Abstract:
A device is disclosed for grinding reel type mower bedknives and blades of rotary type and reel type mowers. The device is capable of manually relief grinding reel blades on an intact mower, and in various stages of disassembly, to a bare reel stripped of its housing, with virtually any relief angle. The device can manually and semiautomatically spin grind a reel type mower reel while the reel is attached to the complete mower or if the reel and supporting structure are removed to a bench, with no further disassembly required. The device can manually grind the front face of a reel type mower bedknife while the bedknife remains attached to the reel housing and can grind the front and top face of a bedknife when it is removed. It can also grind rotary type blades and a variety of other straight edged tools.

Description:
TECHNICAL FIELD 
       [0001]    The Present invention relates generally to machine tools, more specifically to methods and apparatus for sharpening reel blades, bedknife blades, and rotary blades on lawn and turf mowers. 
       BACKGROUND OF THE INVENTION 
       [0002]    Commercial mowers typically utilize both reel type and rotary type mowing units which must be maintained regularly to assure proper operation. Part of such maintenance involves sharpening the reels, bedknives, and rotary blades. This is a time consuming process. Prior art requires at least three separate machines to perform the needed operations. These machines are heavy, expensive, and bulky, requiring a sizable amount of shop space. One machine typically will spin grind and relief grind reels once the reel and supporting structure is removed from the mower and disassembled to some degree. One machine will grind the front and top face of a bedknife once the bedknife and supporting bedbar is removed from the reel housing. And still another machine will grind rotary blades. 
         [0003]    There is a need in the art for a grinding machine that maintains or surpasses the quality and accuracy attained by current heavy, expensive stand alone machines that is capable of performing all the grinding needs of commercial lawn and turfgrass professionals housed in a single machine, that is lightweight and portable enough to attach directly to a reel type mower without removing the cutting unit from the complete mower if desired, providing a degree of flexibility far superior to any grinding machine prior to the present invention. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    The present invention, in one embodiment, is a device for manually relief grinding a reel blade having a radially outer edge of an elongated length and first and second faces, with the first and second faces extending generally radially from the reel axis and the second face being the one that is relief ground. The device has the flexibility to perform the operation on an intact mower, on a cutting unit that has been removed from the mower in its&#39; intact or partially disassembled state, or directly on a bare reel void of its&#39; housing. 
         [0005]    The present invention, in another embodiment, spin grinds the first face, described in the previous embodiment, of all the reel blades making up the reel cylinder simultaneously either manually or semiautomatically with the flexibility to perform the operation directly on an intact mower, or with the intact cutting unit removed from the mower. 
         [0006]    In yet another embodiment, this invention manually grinds the front face of a bedknife of a reel type mower without the need to remove the bedknife and supporting bedbar from the cutting unit housing. 
         [0007]    In another embodiment, this invention manually grinds the front and top face of a bedknife of a reel type mower when the bedknife and supporting bedbar is removed from the cutting unit housing. 
         [0008]    In still another embodiment, this invention manually grinds rotary type mower blades utilizing a center pivot and blade stop allowing precise symmetrical grinding at apposing ends of the blade. This same embodiment is capable of grinding any straight blade (chisel, cutting bar, etc.) found in a maintenance shop. 
         [0009]    While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1 . is a right front perspective view of the invention set up for semiautomatic spin grinding a reel of a reel type mower when the reel and supporting structures are removed from the mower. The reel and supporting structures have been left out for clarity. 
           [0011]      FIG. 2 . is a closeup right front perspective view of the carriage unit portion of the invention. 
           [0012]      FIG. 3 . is a closeup perspective view of the grinder bracket of the invention attached to a commercial grinder in the “reel grinding” configuration. 
           [0013]      FIG. 4 . is a perspective view of the carriage unit right side-rail bracket showing the attached drill bracket used to support a commercial drill used to spin the reel during the spin grind operation. The right carriage unit side-rail and rods are shown in phantom. 
           [0014]      FIG. 5 . is a perspective view of the carriage unit right side-rail bracket with attached drill bracket and drill (shown in phantom). 
           [0015]      FIG. 6 . is a perspective view of the carriage unit, the carriage unit frame, and the carriage unit side rail brackets used to attach the invention to the underside of the reel housing (shown in phantom) of a reel type mower. 
