TW202410992A - Cemented carbide cutting insert for parting metal workpieces - Google Patents

Abstract

A two-cutting-edge parting insert including a first cutting portion, a second cutting portion and an elongated body portion connecting the first and second cutting portions. The elongated body portion has a body width (BW) measurable parallel to a lateral axis and a body length (BL) measurable parallel to an elongation axis. The body width is smaller than both cut widths of the cutting edges of the first and second body portions and fulfills the condition: 0.55mm ≤ BW ≤ 0.95 mm; and the body length fulfills the condition: 2mm ≤ BL ≤ 14 mm.

Description

Carbide cutting inserts for cutting metal workpieces

The subject matter of the present invention relates to a cemented carbide cutting insert for cutting a metal workpiece (hereinafter referred to as "cutting insert" or "insert").

The present invention relates to inserts for cutting metal workpieces. It will be understood that an insert configured for cutting is also configured for grooving because both involve a similar machining process. That is, both operations involve only forward movement relative to one of the workpieces (in other words, there is no sideways or lateral movement of the assembly). The difference between cutting and grooving operations lies only in the extent to which a cutting edge of the insert that cuts or machines a slit-shaped cut (an example of a slit-shaped cut of the type discussed is shown in Figure 7B of WO 2022/084992 and designated "S"; hereinafter also referred to as a "slit") enters the workpiece. In a slotting operation, unlike a parting operation, the slit extends relatively little into the workpiece (i.e., less than about half of the workpiece rotation) and thus does not "sever" the workpiece into two separate pieces. In a parting operation, the slit-shaped cut extends far enough into the workpiece to sever the workpiece (i.e., completely separate one piece from the workpiece).

For clarity, in the description and scope of the invention of this application, the insert is referred to as a cutting insert, but it should be understood that this cutting insert is also inherently configured to produce a narrow groove of the type shown in WO 2022/084992.

To create the slit, a cutting edge of the insert extends along the entire transverse length of the insert (i.e., a transverse direction perpendicular to the forward direction, or the sideways direction). The transverse extent of the cutting edge including the corner is referred to as the cutting width (usually designated as "CW", as illustrated and shown in FIG. 2C of US 11,278,968, although referred to as "cutting width _WC " in that publication).

Obviously, the present invention includes so-called neutral and left-right inserts, wherein, in a plan view of the rake surface (such plan view is illustrated in FIG. 2C of US 11,278,968, although other names used for this view are interchangeable as described in the publication), the cutting edge can extend vertically or obliquely to the forward direction. Referring to FIG. 2, FIG. 3 and FIG. 4 of the present application, plan views of the rake surface of the same insert are shown except that they are neutral and left-right inserts, respectively.

For detailed description, reference is made to FIG. 2 of the present application, which shows an insert 100 extended along an axis of extension _AE . The axis of extension _AE defines a forward (or cutting) direction _DF and a rearward direction _DR opposite thereto. For the purpose of this explanation only, a first cutting edge 102 is selected as an operative cutting edge and is therefore used to cut or groove a workpiece when the insert is moved in a forward direction _DF toward a workpiece (not shown). At the other end of the insert 100 opposite the first cutting edge 102, there is a second cutting edge 104 that becomes operative only after the insert is indexed in a tool bag (not shown).

A transverse axis _AL extending through the frontmost portion of the cutting edge 102 extends perpendicular to the elongation axis _AE and defines a first lateral direction D _S1 and a second lateral direction D _S2 opposite thereto.

For the sake of completeness, it should be noted that a first center axis _AC1 (also referred to as the "vertical axis _AC1 ") extends through the center of the insert and is perpendicular to both the elongation axis _AE and the lateral axis _AL .

A second center axis _AC2 , also shown in FIGS. 5C and 5D , extends through the center of the insert and is perpendicular to the elongation axis _AL and parallel to the transverse axis _AL .

Since the illustrated insert 100 is 180° rotationally symmetric about the first center axis A _C1 (ie, the vertical axis), only the first cutting edge 102 will be discussed in detail.

The first cutting edge 102 includes: a front cutting secondary edge 102A (i.e., the farthest portion of the first cutting edge 102 in the forward direction _DF ); a first left secondary edge 102B, which extends in a substantially backward direction from a first corner 102D connecting the front cutting secondary edge 102A and the first left secondary edge 102B; and a first right secondary edge 102C, which extends in a substantially backward direction from a second corner 102E connecting the front cutting secondary edge 102A and the first right secondary edge 102C.

The first cutting edge 102 seen in FIG. 2 is a neutral cutting edge, which means that the leading cutting edge 102A is substantially parallel to the transverse axis _AL .

3 shows a so-called "left" insert 200 which is identical in all respects except for the cutting edge, the leading minor cutting edge 202A being inclined relative to the transverse axis _AL . More precisely, the leading minor cutting edge 202A extends in the second lateral direction _DS2 and the rearward direction _DR to form an acute angle 204 with the transverse axis _AL .

3 shows a so-called “right” insert 300 that is identical in all respects except for the cutting edge, the leading minor cutting edge 302A being inclined relative to the transverse axis _AL . More precisely, the leading minor cutting edge 302A extends in a first lateral direction _DS1 and a rearward direction _DR to form an acute angle 304 with the transverse axis _AL .

In summary, since different cutting edge shapes fall within the scope of the present invention, the lengths discussed and defined below associated with a forward-most secondary cutting edge 102A should be measured from a forward-most point thereof.

Further general issues associated with these inserts and common cut-off insert characteristics will now be discussed.

