This invention relates to improvements in rounding machines and particularly the knives, the driven faceplates and associated holders for the knives and the adjuster assemblies therefor, and the configuration and mounting of the knives and holders in the rounding machines.

Typical log rounding machines utilize cutting heads having a driven faceplate, a plurality of adjuster assemblies and a plurality of holders mounted thereto, each of which holds a set of knives. Typically each set of knives comprises a roughing knife for reducing the log to a substantially constant diameter and a finishing knife for providing an enhanced surface finish at a desired diameter. The finishing knives are typically arranged to perform a slicing action so as to achieve a smooth surface finish. To this end, known finishing knives have a cutting edge which is arranged so as to extend substantially tangentially and obliquely across the diametral plane of the log (that is a plane containing the longitudinal axis of the log). A centralizing guide is generally associated with each finishing knife for guiding the log along the central axis of the machine.

The roughing knives and the finishing knives generally wear at different rates. Whilst the knives can be adjusted as a set, they must be adjusted individually to accommodate the different amounts of wear if the desired cutting performance is to be achieved. In order to enhance efficient machine operation, complex knife shapes have been developed with various bevels and bezels formed in the respective knives. In a typical arrangement the knives are adjusted so that there is a point of coincidence between the trailing end of the cutting edge of the

roughing knife and the leading end of the cutting edge of the finishing knife. However, in use, such knives need to be sharpened after approximately three hours of normal use. The downtime for removal and replacement of the knives is usually in the order of one half to one hour.

Knives are typically constructed of high speed steel bar although it is known to construct knives having inserts of wear resistant materials such as tungsten fixed to a steel knife body by solder or adhesive to provide a longer lasting cutting edge. Knives utilizing such inserts have not been entirely satisfactory because the heat generated during cutting can damage the bond between the insert and the knife body wherein the insert can loosen or the knife bends due to the different thermal expansion properties of the insert and the knife body. Our co-pending Application No. 40443/95 describes a method of rounding a log which produces less heat at the cutting edge than previously known methods and therefore mitigates this problem. However, knives comprising a high speed steel knife body and an insert are expensive to produce and maintain. Furthermore, knives suitable for use with the presently available knife holders and constructed totally of high wear resistant material such as tungsten are also expensive and their use is generally not an economic proposition.

The present invention aims to alleviate at least one of the above disadvantages and to provide roughing and finishing knives and a holder for such knives which will be reliable and efficient in use.

With the foregoing and other objects in view, this invention in one aspect resides broadly in a knife holder for a rounding machine of the type whereby a log is first rounded to a substantially constant diameter by a leading roughing knife and subsequently is engaged

wit _h a finis _h ing knife to provide a required surface finis _h on said log at said diameter whereby said rounding mac _h ine is adapted such that said roughing knife and said finishing knife orbit a longitudinal axis of said log, characterised in that said knife holder is adapted to hold a relatively thin said roug _h ing _k nife and/or said finishing knife.

_T he log may be maintained in a substantially stationary position and said roughing knife and/or said finis _h ing knife are rotated about said axis. _A lternatively, the log is rotated about said axis and sai _d roug _h ing knife and/or said finishing knife are maintaine _d in a stationary position, or the log and sai _d roug _h ing knife and/or said finishing knife are/is rotated a _b out said axis. Where the log and knives are rotate _d , t _h e rotation may be in opposite directions.

Preferably, the knife holder is adapted to hold a knife having a thickness substantially the same as the t _h ic _k ness of an insert of wear resistant material as norma _ll y used with a steel knife body. Such form of t _h e invention allows the use of a knife comparable in size to an insert and constructed totally of a wear resistant material. It is also preferred that the body of t _h e _h older be shaped to support the knife relatively c _l ose to its cutting edge without contacting the log _b eing roun _d ed whereby the relatively thin knife does not _f racture or bend by any significant amount. In a pre _f erre _{d f} orm of the invention the body of the holder is shape _d so that it approaches the surface of the cut log w _h ere _b y it increases in thickness away from the cutting e _d ge for a substantial distance.

