Method of clamping a Y-axis feed direction parting blade or cutting insert and a holder and tool assembly for same

Abstract

A method of clamping a first cutting insert or an adaptor to a holder. Either the holder includes two insert pockets configured for machining in two different orthogonal directions or the holder includes a single adaptor pocket configured for holding the adaptor in two different orthogonal directions. The method includes the steps of choosing one of two orthogonal directions for machining and securing either the first cutting insert to an appropriate one of the two pockets or securing the adaptor to the adaptor pocket for machining in the chosen orthogonal direction.

Claims

1. A parting tool configured to selectively perform X-axis cutting in a forward direction (DF) and Y-axis cutting in an upward direction (DU) which is perpendicular to the forward direction (DF), the parting tool comprising: a tool holder (12) comprising: a holder head portion (32); a holder shank portion (34) configured to be secured to a machine interface (18); and an adaptor pocket (36, 400) formed in the holder head portion (32) and comprising: a first threaded tool hole (432); a first additional threaded tool hole (432); a tool holder outlet aperture (434) for transferring coolant to the parting adaptor (14); an additional tool holder outlet aperture (434); and a pocket bisector plane (P1) about which the first threaded tool holes (432, 432), and the outlet apertures, (434, 434) have mirror symmetry. a parting adaptor (14) comprising: opposing first and second sides (19A, 19B); a peripheral edge connecting the first and second sides; and a plurality of insert pockets (15A, 15B, 15C, 15D); and an operative cutting insert (16) retained in one of said plurality of insert pockets, the operative cutting insert having a forwardmost cutting edge (30A); wherein: the parting adaptor (14) is configured to be selectively mounted to the adaptor pocket (36) of the tool holder (12): (a) in a first orthogonal position in which the first side (19A) of the parting adaptor faces the adaptor pocket (36) and the forwardmost cutting edge (30A) is oriented such that the parting tool is configured for X-axis cutting; and also (b) in a second orthogonal position in which the second side (19B) of the parting adaptor faces the adaptor pocket (36) and the forwardmost cutting edge (30A) is oriented such that the parting tool is configured for Y-axis cutting.

2. The parting tool according to claim 1, wherein the adaptor pocket (400) comprises: a plurality of peripheral threaded tool holes (450A, 450C); and a plurality of additional peripheral threaded tool holes (450A, 450C); wherein: the plurality of peripheral threaded tool holes (450A, 450C) are mirror symmetric about the pocket bisector plane (P1) with respect to the plurality of additional peripheral threaded tool holes (450A, 450C).

3. The parting tool according to claim 1, wherein: the holder shank portion (34) comprises an upwardmost holder shank surface (52A) and a holder shank cross-sectional shape; the holder shank cross-sectional shape is square or rectangular; and the forwardmost cutting edge (30A) is aligned with the upwardmost holder shank surface (52A) in both the first orthogonal position and the second orthogonal position.

4. The parting tool according to claim 1, wherein: the holder shank portion (34) comprises an upwardmost holder shank surface (52A) and a holder shank cross-sectional shape; the holder shank cross-sectional shape is round; and the holder shank axis (AS) extends to the forwardmost cutting edge (30A) in both the first orthogonal position and the second orthogonal position.

5. The parting tool according to claim 1, wherein: the holder head portion (32) comprises a holder concave front surface (44).

6. The parting tool according to claim 1, wherein: the adaptor pocket (36) comprises an adaptor pocket side surface (46) and a pocket projecting edge (48) extending therealong, the pocket projecting edge (48) comprising a pocket lower abutment surface (48A) and a pocket rear abutment surface (48B); the pocket lower abutment surface (48A) faces the forward direction (DF); and the pocket rear abutment surface (48) faces the upward direction (DU).

7. The parting tool according to claim 1, wherein: the adaptor pocket (36) comprises a pocket projection (53) configured to prevent mounting of the parting adapter in the adaptor pocket in one first and second orthogonal orientations.

8. The parting tool according to claim 7, wherein: the pocket projection (53) comprises a removable pin (53B) secured to a pin hole (53B) formed in the adaptor pocket (36).

9. The parting tool according to claim 1, wherein the adaptor pocket (400) further comprises a biasing hole (436) for providing for a biasing element (438).

