Abstract:
The grinding surface of a grinding stone is formed from a circular conical surface, a drive device for rotation is installed within a housing. The blade of a cutting tool is ground while the longitudinal direction of the cutting tool is aligned with the direction of a generating line of the grinding surface. When grinding the blade, the cutting tool can be aligned with the direction of the generating line of the grinding surface and the blade can be brought in contact with the grinding surface without the handle of the cutting tool and the hand that holds the cutting tool being interfered with the grinder. This is achieved irrespective of in which one of the directions of lines the tip of the blade faces, the lines being obtained by extending the generating line of the grinding surface from both ends of the generating line.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national stage application of PCT/JP2012/060958 filed on Apr. 24, 2012, and claims priority to, and incorporates by reference, Japanese Patent Application No. 2011-098252 filed on Apr. 26, 2011. 
     FIELD OF THE INVENTION 
     The present invention relates to an electric cutting-tool grinder that grinds a cutting-tool by rotating a grindstone by an electric drive source. 
     BACKGROUND OF THE INVENTION 
     A typical grindstone of an electric cutting-tool grinder has a disk shape. The circumferential surface or the end surface of the grindstone is used as a grinding surface. Since the thickness of the grindstone is relatively small, the width of the grinding surface is small when the circumferential surface is used as the grinding surface. Thus, it is not suitable for cutting-tools with a long blade such as a kitchen knife. When the end surface of the grindstone is used as the grinding surface, the blade of the kitchen knife is abutted against the circular grinding surface to cross the grinding surface. Thus, two different grinding motions are simultaneously performed in which the grinding surface rotates toward the blade and in which the grinding surface rotates away from the blade. As a result, half of the blade is pressed by the grinding surface, and the remaining half of the blade is pulled by the grinding surface. Thus, the force that presses the blade and the force that pulls the blade apply force to the blade in the same rotation direction. This tends to rotate the kitchen knife. Thus, the kitchen knife will be unstable and the grinding operation will be difficult to perform. 
     To resolve such a drawback of the disk-like grindstone, a grindstone has been disclosed in Patent Document 1 that has a wider grinding surface and efficiently grinds a blade. According to this grindstone, a conic surface is formed on the circumferential surface of a disk, and the conic surface is used as the grinding surface. Thus, the width of the grinding surface is increased. Since the grinding surface rotates in one direction with respect to the blade by abutting the blade along the generating line of the conic surface, the entire blade is ground uniformly. Also, since grinding is performed in the range of the length of the generating line, the grindstone is capable of grinding the kitchen knife with a long blade. 
     However, the grinder of Patent Document 1 has a great drawback with regard to a kitchen knife that needs to be ground on both surfaces of the blade, that is, first and second blade surfaces such as those of an usuba hocho (Japanese vegetable knife). There is no problem when grinding the first blade surface of the usuba hocho, but there is a problem when grinding the second blade surface. More specifically, when grinding the first blade surface of a thin-bladed kitchen knife, an operator first grasps the handle of the kitchen knife with the right hand, and abuts the first blade surface against the generating line of the grinding surface formed by the conic surface. At this time, the grindstone rotates in a direction away from the blade, and grinds the kitchen knife without any problem. 
     The generating line of the grinding surface formed by the conic surface corresponds to a contour line on both sides when a truncated cone-shaped grindstone is viewed from the front. 
     When grinding the second blade surface, if the kitchen knife held in the right hand is turned over and ground while the kitchen knife is held in the right hand, the rotation direction of the grindstone with respect to the blade is reversed. As described above, there is no problem in grinding when grinding the first blade surface since the grindstone rotates in the direction away from the blade surface. However, in the case in which the second blade surface is ground while the kitchen knife that has been turned over is held in the right hand, the grindstone rotates toward the blade surface. Thus, the grinding surface collides against the blade edge, and the kitchen knife might be lifted while grinding. Therefore, it is difficult to grind smoothly. 
     Thus, the distal end of the blade and the handle of the kitchen knife are flipped over such that the handle of the kitchen knife is located on the left side of the operator&#39;s body by switching the kitchen knife to the left hand. When the kitchen knife is turned over in this manner and the second blade surface is ground, the grindstone rotates in the direction away from the second blade surface like the first blade surface. However, if the handle of the kitchen knife is located on the left side of the operator&#39;s body, when moving the kitchen knife during grinding, the hand and the handle of the kitchen knife interfere with the frame of the grinder, and the movement of the kitchen knife is hindered. Thus, the grinding operation cannot be substantially performed. 
     Also, when grinding the kitchen knife held in the right hand, it is preferable to place the left hand on the blade so that the kitchen knife will be stable. However, in the case with the grinder of Patent Document 1, the frame gets in the way and the operator cannot place the left hand on the blade. 
     Furthermore, in the grinder of Patent Document 1, the motor is exposed and noise during use is loud. Such a grinder is not suitable for household use also in the aspect of the design. Thus, in order to sell it to the general public, the motor is preferably covered by a housing. Furthermore, if a grindstone that needs grinding water is used in this grinder, the grinding water falls onto the motor. Thus, when mounting the grindstone that needs grinding water, the motor is also preferably covered by the housing. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Laid-Open Utility Model Publication No. 52-154790 
     SUMMARY OF THE INVENTION 
     Problems that the Invention is to Solve 
     Accordingly, it is an objective of the present invention to provide an electric cutting-tool grinder that is capable of smoothly grinding a blade without the grinder interfering with a handle of a cutting-tool and a hand that holds the cutting-tool when grinding the cutting-tool such as a thin-bladed kitchen knife that require both surfaces of the blade to be ground. 
