index axis extending through the center of the first and second sides; wherein the adaptor peripheral surface is formed with exactly five pockets. 
     Even though five pockets along an adaptor peripheral surface even further reduces the possible cutting depth, relative to a smaller number of pockets (understanding that for parting off assemblies cutting edges extend wider than the adjacent adaptor portion), nonetheless such number of pockets is believed to be the optimal number for number of cutting edges while still providing chip evacuation space for most applications. Even though it is preferred for all embodiments that pockets are configured to resiliently hold cutting inserts therein, the advantages of a five pocket insert adaptor are believed to even be advantageous in this particular case for inserts (made of a harder material than the insert adaptor itself, e.g. being made of cemented carbide and the insert adaptor being made of steel) which are permanently attached to the insert adaptor (e.g. by brazing). However, as with all ongoing developments, more than five pockets may be feasible, despite the reduced chip evacuation space, for any of the other aspects. 
     In accordance with a third aspect of the subject matter of the present application, there is provided an insert adaptor for parting off having an adaptor index axis and comprising: parallel adaptor first and second sides connected by an adaptor peripheral surface which extends peripherally around the adaptor; the adaptor index axis extending through the center of the first and second sides; wherein the adaptor peripheral surface is formed with a plurality of pockets and bearing surfaces extending between the pockets. 
     Unlike rotating insert adaptors, adaptors in accordance can be mounted along the periphery thereof since at least a portion of that periphery does not come into proximity with a workpiece. 
     It will be understood that an insert adaptor can be formed with many geometric shapes, nonetheless, in particular for parting off applications (in which it is more economical to form as thin a slot as possible to reduce material wastage) it is believed that straight bearing surfaces provide the greatest structural strength for relatively extremely thin adaptors. 
     In accordance with a fourth aspect of the subject matter of the present application, there is provided an insert adaptor for parting off having an adaptor index axis and comprising: parallel adaptor first and second sides connected by an adaptor peripheral surface which extends peripherally around the adaptor; the adaptor index axis extending through the center of the first and second sides; wherein the adaptor peripheral surface is formed with at least three pockets, each of the pockets comprising resilient upper and lower clamp surfaces and/or an ejection gap at a rear end thereof. 
     It will be understood that all references to “inserts” in the present application refers to components which are detachable from an insert adaptor and are not permanently connected thereto (e.g. by brazing). 
     Accordingly, a fifth aspect of the subject matter of the present invention would be use of (or a method of machining) an insert adaptor with only a single insert mounted in a pocket in an operational position and at least the adjacent pockets to said pocket being free of inserts. 
     In accordance with a sixth aspect of the subject matter of the present application, there is provided a tool holder configured for holding an insert adaptor according to any one of the previous aspects. 
     The tool holder is a non-rotating tool holder (i.e. not configured for rotation). Thus an adaptor recess can extend along a side of the tool holder, and need not be perpendicular to an elongated direction thereof as with rotating tools. 
     In accordance with a seventh aspect of the subject matter of the present application, there is provided tool assembly comprising a tool holder according to the previous aspect, an insert adaptor according to any one of first to fourth aspects, and one or more inserts mounted to the insert adaptor. 
     In accordance with an eighth aspect of the subject matter of the present application, there is provided a tool assembly comprising a tool holder and an insert adaptor according to any one of the previous aspects, and an insert mounted to one of the pockets of the insert adaptor; the insert comprising a cutting edge having a cutting edge thickness measured parallel with the adaptor index axis I A , the insert adaptor comprising an adaptor thickness measured parallel with the adaptor index axis I A , which is smaller than the cutting edge thickness; the insert adaptor being mounted to an adaptor recess of the tool holder. 
     In accordance with a ninth aspect of the subject matter of the present application, there is provided a method of indexing a tool assembly comprising the steps of loosening a screw holding an insert adaptor to a tool holder, rotating the insert adaptor until a different insert is located in an active cutting position and fastening the screw to thereby bring the insert adaptor to a secure mounted position. 