10. A parting tool configured to selectively perform X-axis cutting in a forward direction (DF) and Y-axis cutting in an upward direction (DU) which is perpendicular to the forward direction (DF), the parting tool comprising: a tool holder (12) comprising: a holder head portion (32); a holder shank portion (34) configured to be secured to a machine interface (18); and an adaptor pocket (36, 400) formed in the holder head portion (32) and comprising: a planar pocket surface (444); a first plurality of threaded holes (450A, 450C) formed on the pocket surface (444) and configured to secure a parting adaptor in a first orientation for X-axis cutting; and a second plurality of threaded holes (450A, 450C) formed on the pocket surface (444) and configured to secure said parting adaptor in a second orientation for Y-axis cutting; wherein: the first plurality of holes and the second plurality of holes are mirror symmetrically positioned about a bisector plane (P1).

11. The parting tool according to claim 10, wherein the holder head portion (32) comprises a holder concave front surface (44).

12. The parting tool according to claim 10, wherein: the adaptor pocket (36) comprises an adaptor pocket side surface (46) and a pocket projecting edge (48) extending therealong, the pocket projecting edge (48) comprising a pocket lower abutment surface (48A) and a pocket rear abutment surface (48B); the pocket lower abutment surface (48A) faces a forward direction (DF); and the pocket rear abutment surface (48) faces an upward direction (DU).

13. The parting tool according to claim 10, wherein the adaptor pocket (400) further comprises a biasing hole (436) for providing for a biasing element (438).

14. The parting tool according to claim 10, wherein the adaptor pocket (400) comprises: a tool holder outlet aperture (434) for transferring coolant to the parting adaptor (14); an additional tool holder outlet aperture (434); and the outlet apertures, (434, 434) have mirror symmetry about the pocket bisector plane (P1).

15. A tool holder (12) comprising: a holder head portion (32); a holder shank portion (34) configured to be secured to a machine interface (18); and an adaptor pocket (36, 400) formed in the holder head portion (32) and comprising: a planar pocket surface (444); a first plurality of threaded holes (450A, 450C) formed on the pocket surface (444) and configured to secure a parting adaptor in a first orientation for X-axis cutting; and a second plurality of threaded holes (450A, 450C) formed on the pocket surface (444) and configured to secure said parting adaptor in a second orientation for Y-axis cutting; wherein: the first plurality of holes and the second plurality of holes are mirror symmetrically positioned about a bisector plane (P1).

16. The tool holder according to claim 15, wherein the holder head portion (32) comprises a holder concave front surface (44).

17. The tool holder according to claim 15, wherein: the adaptor pocket (36) comprises an adaptor pocket side surface (46) and a pocket projecting edge (48) extending therealong, the pocket projecting edge (48) comprising a pocket lower abutment surface (48A) and a pocket rear abutment surface (48B); the pocket lower abutment surface (48A) faces a forward direction (DF); and the pocket rear abutment surface (48) faces an upward direction (DU).

18. The tool holder according to claim 15, wherein the adaptor pocket (400) further comprises a biasing hole (436) for providing for a biasing element (438).

19. The tool holder according to claim 15, wherein the adaptor pocket (400) comprises: a tool holder outlet aperture (434) for transferring coolant to the parting adaptor (14); an additional tool holder outlet aperture (434); and the outlet apertures, (434, 434) have mirror symmetry about the pocket bisector plane (P1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1A is a side view of a tool assembly in an X-axis feed orientation according to the present invention, further showing a schematic workpiece and a schematic machine interface;

(3) FIG. 1B is a rear view of the tool assembly in FIG. 1A;

(4) FIG. 2 is a side view of the tool assembly in FIG. 1A, with an adaptor thereof oriented in a Y-axis feed orientation, further showing a schematic workpiece (except the pocket being devoid of a pocket projection 53 shown in FIG. 1A and better shown in FIG. 4A);

(5) FIG. 3 is a schematic representation of the adaptor in FIG. 1A being brought from the X-axis feed orientation in FIG. 1A to the Y-axis feed orientation in FIG. 2;

(6) FIG. 4A is a perspective view of the holder and adaptor in the Y-axis feed orientation shown in FIG. 2 but prevented from being mounted by a pocket projection;

(7) FIG. 4B is a side view of the holder and adaptor, corresponding to FIG. 4A;

