US3811232A

US3811232A - Knife edge grinder for rotary reel type cutter head

Info

Publication number: US3811232A
Application number: US00270410A
Authority: US
Inventors: F Reuter
Original assignee: Massey Ferguson Inc
Current assignee: MASSEY COMBINES Corp A CORP OF ONTARIO
Priority date: 1972-07-10
Filing date: 1972-07-10
Publication date: 1974-05-21
Anticipated expiration: 1991-05-21
Also published as: AR198317A1; GB1432873A; FR2192477A5; CA988718A; AU5677973A; AU463002B2; ZA733893B

Abstract

A knife edge sharpener is permanently mounted on a harvester implement having a reel type cutter head for selective sharpening of the knife edges of the cutter head. The sharpener unit is mounted for longitudinal movement along the cutter head and an indexing mechanism is incorporated for engagement with the rotary drive means of the cutter head in correspondence with longitudinal movement of the sharpener along the cutter head.

Description

United States Patent 1191 Reuter [451 May2l, 1974 KNIFE EDGE GRINDER FOR ROTARY REEL TYPE CUTTER HEAD [75] inventor: Floyd W. Reuter, Dearbom Heights,

Mich.

[73] Assignee: Massey-Ferguson lnc., Detroit,

Mich.

[22] Filed: July 10, 1972 [2]] Appl. No.: 270,410

3,638,363 1/1972 Witt et a1 51/249 3.581.446 6/1971 Witt et a1 51/249 2,318,865 5/1943 Johnson 51/95 LH 1.874.331 8/1932 Medholdt 51/249 Primary Examiner0thell M. Simpson Attorney, Agent, or Firm-Robert L. Farris [57] ABSTRACT A knife edge sharpener is permanently mounted on a harvester implement having a reel type cutter head for selective sharpening of the knife edges of the cutter head. The sharpener unit is mounted for longitudinal movement along thecutter head and an indexing mechanism is incorporated for engagement with the rotary drive means of the cutter head in correspondence with longitudinal movement of the sharpener along the cutter head.

4 Claims, 7 Drawing Figures KNIFE EDGE GRINDER FOR ROTARY REEL TYPE CUTTER HEAD The present invention relates to the knife edge sharpener mechanisms and more in particular to an improved knife edge grinder for forage harvesters or similar units employing rotating cutter head assemblies.

Although it is commonly known in connection with harvesters having reel type or similar cutter head units, to provide a built-in cutter head sharpening means for the multiple blades of the cutter head, these known devices have not always been satisfactory due to difficulty in accurate positioning and controlled longitudinal movement of the sharpening device along the cutter head and proper indexing of the cutting blades relative to the position and movement of the sharpening device to obtain proper ground knife edge bevels.

Thus, more commonly it has been the practice in reel type and other cylinder type (such as lawnmowers and the like) rotating cutter heads to dismantle the cutter head from the machine for sharpening of the knife edges by means of an in-plant grinding mechanism. This, of course, requires down-time and prolonged incapacity of the cutting machine at added expense and labor.

It has been very difficult in the past to install grinder units in existing cutter heads of harvesting machines, without interference with related mechanisms of the machine and without exceeding proper design limits of these machines.

Even more importantly, the existing known in-head grinding devices embodied in known reel type or similar rotary cutting machines, as mentioned above, are difficult to position relative to the beveled and usually spirally extending cutting edges of the knives of the cutter head.

Grinding or sharpening of the knife edges of the blades of the cutter head, of course, removes some material from the cutting edge and thus, requires constant adjustment of the grinding tool prior to subsequent replacement of the cutting blades after they are worn down to a certain extent. This constant adjustment is very difficult to obtain in the known in-head grinding devices which is primarily due to the particular geometry of the cutting blades. 7

The most important factor, however, which hitherto prevented widespread application of in-head grinding devices was that certain parts of the in-head grinding device had to be disconnected when the cutter head is in working operation and subsequently had to be reassembled for grinding. This, of course, required additional manual labor and added expense.

The primary object of the present invention resides in the provision of an improved knife edge sharpener device for reel type cutter heads of harvesting machines which is permanently stored on the machine and can be quickly placed into operating position when the knife edges are to be sharpened and which is additionally provided with an indexing mechanism geared to the drive means which provides for movement of the grinder unit along the cutter head to rotatably advance the reel type cutter head in correspondence with longitudinal movement of the grinder unit and in direct relation to the helix position of the individual cutter blades.