     It is understood that the above-said is a summary, and that the following features, either alone or in combination, may be applicable to any of the above aspects:
     A. An insert adaptor can have an adaptor index axis extending through the center thereof. Specifically, the adaptor index axis can extend through the center of adaptor first and second sides of the insert adaptor. The insert adaptor can be formed with pockets along an adapter peripheral surface thereof so that rotation of the insert adaptor about the adaptor index axis brings a different pocket into an operational position. The pockets can preferably be equally circumferentially spaced about the adaptor peripheral surface. Stated differently, the insert adaptor can have rotational symmetry for a degree of rotation fulfilling the condition: (360°/[total number of the pockets]).   B. An insert adaptor can comprise parallel adaptor first and second sides connected by an adaptor peripheral surface which extends peripherally around the adaptor.   C. Adaptor first and second sides can be planar. Stated differently, for example, the adaptor first and second sides can be free of projecting bearing surfaces.   D. An adaptor peripheral surface can be formed with at least three pockets. An adaptor peripheral surface can preferably be formed with three to five pockets. Most preferably the adaptor peripheral surface is formed with exactly five pockets. It will be understood that a larger number of pockets may also be feasible.   E. One or each pocket can be configured for resiliently clamping (holding) an insert. For example, one or each pocket can comprise resilient upper and lower clamp surfaces. It will be understood that the insert adaptors according to the subject matter of the present application are not of the type that have a pocket and screw hole configuration, i.e. that an insert is secured to a pocket with a screw. This is because a screw, or more precisely the screw hole thereof, necessitates a relatively wider insert adaptor which is far less suitable to parting off operations. Accordingly, it will be understood that, except for a screw hole which is part of a fastening configuration, the insert adaptor can be devoid of screw holes. Stated differently, an insert adaptor can be devoid of screw holes associated with pockets. Stated even further differently, each pocket can be devoid of a screw hole.   F. One or each pocket can comprise an ejection gap at a rear end thereof for insert ejection. An ejection gap can be enlarged more than a clamping portion of the pocket preceding it. An ejection gap can have a concave end portion.   G. One or each pocket can be formed with upper and lower clamp surfaces. One or both of the upper and lower clamp surfaces can have a ridge shape. One or both of the upper and lower clamp surfaces can have a crest shape. One of the upper or lower clamp surfaces can have a ridge shape and the other a crest shape. Even though for parting operations side forces are small, such construction may assist insert stabilization. At least one of the upper and lower clamp surfaces can be formed with two contact areas separated by a relief recess. Preferably exactly one of the upper and lower clamp surfaces comprises a relief recess.   H. One or each pocket can be formed with an insert stopper surface, preferably a single insert stopper surface per pocket. The insert stopper surface can be located at a rear end of the pocket. In such case the insert stopper surface can perpendicular to an elongation direction of the pocket or transverse thereto. Alternatively, the insert stopper surface can be located along a periphery of the insert adaptor between a pocket front end and a clamping surface.   I. An adaptor peripheral surface can formed with a plurality of pockets and bearing surfaces extending between the pockets. Each of the bearing surfaces can be straight (stated differently, the bearing surfaces can extend along a straight path when viewed in a side view, i.e. along a central index axis). Each of the bearing surfaces can be planar. It will be understood that an insert adaptor can be formed with many geometric shapes, nonetheless, in particular for parting off applications (in which it is more economical to form as thin a slot as possible to reduce material wastage) it is believed that straight bearing surfaces provide the greatest structural strength for relatively extremely thin adaptors.   J. In an operational position, a forward most bearing surface can extend in a direction directly downward from a cutting edge of the operational insert. Stated differently, a forward most bearing surface in an operational position can be essentially perpendicular to an operational direction D O .   K. A bearing surface can comprise a recessed portion located adjacent a pocket, a non-recessed portion, and a transition portion connecting the recessed and non-recessed portion. Stated differently, a bearing surface can extend, essentially straight, from a pocket with a closest portion thereof to the pocket being recessed.   L. An insert adaptor can have a solid construction (stated differently, the insert adaptor can be devoid of elasticity grooves between the pockets). While such grooves are typically advantageous, for the parting off operations envisioned, it is believed a solid insert adaptor construction is preferred, even though this may complicate insertion and removal of an insert from a relatively more rigid pocket. Stated differently, an insert adaptor can have a solid construction excluding the insert pockets and, where such exists, screw hole. To quantify, an insert adaptor can have a material volume of greater than 50% of an imaginary cylinder encompassing the insert adapter. By encompassing, it is meant the smallest cylinder that can encompass the insert adapter. Preferably, said volume is less than 80% of the imaginary cylinder. Most preferably the volume is greater than 55% and less than 75% of the volume of the imaginary cylinder, with values tending to 65% being further preferred (in the example below, the volume is 836 mm 3  whereas an encompassing cylinder has a volume of 1175 mm 3  which is a volume ratio of 71%). Such solid construction being, in theory, thought to provide optimal constructional strength. Nonetheless, while the insert adaptor can be devoid of elasticity grooves (which open out to an adaptor peripheral surface) the insert adaptor may have release apertures for ejecting inserts (and still be considered to have the above-mentioned solid construction).   