Preferably, the knife holder is adapted to hold a relative _l y thin roughing knife and a relatively thin _f inis _h ing _k nife and preferably such that the cutting edges of the roughing knife and the finishing knife can form a su _b stantially continuous cutting edge. In such

form it is preferred that the holder be constructed and arranged such that in use the cutting edge of the finishing knife can be maintained substantially parallel to the machine axis and that the roughing knife orbits about the machine axis to cut a substantially frustoconical surface on the log and that the cutting edge is substantially contained in a diametral plane containing the machine axis. However, the cutting edge may be contained in a plane parallel to the diametral plane containing the machine axis or a plane inclined to the plane containing the machine axis such that the leading end of the cutting edge is ahead of the trailing end of the cutting edge although adjustment of the knives to accommodate for wear is more difficult. If desired the trailing end of the roughing knife may coincide with the leading end of the finishing knife but in a preferred form wherein the leading end of the cutting edge of the finishing knife is inclined to the machine axis (such as when the leading edge is formed by the junction of an upper side bezel with an under side chamfer), the trailing end of the roughing knife is disposed on a line intermediate the inclined leading portion of the finishing knife- that is, the cutting edge of the finishing knife is slightly ahead of the cutting edge of the roughing knife relative to the diametral plane. Suitably, this arrangement reduces the occurrence of knife tracks on the surface of the log. However, if desired the finishing knife may be positioned further ahead of the roughing knife. The arrangement of a substantially continuous cutting edge formed by the roughing knife and the finishing knife provides a cutting edge with substantially uniform characteristics such that non- uniform wearing is avoided or reduced with a view to achieving extended service life.

The holder may be constructed and arranged such that the under side face of the finishing knife adjacent the cutting edge may be tangential to the finished surface of the log or the under side face adjacent the cutting edge may form an obtuse angle with the diametral plane containing the cutting edge. Preferably such obtuse angle is in the range of between 90° to 110 ^β , and more preferably in the range of between 90° and 92°. This angle is hereinafter referred to as a clearance angle or approach angle. Preferably, the knife has a substantially flat under side face and the cutting edge is formed by the junction of the under side face and a beveled upper side end portion adjacent the cutting edge providing an upper side bezel. However if desired the under side face adjacent the cutting edge may be beveled to form an under side bezel. Furthermore the cutting edge may be defined at least in part by chamfers extending along the under side edges away from the cutting edge. It will be appreciated that raw logs generally are not perfectly circular in cross-section and the cross-section can vary considerably over the length of a log, for example at the junction of a branch with the trunk. Roughing knives therefore are typically of sufficient length to accommodate the largest diameter log able to fit the rounding machine. The outer portion of such knives is therefore in use for only a small amount of time wherein the inner portion of the knife wears at a much greater rate than the outer portion and consequently the relatively unused outer portion is discarded when sharpening takes place. In another form of the present invention the aforementioned problem is mitigated by providing a roughing knife of a width selected such that a large portion of the cutting edge is in use most of the time and an auxiliary roughing knife for cutting any outer

portion of the log not cut by the roughing knife. The knife holder previously described may be adapted to hold such an auxiliary roughing knife also and preferably such an auxiliary roughing knife is also a relatively thin knife. In such form it is preferred that the holder be constructed and arranged such that in use the cutting edge of the auxiliary roughing knife orbits about the machine axis to cut a substantially frustoconical surface on the log and that the cutting edge is substantially contained in a plane parallel to the diametral plane containing the machine axis.

In another aspect this invention resides broadly in a method of rounding a log including: providing a relatively thin finishing knife; providing a relatively thin roughing knife; securing the finishing knife and the roughing knife to a holder as described herein; and mounting the holder in a rounding machine of the type in which said log and said knives move relative to one another with a linear motion along said machine axis and an orbiting motion about said machine axis.