(8) FIG. 4C is an enlarged and slightly rotated view of the encircled portion designated IV in FIG. 4A;

(9) FIG. 5 is one possible pocket of another holder according to the present invention;

(10) FIG. 6A is a side perspective view of yet another tool assembly according to the present invention;

(11) FIG. 6B is an end view of the tool assembly in FIG. 6A, showing the tool assembly in an X-axis feed orientation and a schematic workpiece;

(12) FIG. 6C is a side view of the tool assembly in FIG. 6A, showing the tool assembly in a Y-axis feed orientation and a schematic workpiece;

(13) FIG. 6D is a side perspective view of the tool assembly in FIG. 6A with the Y-axis insert removed; and

(14) FIG. 6E is a side perspective view of the tool assembly in FIG. 6A with the X-axis insert removed.

DETAILED DESCRIPTION

(15) Referring to FIGS. 1A and 1B, a tool assembly 10 is shown, the tool assembly 10 comprising a holder 12, a parting adaptor 14 (generally similar to the parting blade shown in FIGS. 18A to 18C of USPA 2019/0240741, at least with respect to the shape of the parting blade, the straight bearing surfaces, and at least one insert pocket (which in this example is first, second, third and fourth insert pockets 15A, 15B, 15C, 15D) secured to the holder 12, as well as an operative cutting insert 16 secured to the parting adaptor 14.

(16) The contents of USPA 2019/0240741, and most particularly FIGS. 18, 19 and 20, are incorporated herein by reference.

(17) Referring particularly to FIG. 1A, the holder 12 is positioned proximate to a schematic cylindrical rotating workpiece 20. The workpiece 20 has a central workpiece axis AW and during machining is rotated in the counterclockwise direction DCC in this view, as indicated.

(18) For explanation and a frame of reference, the figures show a forward direction DF, a rearward direction DR, an upward direction DU, a downward direction DD, a first sideways direction DS1 and a second sideways direction DS2.

(19) The forward direction DF constitutes an X-axis feed direction in which direction the tool assembly 10 is moved to machine the workpiece 20.

(20) The cutting insert 16 comprises: a rake surface 22 and an opposing insert base surface 24, a forwardmost clearance (relief) surface 26A extending downwardly (as well as slightly inwardly; i.e. in the downward direction DD and slightly in the rearward direction DR) from the rake surface 22 and an opposing insert rear surface 28, a forwardmost cutting edge 30A formed at an intersection of the rake surface 22 and the forwardmost clearance surface 26A.

(21) Preferably, the rake surface 22 comprises a chip forming arrangement (not shown).

(22) Each of the adaptor's first, second, third and fourth insert pockets 15A, 15B, 15C, 15D are identical and equally circumferentially spaced about an index axis center AI (shown in FIG. 3) around which the adaptor 14 has four-way rotational symmetry. As seen in the FIG. 1A, the second insert pocket 15B is seen to comprise a base jaw 17A, a second jaw 17B and a slot end 17C. It is understood that the remaining pockets 15A, 15C and 15D have similar construction.

(23) Reverting to the first insert pocket 15A, adjacent to each of the insert pockets 15, on an external side of the parting adaptor 14, adjacent to the base jaw 17A there is an external pocket relief surface 17D, and adjacent to the second jaw 17B there is an external pocket rake surface 17E.

(24) Briefly referring to FIG. 3, the parting adaptor 14 further comprises first and second main adaptor sides 19A, 19B. First, second, third and fourth peripheral adaptor bearing surfaces 54A, 54B, 54C, 54D connect the first and second main adaptor sides 19A, 19B.

(25) The holder 12 comprises a holder head portion 32 and a holder shank portion 34.

(26) The holder shank portion 34 is secured to a machine interface 18 which can be a tool post or turret, etc.

(27) The holder head portion 32 comprises an adaptor pocket 36.

(28) The holder head portion 32 comprises a holder concave front surface 44, which is useful for structural strength when the holder 12 is used with a standard parting adaptor.

(29) The adaptor pocket 36 comprises an adaptor pocket side surface 46, and a pocket projecting edge 48 extending therealong.

(30) The pocket projecting edge 48 can comprise a pocket lower abutment surface 48A which, in this preferred but non-limiting example, faces the forward direction DF, a pocket rear abutment surface 48B which faces the upward direction DU, and preferably also a pocket relief recess 48C connecting the pocket lower and pocket rear abutment surfaces 48A, 48B.

