AU2002316506A1

AU2002316506A1 - Method and apparatus for clamping a knife

Info

Publication number: AU2002316506A1
Application number: AU2002316506A
Authority: AU
Inventors: Thomas Charles Hinchliff
Original assignee: Key Knife Inc
Current assignee: Key Knife Inc
Priority date: 2001-07-18
Filing date: 2002-07-01
Publication date: 2003-05-22
Anticipated expiration: 2022-07-01

Description

METHOD AND APPARATUS FOR CLAMPING A KNIFE

The subject matter of the present application is related to that of the assignee's companion application entitled KNIFE AND APPARATUS FOR CLAMPING A KNIFE, of Loren R. Schuh and Tobias L. Simonsen, incorporated by reference herein in its entirety.

Background of the Invention

The present invention relates to a method and apparatus for clamping a knife in a wood chipper, such as a disc, drum or conical head chipper, for use in the commercial processing of logs.

In wood chipping apparatus used in the forest products industry, a rotating member is provided for receiving replaceable knives for cutting chips from the log. Each knife is typically clamped to the rotating member between an outer clamping member and an inner clamping member or counterknife, wherein the knife and counterknife together form a surface against which the log is forced to remove chips from the log. The chips themselves have commercial value, and their removal shapes the log into lumber and finishes its surface.

A preferred knife for use in such apparatus is manufactured by Key Knife, Inc., of Tualatin, Oregon ("Key Knife"), and described in Schmatjen, U.S. Patent No. 5,819,826, herein incorporated by reference in its entirety. For convenience when referring to the '826 Patent, terminology employed therein will be used herein as well to describe selected features of the preferred knife. The knife is elongate and symmetrical about a plane that includes the elongate axis, to provide two cutting edges of the knife. Therefore, either of the cutting edges may be

selected for cutting by appropriate installation of the knife. Particularly, when one of the

cutting edges is dulled, the knife maybe removed from the apparatus, turned end-to-end,

and placed back into, the apparatus to obtain a fresh cutting edge, providing an outstanding

advantage over knives having a single cutting edge.

The knife includes a front side which, when the knife is installed in the apparatus,

confronts the counterknife, and a back side which confronts the outer clamping member.

Each cutting edge of the knife defines a line terminating two plane surfaces that form an

angle with respect to one another, known in the art as the knife angle. The front side of the

knife contains one each of the aforementioned plane surfaces (termed "lower knife-edge- joining portions") and the back side of the knife contains one each of the other of the plane

surfaces (termed "upper knife-edge-joining portions").

The front side of the knife further includes a pair of symmetrically disposed deflector ridges projecting therefrom, and extending in the direction of the elongate axis.

The deflector ridges are spaced from the respective cutting edges and terminate the respective lower knife-edge-joining portions.

The front side of the knife still further includes a pressure-applying surface portion

between the deflector ridges. The pressure-applying surface portion makes contact with a

corresponding feature of the counterknife when clamping the knife in the apparatus.

Typically, the lower knife-edge-joining portions and the pressure-applying surface portion

all lie in a single plane. Grinding machines are employed to form the aforementioned surfaces. The time

required for the grinding operation depends on the number of knives that can be ground by

the machine at one time, and this number depends on the size of the knives. The present

inventor has recognized that it would be desirable to reduce the width of a knife to reduce the size of the knife and, therefore, manufacturing time and cost.

However, the distance from the cutting edge of the knife to the respective deflector ridges is determined by the requirements of the chipping apparatus and may not be reduced

without impacting the performance of the apparatus. On the other hand, reducing the width

of the pressure-applying area destabilizes the contact between the knife and the

counterknife.

A prior art counterknife manufactured and marketed by Key Knife, Inc. provides a

contact point between the knife and counterknife that is outside of the space between the

deflector ridges, more particularly 0.583" from the closest one of the deflector ridges. This counterknife permits the use of a knife having a narrower pressure-applying area, providing

for decreased manufacturing costs, while maintaining stable contact with the knife.

In what has heretofore been an unrelated consideration, chipper knives are angled

with respect to the wood being cut, wherein the angle is known to be important to chip quality. As mentioned, the angle between the upper and lower knife-edge-joining portions defines the knife angle. The knife when clamped in the apparatus also defines an angle

known in the art as the "attack angle," and a "relief angle" that is the difference between

the attack angle and the knife angle. Adjustment of one or more of these angles is desirable to account for changed conditions, such as changes in the wood or changes in

environmental factors such as temperature and humidity.