M. An insert adaptor can be formed with a fastening configuration in the center thereof. The fastening configuration can preferably be a single screw hole opening out to the adaptor first and second sides. The single screw hole can be formed in the center of the insert adaptor. The screw hole can be coaxial with the adaptor index axis.   N. An insert adaptor can be formed with a non-central fastening configuration. To elaborate, an insert adaptor can comprise a plurality of screw holes for clamping the insert adaptor to a tool. Stated differently, an insert adaptor can comprise a plurality of screw holes extending through the first and second surfaces. The screw holes can be circumferentially spaced from each other. The spacing can be equal circumferential spacing. There can be a single screw hole for each pocket. The screw hole can also have a dual function as a release aperture.   O. An insert adaptor can comprise a release aperture associated with each pocket.   P. A screw hole can be tapered inwardly from one or both of the adaptor first and second sides. Alternatively, a screw hole can be a simple cylindrical bore. A screw hole can be offset from a corresponding tool hole to bias an insert adaptor in a desired direction.   Q. The insert adaptor can be symmetrical about an adaptor plane bisecting the insert adaptor first and second sides.   R. Inserts configured to be mounted to the insert adaptor can be made of a harder material than the insert adaptor. The insert adaptor can be made of metal. The metal can be preferably be steel. An insert can be made of a material harder than the insert adaptor. The insert can preferably be made of cemented carbide.   S. An insert can comprise a cutting edge. An insert can comprise only a single cutting edge. A cutting edge thickness can be greater than the remainder of the insert. A cutting edge thickness can be greater than an adaptor thickness. The cutting edge thickness can be measured parallel with the adaptor index axis; the insert adaptor comprising an adaptor thickness measured parallel with the adaptor index axis, which is smaller than the cutting edge thickness and the insert adaptor is mounted to an adaptor recess of the tool holder. The cutting edge can be the only cutting edge of the tool assembly positioned for operational use. In other words, the tool assembly is configured for successive insert use, rather than multiple insert use simultaneously (i.e. concurrent use). The insert can have an elongate shape.   T. A tool holder can comprise a tool shank and a tool head extending from the tool shank.   U. A tool shank can be elongated. A tool shank can comprise a quadrilateral cross section (preferably square). A tool shank can be formed with a coolant inlet.   V. An operational direction that the tool holder can be parallel with an elongation direction of an elongated shank thereof. An adaptor index axis can be transverse to said elongation direction, preferably perpendicular.   W. A tool head can comprise an adaptor recess configured for receiving an adaptor therein. The adaptor recess can comprise at least one adaptor seating surface protuberance.   X. A tool head can comprise first and second tool bearing surfaces protruding from the tool holder along a periphery of an adaptor recess. The first and second tool bearing surfaces can be the only bearing surfaces of the tool holder. Stated differently, the tool assembly can be configured that the insert adaptor contacts the tool holder only via three regions thereof (e.g., one of the sides of the insert adaptor, and exactly two of the straight bearing surfaces, preferably which are separated by another bearing surface.   Y. At least one of the tool bearing surfaces can be formed with two contact areas separated by a relief recess. Preferably exactly one tool bearing surface comprises a relief recess.   Z. Imaginary tool bearing surface lines extending from the first and second tool bearing surfaces can form an acute tool bearing surface angle. The tool bearing surface angle can preferably be between 25° to 45°. More preferably 30° to 40°. The first and second tool bearing surfaces can be oriented as two non-adjacent sides of an imaginary pentagon.   AA. A tool head can comprise a back-up bearing surface. The back-up bearing surface can be configured to be spaced apart from an insert adaptor mounted to the tool holder under normal circumstances. Stated differently, the tool assembly is designed with a gap between the insert adaptor and the back-up bearing surface. Only under undesired movement of the insert adaptor would the back-up bearing surface abut the insert adaptor and prevent movement thereof. The back-up bearing surface can be oriented as a side of an imaginary pentagon, positioned between the first and second tool bearing surfaces which constituted additional sides thereof.   BB. A tool head can comprise a tool hole or a plurality of tool holes. The tool hole can be threaded. The tool hole(s) can be non-coaxial (stated differently, off-center) with a screw hole of an insert adaptor to bias the adaptor in a direction when fastened to the tool holder. The direction can be towards a back-up bearing surface.   CC. A tool assembly can comprise a tool holder, an insert adaptor and one or more inserts mounted to the insert adaptor.   DD. A tool assembly can comprise one or more screws for securing the insert adaptor to the tool holder.   EE. A screw can comprise a head portion and a threaded shank portion.   FF. A shank portion can have a shank length at least three times greater than an adaptor thickness of an insert adaptor. Preferably at least five times greater. Such length can allow the insert adaptor to remain connected to a tool holder during indexing, reducing the likelihood of falling parts.   GG. A screw, when the tool assembly is in an operational assembled configuration, can project further than an insert adaptor away from an adaptor recess. It will be understood that if the screw or other fastening configuration would be flush with the insert adaptor, a greater cutting depth could be achieved. Nonetheless, to compensate for a relatively low structural strength of a comparatively thin metal insert adaptor, such non-flush configuration can be used. It will also be understood that the subject matter of the present application can provide a particularly advantageous solution for insert adaptors having an adaptor thickness of less than 3.5 mm, preferably less than 3 mm and most preferably 2 mm or less. Similarly, it will also be understood that the subject matter of the present application can provide a particularly advantageous solution for insert adaptors having a circumscribing circle with an adaptor circumscribing diameter D AC  greater than 30 mm, preferably greater than 35 mm. Additionally, it is preferred that the adaptor circumscribing diameter is less than 50 mm, preferably less than 42 mm.   