One of the first key considerations for a cutting insert is the cutting width CW. The cutting width CW of a cutting insert is generally preferably as small as possible to reduce wear of the workpiece being machined. However, due to strength and machining force considerations, the operator has no choice but to select a relatively large cutting width to ensure that there is no breaking. In US 11,278,968, an invention of the present inventors is described, in which there is a cutting insert that is designed to offset these machining forces to ensure that even an insert that is smaller than previously known inserts does not break under relatively high-force machining conditions. However, the general preference is to select a cutting width that is as small as possible for a given machining operation, taking the machining forces into consideration.

Some common cutting insert features will be described below with reference to the numbers designating features in the drawings in US 11,278,968, all of which are intended to facilitate understanding of typical design features.

At a cutting portion, the front and transverse surfaces (24, 78, 80) adjacent the cutting edge (i.e., extending downwardly therefrom) are typically relieved (i.e., "relief surfaces") so that they do not contact the slit in the workpiece formed by the cutting edge. In other words, they extend in both a downward and inward direction.

The cutting edge (54) is formed along a so-called rake surface (22) of the insert (also referred to as the "upper surface") and an intersection of the front and transverse surfaces (24, 78, 80).

The rake surface (22) typically has a chip forming formation (56) which typically comprises one or more downwardly extending grooves but may alternatively comprise or include upward protrusions, although this is less common.

In a plan view of the rake surface (22), the rearward direction of the cutting edge is similar to the front surface and the side surfaces (24, 78, 80), and at least a portion of the insert body directly adjacent to the rake surface is relieved from the cutting width defined by the cutting edge (see FIG. 2C). In other words, the portion is thinner than the cutting width (i.e., extends in an inward lateral direction on both sides), so that the insert body does not contact the slit formed by the cutting edge in the workpiece.

Currently, the most popular insert material is cemented carbide. During production, cemented carbide is pressed and then sintered. During the sintering process, the insert (especially an insert with a thin elongated shape that is particularly desired in a small cutting width) can become distorted. This is another important design consideration for cutting inserts.

The above features are typical for the type of inserts associated with the present invention (i.e., cemented carbide inserts configured for parting operations).

A second key design consideration for a cutting insert is the depth of cut (hereinafter designated "DC"). A relatively large depth of cut is preferred because it allows a cutting tool to cut smaller and relatively larger diameter workpieces (or relatively deeper grooves, etc.). The depth of cut is limited by the insert or tool having a portion that is wider than the cutting edge that creates the crease. To explain, the cutting edge creates the crease and the insert at least partially enters the workpiece. In a plan view of the rake surface, when an enlarged portion of the insert or tool first reaches the workpiece, the insert cannot advance further without causing undesirable effects because the enlarged portion (of the insert or tool) cannot enter the crease created by the cutting edge. Therefore, it is preferred that in a plan view of the rake surface, at least the insert be as much thinner than the cutting edge as possible (i.e., "relieved" so that it does not contact the walls of the slit being machined).

Therefore, the best solution is to allow an infinite depth of cut in a plan view of the rake surface (at least from the insert) by designing the insert to be thinner overall, and thus the depth of cut is limited only by the tool.

In a first example, this can be provided by an insert having a single cutting edge and the remainder of the cutting insert in a plan view of the rake surface being thinner than the cutting edge. Thus, the single cutting edge provides unlimited depth of cut capability, at least not limited by the insert itself, even though at some point the tool holding it will limit the depth of cut. Hereinafter, this design will be referred to as a classic single cutting edge insert (or "single cutting edge insert").

Probably the most commonly sold cutting insert is a single cutting edge insert (an optional example is the insert shown in US 11,278,968). A single cutting edge insert includes a cutting portion, which in turn includes a rake surface and a clearance surface extending substantially downwardly and inwardly from the rake surface. At an intersection of the rake surface and the clearance surface, only a single cutting edge is formed. Rearward of the cutting portion, the insert further includes a handle portion designed to be fixed or retained to a tool (the "tool" can be a blade or insert holder with a square or round handle, etc.).

Thus, one of the third key considerations for an insert is met by the popular single cutting edge insert, namely, that it can be made with the least amount of expensive carbide material possible and can be pressed to size (i.e., not requiring a separate grind, although in some cases grinding is performed for applications that require it). However, generally speaking, pressed to size inserts lack a grinded surface.

A fourth key design consideration for an insert is the number of cutting edges, with extra cutting edges being preferred because the insert can be used for machining for a total longer amount of time before settling (i.e., increasing "tool life").

Therefore, a second type of highly popular cut-off insert has two cutting edges, the additional cutting edge having a significant advantage over a single cutting edge insert. A double cutting edge insert provides additional economic value to the user by allowing a second cutting edge to be used after a first cutting edge wears out.

In the most common configuration discussed herein, each cutting edge is located at an opposite end of the same rake surface. This design is hereinafter referred to as a classic dual cutting edge insert. The rake surface includes a first and a second rake surface that are both visible in the same plan view of the rake surface. In a plan view of the rake surface, each secondary rake surface is separated by a relatively thin elongated body portion. In other words, the insert includes two cutting portions and a body portion extending therebetween, and each cutting portion includes a respective secondary rake surface of the first and second rake surfaces.

However, the depth of cut that can be produced with this insert is limited by the distance between the two cutting portions (i.e. the point where the cutting insert widens again to come into contact with the resulting slit, which is also the secondary rake surface).

Therefore, the classic dual-edge insert has one major advantage (number of cutting edges) and one major disadvantage compared to a single-edge insert (depth of cut).

The classic dual cutting edge insert design also suffers from a moderate disadvantage, namely, that the cutting width CW cannot be made as small as a single cutting edge insert (e.g., the minimum cutting width offered by the applicant for a single cutting edge insert is 0.6 mm and the minimum cutting width offered for a dual cutting edge insert is 1.4 mm). This difference is a result of the elongated body portion of a classic dual cutting edge insert design becoming distorted during the sintering process if the portion is made unacceptably thin.