Preferably, the method includes arranging the knives such that the cutting edge of the finishing knife is maintained substantially parallel to the machine axis and the cutting edge of the roughing knife is adapted to orbit about the machine axis to form a substantially frustoconical surface on the log and the cutting edge is substantially maintained in a plane containing the machine axis or a plane parallel to the plane containing the machine axis or a plane inclined to the plane containing the machine axis such that the leading end of the cutting edge is ahead of the trailing end of the cutting edge.

Preferably, the method also includes providing a relatively thin auxiliary roughing knife and securing it to the holder as described herein.

In another aspect this invention resides broadly in a method of rounding a log utilising a rounding machine of the type in which the log to be rounded is moved along the machine axis and machined by a roughing knife and a finishing knife which orbit about the machine axis, said knives being mounted in a holder as described herein the roughing knife being adapted to reduce the log to a substantially constant diameter prior to finishing by the finishing knife, the position of the holder being adjustable to round logs to different diameters.

It will be appreciated that the accuracy in which the holder is mounted relative to the faceplate assembly can affect the depth of cut of the knives and thus the cut size of the log. This invention in another aspect aims to reduce the incidence of error in mounting a holder to a faceplate assembly by providing an adaptor assembly including: a first adaptor part having first mounting means for operatively mounting the adaptor part to the faceplate assembly of a log rounding machine; a second adaptor part having second mounting means for operatively mounting a knife holder thereto; and complementary locating means on said first and second adaptor parts for locating the second adaptor part in a desired position relative to said first adaptor part.

Preferably, the first mounting means includes a plurality of apertures through which fixing means, such as bolts or such like, can extend for fixing the first adaptor part to the faceplate assembly and the second mounting means includes a plurality of apertures through which fixing means, such as bolts or such like, can extend for fixing the knife holder to the second adaptor part.

Preferably, the locating means is adapted to assist location of the first adaptor part to a position defined in three dimensions, referred to hereinafter as the x, y and z axes. It is also preferred that the first adaptor part be located relative to the second adaptor part, firstly in the x direction, then the y direction and then the z direction. In a preferred form, location in the z direction is defined by contact between substantially planar faces of the first and second adaptor parts, whilst location in the x direction is defined by engagement of a first projection provided on one of the adaptor parts in a complementary first recess provided in the other adaptor part and location in the y direction is defined by engagement of a second projection provided on one adaptor part in a complementary second recess provided in the other adaptor part. In such form it is preferred that partial engagement of the first projection in the first recess allows movement of the first adaptor part relative to the second adaptor part whilst maintaining location in the x direction until engagement of the second projection in the second recess can occur wherein movement of the first adaptor part relative to the second adaptor part in the z direction allows the planar faces of the first and second adaptor parts to abut thereby defining the position in the z direction. Advantageously, the knife holder and its attached adaptor part can be removed from the rounding machine, the adaptor part removed from the knife holder, the knife removed or otherwise maintained and then reassembled and replaced in the same position thereby minimising adjustment requirements.

In another aspect of the invention, the faceplate assembly and knife holder may be provided with complementary locating means thereon for locating the

knife holder in a desired position relative to the faceplate assembly as described, thereby removing the requirement for an adaptor assembly.

In another aspect this invention resides broadly in a cutter assembly including a holder as described herein and a roughing knife and a finishing knife as described herein. The assembly may also include an auxiliary roughing knife as described herein.