HH. A shank portion can comprise a threaded sub-portion and a threadless sub-portion located between the threaded sub-portion and the head portion. Such screw construction can advantageously provide a non-threaded area for an insert adaptor to rotate thereabout during indexing. The threadless sub-portion can preferably have a smaller diameter than the threaded sub-portion. The threadless sub-portion can have a shank length L S3  (called below “third shank length”) which is measured along the threadless sub-portion  76  and which is greater than an adaptor thickness. Preferably said shank length L S3  can be less than 3 times the adaptor thickness. Each of the constructional features above can further assist user-friendly indexing of the insert adaptor thereabout.   II. A shank portion can comprise a tool-receiving configuration (e.g. a torx® socket). This can allow, when the screw hole extends to both sides of a tool holder, for a user to rotate the screw even from a side of the tool holder opposite the side to which the insert adaptor is clamped.   JJ. A head portion can have a frustoconical shape to reduce projection of the head portion from the tool assembly, allowing a more compact construction. The frustoconical shape can extend to a larger diameter than the shank portion.   KK. A head portion can comprise a tool-receiving configuration.   LL. A coolant channel can extend underneath an adaptor recess.   MM. A coolant channel outlet can open out at a forward most portion of an adaptor recess.   NN. A coolant channel outlet can be aligned with an insert adaptor. Stated differently, the coolant channel outlet can be aligned with an adaptor plane of the insert adaptor.   OO. A method can further comprise the step of replacing one or more worn inserts with different inserts.   PP. Method steps of loosening and fastening the screw can be further defined as loosening and fastening a single screw. Stated differently, a tool assembly can comprise a single screw only for fastening the insert adaptor to the tool holder. Even though a single screw provides less stability than a plurality of screws, it is believed that the advantage of userability (only having to unscrew a single screw, or even only having to partially unscrew a single screw—leaving the screw connected to the tool holder) outweighs the advantage of a more stable mounting construction. This is believed to be also assisted, although not essentially, by the straight bearing surface arrangement described, which provides comparatively strong mounting stability. It will be further noted that if a fastening configuration comprises more than one screw holding the insert adaptor to the tool holder, then indexing of an insert adaptor without removing at least one of the screws may be impossible.   QQ. A method can further comprise loosening the screw such that it is not completely removed from the tool holder, distancing the insert adaptor from the tool holder such that the bearing surfaces of the insert adaptor and tool holder are no longer aligned and then carrying out said rotating of the insert adaptor.   RR. Method steps of loosening and fastening the screw can be further defined as loosening and fastening a single screw via a tool-receiving configuration in a shank portion of a screw.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the subject matter of the present application, and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: 
         FIG. 1A  is a side view of a portion of a cutting tool assembly; 
         FIG. 1B  is an upper view of the portion of the cutting tool assembly in  FIG. 1A ; 
         FIG. 1C  is a front view of the portion of the cutting tool assembly in  FIGS. 1A and 1B ; 
         FIG. 2A  is an upper view an insert adaptor of the cutting tool assembly in  FIGS. 1A to 1C , and a single insert held in a pocket of the insert adaptor; 
         FIG. 2B  is a side view of the insert adaptor in  FIG. 2A ; 
         FIG. 2C  is an enlarged front view of a portion of the insert adaptor in  FIG. 2A , including a pocket thereof; 
         FIG. 2D  is an enlarged side view of the portion of the insert adaptor in  FIG. 2C , including a pocket thereof; 
         FIG. 2E  is an enlarged side view of an alternative pocket of an insert adaptor; 
         FIG. 2F  is an enlarged side view of a yet another alternative pocket of an insert adaptor; 
         FIG. 3A  is a side view of a tool holder of the cutting tool assembly in  FIGS. 1A to 1C ;
       FIG. 3B  is an upper view of the tool holder in  FIG. 3A ;     FIG. 3C  is a front view of the tool holder in  FIGS. 3A and 3B ;     FIG. 4  is a cross section view taken along line IV-IV in  FIG. 3B ;     FIG. 5  is a partially sectioned schematic side view of a screw of the cutting tool assembly in  FIGS. 1A to 1C ;     FIG. 6A  is a side view of a portion of an alternative cutting tool assembly;     FIG. 6B  is an upper view of the portion of the cutting tool assembly in  FIG. 6A ;     FIG. 6C  is a front view of the portion of the cutting tool assembly in  FIGS. 6A and 6B ;     FIG. 7A  is an upper view of an insert adaptor of the cutting tool assembly in  FIGS. 6A to 6C , and a single insert held in a pocket of the insert adaptor;     FIG. 7B  is a side view of the insert adaptor and insert in  FIG. 7A ;     FIG. 8A  is a side view of a tool holder of the cutting tool assembly in  FIGS. 6A to 6C ;     FIG. 8B  is an upper view of the tool holder in  FIG. 8A ; and     FIG. 8C  is a front view of the tool holder in  FIGS. 8A and 8B .   

     
    
    
     DETAILED DESCRIPTION 
     Reference is made to  FIGS. 1A and 1B , illustrating a tool assembly  10  configured for parting off operations. 
     The tool assembly  10  can comprise an insert adaptor  12 , an insert  14  ( FIG. 2B ; such insert designation may additionally or alternatively be designated with a suffix e.g., first, second, third and fourth pockets  14 A,  14 B,  14 C,  14 D,  14 E; further designations below are also made in such manner) mounted to the insert adaptor  12 , a tool holder  16 , and a screw  18  used to secure the insert adaptor  12  to the tool holder  16 . 
     Referring now also to  FIGS. 2A and 2B , the insert adaptor  12  can comprise parallel adaptor first and second sides  20 A,  20 B connected by an adaptor peripheral surface  22 , and can have an adaptor index axis I A  extending through the center of the adaptor first and second sides  20 A,  20 B. 