The typical prior art method for effecting such adjustments is grinding the upper

knife-edge-joining portion, which alters the knife angle and relief angle. The attack angle is not altered by this grinding.

Prior art knives provided by Key Knife, Inc. are distinguished from other prior art

knives in having the pressure-applying area for contacting the counterknife effectively

recessed into the knife. For example, in knives with deflector ridges the pressure-applying area is recessed with respect to the deflector ridges, and in an earlier form of the knife a recessed keyway was provided for the pressure-applying area. Accordingly, the

counterknife contacts the pressure-applying area in a region that is outside of the path of

the moving chips so that packing cannot occur.

The present inventor has recognized that altering the knife angle and attack angle permits better optimization of chip quality than altering the knife angle and relief angle as

is done in the prior art. The contemplated alteration or modification requires altering the angle between the lower knife-edge-joining portions and the counterknife. Where one of

the lower knife-edge-joining portions of a knife having two cutting edges makes contact

with the counterknife, such as in the aforementioned Key Knife, Inc. counterknives, altering the knife and attack angles has heretofore required modifying or changing the

counterknife as well.

Accordingly, there is a need for a method and apparatus for clamping a knife that

provides for decreasing manufacturing costs for the aforedescribed knife, particularly by decreasing the width of the knife, as well as providing for changing the attack angle merely by changing the knife, without impacting the performance of the chipping apparatus employing the knife or destabilizing the contact between the knife and the counterknife.

Summary of the Invention

A method and apparatus for clamping a knife according to the present invention solves the aforementioned problems and meets the aforementioned needs by providing a knife having front and back sides wherein the front side includes a recess extending along an elongate axis of the knife, the front side terminating in respective cutting edges of the knife, and outer and inner clamping members for clamping the knife therebetween. The width of the recess divided ("normalized") by the distance between the cutting edges yields a result that is preferably no more than about 0.31.

The outer clamping member is adapted to receive the back side of the knife, and the inner clamping member is adapted to receive the front side of the knife, the inner clamping member making contact with the front side of the knife at two spaced locations thereon, wherein at least one of the locations is outside the space between the deflector portions a distance from the closest of the deflector portions, wherein the distance normalized by the aforementioned distance between the cutting edges, yields a result that is preferably no more than about 0.22 from the closest of the deflector portions.

Preferably, the recess is defined by two spaced apart deflector portions and the inner clamping member includes a complementary recess for receiving one of the deflector portions. Preferably as well, the back side of the knife includes a depression and the outer clamping member includes a corresponding projection adapted to fit into the depression and establish a third location of contact for clamping the knife.

Therefore, it is a principal object of the present invention to provide a novel and improved method and apparatus for clamping a knife.

It is another object of the present invention to provide a method and apparatus for clamping a knife that provides for reduced cost of manufacturing the knife.

It is still another object of the present invention to provide a method and apparatus for clamping a knife that provides for decreasing the width of the knife without impacting the performance of the chipping apparatus employing the knife.

It is yet another object of the present invention to provide a method and apparatus for clamping a knife that provides for decreasing the width of the knife without destabilizing the contact between the knife and the counterknife.

It is a further object of the present invention to provide a method and apparatus for clamping a knife having two cutting edges that provides for changing the attack angle of the knife without requiring that the counterknife be changed as well.

It is still a further object of the present invention to provide a method and apparatus for clamping a knife having two cutting edges that provides for changing the attack angle of the knife without requiring that the counterknife be changed as well, and without impacting the performance of the chipping apparatus employing the knife.

It is yet a further object of the present invention to provide a method and apparatus for clamping a knife having two cutting edges that provides for changing the attack angle of the knife without requiring that the counterknife be changed as well, and without destabilizing the contact between the knife and the counterknife.

The foregoing and other objects, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the following drawings.

Brief Description of the Drawings

Figure 1 is a side section of a first prior art apparatus for clamping a knife.

Figure 2A is a perspective view of a knife according to the present invention, looking up from below.

Figure 2B is a perspective view of the knife of Figure 1 A, looking down from above.

Figure 3 is a side section of an apparatus for clamping a kmfe according to the present invention.

Figure 4 is a side section of a second prior art apparatus for clamping a knife.