Additionally, there is one minor disadvantage of the classic dual cutting edge insert design (i.e., due to the need for a second cutting portion, which requires more material).

One known design developed to overcome the major drawback of a classic dual cutting edge insert, namely the cutting depth limitation, is a so-called "twist insert". An example of a twist insert can be seen in US 5,156,502. The twist insert differs from the classic dual cutting edge insert in that the two cutting portions are not in a parallel plane, but are twisted relative to each other so that the rake faces do not face exactly in the same direction. This adjustment of the non-operating cutting edge makes the remainder of the insert thinner than the cutting width CW in a plan view of the rake surface of the operating cutting edge.

One of the main advantages of a twist insert over a classic dual-cutting edge insert design is that it allows an unlimited depth of cut (at least relative to the insert and not the tool that holds it).

One disadvantage of twist inserts when compared to classic double cutting edge inserts is that they can only be manufactured with relatively large cutting widths (even more so when compared to the very small cutting widths of smaller single cutting edge inserts) and with some compromises with respect to fixing the insert to a pocket.

In summary, the three well-known and commercially available insert types described above include: a single cutting edge insert, which has the advantage of unlimited cutting depth and is the cheapest insert to produce; a classic dual cutting edge insert, which has one major advantage of the other cutting edge but is significantly limited in cutting depth and slightly limited in cutting width and is more expensive to produce than a single cutting edge insert; and a twisted dual cutting edge insert, which has the advantages of both unlimited cutting depth and two cutting edges, but is more limited with respect to cutting width than the other two.

Since each solution has advantages and disadvantages, the industry has long felt the need for a better solution. Therefore, many different solutions have been considered to provide an even better cutting insert, some of which come from the applicant mentioned below.

One solution that has been developed is a double cutting edge insert with an enlarged central portion (sold by the applicant Iscar under the name DO-GRIP DGN 1002, hereinafter referred to as "DGN insert"), which can produce a small cutting width (1 mm) that is smaller than the cutting width of the classic double cutting edge insert mentioned above, but not the smallest single cutting edge insert, and of course has the advantages of two cutting edges, but due to the enlarged central portion is expensive to produce and the cutting depth is extremely limited (3 mm).

Yet another solution disclosed in USP 10,363,722 B2 is a relatively large double cutting edge insert without an enlarged central portion. By providing such a large insert, a relatively large cutting depth and a relatively small cutting width (less than 1.5 mm stated in the patent) are possible. However, the height of the insert is very large and therefore due to the large amount of material, the insert is expensive and therefore requires a rather unique insert pocket.

An object of the present invention is to provide a novel and improved cutting insert.

This objective is not an easy task, as many solutions have been attempted to improve the cutting insert, a small number of which are described above.

In view of the known variables identified above, in the search for an improved cut-off insert, consideration is given to providing a modified cemented carbide dual cutting edge insert (hereinafter) having a superior (i.e., smaller) cutting width that can compete with a single cutting edge insert within the minimum cutting width range.

It is believed that due to a known deformation problem of a thin elongated insert during a sintering process, such inserts have not been produced to date.

As will be appreciated, the straightness of a cut insert intended to be slit to its greater length range is critical to the cut process.

To elaborate, as mentioned above, the difficulty faced by this design is the inherent problem of producing very thin elongated carbide inserts that are prone to deformation.

This deformation could be counteracted by thickening the insert (which is undesirable here since the cutting width is preferably as small as possible), which would essentially result in a classic double cutting edge insert of a known cutting width.

Alternatively, the deformation can be offset by shortening the insert (which is undesirable here because shortening the distance between the thicker cutting portions results in a relatively smaller cutting depth and reduces the range of diameters of workpieces that can be cut), which will essentially result in an insert with capabilities similar to a DGN insert.

However, another difficulty is that it is not possible to obtain all cutting widths as small as those achievable with a classic single cutting edge insert, regardless of the length of the insert, because the larger size double cutting edge insert will always have a larger width to avoid distortion during the sintering process.

Therefore, in order to minimize the possibility of distortion while still obtaining a favorable cutting width and cutting depth of a certain magnitude, the present invention has a slightly unfavorable cutting width that is greater than a smaller cutting width single cutting edge insert (0.6 mm) but less than a cutting width of a known classic double cutting edge insert (1.4 mm), and is therefore advantageous compared thereto.

To achieve this cutting width, a further compromise is made, namely, to further minimize the risk of deformation, a second step of a length shorter than that of a classic double cutting edge insert is provided, thereby limiting the cutting depth to further reduce the expected deformation. Although this also reduces the suitability for use (i.e., only smaller diameter workpieces can be cut), it is believed that, combined with an advantage over classic single cutting edge inserts due to the presence of two cutting edges, the overall advantage of a classic double cutting edge insert over previously known cutting widths provides at least a possible novel and advantageous insert for a vacant part of the market.

During production of a prototype, despite concerns, it was found that the dimensions described below had small enough deviations to be within acceptable tolerances.

As explained above, many gap-type inserts have been tried, for example, the present invention has a cutting width comparable to the DGN 1002 insert, but a significantly greater cutting depth.

Additionally, the present invention has a smaller depth of cut than an insert according to USP 10,363,722, and a slightly smaller width of cut, but uses much cheaper materials during manufacture.