     The adaptor peripheral surface  22  is formed with pockets  24  (also suffixed, e.g., first, second, third, fourth and fifth pockets  24 A,  24 B,  24 C,  24 D,  24 E). The pockets  24  can preferably be equally circumferentially spaced about the adaptor index axis I A . 
     Preferably, each of the pockets  24 , as shown in the present example, are identical, and, for the sake of succinctness only, a generic pocket designated “ 24 ” shown in  FIGS. 2C and 2D  will be described in detail. 
     The pocket  24  can open out to a front end  26 , and can further comprise a rear end  28 , and opposing upper and lower clamp surfaces  30 ,  32  extending between the front and rear ends  26 ,  28 . 
     A clamping gap  34  can be defined between the upper and lower clamp surfaces  30 ,  32 . 
     An ejection gap  36  can be defined between the clamping gap  34  and the rear end  28 , and in the present example the pocket  24  comprises a single concave end portion  38  at the rearmost end thereof 
     In  FIG. 2C , it is shown that both the upper and lower clamp surfaces  30 ,  32  have a ridge shape, i.e. a convex shape each of which preferably have an apex  40 A,  40 B aligned with an adaptor plane P A  ( FIG. 2C ) bisecting the first and second sides  20 A,  20 B. It will be understood that the opposite shape, i.e. a crest shape, is also one of other possibilities. 
     In the side view of  FIG. 2D , it is shown that one of the clamp surfaces, in this example the upper clamp surface  30  is straight (stated differently, follows a linear path in a side view such as that shown). Whereas the other clamp surface, in this example the lower clamp surface  32  comprises two contact areas  42 A,  42 B separated by a relief recess  42 C, for more secure mounting of the insert  14  (not shown in  FIG. 2D ). 
     The ejection gap  36  can also constitute a relief portion, by being further enlarged than the clamping gap  34 . More precisely, the enlargement referred to is that shown in a side view ( FIG. 2D ) in that a minimum first distance L 1  between, and perpendicular to, the upper and lower clamp surfaces  30 ,  32  is smaller than a parallel minimum second distance L 2  of the ejection gap  36  to the first distance L 1 . 
     The pocket  24  can further be formed with an insert stopper surface  44 . In  FIG. 2D  the insert stopper surface  44  is located along the periphery of the insert adaptor  12  between the front end  26  and the upper clamp surface  30 . The insert stopper surface  44  is transverse, although not necessarily perpendicular to the upper clamp surface  30 . An intermediary surface  45  may or may not be present between the insert stopper surface  44  and a bearing surface  52  adjacent thereto (see for comparison, e.g.  FIG. 2F ). 
     In  FIG. 2E  an alternative insert stopper surface  44 ′ is exemplified as located at a rear end  28 ′ of a pocket  24 ′. The insert stopper surface  44 ′ being essentially perpendicular to an elongation direction D E  of the pocket  24 ″. However, as shown in  FIG. 2F , even an insert stopper surface  44 ″ is located at a rear end  28 ″ of a pocket  24 ″ need not be perpendicular to an elongation direction D E  of the pocket  24 ″ (in this case directed slightly downward along direction D D ). To accommodate different insert shapes, a pocket  24 ″ may include an additional insert stopper surface  44 ″. In some embodiments, there may be two ejection or relief gaps  36 ′,  36 ″. 
     Reverting to  FIGS. 2A and 2B , to facilitate fastening of the insert adaptor  12  to the tool holder  16 , the insert adaptor  12  can be formed with a fastening configuration  46  in the center thereof. Preferably, the fastening configuration  46  is a single screw hole  48  opening out to the first and second sides  20 A,  20 B. The screw hole  48  can comprise a taper portion  50  tapering inwardly from the first and second sides  20 A,  20 B. 
     The adaptor peripheral surface  22  can be formed with a straight bearing surfaces  52  (also suffixed, e.g., first, second, third, fourth and fifth pockets bearing surfaces  52 A,  52 B,  52 C,  52 D,  52 E), i.e. in a side view (e.g.  FIG. 2B ) extending between the pockets  24 . Preferably, the bearing surfaces  52  can also be planar. The bearing surfaces  52  are in the present example preferably arranged to form a basic pentagonal shape. 
     As noted above, the insert adaptor  12  can have a particularly solid construction excluding the insert pockets  24  and the screw hole  48 . To quantify an imaginary circle I C  ( FIG. 2B ) can be extended to an imaginary cylinder with an insert adaptor thickness T A  ( FIG. 2A ) which encompasses the insert adaptor  12 . The insert adaptor  12  can preferably have a material volume of greater than 50% of a volume of said imaginary cylinder. 
     The imaginary circle I C  can further define an adaptor circumscribing diameter D AC . 
     As also shown in  FIG. 2A , the insert  14  comprises a single cutting edge  53  having a cutting edge thickness T 1 , measured parallel with the adaptor index axis I A , which is greater than the remainder of the insert  14 , when measured parallel with the adaptor index axis I A . The cutting edge thickness T 1  is greater than an adaptor thickness T A , measured parallel with the adaptor index axis I A , as required for parting off operations. The insert  14  can have an elongate shape as shown in  FIG. 2B . 