Figure 5 is a side section of a prior art apparatus for clamping a knife wherein the knife is modified by increasing the knife angle.

Figure 6 is a side elevation of a an unmodified knife for use in the apparatus of Figure 3.

Figure 7 is a side elevation of a knife modified for use in the apparatus of Figure 3, showing an increased attack angle. Figure 8 is a side elevation of a knife modified for use in the apparatus of Figure 3, showing a decreased attack angle.

Figure 9 is a side section of the knife of Figure 7 and a counterknife according to the present invention.

Figure 10 is a side section of the knife of Figure 8 and the counterknife of Figure 9.

Detailed Description of a Preferred Embodiment

Referring to Figure 1, a prior art apparatus 10 for clamping a knife 12 is shown. The apparatus 10 is a part of a larger wood chipping, shaping or finishing apparatus which is not shown, which typically employs multiple instances of the apparatus 10 on the periphery of a rotating body, which is typically though not necessarily a chipper disc or a drum style cutting head which may have a cylindrical or conical shape. The apparatus 10 essentially forms a cassette for the knife, although the entire cassette is often referred to in the trade as a knife. Herein, the term "knife" is used to refer to the blade that is clamped between the outer and inner clamping members.

Referring in addition to Figures 2 A and 2B, the knife 12 is elongate and has an elongate axis "L" that is perpendicular to the plane of Figure 1. The knife has a front side 14 and back side 16 and is clamped, for operation, between an outer clamping member 18 and a inner clamping member 20, the inner clamping member typically being referred to as a "counterknife." The counterknife provides a wear surface for receiving and channeling chips cut from the wood through the apparatus. The counterknife is shown as rotatable about a base 21 to open the clamping members for changing the knife. Alternative

schemes providing for opening the clamping members are well known in the art.

The front side 14 of the knife 12 includes spaced deflector ridges 22a and 22b that

project therefrom. The deflector ridges define a channel 24 and a pressure-applying

channel surface portion 24a therebetween (Figure 2A). The channel 24 is effectively a recess in the front side of the knife, which may be provided in other configurations, such as

a keyway. The deflector ridges also define two lower knife-edge-joining portions 28a and 28b that terminate in respective cutting edges 30a and 30b. The counterknife 20 includes a

toe 32 that receives the pressure-applying portion 24a. The force applied to the knife is

transferred to the counterknife and distributed over the toe 32 through the pressure- applying portion 24a.

The back side 16 of the knife 12 includes a clamp-facing surface portion 33 that is substantially planar, and two upper knife-edge-joining portions 35a and 35b that slope from

opposite edges of the clamp-facing surface portion to the cutting edges 30a and 30b. The

knife 12 is typically provided so that the lower knife-edge-joining portion 28a lies in the same plane as the lower knife-edge-joining portion 28b.

The knife 12 when clamped in the apparatus 10 defines an attack angle θ_1; a knife angle θ₂, and a relief angle θ₃ that is the difference between the attack angle and the knife

angle. The knife angle is determined by the knife itself, while the attack and relief angles

are determined by the orientation of the knife in the apparatus 10.

It is often desirable to adjust or alter some combination of the aforementioned angles to suit changing cutting conditions. This has typically been accomplished by grinding the upper knife-edge-joining portion or portions of the knife. As can be appreciated with reference to the angles shown in Figure 1, grinding an upper knife-edge- joining portion alters the knife angle and the relief angles (θ₂ and θ₃), the attack angle remaining the same. For reference in connection with the present invention, it may be noted that grinding a lower knife-edge-joining portion alters the knife angle and the attack angles (θ₂ and θ,), while the relief angle will remain the same.

Chips are cut from wood at the cutting edge of the knife, the chips traveling past the lower knife-edge-joining portion and an outer surface 7 of the counterknife 20.

Now turning to Figure 3, an apparatus 40 for clamping a knife 42 according to the present invention is shown. The width "w" of a pressure-applying portion 46 of the apparatus 40 is narrower than tl e corresponding pressure-applying portion 32 of the apparatus 10. Preferably, according to the invention, the width "w" and the corresponding distance "w" (measured tip-to-tip) between the deflector ridges 22 of the knife 42 is about 0.54" or less for a knife 42 having a total width "W" of about 1.76 to 1.8." The width "w" may be scaled for larger or smaller knives by normalizing it according to the overall width "W", i.e., forming the ratio "w/W," to provide a result that is no more than about 0.31.