According to a first aspect of the present invention, a double cutting edge cutting insert is provided, comprising: a first cutting portion; a second cutting portion; an elongated body portion connecting the first and second cutting portions; a rake surface; a base surface positioned opposite to the rake surface; and a peripheral surface connecting the rake surfaces and the base surface; the peripheral surface comprising: a front sub-surface located at the first cutting portion; a rear sub-surface located at the second cutting portion and positioned opposite to the front sub-surface; a left sub-surface connecting the front and rear sub-surfaces and located at one side of the cutting insert; and a right sub-surface connecting the front and rear sub-surfaces and positioned opposite to the left sub-surface; the body portion is elongated along an elongation axis extending through the center of the body portion; the elongation axis ( _AE ) defines a forward direction ( _DF) from the second cutting portion toward the first cutting portion. ) and a rearward direction ( _DR ) opposite to the forward direction; the cutting insert has an insert length (IL) measured along the elongation axis ( _AE ); the cutting insert has a height (H) measured perpendicular to the elongation axis ( _AE ); a first center axis ( _AC1 ) is defined as being perpendicular to the elongation axis and extending through the center of the cutting insert and through the base surface and the rake surface, the first center axis ( _AC1 ) defining an upward direction ( _DU ) from the base surface toward the rake surface and a downward direction ( _DD ) opposite to the upward direction; a second center axis ( _AC2 ) is defined as being perpendicular to both the elongation axis ( _AE ) and the first center axis ( _AC1 ) and extending through the center of the cutting insert, the second center axis ( _AC2 ) defines a first lateral direction ( _DS1 ) and a second lateral direction ( _DS2 ) opposite thereto; the first cutting portion comprises: a first front cutting surface, which is located at the front cutting surface; a first front clearance surface, which is located at the front surface; a first left clearance surface, which is located at the left secondary surface; a first right clearance surface, which is located at the right secondary surface; a first cutting edge, which is formed at an intersection of the first front cutting surface and each of the first front clearance surface, the first left clearance surface and the first right clearance surface; the first cutting edge comprises: a first front cutting secondary edge, which is located along the A first front cutting edge extends from an intersection of the first front cutting edge and the first front clearance surface; a first left side secondary edge extends along an intersection of the first front cutting edge and the first left clearance surface; a first right side secondary edge extends along an intersection of the first front cutting edge and the first right clearance surface; a first left corner is formed at an intersection of the first front cutting secondary edge and the first left side secondary edge; and a first right corner is formed at an intersection of the first front cutting secondary edge and the first right side secondary edge; the first The second cutting portion includes: a second front blade surface, which is located at the front blade surface; a second front clearance surface, which is located at the rear surface; a second left clearance surface, which is located at the right surface; a second right clearance surface, which is located at the left surface; a second cutting edge, which is formed at an intersection of the second front blade surface and each of the second front clearance surface, the second left clearance surface and the second right clearance surface; the second cutting edge includes: a second front cutting secondary edge, which is formed along the second front blade surface a second left-side secondary edge extending along an intersection of the second front cutting surface and the second left-side secondary edge; a second right-side secondary edge extending along an intersection of the second front cutting surface and the second right-side secondary edge; a second left corner formed at an intersection of the second front cutting secondary edge and the second left-side secondary edge; and a second right corner formed at an intersection of the second front cutting secondary edge and the second right-side secondary edge; a transverse axis ( _AL ) extending through a frontmost portion of the first cutting edge, the transverse axis ( _AL ) extending parallel to the second center axis ( _AC2 ) and defining a first lateral direction ( _DS1 ) and a second lateral direction ( _DS2 ) opposite to the first lateral direction ( _DS1 ). ), the first cutting edge has a first cutting width (CW1) that can be measured parallel to the transverse axis and from the first left corner to the first right corner; the second cutting edge has a second cutting width (CW2) that can be measured parallel to the transverse axis and from the second left corner to the second right corner; the elongated body portion has a body width (BW) that can be measured parallel to the transverse axis and a body length (BL) that can be measured parallel to the elongated axis; wherein the body width (BW): is smaller than both the first cutting width (CW1) and the second cutting width (CW2); and satisfies the condition: 0.55 mm ≤ BW ≤ 0.95 mm; and the body length (BL): satisfies the condition: 2 mm ≤ BL ≤ 14 mm.

In other words, according to a second aspect of the present invention, a double-cutting-edge cutting insert is provided, which includes: a first cutting portion; a second cutting portion; a body portion connecting the first and second cutting portions; a front cutting surface; a base surface positioned opposite to the front cutting surface; and a peripheral surface connecting the front cutting surface and the base surface; the first cutting portion includes a first front cutting surface located at the front cutting surface; the second cutting portion includes a second front cutting surface located at the front cutting surface; the body portion has a body width (BW) measurable parallel to the transverse axis and a body length (BL) measurable parallel to the elongation axis; the body width (BW): satisfies the condition: 0.55 mm ≤ BW ≤ 0.95 mm; and The body length (BL): meets the following conditions: 2 mm ≤ BL ≤ 14 mm.

It will be appreciated that according to each of the above aspects, we have discovered that a body portion having a given size can be produced within an acceptable amount of distortion.

Preferably, the body width (BW): satisfies the condition: 0.65 mm ≤ BW, and more preferably 0.75 mm ≤ BW. It will be appreciated that increasing the body width can reduce the amount of distortion. BW ≤ 0.85 mm is also preferred to allow for sufficient clearance with the cutting width.

Although a body length even just greater than 2 mm is beneficial, since it is known from the DGN insert that there is a market demand for a cutting depth DC of only 3 mm (remember that the cutting portion itself has a length), it is of course better if the body length (BL) is longer. For example, it is better if the body length (BL) satisfies the condition: 6 mm ≤ BL, more preferably 8 mm ≤ BL. It will be appreciated that although increasing the body length increases distortion, it allows a greater number of machining operations to be feasible (e.g., cutting off relatively large workpieces). In addition, it provides another advantage over smaller single cutting edge inserts, namely: the overall length of the insert is longer and is therefore easier to hold and move. However, a body length that is too large is considered to risk increasing distortion to an unacceptable level, and therefore an upper limit of 14 mm is defined above to avoid increasing distortion to an unacceptable amount. Preferably, the condition BL ≤ 12 mm and more preferably BL ≤ 11 mm is met.