     Referring to  FIGS. 3A to 3C , the tool holder  16  can comprise an elongated tool shank  54  and a tool head  56  extending therefrom. 
     The tool shank  54  can preferably be formed with a coolant inlet  57  that can be optionally closed with a plug  58  ( FIG. 1A ) when not in use. 
     The tool head  56  can comprise an adaptor recess  60  configured for receiving the insert adaptor  12  therein. The adaptor recess  60  can comprise at least one adaptor seating surface protuberance  62  which protrudes further than a remainder  63  of the adaptor recess  60  for stable contact with one of the insert adaptor&#39;s first and second sides  20 A,  20 B. 
     The tool head  56  can further comprise first and second tool bearing surfaces  64 A,  64 B protruding from the tool holder  16  along a periphery of an adaptor recess  60 . 
     In the side view of  FIG. 3A , it is shown that the first tool bearing surface  64 A can be straight (stated differently, follows a linear path). Whereas the other clamp surface, in this example the second tool bearing surface  64 B comprises two contact areas  65 A,  65 B separated by a relief recess  65 C, for more secure mounting of the insert adaptor  12 . 
     Imaginary tool bearing surface lines I T1 , I T2  extending from the first and second tool bearing surfaces  64 A,  64 B can form an acute tool bearing surface angle A 1 . 
     The tool head  56  can further comprise a back-up bearing surface  66 . 
     At each end of the of the first and second tool bearing surfaces  64 A,  64 B and the back-up bearing surface  66 , relief portions  67  (also suffixed, e.g., first, second, third, fourth relief portions  67 A,  67 B,  67 C,  67 D) are formed to provide a gap between the second, third, fourth and fifth inserts  14 B,  14 C,  14 D,  14 E (or more precisely the cutting edges thereof) and the tool head  56 . 
     The tool head  56  can further comprise a tool hole  68 . The tool hole  68  can be internally threaded and also a through-hole (i.e. extending completely through the tool head  56 ). Preferably, the tool hole  68  can be configured to bias the insert adaptor  12  in a biasing direction D B  towards the back-up bearing surface  66  for particularly strong clamping. 
     Referring to  FIG. 1B , a recessed tool head front surface  69 , which is preferably concave, can facilitate cutting depth. It will be understood that the cutting depth in this particular example extends to the first cutting depth D C1  limited by the screw  18  projecting from the insert adaptor  12 , but could potentially, in other embodiments, extend to a second cutting depth D C2  corresponding to a length to a rearmost portion of the tool head front surface  69 . 
     Referring to  FIG. 5 , the screw  18  which has optionally preferred features is shown. 
     The screw  18  comprises a head portion  70  and a threaded shank portion  72 , and can have an overall screw length L S . 
     The head portion  70  can have a frustoconical shape as shown to reduce projection shown in  FIG. 1B , and can comprise a tool-receiving configuration  74 . 
     A frustoconical surface  73  of the head portion  70  can form an angle A 2  of 45°±5°. 
     The shank portion  72  can comprise a threaded sub-portion  75  and a threadless sub-portion  76 . 
     The shank portion  72  can have a shank length L S1  at least three times greater than an adaptor thickness A T  of the insert adaptor. Preferred values being recited above. It will be clarified that the shank length L S1  referred to only the part of the shank portion  72  comprising threading (for gripping the tool holder  16 ), and does not include non-threaded portions as exemplified by a second shank length L S2 , or a third shank length L S3  which is measured along the threadless sub-portion  76 . 
     The shank portion  72  can further comprise a tool-receiving configuration  78 . 
     Referring to  FIG. 4 , a coolant channel  80  originating from the coolant inlet  57  ( FIG. 3A ) can extend under the adaptor recess  60 . In order to achieve flow to a narrow slit region during a parting off operation, the coolant channel  80  can open out at a coolant outlet  82  (see also  FIGS. 1B and 3B ) aligned with and directly underneath a forwardmost portion of the adaptor recess  60 , and directed to an active cutting edge ( FIG. 1B ). The coolant channel  80 , in other words, requires a curved path to achieve the desired coolant outlet  82  position. Preferably there is only a single coolant outlet  82 . As shown, the coolant channel  80  can, using traditional channel forming methods such as drilling, comprise a number of straight coolant channel sections  84 A,  84 B,  84 C,  84 D. Although, under more recent additive manufacturing methods, the coolant channel  80  could be formed with one or more curved sections (not shown). 
     To further detail operation: one, or preferably each of the pockets  24  can have an insert  14  mounted thereto before the insert adaptor  12  is in the clamped position shown in  FIGS. 1A to 1C  (preferably the inserts  14  are mounted while the insert adaptor  12  is not mounted at all to the tool holder  16 ). 
     The insert  14  can be mounted to the pocket  24  by sliding it from the front end  26  of the pocket  24  towards the rear end  28  thereof which forces the opposing upper and lower clamp surfaces  30 ,  32  to slightly separate, with the elasticity of the insert adaptor  12  causing them to resiliently clamp the insert  14  therebetween (notably the insert  14  is configured to preferably contact only the upper clamp surface  30  and the two contact areas  42 A,  42 B of the lower clamp surface  32 ). 