Decreasing the width "w" decreases the overall width "W" of the knife 42 with respect to the knife 12, providing the outstanding advantage of decreasing manufacturing cost for the knife for the reason mentioned above.

The knife 42 is clamped between an outer clamping member 48 and a counterknife 50. According to the invention, an outer surface the counterknife 50 includes a toe 52 that, corresponding to the pressure-applying portion 46, has a narrower width than that of the corresponding prior art toe 32 (Figure 1). The toe 52 includes a first contact surface 55 adjacent the recess, or one of the deflector ridges 22 of the knife, which establishes a first point of contact between the knife and the apparatus 40.

Also according to the invention, a second contact surface 57 is provided on the counterknife 50 that is outside the recess, or space between the deflector ridges of the knife. The distance "d " between the first contact surface 55 and the second contact surface 57 (outside edge to outside edge) is preferably as great as or may be greater than the width "w" of the prior art toe 32 (Figure 1), to ensure that decreasing the width of the knife does not destabilize contact between the knife and the counterknife.

In a preferred embodiment of the invention, "d," is about 0.70" for a knife having an overall width "W" of about 1.76 - 1.8", or between about 0.65" to 0.75," for a normalized value in the range of about 0.036 - 0.043. The distance "d2" between the deflector ridges and the respective cutting edges remains the same as in the prior art to ensure that the performance of the chipping apparatus employing the knife is not impacted.

Turning to Figure 4, a prior art counterknife 72 manufactured and marketed by Key Knife, Inc. establishes a contact surface 74 that provides a surface of contact with a corresponding prior art knife 70 having an overall width "W" of 2.03" that extends outside the space defined between the deflector ridges of the knife 70 a distance "Dl" of about 0.58" from the nearest deflector ridge. However, as mentioned, the present inventor has recognized that changing the knife and attack angles θ₂ and θ_l9 rather than the knife and relief angles as in the prior art, provides the most effective control over the quality of wood chips, and that the magnitude of Dl severely limits or prevents this possibility. Figure 5 shows the knife 70 wherein the knife angle θ₂ for both cutting edges 30a

and 30b is modified by grinding the lower knife-edge-joining portions 28, resulting in an

increased knife angle θ₃ for both cutting edges and an increased attack angle θ_j for the cutting edge 30a when the knife is clamped in the chipping apparatus. As shown, the

grinding causes separation of the lower knife-edge-joining portion 28b associated with the

cutting edge 30b from the contact surface 74, destabilizing the contact between the knife and counterknife.

To solve this problem, the contact surface 74 is moved closer to the deflector ridges

22. Turning to Figure 6, the knife 42 of the present invention includes flat portions (hereinafter "flats") 64 corresponding to each deflector ridge outside the channel between

the deflector ridges. The flats are substantially parallel to the pressure-applying channel surface 24a (Figure 2A), and serve as a convenience in manufacturing. However,

according to the invention, these flats are used for the additional purpose of providing a region of contact for the contact surface 57 of the counterknife 50 (Figure 3).

In a preferred embodiment of the invention, the outer end of the flat 64 is located a

distance "s" from the recess, or the tip "T" of the deflector ridge, that is equal to the typical

radius "r" of 0.25" of the deflector ridge plus a distance 0.10" corresponding to the width of

the flat, or about .35." For a knife 42 having an overall width "W" (Figure 3) of about 1.8",

this normalizes to a ratio "s/W" of 0.194.

Preferably, the ratio "s/W" is no more than about 0.22, and may be significantly less than 0.194 where the recess is defined more sharply than by use of the radiused

deflector ridge. However, persons of ordinary skill in the art will appreciate that the distance "s" may be increased and the present capability to alter the knife and attack angles maybe retained by sacrificing the width of the lower-knife-edge joining portions 28. However, it is believed that the prior art ratio of about 0.29 is too large to be satisfactory for the purposes described herein. It may be noted that the ratio s/W also defines the maximum distance that the contact surface 57 may be located from the recess, or the nearest deflector ridge, since the contact surface 57 makes contact with one of the flats.

Each flat extends preferably between 0.08" and 0.12" for the 1.8" wide knife 42, which normalizes to a ratio within the range of about 0.045 to 0.065. Preferably, two flats are symmetrically provided, corresponding to each of the deflector ridges, so that the knife may be turned end-to-end with substantially identical functionality.