           [0016]      FIG. 7 . is a perspective view of the carriage unit with attached grinder bracket, the carriage unit frame, and the carriage unit side-rail brackets configured with an additional set of brackets (in phantom) used to support a barren reel for relief grinding. The base stand used to support the carriage unit frame is not shown. 
           [0017]      FIG. 8 . is a perspective view of a portion of the invention showing the orientation of the relief grind bracket used to trap a reel blade during relief grinding. 
           [0018]      FIG. 9 . is a front right perspective view of the base stand used to support the carriage unit frame (shown in phantom), or the reel housing whenever the invention is not used directly on the intact mower. 
           [0019]      FIG. 10 . is a perspective view of  FIG. 9  with the additional attachment of the bedknife/rotary blade bar (shown in phantom). 
           [0020]      FIG. 11 . is a perspective view of  FIG. 10  with the additional attachment of the bedbar brackets (shown in phantom). 
           [0021]      FIG. 12 . is a perspective view of  FIG. 11  showing the attachment of a bedknife (in phantom) and the right bedknife bracket and finger (shown in phantom). 
           [0022]      FIG. 13 . is a perspective view of  FIG. 12  showing the attachment of the commercial grinder (shown in phantom) orientated to allow bedknife front face grinding. 
           [0023]      FIG. 14 . is a perspective view of  FIG. 10  showing the attachment and orientation of a rotary mower blade and grinder in phantom. 
           [0024]      FIG. 15 . is a partial perspective view of the left side of the carriage unit showing caliper bracket attachment and orientation to allow micro-adjustment of the invention to a reel of a reel type mower. 
           [0025]      FIG. 16 . is a closeup perspective view of the right side of the grinder bracket and right bedknife bracket and finger attached to the carriage unit showing the relationship between the bedknife finger and a reel blade when grinding the front face of a bedknife within its&#39; reel housing. 
           [0026]      FIG. 17 . is a closeup perspective view of the left side of the carriage unit showing the relationship between the left bedknife bracket finger and a reel blade when grinding the front face of a bedknife when it remains attached to the reel housing and also showing the left bedknife bracket finger location (in phantom) when relief grinding a reel blade. 
           [0027]      FIG. 18 . is a perspective view of the grinder bracket of  FIG. 3  attached to a commercial grinder in the “rotary blade” position. 
           [0028]      FIG. 19 . is a front left closeup perspective view of the bedbar and carriage unit showing the configuration and orientation of the caliper bracket and bedknife during the micro-adjusting phase of grinding the top face of a bedknife. 
           [0029]      FIG. 20 . is a front left closeup perspective view of the bedbar and carriage unit showing the configuration and orientation of the caliper bracket and bedknife during the micro-adjusting phase of grinding the front face of a bedknife when it is removed from the reel housing. 
           [0030]      FIG. 21 . is a front perspective view of a reel within its support housing sitting on the base stand with the carriage unit attached in a three point configuration. 
           [0031]      FIG. 22 . is a closeup front partial perspective view of the components making up the rear attachment of the carriage unit stabilizer bar to the base stand when using a three point attachment configuration. 
           [0032]      FIG. 23 . is a perspective view of the reel clamp used when attaching the carriage unit to a fully assembled reel-type mower in a three point attachment configuration. A reel roller is shown in phantom. 
           [0033]      FIG. 24 . is a perspective view of the reel clamp of  FIG. 23  from a different angle. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Referring to the drawings, wherein like reference numerals designate like or corresponding elements throughout the views, the assembly and modes of action will be thoroughly explained. 