(31) The holder shank portion 34 further has a holder shank axis As, which is shown for understanding of the position thereof had the holder shank cross-sectional shape have been round.

(32) A forwardmost imaginary line L1 extends in the X-axis direction (which in the reference directions shown is the forward direction DF) from an upwardmost holder shank surface 52A to the forwardmost cutting edge 30A.

(33) In the present example, the name upwardmost holder shank surface is the forwardmost surface of the shank in the Y-axis direction (which in the reference directions shown is the upward direction DU), and the names are arbitrarily referenced herein relative to the X-axis direction, i.e. it is the holder shank surface most in the upward direction DU in FIG. 1A; it will be understood that the name upwardmost is merely a name and that for a square or rectangular shanks the surface indicated as 52A is the relevant reference surface as known in the art). For cylindrical or other round type shanks, the forwardmost surface is a thin line-like portion of the shank which is parallel to the holder shank axis AS and is the forwardmost portion of the shank in the Y-axis direction.

(34) Since the position of the holder shank portion 34 is set from its connection with the machine interface 18, the position of the forwardmost cutting edge 30A is calibrated as zero in the CNC machine and does not require any offset to be input.

(35) Even without the forwardmost imaginary line L1, which is a useful explanatory aid as shown in the side view of FIG. 1A, it is understood that the forwardmost cutting edge 30A is directly in the forward direction DF from the upwardmost holder shank surface 52A.

(36) As further elaborated below, the adaptor pocket 36 is formed with a pocket projection 53 in the form of a pin 53A secured to a pin hole 53B (better shown in FIG. 4C).

(37) Referring now to FIG. 2, to arrive at the shown position from FIG. 1A, the parting adaptor 14 was removed from the holder 12 and, for example, a two-step sequence comprising one rotation and one flip may be executed. For example, after removal, the parting adaptor 14 may first be rotated clockwise (90) about the parting blade's index axis AI and then flipped from right-to-left, before being reinserted. In another sequence, the transition from FIG. 1A to FIG. 2 can be achieved by first flipping the parting adaptor 14 from left-to-right, and then rotating it 90 counter-clockwise, before being reinserted. A further sequence is described below, with respect to FIG. 3. Any of these sequences results in the parting adaptor 14 to now be oriented in a second orthogonal direction for machining the workpiece 20. With any of these sequences, the parting adaptor 14 has effectively been pivoted about the forwardmost cutting edge 30A to now be oriented in said second orthogonal direction for machining the workpiece 20.

(38) Additionally, after removing the parting adaptor 14 but before remounting it to the holder 12, the pin 53A, shown in FIG. 1A, was first removed from the pin hole 53B and subsequently the parting adaptor 14 was mounted to the adaptor pocket 36.

(39) More specifically, in the reconfigured tool, the upward direction DU is now also the Y-axis feed direction in which direction the tool assembly 10 is moved relative to the workpiece 20 in order to machine the workpiece 20 (which now is rotated in the clockwise direction DC).

(40) Since the forwardmost cutting edge 30A in both positions (i.e. both in FIGS. 1A and 2) is aligned with the so-called upwardmost holder shank surface 52A, the only calibration needed for the orientation in FIG. 2 is in the forward and rearward directions DF, DR to ensure the forwardmost cutting edge 30A is aligned with a central workpiece axis AW as schematically shown by a second imaginary line L2 extending perpendicular to the forward and rearward directions DF, DR from the center point WC to the forwardmost cutting edge 30A.

(41) A diagonal plane P (FIG. 2) can extend through the forwardmost cutting edge 30A and through opposing jaws of an insert pocket.

(42) While the terms index and reverse are known in the art, there is no term known to the applicant for changing the orientation of a particular tool or cutting insert from the X-axis orientation to the Y-axis orientation (i.e. to change between said two different orthogonal orientations).

(43) One way is to define that the insert pocket rake and relief sides are pivoted (with the present shaped adaptor being pivoted at an angle of 180) relative to each other.

(44) Alternatively defined, the operative cutting insert 16 and the parting adaptor 14 it is mounted to can be flipped (i.e. rotated 180) about the diagonal plane P (FIG. 2). At least the insert pocket is mirror symmetric in a first orientation to a second orientation achieved after the parting adaptor 14 is flipped about the diagonal plane P.

