Cutting tool and cutting insert therefor

Cutting Tool and Cutting Insert Therefor 1SCAR LTD.

The inventor:Gil Hecht υοπ Ρυ - I -

CUTTING TOOL AND CUTTING INSERT THEREFOR

FIELD OF THE INVENTION 5 [001] The present invention relates to metal cutting tools for grooving, parting and turning having a cutting insert releasably secured therein via a screw.

BACKGROUND OF THE INVENTION 10 [002] US7094006 discloses a cutting tool in which the cutting insert has two abutment surfaces transverse to two side surfaces and the insert pocket has two sidewallstransverse a the base wall. When the cutting insert is retained in the insert pocket a firstabutment surface abuts a first sidewall of the insert pocket, a second abutment surfacesabuts a second sidewall of the insert pocket and a side surface of the cutting insert abuts 15 the base wall of the insert pocket. The first sidewall is elongated in form, extendinglongitudinally rearwardly from a forward end of the cutting tool. The first side wall islocated on a lower support member in the form of a relatively thin narrow strip of thetool body.

[003] Insert securing methods that do not require a lower support member of the type 20 described above use specially designed protrusions (or recesses) extending from the toolshank, abutting matching recesses (protrusions) in the base of the cutting insert, asdescribed, for example, in DE022005016610U1 and EPI657012. EPI657012 disclosesa securing method with an elevated boss having studs oriented around the screw bore ina double-Y formation. While the insert is in a secured position, the boss and studs of 25 the cutting insert abut matching recesses in the insert pocket. The abutment surfacesdescribed in DE022005016610U1 and EPI657012 have a non-parallel orientation withrespect to a screw bore axis. This allows for machining forces exerted onto the cuttinginsert and eventually the abutment surfaces, to have an element in the direction of thescrew bore axis. Swiss-type automatic machines are known to require the use of small 30 cutting tools secured with high accuracy in the machine. In this field, cutting edgelocation accuracy is attained either by an accurate abutment ( which is most likelyachieved by a rather expensive grinding of the abutment surfaces) or by grinding thecutting portion. Achieving an accurate abutment is somewhat difficult when the -2- 202026/2 abutment surfaces are created by form-pressing and sintering (withou t grinding) asdisclosed, for example, in DE022005016610U1.

[004] It is therefore an object of the present invention to provide a new cutting tool andcutting insert therefore having an abutment arrangement that significantly reduces orovercomes the aforementioned disadvantages.

SUMMARY OF THE INVENTION

[005] In accordance with the subject matter of the present invention there is provided acutting tool comprising: an insert holder having a forward end and comprising: an insert pocket at the forward end, a shank extending rearwardly from theinsert pocket and first and second holder surfaces extending rearwardly from theforward end; wherein the insert pocket comprises: a base surface located between the second holder surface and an imaginaryplane M passing through the first holder surface; a pocket bore opening out to the base surface; first and second major support surfaces extending from the base surface andlocated on opposite sides of the pocket bore, the first major support surface being closerto the forward end than the second major support surface; and a minor support surface extending from the base surface and located furtherfrom the forward end than the first major support surface, the minor support surfacebeing transverse to the first and second major support surfaces; and an indexable cutting insert retained in the insert pocket of the insert holder, thecutting insert comprising: first and second side surfaces and a peripheral surface extending therebetween; two cutting portions located at opposite ends of the cutting insert; an insert bore opening out to both side surfaces, the insert bore having an insert bore axis S about which the cutting insert has 180° rotational symmetry; -3- 202026/2 two major abutment surfaces extending from the second side surface andlocated on opposite sides of the insert bore, each major abutment surface being closer toone cutting portion than to the other cutting portion; first and second minor abutment surfaces extending from the second sidesurface, wherein in a plan view of the second side surface the first and second minorabutment surfaces are transverse to the two major abutment surfaces; and two base abutment surfaces distanced from the second side surface and facingaway therefrom, each base abutment surface associated with one major abutment surfaceand one minor abutment surface; wherein the abutment surfaces are suitable for being organized into first and second setsof insert abutment surfaces having overlapping membership, only one set capable ofbeing operative at a given time, the first set comprising the two base abutment surfaces,the two major abutment surfaces and the first minor abutment surface, the second setcomprising the two base abutment surfaces, the two major abutment surfaces and thesecond minor abutment surface; and wherein: the two base abutment surfaces abut the base surface of the insert holder; a first of the two major abutment surfaces abuts the first major support surface;a second of the two major abutment surfaces abuts the second major support surface;and one of the minor abutment surfaces abuts the minor support surface.

[006] Any of the following features, either alone or in combination, may be applicableto the above aspect of the subject matter of the application: [007] The base abutment surfaces can be parallel to the second side surface.