Referring back to Figure 3, the outer surface 53 of the counterknife is preferably relieved, with respect to a plane defined by the contact surfaces 55 and 57, for the entire distance between the contact surfaces to provide for just two points of contact between the knife and counterknife 50, to provide for greater stability of contact and extreme insensitivity to dimensional variations between the parts. Moreover, at a recess 60, the outer surface 53 is relieved to a greater degree to accommodate one of the deflector ridges. The deflector ridges are preferably substantially identical, and the recess 60 is preferably shaped and dimensioned to wholly receive one or the other, so as to leave a clearance therebetween.

The outer clamping member 48 preferably includes an interlocking feature 61 (Fig. 3), such as a projection, adapted to fit into corresponding interlocking feature 62 (Figs. 2A, 2B) of the back side 16 of the knife, such as a recess or, more particularly in the preferred embodiment, a groove which is preferably semi-cylindrical or, more preferably,

substantially half-cylindrical, as disclosed in the aforementioned application entitled

KMFE AND APPARATUS FOR CLAMPING A KNIFE. This establishes a third location

of contact for clamping the knife, and also provides the outstanding advantage of holding

the knife to the outer clamping member for changing the knife when the outer and inner

clamping members are opened with respect to one another, in orientations of the knife

wherein the knife rests on the outer clamping member when the knife is undamped in the chipping apparatus.

Turning to Figure 7, a side elevation of the knife 42 modified for use in the

apparatus of Figure 3 is shown. The knife is modified by grinding, preferably, both of the

lower knife-edge-joining portions 28a and 28b, so that the knife can be turned end-to-end

to permit consecutive use of two cutting edges. The knife-edge-joining portion 28a prior to

modification is shown in solid lines, and same portion as modified (28a') is shown in dotted lines. With reference to a given relief angle θ₃ as defined by the apparatus, it can be seen that the original attack angle θ,₀ is increased by the grinding, to θ .

Conversely, with reference now to Figure 8 wherein another side elevation of the

knife 42 is shown, the knife may be modified by grinding the lower knife-edge-joining

portions to form an undercut 80, to pennit decreasing the attack angle θι₀ to θ_ld.

Turning to Figure 9, the knife 42 of Figure 7 as modified by increasing the knife

and attack angles is shown supported by a counterknife 50 according to the present

invention. It can be seen that, due to the placement of the contact surface 57 for making

contact between the knife and counterknife, the same counterknife used to support the unmodified knife can support the modified knife. Moreover, because the contact surface

57 is outside the space between the deflector ridges, greater contact stability is provided.

Similarly, turning to Figure 10, the knife 42 of Figure 8 as modified by decreasing the knife

and attack angles is shown supported by the same counterknife 50, providing for the same

outstanding advantages.

According to the above principles, a series of knives is preferably provided having

varying knife angles. A knife having a selected base angle, e.g., 31°, is provided in the

series wherein the lower knife-edge-joining portions 28a and 28b are arranged to be

coplanar, and knives wherein this condition is not met may be provided in advance, rather

than obtained from the base knife at the point of use by grinding. Other knives in the series may have angles that vary above the base angle (corresponding to Figures 7 and 9) and below the base angle (corresponding to Figures 8 and 10) in selected, e.g., 2°, increments.

It is to be recognized that, while a specific method and apparatus for clamping a

knife has been shown and described as preferced, other configurations could be utilized, in addition to configurations already mentioned, without departing from the principles of the

invention.

The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no

intention of the use of such terms and expressions to exclude equivalents of the features

shown and described or portions thereof, it being recognized that the scope of the invention

is defined and limited only by the claims which follow.

Claims

Claims:

1. A knife for use in a wood chipping apparatus, the knife having an elongate axis, and front and back sides co-terminating in two cutting edges defining an overall width "W" of the knife, wherein said front side includes a recess extending along said elongate axis, wherein the distance "w" of said recess, divided by the width "W," results in a value that is no more than about 0.31.

2. The knife of claim 1, wherein said recess is defined by two spaced-apart deflector ridges having respective tips, wherein the distance "w" is measured between said tips.