Preferably, the first cutting width (CW1) and the second cutting width (CW2) meet the conditions: 0.75 mm ≤ CW1, CW2 ≤ 1.1 mm, more preferably 0.9 mm ≤ CW1, CW2 ≤ 1.1 mm. It will be appreciated that although for smaller single cutting edge inserts this cutting width is not as advantageous as the minimum cutting widths (~0.6 mm), it is still superior to the smallest double cutting edge insert known to the applicant at this time. It will also be appreciated that a reduction in cutting width means that the insert is less able to handle the cutting forces and therefore to maintain a possibility of machining at a reasonable feed rate, a minimum cutting width value of 0.8 mm is preferred, more preferably 0.9 mm. Similarly, to have an increased benefit over the cutting width of known classic double cutting edge inserts, a maximum cutting width value of 1.1 mm is preferred. An optimum cutting width is equal to 1.0 mm ± 0.04 mm. Another optimum cutting width is equal to 0.8 mm ± 0.04 mm.

Preferably, the cut-off insert has a first operating length OL1, measurable from a forward-most point of the first cutting edge parallel to the axis of elongation to an intersection of the body portion and the second cutting portion (i.e., where the insert begins to widen relative to the body portion), satisfying the condition: 5 mm ≤ OL1 ≤ 15 mm. More preferably, the condition 9 mm ≤ OL1 ≤ 13.5 mm is satisfied, and most preferably, 11 mm ≤ OL1 ≤ 12.5 mm. As explained above, although increasing the body length increases distortion, it allows a greater number of machining operations to be feasible and allows an insert that is easier to hold. However, a length that is too large risks increasing distortion to unacceptable levels, and therefore an upper limit is preferred.

The cutting insert may comprise an insert length IL measurable parallel to the axis of elongation _AE . Preferably, the insert length IL satisfies the condition 4 mm ≤ IL ≤ 16 mm, more preferably 11 mm ≤ IL ≤ 15 mm and most preferably 13 mm ≤ IL ≤ 14 mm.

The first cutting portion 110 further comprises a first cutting portion length L _C1 measurable parallel to the elongation axis _AE . Preferably, the first cutting portion length L _C1 satisfies the condition 1.25 mm ≤ L _C1 ≤ 1.5 mm and most preferably 1.30 mm ≤ L _C1 ≤ 1.40 mm. For a second cutting portion length L _C2 , the same values are preferred.

Preferably, the cut inserts are pressed to size (and thus not ground and thus have no ground surface). For example, pressing to size increases manufacturing advantages over larger types of inserts, such as DGN inserts and inserts disclosed in USP 10,363,722. Notably, ground inserts are identifiable because they exhibit oriented lines. To elaborate, one can tell if an insert has been ground because even after a very fine post-processing of a coating, such as polishing, the post-processing removes material and leaves a visible pattern of parallel lines, as opposed to non-ground inserts which have more random markings.

Preferably, the cutting insert is 180° rotationally symmetrical about the first center axis _AC1 .

Preferably, a height H of the body portion satisfies the condition 3.5 mm ≤ H ≤ 4.5 mm, more preferably 4.0 mm ≤ H ≤ 4.3 mm. This corresponds to the height of a classic double cutting edge insert, and it is preferred not to reduce this dimension, since this would increase distortion without significant benefit.

However, we have found that the corners are preferably produced with a radius R satisfying the condition 0.8 mm ≤ R ≤ 1.20 mm, which is an improvement over the 0.16 mm radius of the applicant's existing classic double cutting edge insert.

Preferably, each of the first and second cutting portions comprises a chip former arrangement. More preferably, the chip former arrangement comprises a single recess.

The above inserts will now be compared using an arbitrary grading system of 1 to 5 (relative values assigned after careful observation of such inserts compared to each other), with "1" being the lowest rating and "5" being the highest rating, and using the following criteria: (a) depth of cut (where a larger depth of cut is better), (b) width of cut (where a smaller width of cut is better, the values shown are the minimum values for the applicant's products and patents, and are approximate in the event that a real world product is not on the market), (c) material cost (where a relatively small amount of material is better; although not mentioned in the name "material cost", manufacturing complexity is also included in this category), and (d) dual cutting edges (where dual cutting edges are better than a single cutting edge).

Although the values shown below are subjective and subject to many factors, they indicate the basic factors to consider when developing inserts of the present application customized for smaller cutting width applications. Insert type Cutting depth Cutting width CW (minimum CW) Material costs Blade efficiency (number of blades) Total Classic single cutting edge insert 5 (unlimited) 5 (0.6 mm) 5 3 (one) 18 Classic double cutting edge insert 4 4 (1.4 mm) 4.5 5 (two) 17.5 Twisted double cutting edge insert 5 (unlimited) 3 (3 mm) 4.5 5 (two) 17.5 DGN 1002 1 (3mm) 4.5 (~1 mm) 3 5 (two) 13.5 USP 10,363,722 4.5 4 (~1.5 mm or less) 3 5 (two) 16.5 The invention 3 4.5 (~1 mm) 4.5 5 (two) 17

In general, at least in terms of this minimum cutting width size, the classic single cutting edge still has an advantage over the remaining double cutting edge types.

However, at a unique cutting width size of about 0.8 mm and about 1 mm (or more precisely, between 0.8 mm ± 0.1 mm and 1 mm ± 0.1 mm), it is believed to be beneficial to introduce a new dual cutting edge insert of one of the classic dual cutting edge insert types.

After producing a prototype, we found that the distortion was at an acceptable level at this size.

Some hints about the values are:

The cut width values assume that the application for which the smaller cut width is selected is desirable. For heavy machining applications, a smaller cut width may conversely be undesirable, as structural strength may outweigh the savings in workpiece material.