(45) Yet, alternatively defined, the insert pocket can be pivoted 180 about a bisector line LB extending through the center of two orthogonal positions. The bisector line LB can be defined as extending through a predetermined cutting edge position defined by the insert pocket, as known in the art (the position occupied by the cutting edge 30A. More precisely the bisector line LB extends through the center of the parting adaptor 14 (not meaning necessarily through an index axis center AI, depending on the shape of the parting adaptor 14, but rather this means equally spaced from the first and second main adaptor sides 19A, 19B.

(46) Still alternatively defined, relative to an operative cutting insert 16, the forwardmost cutting edge 30A can be held in a single position and the insert (as well as any component it is mounted to such as the adaptor) is pivoted about the front cutting edge by 180. In other words, the opposite ends of the cutting edge 30A (which is seen in FIGS. 1A and 2 to extend into the sheet) are reversed.

(47) To ensure understanding, now referring to FIG. 3, it is shown schematically how such change of position is accomplished (rather than simply showing a pivoted adaptor which is what is shown in FIG. 1A to FIG. 2, which is difficult to understand with a symmetric object using 2D drawings, a more elaborate explanation which can be shown is now exemplified for understanding, not that such exact sequence of movements are needed in practice).

(48) The same adaptor 14 as described above is shown in first (initial), second (intermediate) and third (final) positions 14A, 14B, 14C, relative to the forward direction DF.

(49) In the uppermost drawing, the adaptor's first position 14A can for example correspond to the orientation shown in FIG. 1A. (this example using the directions shown in FIG. 1A for the sake of explanation only; it could alternatively be the orientation in FIG. 2, in which case the forward direction DF shown in the first position 14 would be replaced with the upward direction DU and so forth, mutatis mutandis.).

(50) From its initial position, the adaptor 14 (or an insert) in the initial position 14A is rotated 90 in the counterclockwise direction DCC, while keeping the forwardmost cutting edge 30A in the same position (i.e. not undergoing translational motion, but only rotational motion (for ease of understanding the adaptor 14 in the translated position 14B is drawn in a different, translated, position, but could be imagined to be adjacent the first position 14A with the forwardmost cutting edge 30A in the same, untranslated, location); such that the rake surface 22 of the adaptor 14 in the intermediate position 14B is now orthogonal to the first position 14A).

(51) While keeping the rake surface 22 (and the forwardmost cutting edge 30A) in the same position (i.e. not undergoing translational motion) the adaptor 14B is flipped from right-to-left as indicated by the arrow 56.

(52) Consequently, the adaptor 14 in final position 14C is in the second orthogonal orientation, which in this case is the Y-axis feed orientation, or the upward direction DU (using the non-limiting relative directions in this example).

(53) Referring now to FIGS. 4A to 4C, if the pin 53A would not have been removed from the pin hole 53B, the adaptor 14 would not have been able to be mounted to the adaptor pocket 36 in the orientation shown in FIG. 2. In the shown example, when attempting to mount the adaptor 14 to the holder 12 in the same orientation as FIG. 2, the external pocket relief surface 17D abuts the pin 53A. Thus the pocket projection prevents incorrect mounting of the adaptor 14, when one of the specific orientations is going to be repeatedly used for machining.

(54) The position of the pocket projection, while non-limiting, is particularly useful in an insert pocket location (i.e. where the insert pocket will be located on the adaptor pocket 36) when an insert pocket is asymmetric. This is because when the adaptor 14 is being mounted correctly, the user does not have to carry out any extra actions for mounting, and does not even need to notice or attend to the pocket projection.

(55) While the above-examples did not relate to a specific way in which a parting adaptor 14 is mounted (i.e. secured) to a holder 12, FIG. 5 will detail one exemplary way.

(56) Referring to FIG. 5 of the present application, it will be noted that FIG. 19A of USPA 2019/0240741 has a tool holder 404 and an adaptor pocket similar, but by no means identical, to the adaptor pocket 400 of FIG. 5.