In order that this invention may be more readily understood and put into practical effect reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:

Figure 1 is a pictorial representation of a cutter assembly according to the invention illustrating the cutting position relative to a log;

Figure 2 is a pictorial representation of the cutter assembly of Figure 1 in line for assembly; Figure 3 is a pictorial representation of the relationship between the knife body, knife inserts and adjuster bolts of the cutter assembly of Figure 2 when assembled; Figure 4 is a pictorial view of the knife holder body and knife inserts of Figures 1 to 3 from the under side;

Figure 5 is a side view of a cutter assembly illustrating the preferred position of the roughing knife and the finishing knife according to the invention relative to a log to be cut;

Figure 6 is a side view of the cutter assembly of Figure 5 with the knives and wedge member additionally shown disassembled; Figure 7 is an end view of a cutting assembly machine utilising four cutter assemblies

according to the invention rounding a log to a diameter of approximately 200 mm;

Figure 8 is an end view of the cutting assembly machine of Figure 7 with the cutter assemblies set for rounding a log to a diameter of approximately 50 mm;

Figure 9 is a pictorial view of the knife holder body and knife inserts of Figure 4 with a jig fitted for setting the knife adjustments; Figure 10 is a pictorial view of an retainer castings for the cutter assembly of Figures 1 to

9;

Figure 11 is a front view of the alternative adaptor and retainer castings of Figure 10; Figure 12 is a pictorial view of a casting for an alternative knife holder body for the cutter assembly of Figures 1 to 9;

Figure 13 is a pictorial view of an alternative main retainer for the cutter assembly of Figures 1 to 9, with jig support recesses additionally shown;

Figure 14 is a wireframe pictorial view of the top and side of another retainer;

Figure 15 is a wireframe pictorial view of the retainer of Figure 14, and

Figure 16 is a diagrammatic pictorial view of the further retainer of Figure 15 in relation to a finger portion.

The cutter assembly 10 illustrated in Figures 1 to 9 is adapted for use in a log rounding machine of the type in which a log 9 to be rounded moves along the machine axis 8 and is rounded by knives retained in the cutter assembly 10 which orbits about the machine axis 8. The cutter assembly 10 includes a steel knife holder 11 having a solid steel body portion 12 bolted

to an adjacent solid steel guide finger portion 13 at one end of the solid steel body portion 12.

The body portion 12 has an under side face 12a comprising a first part 12aa and a second part 12ab which in use are positioned adjacent the surface of the log to be cut and an upper side face 12b. The under side face 12a and upper side face 12b substantially converge to form a leading edge comprising several parts as will be described hereinafter, a rear side face 12c and an end face 12e opposed to a machined end face 12d.

The guide finger portion 13 has an under side face 13a, an upper side face 13b, a rear side face 13c and two opposed machined end faces 13d and 13e. The end face 13e is adapted to abut complementary the machined end face 12d. An elongate spigot 12f of rectangular cross-section projects from end face 12d and engages in a complementary open sided rectangular recess (referred to hereinafter as the adaptor recess 13f) provided in the guide finger portion 13 and extending inwardly from the end face 13e. The adaptor recess 13f is defined by an inner elongate face 13g, an elongate upper face 13h and an elongate lower face 13i and opens opposite the inner face 13d through which the elongate spigot 12f enters the adaptor recess 13f. The adaptor recess 13f also opens at respective leading and trailing ends.

As the upper side and under side faces 13a and 13b converge towards the leading edge they form a substantially planar guide face 13j (provided on a replaceable hardened insert 13k) on its under side (the log side) parallel to the upper and lower faces 13h and 13i of the adaptor recess 13f and adapted to bear against or just clear the finished surface of the log being rounded.

The guide finger portion 13 is adapted to be secured to the faceplate assembly 50 of the rounding machine for rotation therewith and for this purpose includes respective threaded apertures 51 extending inward from face 13b and adapted to receive respective bolts extending through complementary apertures 52 provided in the faceplate assembly 50.