The present invention will be best understood by reference to the following detailed description having reference to the attached drawings in which:

FIG. 1 is a side elevational view of the sharpening device in accordance with the present invention for a reel type cutting mechanism of a harvesting machine, only a fragment of which is illustrated, illustrated in position for sharpening of the cutter blade knife edges;

FIG. 2 is a fragmentary front elevational view of the sharpening device illustrated in FIG. 1 with alternate positions of the device resulting from its movement shown in phantom lines;

FIG. 3 is a fragmentary cross-sectional view through the indexing mechanism of the sharpening device in FIG. 1 taken along line 3-3 thereof;

FIG. 4 is a cross-sectional view of the indexing mechanism of FIG. 3 taken along line 4--4 thereof;

FIG. 5 is a fragmentary cross-sectional view of the support and transverse movement mechanism of the sharpening device taken along line 5-5 of FIG. 3;

FIG. 6 is an enlarged fragmentary view of the indexing mechanism for the reel taken along line 66 of FIG. 1 and partly shown in cross section; and

FIG. 7 is a similarly enlarged cross-sectional view through manual operating means for causing movement of the grinder unit along the cutter head while simultaneously actuating the indexing mechanism for the reel taken along line 7-7 of FIG. 1.

With continuing reference to the Figures in the drawings, numeral 10 generally represents a frame of a harvesting machine such, as for instance, a forage harvester. The harvesting machine may be of any known construction commonly supported on wheels, as is known, for traveling over the ground. The harvested crop or other plant material is fed from the harvester table into a cutter head housing 13 for further processing. The housing 13 includes opposed sidewalls l2 and 14, a top wall 15 and a hinged rear wall or cover 16.

Housing 13 supports a rotary wheel type cutter head assembly 17 supported on a rotatable shaft 18 (FIG. 6) which is conventionally drive connected to the drive mechanism of the harvesting machine (not shown). The cutter head assembly 17 supports a plurality of individual longitudinal cutting blades 20 each of which has a beveled knife edge 22. The cutting blades 20 are equally radially spaced from cutter head drive shaft 18 and are further equally angularly spaced in circumferential direction. The cutting blades 20 extend along parallel helical or spiral contours so that upon rotation of the cutter head 17 each cutting blade 20 in succession engages the standing crop starting from the leading end of the cutting blade 20 and gradually moving over to the trailing end of the cutting blade 20 as the cutter head 17 rotates to obtain a slicing action.

As is known, the cutter head assembly 17 is provided to reduce the harvested crop or other plant material prior to discharge from the machine.

As is also known, during prolonged operation of the cutter head attachment the knife edges 22 of the cutting blades 20 become dulled or, in instances, may be chipped by engagement with stones or other hard foreign objects carried by the crop material. Thus, the knife edges 22 have to be sharpened or ground periodically to maintain maximum cutting capacity of the cutter head 17. To this end, the present invention provides an improved cutter 17 head grinding mechanism permanently carried on the cutter head housing 13 as will be described in the following.

In front of the hinged housing cover 16 a longitudinal crossbar assembly 24 is provided which extends in longitudinal parallel direction relative to the cutter head assembly 17. The longitudinal crossbar assembly 24 is supported on a frame bracket 26 which is suitably secured to the housing frame. The top of crossbar assembly 24 defines opposite

parallel slide ways

28 and 30 respectively which are to be engaged by pairs of rollers 32 supportinga carriage 34. The carriage 34, thus, is supported by and longitudinally movable along crossbar assembly 24.

The carriage 34 supports a grinder unit 35, including motor 36, by means of support plate 38. The carriage 34 and support plate 38 are provided with

boss portions

40 and 42 on both sides of the motor 36. The

boss portions

40 and 42 are each provided with coaxially aligned

bores

44 and 46, respectively, illustrated in FIG. which are adapted to receive a pair of

parallel guide rods

45 and 47. The upper portion of the carriage 34 at one transverse end thereof is provided with a bore 49 which is coaxially aligned with a bore 51 in a boss 53 on the lower portion of the carriage 34 and adapted to receive a threaded adjusting rod 50 which is longitudinally stationarily but rotatably retained in the boss 53. Adjusting rod 50 is provided with a hand wheel 54 by which rod 50 can be rotated to cause adjustment of motor 36 transverse to the longitudinal direction of crossbar assembly 24 towards and away from the cutter head assembly 17. Motor 36, which may be an electric motor. has a drive shaft 56 which supports a grinding stone 58, illustrated in FIG. I. Grinding stone 58 is of towards or away from the worm 64 so as to selectively increase or decrease frictional rotational resistance of the worm 64.