     A tool, such as a soft face hammer (not shown) would typically be used for mounting. The pockets  24  may have a relative rigidity for resilient type pockets in view of the insert adaptor  12  preferably being free of elasticity grooves, which are omitted in preferred embodiments order to maintain sufficient insert adaptor constructional strength for ultra-thin parting off operations. 
     Thereafter, the insert adaptor  12  can be clamped to the tool holder  16  via fastening of the screw  18 . In an operational position the insert adaptor  12  contacts the tool holder  16  only via the first side  20 A and exactly two of the straight bearing surfaces (e.g. the second and fourth bearing surface  52 B,  52 D. Notably, a gap  86  is typically designed between the insert adaptor  12  and the back-up bearing surface  66 . 
     In  FIGS. 1A to 1C , only the first insert  14 A is in an operational position to part-off a workpiece (not shown) typically by the tool assembly  10  being moved in the operational direction D O  shown. 
     After the first insert  14 A is worn, either it can be replaced by being ejected (e.g. a portion of an ejection tool (not shown) can be inserted through the ejection gap  34  to eject the first insert  14 A by a step of levering the ejection tool against the rear end  28 , and a different insert which is not shown can be inserted as described above) or by indexing of the insert adaptor  12 , until each of the inserts  14  are successively worn and then all replaced. 
     The insert adaptor  12  can be either removed completely for indexing or preferably a step of loosening the screw  18  (via either of the receiving configurations  74 ,  78 ) while maintaining partial attachment of the screw  18  to the tool head  56  is carried out. Subsequent to such loosening, the insert adaptor  12  is moved away from the tool head  56  such that it can be rotated without contacting the first and second tool bearing surfaces  64 A,  64 B and rotated to bring an adjacent insert  14  into an operative position. Subsequently, the insert adaptor  12  is moved back into contact with the tool head  56  and clamped via fastening of the screw  18 . Such indexing being user friendly due to the extremely low likelihood of falling parts. 
     Reference is made to  FIGS. 6A to 8C , an alternative tool assembly  110  is shown to comprising of an insert adaptor  112 , an insert  114  and a tool holder  116 . Reference numerals for corresponding elements have been shifted by a value of “100”. 
     The alternative tool assembly  110  is essentially similar to the previously described tool assembly  10 , except for three notable differences. The first notable difference is the use of non-centrally located screw(s)  118  (and screw hole(s)  137 ) to hold the insert adaptor  112  to the tool holder  116 . The second notable difference is that the screw holes  137  are not tapered but are simple cylindrical bores. The third is the location of the operational insert  114  relative to the orientation of the bearing surfaces  152 . 
     Clearly there is also a different insert type and pocket, however, aside from described differences or clearly visible differences such as the insert type, it should be assumed that all the other functional features described above, as well the present notable differences, are applicable to any embodiment of the present invention. The focus on the description below will focus on the notable or visible differences, and undescribed portions can be assumed to correspond to those exemplified above. 
     Referring now also to  FIGS. 7A and 7B , the insert adaptor  112  can comprise parallel adaptor first and second sides  120 A,  120 B connected by an adaptor peripheral surface  122 , and can have an adaptor index axis I A  extending through the center of the adaptor first and second sides  120 A,  120 B. 
     The adaptor peripheral surface  122  is formed with pockets  124  (also suffixed, e.g., first, second, third, fourth and fifth pockets  124 A,  124 B,  124 C,  124 D,  124 E). It will be understood that each insert  114  (only one insert being shown, however clearly there can be several simultaneously mounted) and pocket  124  in the present example are identical and hence explanation will be limited to a single example thereof. 
     Using the fifth pocket  124 E for explanation, it opens out to a front end  126 , and can comprise a rear end  128 , and opposing upper and lower clamp surfaces  130 ,  132  extending between the front and rear ends  126 ,  128 . 
     A clamping gap  134  can be defined between the upper and lower clamp surfaces  30 ,  32 . 
     An ejection gap  136 E (also suffixed, e.g., first, second, third, fourth and fifth ejection gaps  136 A,  136 B,  136 C,  136 D,  136 E) can be defined between the clamping gap  134  and the rear end  128 . 
     Each ejection gap  136  can be accompanied by a release aperture  137  (also suffixed, e.g., first, second, third, fourth and fifth release apertures  137 A,  137 B,  137 C,  137 D,  137 E). The fifth release aperture  137 E being functionally connected to the fifth pocket  124 E and fifth ejection gap  136 E thereof. 
     As is known in the art, a tool with two projections (not shown) can be inserted into both the fifth ejection gap  136 E and the fifth release aperture  137 E to eject an insert  114  (not shown in the fifth pocket  124 E but rather in the first pocket  124 A). 
     Notably, as the release aperture  137  does not open out to the adapter peripheral surface  122  it does not weaken the insert adaptor  112  to the extent that an elasticity groove (not shown) would. 
     Now referring to the first pocket  124 A, it can further be formed with an insert stopper surface  144 . The insert stopper surface  144  is located along the periphery of the insert adaptor  112  adjacent the front end  126  and the upper clamp surface  130 . 