Although it is essentially true that a double cutting edge is better than a single cutting edge, the indication that a double cutting edge is far better than a single cutting edge is not accurate because, in practice, one insert often breaks, meaning that the operator loses the ability to utilize the second cutting edge of the same insert (which is usually a more expensive insert than the single cutting edge insert).

In summary and in view of the above table, a cut-off insert according to the present invention is: better than a single edge insert because it has a double edge insert, but is significantly inferior to the single edge insert in terms of cutting depth and slightly inferior to the single edge insert in terms of cutting width; slightly better than a classic double edge insert because it has a slightly smaller cutting width, but is inferior to the classic double edge insert in terms of cutting depth; better than a twisted double edge insert because it has a significantly smaller cutting width, but is inferior to the twisted double edge insert in terms of cutting depth; better than a DGN insert because it has a greater cutting depth and a smaller manufacturing cost; and slightly better than the insert disclosed in USP 10,363,722 in terms of cutting width and a smaller manufacturing cost than it, but inferior to it in terms of cutting depth.

Figures 1, 2 and 5A to 5E show an exemplary cutting insert 100 according to the present invention, which will be described in further detail below. Figures 3 and 4 also show cutting inserts according to the present invention, but the differences from the cutting insert 100 have been described in sufficient detail above.

The cutting insert 100 includes a first cutting portion 110, a second cutting portion 112, and an elongated body portion 114 connecting the first and second cutting portions.

An arrow designated "116" shows the area where a cutting portion (in this example, the second cutting portion 112) transitions into the elongated body portion 114 (hereinafter referred to as a "transition area 116"). Although this is visible by thinning the cutting portion until it reaches the width of the elongated body portion, it should also be understood that a cutting portion is functionally connected to a cutting function (i.e., in contact with a workpiece (not shown) and chips machined therefrom) while a body portion is not configured to provide a cutting function.

The cutting insert 100 further includes a rake surface 118 , a base surface 120 (also referred to as a “lower surface”; the base surface has no cutting edge) and a peripheral surface 122 .

2, the body portion 114 is elongated along an elongation axis _AE extending through the center thereof. The elongation axis _AE defines a forward direction _DF from the second cutting portion 112 toward the first cutting portion 110 and a rearward direction _DR opposite thereto.

Referring also to the remainder of the figure, a first center axis _AC1 ("vertical axis") is defined as perpendicular to the elongation axis _AE and extends through the center of the cutting insert 100 and through the base surface 120 and the rake surface 118, and as shown in Figure 5C, defines an upward direction _DU and a downward direction _DD .

A second center axis _AC2 is defined as being perpendicular to both the elongation axis _AE and the first center axis _AC1 and extending through the center of the cutting insert 100. The second center axis _AC2 defines a first lateral direction D _S1 and a second lateral direction D _S2 opposite thereto.

The cut-off insert 100 includes an insert length IL that can be measured parallel to the elongation axis _AE .

For the sake of brevity, some of the following description may be directed to only one portion of the cut-off insert 100 because it is rotationally symmetric about the first center axis _AC1 , and it should be understood that these features also exist on the opposite end.

The peripheral surface 122 includes a front sub-surface 122A located at the first cutting portion 110 , a rear sub-surface 122B located at the second cutting portion 112 , a left sub-surface 122C, and a right sub-surface 122D.

The first cutting portion 110 includes a first rake surface 110A at the rake surface 118. The first rake surface 110A includes a chip former arrangement 124 in the form of a single depression.

The first cutting portion 110 further includes a first front clearance surface 110B located at the front secondary surface 122A, a first left clearance surface 110C located at the left secondary surface 122C; and a first right clearance surface 110D located at the right secondary surface 122D. Notably, the illustrated preferred secondary clearance surfaces (which are inclined inwardly) do not extend all the way to the base surface 120, however, it is also possible that they extend to the base surface 120. As shown in the preferred embodiment, the secondary clearance surfaces extend less than one-third of the height H of the cutting insert 100.

The first cutting edge 102 is formed at an intersection of the first front secondary rake surface 110A and each of the first front secondary clearance surface 110B, the first left secondary clearance surface 110C, and the first right secondary clearance surface 110D.

A portion of the cutting edge 102 is described above with reference to FIG. 2 .

The first cutting portion 110 further includes a first cutting portion length L _C1 that can be measured parallel to the elongation axis _AE . Similarly, the second cutting portion 112 can include a second cutting portion length L _C2 .

Behind the cutting edge, in a plan view of the rake surface (22), similar to the rake surface and lateral surfaces (24, 78, 80) of US 11,278,968, at least a portion of the insert body immediately adjacent to the rake surface is relieved from the cutting width defined by the cutting edge (see FIG. 2C). In other words, the portion is thinner than the cutting width (i.e., extends in an inward lateral direction on both sides), so that the insert body does not contact the slit in the workpiece formed by the cutting edge.

The first cutting edge 102 has a first cutting width CW1 and the second cutting edge 104 has a second cutting width CW2.

The elongated body portion 114 has a body width BW and a body length BL.

The insert length IL is equal to the body length BL plus the first and second cutting portion lengths _LC1 and _LC2 (IL = BL + _LC1 , + _LC2 ).

Because the cut-off insert 100 only enters a narrow seam until the width of the insert body widens, (considering that the body width BW is designed to be as wide as possible (even at its thinnest portion) to avoid unnecessary weakening of the structure), when the first cutting portion 100 is the operative cutting portion (i.e., the cut-off insert 100 is relatively moving in the forward direction _DF toward a workpiece), the cutting depth DC is effectively equal to a first operative length OL1 that can be measured from a forward-most point of the first cutting edge 102 to a transition region 116 between the extended body portion 114 and the second cutting portion 112.