In order to traverse the motor 36 along the longitudi- 5 nalcrossbar 24, the carriage 34 is engaged by the worm i x As is known, the cutting blades are arranged Iongitudinally in radially spaced positions relative to the rotating shaft 18 of the cutter head assembly 17 with the krii fe edge 22 extending generally along a spiral or helical line as illustrated in FIG. 1. Since the grinding unit 35 can only travel along a straight line parallel to the cutter head assembly 17 but the cutting blades 20 have'a spiral shape, some form of adjustment must be provided to rotate cutter head assembly 17 in unison with the straight line movement of the grinding unit 35 travel along the crossbar assembly 24.

the rotary type and adapted to' be selectively placed cutting blades 20. The motor, as will be understood, is suitably connected by conduits to an electric power source such as the battery of the harvesting machine.

With reference to FIG. 5, the selected grinding position of motor 36 relative to the cutting edge 22 is preferably locked in place by a pair of lock nuts I34 on the adjusting rod 50 and engageable with the upper portion of the carriage 34. I

Under normal operating conditions of the machine, i.e., during cutting operationsof the cutter head assembly 17, the hinged rear cover 16 of housing 13 will be in closed position against the frame of the cutter housing 13 and will be secured at the lower end of the cover 16 by means of lock assembly 60. In this position, the grinder unit is retained in stored position at the side into grinding engagement against knife edges 22 of the 35 to maintain the knife edges 22 of the engaged cutting blade 20 in engagement with the grinding stone 58. It is also necessary to properly position each cutting blade 20 for'grinding prior to starting the grinding unit35 At the same time, the grinding unit must be adjusted in position relative to the knife edges 22 to be able to perform proper grinding of the knife edges 22 of the cutting blades 20. Obviously, the bevel of the knife edge 22 must not be too steep nor too short to permit positioning of the knife edge 22 as close to a shear bar (not illustrated) of the cutter head 17 as possible. Likewise, the knife edge 22 of the cutting blades 20 must not be ground hollow since this provides an extremely thin edge which will break or chip easily and thusmake of the cutter head housing 13, as shown in phantom at ,1

As more clearly shown in detail in FIG. 4 the cooperating member 62 for worm 64, which is disposed at one side below the carriage member 34, need not be threaded in correspondence with the threads of the 6 worm 64 but instead a simple screw 130 may be provided which has a tapered tip 132 for mating engagement with the worm 64. The screw 130 is adjustable the cutting blade inoperable. Preferably, the knife edge 22 of the cutting blades 20 should be ground such as to provide a proper cutting edge bevel which will permit positioning of the cutting blades 20 close to the shear bar and to provide a small clearance between the heel of the cutting blade and the blade supports of the cutter head assembly to permit clean cutting and easy feeding of the crop between the cutting blades of the cutter head and the shear bar. Thus, the knife edges 22 of the cutting blades 20 have to be ground to the proper bevel length and at a proper angle. Preferably, between onehalf inch to one inch of bevel length together with a bevel of about 25 degrees is used.

In order to protect the operator or any other person near the machine against sparks and grinding debris during operation of the grinding unit 35, a protective shield 128 illustrated -in FIGS. 1 and 2 is provided which is attached to the motor support plate 38.

An indexing mechanism for the cutter head assembly 17 which is geared to the longitudinal movement of the grinding unit motor 36 is provided to position an individual cutting blade20 and its knife edge 22 relative to the cutter head 17.

- The cutter head shaft 18 outwardly of side wall 14 is provided'with an indexing plate which, as shown in FIGS. 1 and 6, is nonrotatably secured to the outer end 19 of cutter head shaft 18. The indexing plate 70 is provided with a plurality of circumferentially equally spaced notches 72.