[008] The major and minor abutment surfaces can be planar.

[009] The major and minor abutment surfaces can be perpendicular to the second sidesurface.

[0010] In a plan view of the second side surface, the major abutment surfaces can beparallel to one another and to an insert longitudinal axis Al of the cutting insert, theinsert longitudinal axis Al passing through the insert bore axis S and through the cuttingportions. -4- 202026/2 [0011] The major abutment surfaces can face in opposite directions.

[0012] The cutting insert can further comprise two support beams which protrude fromthe second side surface, each support beam has one base abutment surface, formedthereon , one major abutment surface, and one minor abutment surface. 5 [0013] The base surface, the first and second major support surfaces and the minor support surface can be planar.

[0014] The first and second major support surfaces and the minor support surface can beperpendicular to the base surface.

[0015] The pocket bore can have a pocket bore axis P; and 10 in a plan view of the base surface, the first and second major support surfaces can be parallel to one another and are parallel to and located on either side of a holderlongitudinal axis A2, the holder longitudinal axis A2 passing through the pocket boreaxis P and through the shank.

[0016] The first and second major support surfaces can face in opposite directions. 15 [0017] The first and second major support surfaces can be located on a longitudinal projection protruding from the base surface.

The base surface can comprise an upper base support surface on one side of thelongitudinal projection; and a lower base support surface on an opposite side of thelongitudinal projection. 20 [0018] Only the upper base support surface, the lower base support surface, the first and second major support surfaces and the minor support surface are configured to supportabutment surfaces formed on a cutting insert, when a cutting insert is retained in theinsert pocket.

[0019] The base surface can comprise an upper base support surface and a lower base 25 support surface; a first of the two base abutment surfaces abuts the upper base support surface;and a second of the two base abutment surfaces abuts the lower base supportsurface (58b). 30 202026/2 -5 -

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a better understanding of the present invention and to show how the samemay be carried out in practice, reference will now be made to the accompanyingdrawings, in which:

Fig. 1 is an isometric view of an assembled cutting tool according toembodiments of the present invention;

Fig. 2 is an isometric exploded view of the cutting tool of Fig. 1;

Fig. 3 is a side view of the cutting insert shown in Fig. 1;

Fig. 4 is an isometric view of the cutting insert of Fig. 3;

Fig. 5 is a side view of the shank shown in Fig. 1; andFig. 6 is an isometric view of the shank of Fig. 5.

[0021] It will be appreciated that for simplicity and clarity of illustration, elementsshown in the figures have not necessarily been drawn accurately or to scale. Forexample, the dimensions of some of the elements may be exaggerated relative to otherelements for clarity, or several physical components may be included in one functionalblock or element. Further, where considered appropriate, reference numerals may berepeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In the following description, various aspects of the present invention will bedescribed. For purposes of explanation, specific configurations and details are set forthin order to provide a thorough understanding of the present invention. However, it willalso be apparent to one skilled in the art that the present invention may be practicedwithout the specific details presented herein. Furthermore, well-known features may beomitted or simplified in order not to obscure the present invention.

[0023] Reference is made to Figs. 1 and 2 showing, respectively, an isometric view andan isometric exploded view of a cutting tool 10 in accordance with embodiments of theinvention. The cutting tool 10 includes an insert holder 12 and an indexable cuttinginsert 14 releasably retainable in the insert holder 12 by a screw 16. Reference is furthermade to Figs. 2, 3 and 4 showing the cutting insert 14 in isometric and side views. The -6- 202026/2 cutting insert 14 has generally parallel first and second side surfaces 18, 20 and aperipheral surface 22 extending therebetween. The cutting insert 14 has an insert bore24 opening out to the first and second side surfaces 18, 20 and an insert bore axis Sabout which the cutting insert has a 180° rotational symmetry. The insert bore axis Sbeing perpendicular to the first and second side surfaces 18, 20. The cutting insert 14has two cutting portions 26 at opposite ends thereof and a clamping portion 27 locatedbetween the cutting portions 26. The cutting insert has an insert longitudinal axis Alpassing through the cutting portions 26 and the insert bore axis S. Each cutting portion26 has a rake surface 28 and a relief surface 29 which meet at a cutting edge 30. Theclamping portion 27 may have, according to applications of the invention, first andsecond support beams 32’, 32” protruding from the second side surface 20 and locatedon each side of the pocket bore. The first and second support beams 32’, 32” will alsobe denoted by the joint reference numeral 32. Each support beam 32', 32" has a supportsurface 34 which according to some embodiments may be parallel to the second sidesurface 20. Each support beam 32', 32" has a major abutment surface 36 and at least oneminor abutment surface 38 transverse to the major abutment surface 36. According tosome embodiments, the major and minor abutment surfaces 36, 38 are planar andperpendicular to the second side surface 20. According to embodiments of theinvention, the major abutment surfaces 36 are parallel one to another and face inopposite directions.