In order to allow easy removal and replacement of the body portion 12 in the same location relative to the guide finger portion 13, which can remain fixed to the faceplate assembly 50 whereby the cutter assembly 10 can be removed for knife maintenance, the body portion 12 includes a second elongate spigot 12m of rectangular cross-section which projects from the machined end face 12d at right angles to the elongate spigot 12f and engages in a complementary open sided rectangular recess 13m provided in the guide finger portion 13 and extending inwardly from the end face 13e at right angles to adaptor recess 13f. The second elongate spigot 12m is half the thickness of elongate spigot 12f and the rectangular recess 13m is half the depth of the adaptor recess 13f. It will be seen that partial engagement of the elongate spigot 12f in the adaptor recess 13f allows sliding movement in the direction of the elongate spigot 12f between the adaptor and the guide finger portion 13 until the second elongate spigot 12m and the rectangular recess 13m come into alignment wherein they will engage, and the elongate spigot 12f can engage fully within the adaptor recess 13f.

An upper recess 14 is provided in the upper side of the body portion 12 adjacent the guide finger portion 13 and is adapted to slidably receive a main retainer 15 therein for clamping a relatively thin finishing knife 16 and a relatively thin roughing knife 17 partially within the recess so as to extend forward

beyond the knife holder 11 for cutting the log to be rounded. The finishing and roughing knives in this embodiment are approximately 3 mm thick, but a thickness of 4 mm is also believed to be satisfactory. The upper recess 14 is defined in a direction towards the log (the under side) by adjacent substantially planar support faces 18 and 19 which are inclined to each other and meet along a common line 20. The support face 18 and the under side face 12aa converge to form a leading edge 18a and the support face 19 and the under side face 12ab converge to form a leading edge 19a. It will be appreciated that the under side surfaces 12aa and 12ab meet along a common line lying in a plane substantially parallel to the face 13g.

The support faces 18 and 19 are adapted to support the finishing knife 16 and roughing knife 17 respectively thereon. The main retainer 15 has two adjacent clamping faces 26 and 27 which complement the support faces 18 and 19 respectively for clamping the knives 16 and 17 respectively between the support and clamping faces 18 and 26 respectively and 19 and 27 respectively.

The inner face I3g of the adaptor recess 13f defines one end face of the upper recess 14 and the other end of the recess is defined by a shoulder 24 provided in the body portion 12. The leading edge 18a of the support face 18 lies in the same plane as the guide face 13j of the guide finger portion 13 whilst the leading edge 19a of the support face 19 makes an angle of approximately 40° to the leading edge 18a so that, in use, the cutting edge 17a of the roughing knife 17 is inclined at approximately 40" to the machine axis 8 and forms an acute angle with the finished surface of the log as cut by the finishing knife 16.

In this arrangement the cutting edge 16a of the finishing knife 16 can be maintained substantially parallel to the machine axis 8 and the roughing knife

17 can orbit about the machine axis 8 to cut a substantially frustoconical surface on the log.

The support face 18 is inclined upwardly away from its leading edge 18a towards the upper face 13h of the adaptor recess and forms a wedge shaped recess adapted to receive a complementary wedge shaped projection 15a provided at one end of the main retainer 15. A similar wedge shaped projection 15b provided at the opposite end of the main retainer 15 is adapted to engage in a complementary wedge shaped recess 24a provided in the shoulder 24. The wedge shaped recess 24a is defined by an upper face 24b which lies in a plane parallel to the upper face 13h of the adaptor recess 13f so that the wedging angle between face 24b and the support face 19 is the same as the angle between the upper face 13h and the support face 18 and a lower face 24c which is parallel to the inner face 13g.

It will be appreciated that the width of the adaptor recess 13f is constant between the inner and lower faces 13g and 24c respectively, allowing the main retainer 15 to move freely into and out of the adaptor recess 13f, but such movement causes movement towards the support faces 18 and 19. By this action the finishing knife 16 placed between the wedge clamping face 26 and the support face 18 and the roughing knife 17 placed between the wedge face 27 and support face 19 can be tightly clamped.