     The insert adaptor  112  can be formed with a fastening configuration  146  which, differing to the previous example, is not in the center thereof. To elaborate, the fastening configuration  146  comprises one or more screw holes which in the present non-limiting example also have the dual function of being the release apertures  137 . 
     In the present example, in the operational position shown in  FIG. 6A , there are three release apertures  137 C,  137 D,  137 E ( FIG. 7B ) that function as screw holes when the insert  114  shown is. Stated generally, the screw holes furthest from the insert  114  are used to maximize cutting depth obtainable. 
     The benefits of using a central fastening configuration  46  are mentioned above, for example, ease of indexability of the insert adaptor  12 , less components, less manufacturing related to components, greater ease to produce a smaller adaptor  12 . By contrast, the benefits of one or more non-centrally located screw holes (stated differently, circumferentially located screw holes) as exemplified here is that greater cutting depth is possible (the previous example being limited to the center of the adaptor due to the presence of the protruding screw). 
     Initially it was believed that the benefits of a single central fastening configuration  46  were superior. However, surprising benefits have also been found for the alternate arrangement. Since the inserts  114  (noting the particular insert shape is not important to this advantage) are easily ejected and replaced multiple times before the pocket  124  wears out, the detriment of completely removing all three screws  118  (e.g.  FIG. 6A , also suffixed  118 C,  118 D,  118 E) in order to index the insert adaptor  112 , is far less detrimental than for other designs (e.g. a single pentagonal insert with integral multiple edges spaced along the periphery thereof). 
     Thus the previously considered modest advantage of a slightly greater cut depth is not as significantly disadvantaged by multiple screws as was initially believed, further increasing the cost effectiveness of such insert adaptors. 
     In the present example the screw holes  137  are not tapered, nor are the screw holes  137  offset with the tool holder&#39;s tool holes  168  (also suffixed  168 C,  168 D,  168 E). Stated differently, in the present example the screw holes  137  are simple cylindrical bores. Surprisingly, it has been found that even without the tapering and/or offset exemplified in the previous embodiment, which assists in biasing an insert adaptor onto a tool holder, appropriate clamping of the insert adaptor to a tool holder has been achieved. This is by far the simplest design, however certainly the option remains to taper and/or offset the screw holes (as in the previous example) to provide a biasing effect. All three options being feasible for any embodiment of the present invention. 
     It is also theoretically possible for an insert adaptor to comprise both screw holes and release apertures, or merely screw holes (depending on the method of insert removal) however, in embodiments where both release apertures and screw holes are used, it is clearly advantageous in terms of structural strength and production to have a combined function. 
     The adaptor peripheral surface  122  can be formed with a straight bearing surfaces  152  (also suffixed, e.g. first, second, third, fourth and fifth bearing surfaces  152 A,  152 B,  152 C,  152 D,  152 E), i.e. in a side view (e.g.  FIG. 2B ) extending between the pockets  24 . 
     One of the notable differences mentioned above is the location of the operational insert  114  relative to the orientation of the bearing surfaces  152  (specifically the first bearing surface  152 A directly below the insert  114 ). As will be best understood from  FIG. 6A , the first bearing surface  152 A extends directly underneath the insert  114 . Stated differently the first bearing surface  152 A in an operational position is essentially perpendicular to the operational direction D O . To elaborate, by comparison, in the previous example the bearing surface  52 B was essentially parallel with the operational direction D O , whereas it can be seen that in the present example the corresponding lower bearing surface forms an acute lower surface bearing angle a the operational direction D O . The angle a is preferably fulfills the condition: 5°&lt;α&lt;25°, more preferably 10°&lt;α&lt;20° and most preferably 13°&lt;α&lt;19°. 
     It will be understood that such orientation provides better support underneath an insert. This is achieved by rotating the bearing surfaces  152  relative to the pocket  124  positions (relative to the previous example). This advantageous rotation can also optionally be incorporated for other insert types such as that shown in the previous example. However, for the angled insert type shown in the present figures such orientation is believed necessary. 
     A further improvement in the bearing surface  152  is that it can comprise an optional but preferred recessed portion  153  directly adjacent the insert  114 . The bearing surface  152  can thus comprise a recessed portion  153 , a transition portion  155  and a non-recessed portion  157 . 
     By not having an entirely straight bearing surface  152 , but including a recessed portion  153 , any deformation caused by the insert  114  (caused by impacts during machining) more significantly affects the recessed portion  153  rather than the non-recessed portion  157 . Thus any deformation or at least less deformation occurs in the non-recessed portion  157  used for abutment with the tool holder  116 . Clearly, this feature can be beneficially incorporated into any embodiment. 
     Referring to  FIGS. 8A to 8C , the tool holder  116  is generally similar, the notable difference being the three tool holes tool holes  168  and the rotated tool bearing surfaces  164 A,  164 B which are configured to contact the non-recessed portions  157  of each bearing surface  152 . The remaining features are generally similar to the previous example. 
     The description above includes exemplary embodiments and details for enablement, if needed, of claimed subject matter, and does not exclude non-exemplified embodiments and details from the claim scope of the present application.