(57) Corresponding features in FIG. 19A of USPA 2019/0240741 and present FIG. 5 are denoted with the same reference characters. Specifically, both adaptor pockets comprise: a first threaded tool hole 432 and a tool holder outlet aperture 434 for transferring coolant to a parting adaptor 14; a biasing hole 436 for providing for a biasing element 438 (FIG. 20A of USPA 2019/0240741); a pocket surface 444 provided with a plurality of peripheral threaded tool holes 450A, 450C (noting that in the present preferred embodiment only two peripheral threaded tool holes were found necessary instead of three as shown in USPA 2019/0240741).

(58) Referring now only to FIG. 5 of the present application, in order to configure the adaptor pocket 400 for two different orthogonal orientations, additional elements were added with corresponding elements being suffixed with an apostrophe ().

(59) Therefore, an additional first threaded tool hole 432, an additional tool holder outlet aperture 434, and two additional peripheral threaded tool holes 450A, 450C were added. As seen in the plan view of FIG. 5, the adaptor pocket 400 has a pocket bisector plane P1, about which the first threaded tool holes 432, 432, the outlet apertures, 434, 434, and the peripheral threaded tool holes 450A, 450A. 450C, 450C have mirror symmetry.

(60) In the present example a biasing hole 436 and biasing element 438 are only provided for a single orientation. However, it will be understood that an additional biasing hole (not shown) could be provided and the biasing element 438 could be mounted to the additional biasing hole, if desired. In such case, the entire pocket surface 444 would have mirror symmetry about the pocket bisector plane P1.

(61) It will be understood that FIG. 5 only shows one possible, out of many, modifications that can enable said two different orthogonal orientations.

(62) It will be understood that an adaptor should have abutment surfaces (or external surfaces) to allow for more than one orthogonal orientation. These abutment surfaces can then be mounted to the same pocket surfaces in order to maintain a similar cutting edge position.

(63) Finally, referring to FIGS. 6A to 6C, an example is shown of a tool assembly 100 configured for two different orthogonal orientations.

(64) The tool assembly 100 comprises a holder 102 and at least one (and in the example shown, two), cutting inserts 104, 106 which are identical but are called herein an X-axis cutting insert 104 and a Y-axis cutting insert 106, for purposes of explanation.

(65) The X-axis cutting insert 104 is secured to an X-axis insert pocket 105 (FIG. 6C) and the Y-axis cutting insert 106 is secured to a Y-axis insert pocket 107 (FIG. 6D).

(66) Preferably the holder comprises a shank portion 108 and a head portion 110. The X-axis pocket 105 and the Y-axis pocket 107 are both formed on the head portion 110 and both open out to an end surface 120 of the head portion 110. However, a X-axis pocket seating surface 105A and a Y-axis pocket seating surface 107A face in different, orthogonal directions.

(67) An external rib 112, preferably extending perpendicular to a longitudinal axis AL of the shank portion 108, provides a stopper function between the head portion 110 and the shank portion 108.

(68) In FIG. 6B, the X-axis cutting insert 104 is oriented to machine the workpiece 114 in a designated X direction. In this cutting configuration, a resulting first cutting force FX (i.e. the majority of the cutting force portion tangential to the workpiece 114, noting that the overall cutting force is a little more directed towards the shank portion 108) experienced by the operative X-axis cutting insert 104 is directed transverse to an interface direction D1 (direction D1 being basically from the head portion 110 towards the machine interface in which the shank portion 108 is retained). As seen in FIG. 6A, the interface direction D1 substantially extends along the length of the shank portion 108.

(69) In FIG. 6C, the Y-axis cutting insert 106 is oriented to machine the workpiece 116 in a designated Y direction. In this cutting configuration, a resulting second cutting force FY (i.e. the majority of the cutting force portion tangential to the workpiece 114) experienced by the operative Y-axis cutting insert 106 is directed parallel to a direction D1 from the head portion towards the machine interface in which the shank portion 108 is retained. And again, as seen in FIG. 6C, the direction D1 substantially extends along the length of the shank portion 108. In some embodiments, D1 can extend in the rearward direction DR.

(70) Since the X-axis and Y-axis insert pockets 105, 107 have been positioned distant to each other, in this preferred example at diametrically opposed corners of the head portion 110, they can be mounted simultaneously to the holder 102 and the workpieces 114, 116 can be machined, even though only one of the two inserts would be operational, at any given time.

(71) If there is no need for machining in both orientations in a single mounting, the holder 102 can optionally have only a single cutting insert mounted thereto as shown in FIGS. 6D and 6E.