After the insert is indexed to the second cutting portion 112 (ie, a second operating length OL2), the cut-off insert 100 will have a same cutting depth DC.

The insert may have a first insert ratio R1 defined as the ratio of the cutting depth to the first cutting width (R1 = DC/CW1). Thus, for an insert having a cutting depth DC = 12 mm and a first cutting width CW1 = 1 mm, the first insert ratio is 12. Preferably, the first insert ratio R1 of a cutting insert according to the subject matter of the present application satisfies the condition: 6 ≤ R1 ≤ 16, more preferably 10 ≤ R1 ≤ 14, and most preferably 11 ≤ R1 ≤ 13.

The insert may have a second insert ratio R2 defined as the ratio of the length IL of the insert to the height H of the insert (R2 = IL/H). Thus, for an insert having a length IL = 14 mm and a height H = 4 mm, the second insert ratio is 3.5. Preferably, the second insert ratio R2 of a cutting insert according to the subject matter of the present application satisfies the condition: 1 ≤ R2 ≤ 4.5, more preferably 2.5 ≤ R2 ≤ 3.8, and most preferably 3 ≤ R2 ≤ 3.6.

100: insert/cutting insert 102: first cutting edge 102A: front cutting secondary edge 102B: first left secondary edge 102C: first right secondary edge 102D: first corner 102E: second corner 104: second cutting edge 110: first cutting portion 110A: first front cutting surface 110B: first front clearance surface 110C: first left clearance surface 110D: first right clearance surface 112 : Second cutting portion 114: Extended body portion 116: Transition region 118: Front cutting surface 120: Base surface 122: Peripheral surface 122A: Front secondary surface 122B: Rear secondary surface 122C: Left secondary surface 122D: Right secondary surface 124: Chip former configuration 200: Left insert 202A: Forward cutting secondary edge 204: Sharp angle 300: Right insert 302A: Forward cutting secondary edge 304: Sharp angle A _C1 : Center axis/vertical axis/first center axis A _C2 : Second center axis A _E : Elongation axis _AL : Transverse axis BL: Body length BW: Body width CW: Cutting width CW1: First cutting width CW2: Second cutting width DC: Cutting depth _DD : Downward direction _DF : Forward direction/cutting direction _DR : Backward direction _DS1 : First side direction _DS2 : Second side direction _DU : Upward direction H: Height _LC1 : First cutting part length _LC2 : Second cutting part length IL: Insert length OL1: First operating length OL2: Second operating length R: Radius R1: First insert ratio R2: Second insert ratio

For a better understanding of the subject matter of the present invention and to show how the subject matter of the present invention is implemented in practice, reference will now be made to the accompanying drawings derived from a scale model, in which: FIG. 1 is a perspective view of a cutting insert according to the present invention; FIG. 2 is a plan view of a front blade surface of the insert in FIG. 1; FIG. 3 is a plan view of a front blade surface of another insert according to the present invention and differs from the insert in FIG. 1 only in that it is a "left" type insert; FIG. 4 is a plan view of a front blade surface of another insert according to the present invention and differs from the inserts in FIG. 1 and FIG. 3 only in that it is a "right" type insert; FIG. 5A is a front view of the insert in FIG. 1; FIG. 5B is a plan view of the front blade surface of the insert in FIG. 5A (and is the same view as FIG. 2); FIG. 5C is a right side view of the insert in FIG. 5A; FIG. 5D is a bottom view of the insert in FIG. 5A; and FIG. 5E is a rear view of the insert in FIG. 1.

100: Insert/cut insert

102D: First corner

102E: Second corner

104: Second cutting edge

110A: First front cutting surface

116: Transition area

122C: Left secondary surface

122D: Right subsurface

124: Chip former configuration

A _E : Elongation axis

BL: body length

CW: cutting width

CW1: First cutting width

CW2: Second cutting width

DC: cutting depth

IL: Insert length

L _C1 : Length of the first cutting part

L _C2 : Length of the second cutting part

OL1: First operation length

OL2: Second operation length

R: Radius

Claims (20)