       Spin Grinding on the Intact Mower 
       [0035]    With regard to spin grinding a reel of a reel type mower particular attention is directed toward  FIGS. 1-7 ,  9 ,  15 ,  21 - 24 . When performing this operation on the intact mower, the reel stand consisting of members  1 - 9  of  FIG. 9  is not required. By utilizing a vehicle hoist the complete mower is raised to a comfortable working height. The reel is stabilized and the carriage unit frame, shown in  FIG. 6  consisting of two parallel rods  9 , a left  11  and right  10  side-rail, and a main carriage unit  12 , affixed with a set of carriage unit side-rail brackets  17 + 18 , is releasably attached directly to the reel housing  16  by the front  19  and rear  20  attachment bracket of the left  18  and right  17  side-rail brackets. By using a variety of bracket extensions (not shown) connected to the front  19  and/or rear  20  attachment bracket, and pre-adjusting the width of the carriage unit frame using the rod  9  set screws  73  ( FIG. 1 ) and rod  9  snap rings  54 , a configuration for releasable four point attachment to any style reel housing  16  ( FIG. 6 ) can be accomplished. By utilizing a stabilizer bar  103  ( FIG. 21 ), with an adjustable center post  104  ( FIG. 22 ), attached to the carriage unit side-rail brackets&#39; universal rear stump  20  ( FIG. 21 ) with a pair of stabilizer bar brackets  105  and a mower unit rear roller clamping device consisting of a two part  106 , 107  (FIGS.  23 , 24 ) expandable roller clamp and a slidable stabilizer bar post clamp  108 , a means for releasable three point attachment to a reel housing can be accomplished. 
         [0036]    Once the carriage unit frame with affixed side-rail brackets  17 , 18  ( FIG. 6 ) is securely attached to to the reel housing  16 , the caliper bracket  83  ( FIG. 15 ) is releasably attached to the left side of the carriage unit  12  with a knob  85 . The carriage unit right side-rail bracket  17  ( FIG. 4 ) is adjusted in the horizontal and vertical plane to bring the carriage unit frame into a position parallel to the longitudinal axis of the reel in two perpendicular planes. The horizontal adjustment is accomplished by loosening the two horizontal lock knobs  51  and turning the horizontal micro-adjust knob  23  clockwise or counterclockwise until horizontal caliper  86  ( FIG. 15 ) readings to the center post of the reel  82  at each end become equal. Likewise the vertical adjustment is accomplished by loosening the vertical lock knob  44  ( FIG. 4 ) and turning the vertical micro-adjust knob  43  clockwise or counterclockwise until the vertical caliper  84  ( FIG. 15 ) readings to the center post of the reel  82  at each end become equal. 
         [0037]    The previous attachment and adjustment procedure is essentially the same whenever a reel of a reel type mower is either spun or relief ground or the bedknife ground within its&#39; housing. 
         [0038]    Next the grinder bracket  37  ( FIG. 3 ) is releasably attached to a commercially available 4½″ angle grinder  25  in the “reel grinding” position and tightened so the grinder pointer  33 , attached to the grinder housing with fastener  77 , is aligned with a specific side-scale mark  75  on the grinder bracket  37  that will allow the grinder wheel  76  to make contact with the reel blades when the grinder bracket  37  is releasably attached to the carriage unit bracket  29  ( FIG. 2 ), using post  36  ( FIG. 3 ), and tightened when the carriage unit bracket pointer  34  ( FIG. 2 ) is aligned with a specific grinder bracket  37  ( FIG. 3 ) top scale mark  74 . 
         [0039]    As shown in FIG.  2 ., the grinder supporting (grinder and grinder bracket not shown) carriage unit is made up of a main unit  12  that traverses on two parallel rods  9  via linear bearings  28 . The carriage unit bracket  29 , that supports the grinder bracket, slides on a track inward, towards the surface to be ground, and outward, away from the surface to be ground, using a lead screw  30  controlled by an adjusting wheel  31  and locked in position using two knobs  26 . 
         [0040]    The carriage unit  12  holds the drive cup  32  that captures the bearing mounted post  71  ( FIG. 1 ) attached to a looped chain  70  driven by a small electric motor used for traversing the carriage unit  12  to and fro automatically when the autodrive assembly  64  is employed. 
         [0041]    If an independent reel backlapping feature is supplied with the particular mower being sharpened, the reel can be turned in the backwards rotation utilizing the mowers&#39; own power and a separate power supply to spin the reel is not needed. If a mower backlapping feature does not exist, or the reel and supporting structures are removed from the mower for sharpening, an external power supply for spinning the reel is achieved using a commercially available reversible drill  48  ( FIG. 5 ). The drill is fixtured with a ⅜″ drive socket  78 +/−a coupler to allow the drill to be seated into the splined reel end to facilitate spinning the reel. The adjustable drill bracket  46 , 47  is releasably attached to the carriage unit side-rail bracket  17  or  18  via the side-rail bracket drill clamp  45  and a knob  50 . The drill is adjustably positioned centered and parallel to the reel centerpost and clamped in place with knob  49 . 