Also attached to the outer end 19 of the cutter head shaft 18 is a cylindrical member 74 which abuts against the outer surface of indexing plate 70 and is rotatable around the cutter head shaft outer end 19 by means of a bearing 76. The cylindrical member 74 is retained on the outer end 19 of shaft 18 by means of a plate 78 abuting against the outer end of cylindrical member 74 and which is clamped to the outer end 19 of shaft 18 by means of bolts 80. A lever 82 is attached to cylindrical member 74 adjacent the outer surface of indexing plate 70 by means of welding or the like. The free end of lever 82 supports a pivoted socket member 84 attached for rotation by means of threaded pin 86. The socket member 84 at the end of lever 82 is provided with a threaded bore 88 to receive the threaded portion 90 of a rotatable actuating rod 92 which extends along the outside of housing 13 towards worm 64 of the motor carriage 34 of the grinding unit 35.

The other end of actuating rod 92 is provided with a bevel gear 94 which is supported for rotation within the

arms

96 and 98 of a bifurcated bracket 100 as more clearly seen in FIG. 3. As shown in FIG. 3, the bridge portion of supporting bracket 100 is provided with a bearing assembly 102 to accommodate rotation of actuating rod 92.

With further reference to FIGS. 1, 3 and 7, the bevel gear 94 of actuating rod 92 is in constant mesh with another bevel gear 104 right angularly disposed relative to the axis of actuating rod 92. Bevel gear 104 is attached to the outer end of worm 64 and which worm 64 is adapted to initiate longitudinal movement of motor 36 and supporting carriage 34 along crossbar 24 as previously described. The outer end ofworm 64 and attached gear 104 are supported for rotation within the arm 96 of bifurcated bracket 100 by means of a suitable bearing 106.

As best seen in FIGS. 1 and 7, the bifurcated supporting bracket 100 has a leg extension 107 which is provided at its lower end with a cylindrical boss portion 108. Boss portion 108 has a bore 110 for rotatable support of the shank end 112 of a crank 114. The crank 114 supports a spur gear 116 having teeth 118 in constant mesh with a pinion gear 120. Gear 120 is supported on the reduced diameter unthreaded outer end 65 of worm 64 which extends through both

arms

96 and 98 of bracket 100. Gear 120 is of considerably smaller diameter than spur gear 116, to thereby provide an increase in rotational speed of worm 64 over that of the crank 114.

Referring back to FIGS. 1 and 6, lever 82 is provided with a pin [22 to which is attached one end ofa tension spring 124. The other end of spring 124 is secured to a ratchet 126 disposed adjacent the circumference of indexing plate 70. Ratchet 126 is adapted to selectively engage one of the circumferential notches 72 on indexing plate 70. By engagement of ratchet 126 within selected notch 72 of indexing plate 70, a drive connection is established between lever 82, actuating rod 92 and indexing plate 70.

Rotation of crank 114 causes rotation of spur gear 116 which in turn rotates pinion gear 120 which is secured to the outer end 65'of worm 64 as illustrated in FlG. 7. Rotation of worm 64, which is longitudinally stationarily retained, causes movement of carriage 34 along crossbar 24 by movement of rollers 32 relative to edge 22 to be ground to the desired dimension.

Simultaneously with rotation of worm 64 by means of cooperatively engaged

bevel gears

104 and 94, the actuating rod 92 of the indexing mechanism is rotated at a slightly faster speed of rotation than worm 64. Rotation of actuating rod 92 causes angular movement of lever 82 by means of threaded engagement within socket 84 at the lower end of lever 82. Since ratchet 126 is snapped into engagement within a notch 72 of the indexing plate 70 and held therein by means of tension spring 124, indexing plate 70 will be rotated in correspondence with angular movement of lever 82 by means of rotation of actuating rod 92. Since indexing plate 70, as previously described, is attached to the end 19 of shaft 18 of the cutter head assembly 17, the cutter head will be rotated in correspondence therewith to progressively position the helical longitudinal surface of knife edget22 of cutting blade 20 relative to the grinding wheel 58 and in direct relation to longitudinal movement of grinding motor 36 along crossbar 24.

During the sharpening or grinding operation, the power drive mechanism of the cutter head assembly 17 is rendered inoperative such as by disengaging a transmission (not illustrated) located intermediate of the drive and cutter head 17 to prevent accidental unexpected movement of the cutter head 17 and to allow freedom of movement for proper indexing thereof.