A double cutting edge cutting insert, comprising: a first cutting portion; a second cutting portion; an elongated body portion connecting the first and second cutting portions; a rake surface; a base surface positioned opposite the rake surface; and a peripheral surface connecting the rake surface and the base surface; the peripheral surface comprising: a front subsurface located at the first cutting portion; a rear subsurface located at the second cutting portion and positioned opposite the front subsurface; a left subsurface connecting the front and rear subsurfaces and located at one side of the cutting insert; and a right subsurface connecting the front and rear subsurfaces and positioned opposite the left subsurface; the body portion is elongated along an elongation axis extending through the center of the body portion; the elongation axis ( _AE) is a right subsurface connecting the front and rear subsurfaces and positioned opposite the left subsurface. ) defines a forward direction ( _DF ) from the second cutting portion toward the first cutting portion and a rearward direction ( _DR ) opposite to the forward direction; the cutting insert has an insert length (IL) measured along the elongation axis ( _AE ); the cutting insert has a height (H) measured perpendicular to the elongation axis ( _AE ); a first center axis ( _AC1 ) is defined as being perpendicular to the elongation axis and extending through the center of the cutting insert and through the base surface and the rake surface, the first center axis ( _AC1 ) defining an upward direction ( _DU ) from the base surface toward the rake surface and a downward direction ( _DD ) opposite to the upward direction; a second center axis ( _AC2 ) is defined as being perpendicular to the elongation axis ( _AE ) and the first center axis ( _AC1 ) and extending through the center of the cutting insert, the second center axis ( _AC2 ) defining a first lateral direction ( _DS1 ) and a second lateral direction ( _DS2 ) opposite thereto; the first cutting portion comprising: a first rake surface located at the rake surface; a first front clearance surface located at the front surface; a first left clearance surface located at the left secondary surface; a first right clearance surface located at the right secondary surface; a first cutting edge formed at an intersection of the first front rake surface and each of the first front clearance surface, the first left clearance surface and the first right clearance surface; the first cutting edge comprising: a first front-most cutting secondary edge extending along an intersection of the first rake surface and the first front clearance surface; a first left-side secondary edge extending along an intersection of the first rake surface and the first left-side secondary clearance surface; a first right-side secondary edge extending along an intersection of the first rake surface and the first right-side secondary clearance surface; a first left corner formed at an intersection of the first front-most cutting secondary edge and the first left-side secondary edge; and a first right corner formed at an intersection of the first front-most cutting secondary edge and the first right-side secondary edge; the second cutting portion comprises: a second rake surface located at the rake surface; a second front clearance surface located at the rear secondary surface; a second left clearance surface located at the right secondary surface; a second right clearance surface located at the left secondary surface; a second cutting edge formed at an intersection of the second front rake surface and each of the second front clearance surface, the second left clearance surface, and the second right clearance surface; the second cutting edge includes: a second frontmost cutting edge extending along an intersection of the second front rake surface and the second front clearance surface; a second left side secondary edge extending along an intersection of the second front rake surface and the second left clearance surface; a second right side secondary edge extending along an intersection of the second front rake surface and the second right clearance surface; a second left corner formed at an intersection of the second frontmost cutting secondary edge and the second left side secondary edge; and a second right corner formed at an intersection of the second frontmost cutting secondary edge and the second right side secondary edge; a transverse axis (A _L ) extends through a frontmost part of the first cutting edge, the transverse axis ( _AL ) extends parallel to the second center axis ( _AC2 ) and defines a first lateral direction ( _DS1 ) and a second lateral direction ( _DS2 ) opposite to the first lateral direction ( _DS1 ); the first cutting edge has a first cutting width (CW1) that can be measured parallel to the transverse axis and from the first left corner to the first right corner; the second cutting edge has a second cutting width (CW2) that can be measured parallel to the transverse axis and from the second left corner to the second right corner; the elongated body portion has a body width (BW) that can be measured parallel to the transverse axis and a body length (BL) that can be measured parallel to the elongated axis; wherein: the body width (BW): Smaller than both the first cutting width (CW1) and the second cutting width (CW2); and satisfying the condition: 0.55 mm ≤ BW ≤ 0.95 mm; and the body length (BL): satisfying the condition: 2 mm ≤ BL ≤ 14 mm. The cut-off insert of claim 1, wherein the body width (BW) satisfies the condition: 0.65 mm ≤ BW ≤ 0.95 mm. The cut-off insert of claim 2, wherein the body width (BW) satisfies the condition: 0.75 mm ≤ BW ≤ 0.95 mm. The cut-off insert of claim 1, wherein the body width (BW) satisfies the condition: 0.55 mm ≤ BW ≤ 0.85 mm. The cut-off insert of claim 1, wherein the body length (BL) satisfies the condition: 6 mm ≤ BL ≤ 14 mm. The cut-off insert of claim 5, wherein the body length (BL) satisfies the condition: 8 mm ≤ BL ≤ 14 mm. The cut-off insert of claim 1, wherein the body length (BL) satisfies the condition: 2 mm ≤ BL ≤ 12 mm. The cut-off insert of claim 7, wherein the body length (BL) satisfies the condition: 6 mm ≤ BL ≤ 11 mm. A cutting insert as claimed in claim 1, wherein the first cutting width (CW1) and the second cutting width (CW2) satisfy the condition: 0.75 mm ≤ CW1, CW2 ≤ 1.1 mm. A cutting insert as claimed in claim 9, wherein the first cutting width (CW1) and the second cutting width (CW2) satisfy the conditions: 0.76 mm ≤ CW1, CW2 ≤ 0.84 mm. A cutting insert as claimed in claim 9, wherein the first cutting width (CW1) and the second cutting width (CW2) satisfy the condition: 0.9 mm ≤ CW1, CW2 ≤ 1.1 mm. A cutting insert as claimed in claim 11, wherein the first cutting width (CW1) and the second cutting width (CW2) satisfy the condition: 0.96 mm ≤ CW1, CW2 ≤ 1.04 mm. A cutting insert as claimed in claim 1, wherein the cutting insert has a first operating length (OL1) measurable from a frontmost point of the first cutting edge parallel to the extension axis ( _AE ) to an intersection of the main body portion and the second cutting portion, which satisfies the condition: 5 mm ≤ OL1 ≤ 15 mm. A cutting insert as claimed in claim 13, wherein the first operating length (OL1) satisfies the condition: 9 mm ≤ OL1 ≤ 13.5 mm. A cutting insert as claimed in claim 14, wherein the first operating length (OL1) satisfies the condition: 11 mm ≤ OL1 ≤ 12.5 mm. A cutting insert as claimed in claim 1, wherein the cutting insert has no polished surface. The cut-off insert of claim 1, wherein the height (H) of the body portion satisfies the condition, 3.5 mm ≤ H ≤ 4.5 mm. A cutting insert as in claim 1, wherein the first cutting portion further comprises a first cutting portion length (L _C1 ) which is parallel to the elongation axis _AE and satisfies the condition 1.25 mm ≤ L _C1 ≤ 1.5 mm. A cutting insert as claimed in claim 1, wherein a first insert ratio (R1) is defined as a ratio of a cutting depth (DC) to the first cutting width (CW1) (R1 = DC/CW1), and satisfies the condition: 6 ≤ R1 ≤ 16. The cut-off insert of claim 1, wherein a second insert ratio (R2) is defined as a ratio of the insert length (IL) to the insert height (H) (R2 = IL/H), and satisfies the condition: 1 ≤ R2 ≤ 4.5.