3. The knife of claim 1 , wherein said recess defines a pressure-applying channel surface, wherein the front side of the knife includes a first flat adjacent and outside the recess that is substantially parallel to said channel surface, wherein an outer end of said flat portion is located a distance from said recess that, divided by "W," results in a value that is no more than about 0.22.

4. The knife of claim 2, wherein said recess defines a channel surface between said deflector ridges, wherein the front side of the knife includes a first flat adjacent one of said deflector ridges and outside said recess that is substantially parallel to said channel surface, wherein an outer end of said flat portion is located a distance from the tip of said one of said deflector ridges that, divided by "W," results in a value that is no more than about 0.22.

5. The knife of claim 4, wherein said flat extends a distance that, divided by

"W," results in a value within the range of about 0.045 to 0.065.

6. The knife of claim 4, wherein the front side of the knife includes a second

flat adjacent the other of said deflector ridges and outside said recess that is substantially

parallel to said channel surface, wherein an outer end of said second flat is located a distance from the tip of said one of said deflector ridges that, divided by "W," results in a

value that is no more than about 0.22.

7. The knife of claim 1, wherein said back side of said knife includes a groove

having a substantially semi-circular cross-section in a plane perpendicular to said elongate axis.

8. The knife of claim 2, wherein said back side of said knife includes a groove

having a substantially semi-circular cross-section in a plane perpendicular to said elongate

axis.

9. The knife of claim 8, wherein the knife is bilaterally symmetric about a

plane parallel to said elongate axis.

10. A counterknife for a knife used in a wood chipping apparatus, the knife

having a front side terminating in at least one cutting edge, the counterknife comprising an

outer surface for disposition proximate the front side of the knife, said outer surface having

two spaced-apart contact surfaces that are raised in elevation relative to the remainder of

said outer surface, said contact surfaces being spaced a maximum of about 0.65" to 0.75"

apart as measured from corresponding outside edges.

11. The counterknife of claim 10, further including a recess in said front side

having a shape and size specially adapted for receiving a deflector ridge of the knife.

12. A wood chipping apparatus comprising:

a knife having front and back sides co-terminating in two cutting edges for the knife, wherein the distance between the cutting

edges defines an overall width of the knife, the knife having

a recess in said front side; and

a counterknife for receiving and making contact with the front side

of the knife at just two spaced locations thereon, wherein at

least one of said locations is outside said recess a distance

"s," wherein the ratio "s/W" is no more than about 0.22.

13. The apparatus of claim 12, wherein the other of said locations makes

contact with said knife within said recess.

14. The apparatus of claim 12, further comprising an outer clamping member

having an inner surface for disposition proximate said back side of said knife, wherein said back side includes an interlocking feature adapted to interlockingly engage a

complementary interlocking feature of said surface of said outer clamping member.

15. The apparatus of claim 14, wherein said interlocking feature of said back

side of said knife is a semi-cylindrical groove.

16. The apparatus of claim 15, wherein said groove is substantially half-

cylindrical.

17. The apparatus of claim 12, wherein said channel is defined by two spaced-

apart deflector ridges projecting from said front side of said knife, and wherein said counterknife includes a recess proximate at least one of said locations that is adapted to

receive one of said deflector ridges with a clearance therebetween.

18. The apparatus of claim 17, wherein the other of said locations makes

contact with said knife within said recess.

19. The apparatus of claim 17, further comprising an outer clamping member

having an inner surface for disposition proximate said back side of said knife, wherein said

back side includes an interlocking feature adapted to interlockingly engage a

20. The apparatus of claim 19, wherein said interlocking feature of said back

side of said knife is a semi-cylindrical groove.

21. A method for optimizing the quality of wood chips cut by a knife, the knife

having front and back sides the front side having a planar upper lαiife-edge-joining portion

and the back side having a planar lower knife-edge-joining portion, the upper and lower

knife-edge-joining portions terminating in a cutting edge, the method comprising:

originally providing the knife so that the upper and lower knife- edge-joining portions are disposed with respect to one

another at a predetennined angle;

grinding the lower knife-edge-joining portion to alter said angle to a

predetermined second angle; and

employing the knife after said step of grinding to cut wood chips.

22. The method of claim 21 , wherein, as a result of said grinding, the lower knife-edge-joining portion remains planar, so that said second angle is greater than said first angle.

23. The method of claim 21 , wherein, as a result of said grinding, for a portion of said lower knife-edge-joining portion that remains planar, said second angle is less than said first angle.