The grinding of each cutter blade 20 is started at one endthereof and advanced longitudinally along the cutting blade 20 towards its opposite end by movement of the grinding unit 35 which is advanced by the worm 64 as described above. Preferably, a series of longitudinal passes are made across each cutting blade 20, and the grinding unit 35 is periodically advanced transverse of the worm 64 by adjusting rod 50 until sufficient material has been removed from the blade 20 in the worst condition to present a uniform continuous bevel, free of nicks, gauges and the like, over the length of the cutting blade 20. Each cutting blade 20 then is subsequently ground to match that of the initially ground cutting blade 20 to obtain a uniform clearance between all of the cutting blades 20 andthe shear bar. The number of passes and speed of advance of the grinding unit 35 are controlled by the speed of rotation of the crank 114 and a function of the depth of cut of the grinding unit 35 on the cutting blade 20.

As noted above, the notches 72 on the indexing plate correspond to the positions of the cutting blades 20 on the cutting head 17. Thus, when the cutting head assembly 17 is disengaged from the drive source, the indexing plate 70 is free to be manually positioned to be engaged by the ratchet 126 when the ratchet 126 is moved to the position illustrated in FIGS. 1 and 6. The above engagement of the indexing plate 70 should be made with the grinding unit 35 in the starting position described above to thereby coordinate the movement of the cutter head 17 and the longitudinal travel of the grinding unit 35. Upon completion of the sharpening of a cutter blade 20, the indexing plate 70 is advanced to the next notch 72 with the grinding unit 35 again placed in the starting position to enable the procedure to be repeated.

During operation of the harvesting machine, the ratchet 126 is backed away from the indexing plate 70 and positioned against the lever 82 where the spring 124 maintains the ratchet 126 against the lever 82. With the ratchet 126 against the lever 82, the indexing plate 70 is free of the ratchet 126 for increased rotation under normal operating conditions. As a safety feature and to prevent damage to the indexing mechanism, the ratchet 126 is designed to allow rotation of the indexing plate 70 with the ratchet in the engaged position should it be left there inadvertently and the machine placed in operation. The spring 122 has sufficient force to hold the ratchet 126 in engagement when the'cutter head 17 is disengaged, but will allow it to release the indexing plate 70 under the force of the drive mechanism for the machine.

As an important improvement of the present invention, no portion of the indexing or grinding mechanism needs to be detached from the forage harvester structure during normal cutting operation of the forage harvester. This provision considerably reduces down-time of the harvester machine as well as reducing manual labor. Under normal cutting operation of the harvesting machine, the grinder motor 36 and the associated driving mechanism is simply moved along the transverse beam 24 in front of the cutter head housing 13 to the inactive position indicated in phantom to the right in FIG. 1. The housing cover 16 will then be replaced in closed position over the cutter head assembly opening and secured to cutter housing 13 by fasteners 60.

Although the present invention has been described by way ofa preferred embodiment it will be obvious to a person skilled in the art to make various changes in arrangement and detail without departing from the spirit and essential characteristic of the invention as defined in the appended claims.

1 claim:

1. A knife edge sharpening device for use with a reel type cutter head supported for rotation within a housing, the reel type cutter head including a central supporting shaft and a plurality of longitudinal cutting blades circumferentiallyspaced around the central supporting shaft of said cutter head, each of said blades extending helically in a longitudinal direction and each having a knife edge, said housing having opposite sidewalls and a longitudinal access opening between the sidewalls, the improvement characterized by said sharpening device comprising a grinder unit having a rotating grinding stone, said grinder unit being mounted in position adjacent said reel type cutter head and having a rotating axis substantially normal to the axis of the central supporting shaft of said cutter head,

arm rotatably supported on the shaft adjacent said plate, ratchet means engageable with a selected one of said circumferential notches of said indexing plate adapted to selectively drivingly connect said lever arm with said plate, bias means connected between said lever arm and said ratchet means to resiliently retain said ratchet means in engagement within said notch, and force transmitting means connecting said lever arm with said driving mechanismffor angular displacement of said lever arm to thereby intermittently rotate said indexing plate, said force transmitting means including pivoted socket means rotatably connected to said lever arm, said socket means having a threaded bore, and a rotatable actuating rod having one end threadedly engaged within said socket means and the other end in driving engagement with the rotatable driving mechanism so that rotation of said force transmitting means causes angular displacement of said lever arm.

2. The sharpener device according to claim I further characterized by said mounting means having provisions on said housing to permit movement of said grinding unit into inactive stored position on the housing re mote from the cutter head.