The main retainer 15 can be forced into the clamping position in the upper recess 14 and suitably retained there by extending a bolt 25 through a passage 21 provided in the body portion 11 to engage in a complementary threaded passage 21b in the main retainer

15. Advantageously, the passage 21 is oversized for the bolt 25 whereby the main retainer 15 can move sideways to a limited extent to wedge in an optimum clamping position. A raised land 28 is provided in the body portion 11 at the rear of the recess between the adaptor 13 and the shoulder 24 and the main retainer 15 is relieved towards its rear end (trailing end) to provide a complementary land 15d adapted to abut the raised land 28. The raised land 28 is parallel to the support face 19 whereby tightening of the bolt 25 is effective to force the leading edge of the main retainer 15 downward whilst the main retainer 15 pivots about the complementary land 15d to effectively force the clamping faces 26 and 27 into engagement with the upper faces of the knives 16 and 17 respectively so that they may be clamped in their operative positions as close as possible to their respective cutting edges.

A central recess 29 impinging into the raised land 28 provides clearance for a complementary projection provided in the complementary land 15d. The complementary projection functions as a structural stiffening land for the main retainer 15.

A pair of spaced apart passages 31 and 32 extend through the body portion 11 for receiving two respective set bolts 33 and 34 and each include a threaded portion for inward and outward movement of the respective set bolts 33 and 34. The passages 31 and 32 are inclined to the support surface 19 whereby the set bolts 33 and 34 are operable to effect movement of the knife 17 forward towards the leading edge 19a, but, to an extent, limited by binding of the set bolts 33 and 34 in respective recesses 35 and 36 formed in the support surface 19. Advantageously, this limiting ensures that knives of too little length away from the leading edge are not utilised. A similar arrangement

is provided for the finishing knife 16 with a set bolt 38 in an aperture 39.

A second recess 41 is provided in the body portion 12 and is separated from the upper recess 14 by a spur portion 42 defined on one side by a first shoulder 24 and on the other side by second shoulder 43. The second recess 41 is adapted to slidably receive an auxiliary roughing knife 46 having a cutting edge 46a and an oversize retainer 47a in a manner similar to that previously described in relation to the roughing knife 17 and the main retainer 15. Adjustment of the auxiliary roughing knife 46 can be achieved by screwing a set bolt 47 in a passage 48 to bind in a recess 49 in a similar manner to the set bolts 33 and 34.

Referring to Figures 10 and 11, an alternative adaptor 13m is cast as a bidirectional part, but in the alternative form is machined for the rotation required. The wedge shaped projection 15a of an alternative main retainer 15m is cast in the alternative form with an upper surface 101 parallel to the cutting edge 17a of the roughing knife 17. The alternative adaptor 13m has, in an aperture 102, an adjusting grub screw (not shown). The grub screw is to be adjusted against the upper surface 101 so that the alternative main retainer 15m applies near equal pressure to both the finishing knife 16 and the roughing knife 17 before the alternative main retainer 15m is locked in place by the bolt 25. The alternative adaptor 13m has an additional land 104 for clamping a knife setting jig if the need arises. The alternative main retainer 15m now extends beyond the back edge of the knife holder body 11. The purposes for this are: Firstly, to provide a striking face (or anvil)

111 to aid the operator with releasing the retainer during knife changes;

Secondly, to provide a jig mounting surface 112, and a mounting aperture 113, that is parallel to the under side surface that contacts the roughing knife 17. This is to assist with the machining of the under side surface;

Thirdly, to provide a jig mounting surface 114, and a mounting aperture 115, that is parallel to the under side surface that contacts the finishing knife 16. This is to assist with the machining of the under side surface.

Parallel jig support recesses may also be provided in respective top surfaces 116 and 117 in the alternative oversize retainer 15m.

An alternative knife retainer 47m now extends beyond the back edge of the knife holder body (not illustrated). The purposes for this are firstly, to provide a striking face (or anvil) 121 to aid the operator with releasing the alternative oversize retainer 47a during knife changes, and secondly, to provide a jig mounting surface 122, and a mounting aperture 123, that is parallel to the under side surface that contacts the oversize roughing knife 46. This is to assist with the machining of the under side surface.