         [0042]    Next the auto drive assembly as shown in  FIG. 1 , used to automatically traverse the carriage unit to and fro during spin grinding, is releasably attached to the carriage unit side-rails  10 , 11 . The autodrive assembly consists of a main portion  64  that supports a small electric motor housed in a protective box  66  that drives a continuously looped chain  70 , between two sprockets  69 , onto which a bearing mounted post is fixed  71  that mates with the drive cup  32  of the carriage unit  12  when the assembly is attached. Chain movement is started and stopped using a control switch  79 . The width of the autodrive assembly is adjustable to fit various reel sizes by use of a sliding accessory portion  65  and tightening knob  67 . The autodrive assembly is releasably attached to the carriage unit side-rails  10 , 11  via locating posts  21  and clamping knobs  68 . 
       Spin. Grinding a Reel Removed from its Housing 
       [0043]    Spin grinding a reel within its&#39; support housing that has been removed from the mower unit is essentially the same as when the cutting unit remains attached to the mower with the addition of a reel stand employed to hold the reel housing in a position that allows carriage unit frame attachment. Referring to FIGS.  6 , 9  the reel stand is assembled with the two base parts  1 , 2  connected via an extension  3  and stabilized with a rear strap  6 , supporting the rear clamping brackets  7 , 8 , forming a tripod. The extension  3  is adjusted and tightened in place when the distance between the reel roller supports  4  is equal to the distance between the rear roller support points  72  ( FIG. 6 ) of the reel rear roller. The two stand straps  5  ( FIG. 9 ) are removed and not used. The reel and housing  16  ( FIG. 6 ) is lifted onto the stand aligning the rear roller positions  72  onto the roller supports  4  ( FIG. 9 ). The reel housing is positioned vertically, so the underside of the reel housing is accessible, and clamped in this position using the rear stand clamps  7 , 8  releasably attached to the reel housing. 
         [0044]    If a three point carriage unit attachment configuration is employed when using the base stand, the reel clamp components  106 , 107 , 108  ( FIG. 23 ) are replaced with the base stand three point bracket components  100 , 101 , 102  ( FIG. 22 ). 
       Relief Grinding 
       [0045]    Manually relief grinding the blades of a reel type mower involves initial setup and attachment of the carriage unit frame to the reel housing as described previously. It can be performed on the complete mower, when the cutting unit is, removed from the mower, or on a barren reel void of its&#39; bearings. This procedure is most often performed after the reel has been spin ground returning it to a cylinder. 
         [0046]    The autodrive assembly  64  ( FIG. 1 ), drill  48  ( FIG. 5 ), and drill bracket  46 , 47  are removed after spin grinding. 
         [0047]    The grinder bracket  37  ( FIG. 3 ) to grinder tightening nuts  80  and the carriage unit bracket  29  ( FIG. 2 ) to grinder bracket  37  ( FIG. 3 ) nut  36  is loosened and the grinder brackets&#39; 37 top-scale  74  and side-scale  75  are aligned with their respective pointer  34  ( FIG. 2 ),  33  ( FIG. 3 ) positions to allow the grinder wheel  76  to make contact with the second face of a reel blade producing the desired relief angle when grinding. The relief grind bracket  53  ( FIG. 8 ) is releasably attached to the carriage unit clamp  27  and locked in a position with the knob  59  that allows this bracket to support a reel blade  52  from beneath effectively trapping the reel blade  52  between the bracket  53  and the grinding wheel when the carriage unit traverses from one end of the reel blade to the other producing even contact of the grinder wheel on the reel blade second face its&#39; entire length. Additional travel of the carriage unit  12  to the right side of the reel blade allows the relief grind bracket  53  to clear the reel blade  52  allowing the next blade on the reel to be manually aligned with the relief grind bracket  53  and effectively trapped between the bracket  53  and the grinder wheel as the carriage unit  12  is manually traversed to the left the length of the reel blade  52  and then traversed back to the right. This procedure is repeated until all reel blades have been relief ground. The carriage unit depth of grind adjustment wheel  31  ( FIG. 1 ) is turned ⅛ turn counterclockwise prior to starting a new cycle thru the individual reel blades  52  ( FIG. 8 ). These steps are repeated until only 1/32″ of spin grind remains on the reel blades&#39; first face. 