3. In combination with a harvesting machine such as a forage harvester having a reel type cutter head supported within a housing, said cutter head having a central support shaft, a plurality of helically positioned cutting blades and a cutter head shaft for rotatable support of the blades, said cutter head being adapted for rotation to cut crop material, the improvement characterized by a grinding unit mounted adjacent said cutter head for longitudinal movement therealong to selectively sharpen the knife edges of said cutting blades when said cutter head is not in operation;

an indexing mechanism having means cooperatively interconnecting said cutter head shaft with said grinding unit, longitudinal way means for support of said grinding unit for movement past said cutter head, rotatable drive means drivingly interconnecting said grinding unit with said indexing means so that upon actuation of said rotatable drive means said grinding unit will be longitudinally moved along said way means past said cutter head while simultaneously intermittently rotating said cutter head by actuation of said indexing means, said indexing means including a lever arm attached to the cutter head, and an actuating rod with a threaded portion for moving the lever arm upon rotation of the actuating rod relative to other portions of the indexing mechanism operatively connecting the lever arm to the portion of the rotatable drive means which advances the grinding unit.

4. The combination as defined in claim 3 characterized by said indexing means being selectively drivingly connectable to said cutter head shaft and to said rotatable drive means, said indexing means comprising a plate member attached to said cutter head shaft, said lever arm being rotatably journaled on said cutter head shaft, and ratchet means for selective drive connection of said actuating lever arm with said plate member, said ratchet means permitting independent rotation of said cutter head and said plate member relative to said lever arm when said cutter head is in operation.

a k k

Claims

1. A knife edge sharpening device for use with a reel type cutter head supported for rotation within a housing, the reel type cutter head including a central supporting shaft and a plurality of longitudinal cutting blades circumferentially spaced around the central supporting shaft of said cutter head, each of said blades extending helically in a longitudinal direction and each having a knife edge, said housing having opposite sidewalls and a longitudinal access opening between the sidewalls, the improvement characterized by said sharpening device comprising a grinder unit having a rotating grinding stone, said grinder unit being mounted in position adjacent said reel type cutter head and having a rotating axis substantially normal to the axis of the central supporting shaft of said cutter head, mounting means for supporting said grinder unit for longitudinal movement along said cutter head, rotatable driving mechanism connected between said grinder unit and said mounting means, and indexing means cooperatively connected between said driving mechanism and said cutter head to effect positive intermittent rotation of said cutter head at a predetermined speed ratio simultaneously with longitudinal movement of said grinder unit along said cutter head; said indexing means including a plate having a plurality of notches, said plate being mounted on the central supporting shaft of said cutter head, a lever arm rotatably supported on the shaft adjacent said plate, ratchet means engageable with a selected one of said circumferential notches of said indexing plate adapted to selectively drivingly connect said lever arm with said plate, bias means connected between said lever arm and said ratchet means to resiliently retain said ratchet means in engagement within said notch, and force transmitting means connecting said lever arm with said driving mechanism for angular displacement of said lever arm to thereby intermittently rotate said indexing plate, said force transmitting means including pivoted socket means rotatably connected to said lever arm, said socket means having a threaded bore, and a rotatable actuating rod having one end threadedly engaged within said socket means and the other end in driving engagement with the rotatable driving mechanism so that rotation of said force transmitting means causes angular displacement of said lever arm.

2. The sharpener device according to claim 1 further characterized by said mounting means having provisions on said housing to permit movement of said grinding unit into inactive stored position on the housing remote from the cutter head.

3. In combination with a harvesting machine such as a forage harvester having a reel type cutter head supported within a housing, said cutter head having a central support shaft, a plurality of helically positioned cutting blades and a cutter head shaft for rotatable support of the blades, said cutter head being adapted for rotation to cut crop material, the improvement characterized by a grinding unit mounted adjacent said cutter head for longitudinal movement therealong to selectively sharpen the knife edges of said cutting blades when said cutter head is not in operation; an indexing mechanism having means cooperatively interconnecting said cutter head shaft with said grinding unit, longitudinal way means for support of said grinding unit for movement past said cutter head, rotatable drive means drivingly interconnecting said grinding unit with said indexing means so that upon actuation of said rotatable drive means said grinding unit will be longitudinally moved along said way means past said cutter head while simultaneously intermittently rotating said cutter head by actuation of said indexing means, said indexing means including a lever arm attached to the cutter head, and an actuating rod with a threaded portion for moving the lever arm upon rotation of the actuating rod relative to other portions of the indexing mechanism operatively connecting the lever arm to the portion of the rotatable drive means which advances the grinding unit.