Referring to Figures 12 and 13, an alternative knife body holder 11m is suitably recessed to accommodate the alternative retainers 15m and 47m. The raised land 28 is now located in a more rearward position to improve stability of the alternative body portion 11m than for the knife body holder 11 described in relation to Figures 1 to 10. The purpose for the size the size and clearances around the raised land 28 is to permit the support surface 19 to be machined with an angled cutter whilst the machining centre is set up

for machining the mounting faces 12d, 12f, 12m and so forth.

Two extra apertures 141 and 142 are provided as jig mounting apertures. The aperture 141 is recessed, such as with a counterbore, to permit a bolt or such like to be fitted with its head below the surfaces to be machined.

A recess 143 is formed to give corner clearances for the milling cutter when machining the machined end face 12d. The surface area of the recess 143 is also enlarged sufficient to accommodate the stamping of identification numbers.

The alternative main retainer 15m includes a striking face 111 extending rearward beyond respective edges 151, 152 and 153.

Respective jig support faces 154 and 155 are recessed below a top surface 117 and are parallel to the jig mounting surface 112. A jig support face 156 is recessed below the top surface 117 and is in the same plane as the jig mounting surface 114. A jig support face 157 is recessed below the top surface 116, and is parallel to the jig mounting surface 114.

Referring to Figure 14, a main knife retainer 215 includes a adjuster bolt aperture 211 for receiving an adjuster bolt, drawbolt, grub screw or such like (not shown) for adjustment in the direction of an adjustment arrow 212 in order to maintain alignment of the main knife retainer 215 when bolted down. The other opposing force acting on the main knife retainer 215 are shown by respective arrows 212, 213 and 214. A corner edge 218 is adjusted to the intersection of the top surface planes of the knives.

Referring to Figures 15 and 16, a further retainer 225 is modified by changing a surface 223 from horizontal to 40", and parallel to the slope of the roughing knife cutting edge 17a to permit the

alternative finger 13n into close engagement therewith, as shown in particular in Figure 16.

Referring to the invention generally as described above, the body portion 12 is constructed such that it can be mounted to a faceplate whereby in use, the cutting edge 16a of finishing knife 16 can be contained in a diametral plane (that is a plane containing the machine axis) and be parallel to the machine axis whilst the cutting edge 17a of the roughing knife 17 can be contained in the same diametral plane but be inclined to the machine axis. In such arrangement the support face 18 forms an obtuse angle with the diametral plane containing the axis of the log to be cut and the cutting edge 16a and the under side faces 12aa and 12ab of the body portion 12 approach the cut surface of the log adjacent the cutting edges. It will be seen that the under side face 12aa forms substantially a part cylindrical surface having an axis parallel to the log to be cut and thus utilises the maximum amount of space available to support the knives without impinging on the surface of the log.

Similarly, the under side surface 12ab also forms substantially a part cylindrical surface but having an axis parallel to a line lying in a plane containing the axis of the log but making an angle of 40° to it. Suitably this construction provides the necessary support for the relatively thin knives 16 and 17 whereby the knives will not suffer from fracture whilst maintaining a desirable cutting angle of the knife relative to the log. The thickness of the body portion 12 between the under side surfaces 12aa and 12bb and the respective support surfaces 18 and 19 can be increased by increasing the angle the finishing knife and the roughing knife make with the log. The body portion 12 can have mounted to it a jig which consists of a G-clamp-type mounting 99 with a

thumb screw 98 for locking the mounting 99 to the body portion 12. The mounting 99 extends towards and beyond the front of the body portion 12 and terminates in a bar 97 to which the knife insert cutting edges can be set. After the knives have been set, forward and/or downward movement of the jig can be undertaken without damage to the knife edges by releasing the thumb screw 98.

It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as claimed in the following claims.