         [0048]    To help manually align individual reel blades with the relief grind bracket during relief grinding the left bedknife bracket  87  ( FIG. 17 ) and finger  91  is releasably attached to the left side of the carriage unit  12  and adjusted into a position  89  to give a reference point as to where the next reel blade is aligned to allow it to be trapped by the relief grind bracket during the grinding operation. 
         [0049]    Performing the relief grind procedure on a barren reel requires the use of an additional set of brackets  38  ( FIG. 7 ) attached to the carriage unit side-rail brackets  17 , 18  fixtured with a set of end bearings  39 , one of which is adjustable via a lead screw  94  allowing direct reel attachment to the carriage unit. 
       Grinding the Front Face of a Bedknife within its&#39; Housing 
       [0050]    This procedure can be accomplished on the complete mower or when the cutting head has been removed from the mower. Initial attachment and adjustment of the carriage unit frame to the reel housing is the same as described earlier when spin grinding a reel on the intact mower. The only difference being changing the set angle of the grinder in both planes and attaching two brackets used to rotate the reel blades away from the grinder wheel as the length of the bedknife is ground. 
         [0051]    Referring primarily to FIGS.  2 , 3 , 16 , 17  the grinder bracket  37  ( FIG. 3 ) to grinder tightening nuts  80  and the carriage unit bracket  29  ( FIG. 2 ) to grinder bracket nut  36  ( FIG. 3 ) is loosened and the grinder brackets&#39; top scale  74  and side scale  75  are aligned with their respective pointer  34 , 33  positions to allow the grinder wheel  76  ( FIG. 16 ) to make contact with the front face of the bedknife at the desired front face angle when grinding commences. 
         [0052]    In order for the carriage unit to traverse the length of the bedknife, while grinding its&#39; front face, without the grinder wheel making contact with the reel blades a means is described for rotating the said reel blades out of the way, providing grinder wheel clearance, as the grinding wheel traverses the length of the bedknife. This is accomplished by using a set of brackets releasably attached to either side of the carriage unit. The right bedknife bracket  60  and accompanying finger  58  is attached to the carriage unit clamp  27  ( FIG. 2 ) with a knob  59 . The finger  58  ( FIG. 16 ), by way of a slot and tightening nut  61 , is aligned so its&#39; leading edge makes contact with the underside of a reel blade  52  and thus rotates the said reel blade out of the way of the grinding wheel  76  as it traverses to the left along the front face  95  of the bedknife  57 . 
         [0053]    The left bedknife bracket  87  ( FIG. 17 ) and accompanying finger  91  are attached to the carriage unit  12  with a knob  85 . The finger  91 , by way of a slot and tightening nut  90 , is aligned so its&#39; leading edge  88  makes contact with the top side of a reel blade  52  and thus rotates the said reel blade out of the way of the grinding wheel as the carriage unit  12  traverses to the right along the front face  95  of the bedknife  57 . 
       Grinding the Front Face of a Bedknife (when Removed) 
       [0054]    Referring primarily to FIGS.  9 - 13 , 18 , 20  the two main portions of the base stand  1 , 2  are assembled with straps  5  attached and joined together with an adjustable extension  3  that allows the carriage unit frame, consisting of the carriage unit left  11  and right  10  side-rails, carriage unit rods  9 , and main carriage unit  12 , to be releasably attached and secured to the stand straps  5  using the lower straps&#39; slot  96  and a knob  51 . 
         [0055]    The bedknife/rotary blade bedbar, consisting of a bedbar  13  ( FIG. 10 ) fixtured between, a left  15  and right  14  bedbar side-rail, is releasably attached to the carriage unit side-rails  10 ,  11  using the middle  97  and upper  98  protruding bolts and knobs. To this bedbar  13  ( FIG. 11 ) is releasably attached the left  56  and right  55  bedbar brackets. These bedbar brackets house several variably sized holes used to secure the bedknife support frame  93  parallel in the vertical plane to the carriage unit frame. These bedbar brackets  55 , 56  are slotted to allow adjustment of the bedknife support frame  93  parallel to the carriage unit frame in the horizontal plane. 