[0024] Reference is made to Figs. 5 and 6 showing the insert holder 12 in respectiveside and isometric views. The insert holder 12 has an insert pocket 44 adjacent aforward end and a shank 46 extending rearwardly from the insert pocket 44. The insertholder 12 has a front holder surface 48 at the forward end of the insert holder 12 withopposing first and second holder surfaces 50, 52 and opposing upper and lower holdersurfaces 54, 56 extending rearwardly from the front holder surface 48. The insert holderhas a holder longitudinal axis A2 passing through the shank and the pocket bore axis P.In accordance with some embodiments, the upper and lower holder surfaces 54, 56 areperpendicular to the first and second holder surfaces 50, 52, respectively. The insertpocket 44 opens out to the upper and lower holder surfaces 54, 56 and to the first andfront holder surfaces 50, 48. The insert pocket 44 includes a base surface 58, a -7- 202026/2 longitudinal projection 60 and a pocket bore 62 having a pocket bore axis P and openingout to the base surface 58. According to some embodiments, the base surface 58 isplanar and parallel to the first and second holder surfaces 50, 52. The base surface 58 islocated between the second holder surface 52 and an imaginary plane M passing through 5 the first holder surface 50. The longitudinal projection 60 projects from the base surface58 and extends rearwardly from a front end of the insert pocket 44. According to someembodiments, the pocket bore 62 divides the longitudinal projection 60 into front andrear projections 64, 66. The front and rear projections 64, 66 have front and rearprojection surfaces 68, 70 respectively. The front and rear projections 64, 66 have first 10 and second abutment surfaces 72, 74 respectively. In accordance with embodiments ofthe invention, the rear projection 64 has a third abutment surface 76, located rearwardand upward of the pocket bore axis P in a plan view of the base surface 58. Accordingto some embodiments, the first and second abutment surfaces 72, 74 are parallel to eachother, face opposite directions and are transverse to the third abutment surface 76. The 15 first, second and third abutment surfaces 72, 74, 76 may be perpendicular to the basesurface 58.

[0025] When the cutting insert 14 is in a securely retained position in the insert pocket44 (see Fig. 1) with the screw 16 located in the insert bore 24 and threadingly receivedin the pocket bore 62, the two support surfaces 34 of the cutting insert 14 abut the base 20 surface 58 of the insert holder 12, one of the minor surfaces 38 abuts the third abutmentsurface 76, the major abutment surface 36 of the first support beam 32' abuts the firstabutment surface 72 of the front projection 64, and the major abutment surface 36 of thesecond support beam 32" abuts the second abutment surface 74 of the rear projection 66.[0026] In accordance with the present invention, when the cutting insert 14 is securely 25 retained in the insert pocket 44 the front and rear projection surfaces 68, 70 are notabutted by any surface of the cutting insert 14.

[0027] Another position of the cutting insert 14, referred to herein as a seated position, is when the cutting insert 14 is seated in the insert pocket 44 and the screw 16 is located in the insert bore 24, partially threaded in the pocket bore 62, but not tightened. In the 30 seated position, the pocket bore 62 and the insert bore 24 are eccentric in the forward to rearward direction. When the screw 16 is tightened, the cutting insert 14 is forced -8- 202026/2 rearwardly, causing the minor abutment surface 38 to slide over the third abutmentsurface 76 until they reach full abutment. The tightening of the screw 16 gives rise to alocking force FI perpendicular to the third abutment surface 76 (shown illustratively inFig. 5). Since the third abutment surface 76 is transverse to the first and second 5 abutment surfaces 72, 74 the locking force FI generates a clockwise directed torque T(see Figs. 1 and 5) on the cutting insert 14 with respect to the insert bore axis S, whichrotates the cutting insert 14 in the clockwise direction. The torque T generates, in turn,perpendicular abutment forces F2 and F3 on the first and second abutment surfaces 72,74 respectively (shown illustratively in Fig. 5). Cutting forces applied to the cutting 10 insert 14 operate to enhance the forces F2 and F3 thereby increasing the locking of thecutting insert 14 in the insert pocket 44.

[0028] While the present invention has been described with reference to one or morespecific embodiments, the description is intended to be illustrative as a whole and is notto be construed as limiting the invention to the embodiments shown. It is appreciated 15 that various modifications may occur to those skilled in the art that, while notspecifically shown herein, are nevertheless within the scope of the invention.