         [0056]    The grinder bracket  37  ( FIG. 18 ) is releasably attached to a commercially available grinder  25  in the “rotary blade” position and secured with tightening nuts  80 . The grinder bracket  37  is in turn releasably attached to the carriage unit bracket  29  ( FIG. 2 ) using the rotary blade post  35  ( FIG. 18 ). This configuration allows the grinder wheel  76  edge to be used during grinding procedures when the bedbar  13  ( FIG. 12 ) is employed (the grinder wheel face is used for grinding procedures when the bedbar  13  is not employed). 
         [0057]    Initially the bedbar left  15  and right  14  side-rails&#39; witness marks are set to a carriage unit side-rail scale  42  mark. This scale setting in combination with a bedbar bracket  55 , 56  scale setting  99 , and rotation of the bedknife support frame  93 , while advancing the grinder wheel toward or away from the bedknife face with the carriage unit depth of grind adjustment wheel  31 , will allow the operator to fix the position of the bedknife  57  front face such that the desired front face grind angle can be achieved when the grinder wheel contacts the bedknife during grinding. 
         [0058]    To assure complete alignment accuracy, the caliper bracket  83  ( FIG. 20 ) is configured in such a way that, when releasably attached to the left side of the carriage unit  12 , a measurement can be taken vertically with the caliper  86  to the top milled portion of the bedknife  57  on either end, and the right bedbar side-rail  14  ( FIG. 12 ) micro-adjusted using the knob  23  until the bedknife becomes parallel to the carriage unit frame to within 0.001″. 
         [0059]    If more than one of the same style bedknife is to be sharpened, the right bedknife bracket  60  ( FIG. 13 ) and finger  58  can be configured and releasably attached to the carriage unit clamp  27  so the fingers&#39; leading edge contacts the flat underside portion of the bedknife  57 . Set in this manner the bracket becomes a guide to quickly and accurately attach and align a new bedknife for grinding and produce the same grind angle as the first. 
       Grinding the Top Face of a Bedknife 
       [0060]    Grinding the top face  92  ( FIG. 19 ) of a bedknife is carried out after the front face has been ground. If attached, the right bedknife bracket  60  ( FIG. 13 ) is removed. The bedbar brackets  55 , 56  are loosened and moved to a pre-determined bedbar scale setting  99 . By loosening the bolts connecting the bedknife housing  93  to the bedbar brackets  55 , 56  and rotating the bedknife  57 , while simultaneously advancing the grinder wheel  76 , via the adjusting wheel  31 , inwards or outwards, the operator can achieve the desired top face  92  ( FIG. 19 ) grind angle. 
         [0061]    Once the bedknife position is fixed the caliper bracket  83  can be configured and releasably attached to the carriage unit  12  with a tightening knob  85  to allow the calipers&#39;  86  post to make contact with the factory machined area posterior to the bedknife top face  92 . The use of this caliper  86 , in conjunction with the micro-adjust knob  23  ( FIG. 13 ) located on the right bedbar side-rail  14 , allows the operator to align the length of the bedknife within 0.001″ parallel to the carriage unit frame prior to grinding. 
       Grinding Rotary Blades 
       [0062]    Grinding rotary mower type blades  24  ( FIG. 14 ) requires the same setup procedures explained previously in grinding a bedknife removed from the reel housing except the bedbar brackets  55 , 56  ( FIG. 12 ) are removed and a threaded post  63  ( FIG. 14 ) with a tightening knob, affixed to a rail, is positioned in the track at the midportion of the top face of the bedbar  13 . A rotary blade  24  is placed onto the centerpost  63  and positioned such that, as the grinder wheel  76  is advanced toward the rotary blade edge utilizing the carriage unit adjusting wheel  31 , contact between the blade  24  edge and the grinder wheel  76  edge produces the desired grinding angle and taper during grinding. The rotary blade  24  is releasably fixed in this position with a tightening knob on the centerpost  63 . A slotted blade stop is adjustably attached to the bedbar  13  at position  62  and abutted to the back edge of the rotary blade  24  and fixed in this position with a tightening knob. By loosening the centerpost  63  knob the rotary blade can be turned end for end on its&#39; center axis, butted up to the blade stop, retightened at the centerpost  63 , and be in a position that will produce a symmetrical grind to the first end.