     Means for Solving the Problems 
     In accordance with one aspect of the present invention, an electric cutting-tool grinder including a rotary grinding member that has a grindstone is provided. The rotary grinding member is secured to a rotary shaft rotated by a rotation drive unit to rotate integrally with the rotary shaft. The grindstone includes a grinding surface formed by a conic surface. The rotary grinding member is rotated in a plane perpendicular to the rotary shaft. The rotation drive unit is mounted in a housing. A blade of a cutting-tool is ground with a longitudinal direction of the cutting-tool aligned with the direction of a generating line of the grinding surface, 
     The electric cutting-tool grinder includes means for permitting the cutting-tool to be aligned with the direction of the generating line of the grinding surface and permitting the blade to be abut against the grinding surface without a handle of the cutting-tool and a hand that holds the cutting-tool being interfered by the grinder in the case in which the blade is ground with a tip of the blade of the cutting-tool facing the extending direction of either end of the generating line of the grinding surface. 
     Thus, the grinding operation is smoothly performed without the cutting-tool and the hand that holds the cutting-tool being interfered with by components of the grinder in either of the cases in which the first blade surface of the blade is abutted against the grinding surface while aligning the cutting-tool held in the right hand with the generating line of the grinding surface, and in which the second blade surface of the blade is abutted against the grinding surface by flipping over the tip of the blade of the cutting-tool and the handle and switching to the left hand so that the cutting-tool is turned over. 
     The electric cutting-tool grinder preferably includes a guide for moving the cutting-tool that is being ground along the direction of the generating line of the grinding surface. In this case, the guide allows the cutting-tool to be ground in a stable manner. 
     The generating line located at the highest position of the grinding surface preferably extends horizontally, and the blade of the cutting-tool is preferably ground in a state in which the blade is arranged above the generating line. In this case, the cutting-tool is held horizontally during grinding. Thus, the operation is performed in a more stable manner. 
     The housing is preferably formed to incline with respect to a vertical line at a predetermined angle, and the predetermined angle is preferably the same angle as the inclination angle of the conic surface, which forms the grinding surface of the grindstone, with respect to the rotary shaft. Further, the rotary shaft preferably also extends diagonally at the same angle as the housing. In this case, the cutting-tool is held horizontally during grinding as in the above-described case. 
     The housing preferably includes an upper surface portion and an outer circumferential surface, which are formed to be perpendicular to each other, and the rotary shaft preferably extends in the same direction as the direction in which the housing extends. In this case, the generating line of the grinding surface formed by the conic surface is not parallel to the upper surface of the housing and is not parallel to the direction in which the outer circumferential surface of the housing extends. Thus, a space is generated between the handle of the cutting-tool extending in the direction of the generating line and the housing, or the upper surface or the outer circumferential surface of the cover when the cover is mounted on the housing. Thus, the hand or the handle of the cutting-tool does not interfere with the outer circumferential surface of the housing during grinding. 
     Also, when the tip of the blade of the cutting-tool and the handle are flipped over and the cutting-tool is turned over so that the second blade surface of the blade abuts against the grinding surface, a space is generated between the handle of the cutting-tool and the housing, or the upper surface or the outer circumferential surface of the cover when the cover is mounted on the housing in the same manner. Thus, the hand or the handle of the cutting-tool does not interfere with the components of the grinder during grinding. Thus, the grinding operation is smoothly performed. 
     The electric cutting-tool grinder preferably includes means for automatically supplying grinding water to the grinding surface of the grindstone. In this case, it is unnecessary to frequently stop the operation to supply the grinding water to the grinding surface during the grinding operation, and the cutting-tool is efficiently ground. 
     The electric cutting-tool grinder preferably includes a drainage container detachably mounted on the housing. In this case, the housing has an upper surface portion, and the rotary grinding member is mounted above the upper surface portion. The rotary grinding member is covered by a cover. A passage is provided for discharging the grinding water that has collected on the upper surface portion of the housing via the inner surface of the cover to the drainage container as drainage. In this case, the drainage container is easily removed from the housing, and the drainage water is easily drained from the grinder. 
     The housing preferably includes an upper surface portion for preventing the grinding water that splashes during use from entering the housing. The rotary grinding member is preferably located on the upper side of the upper surface portion. In this case, a cover that covers the rotary grinding member is detachably mounted on the housing, and part of the grinding surface is exposed from part of the cover. In this case, the exposed amount of the grindstone is reduced, and the grinding water is efficiently prevented from splashing to the outside. Furthermore, the strength of the cover is prevented from being reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a cutting-tool grinder according to one embodiment of the present invention as viewed from the front; 
         FIG. 2  is a right side view illustrating the cutting-tool grinder; 
         FIG. 3  is a plan view illustrating the cutting-tool grinder; 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a perspective view illustrating the grindstone; 
         FIG. 6  is a central cross-sectional view illustrating the grindstone; 
         FIG. 7  is a perspective view illustrating the cover; 
         FIG. 8  is a perspective view illustrating a blade support mounted on the cover; 
         FIG. 9  is a perspective view illustrating the blade support as viewed from the lower side; 
         FIG. 10  is a perspective view illustrating an engagement structure of the grinder main body with the cover; 
         FIG. 11  is a perspective view illustrating an engagement structure of the cover with the grinder main body; 
         FIG. 12  is a perspective view illustrating a state in which the first blade surface of the kitchen knife is ground; and 
         FIG. 13  is a perspective view illustrating a state in which the second blade surface of the kitchen knife is ground. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A cutting-tool grinder  1  according to one embodiment of the present invention includes a grinder main body  2 , a cover  3 , and a drainage container  4 . As shown in  FIG. 4 , the grinder main body  2  includes a housing  5  and a rotation drive unit, which is a motor  6  located in the housing  5 . A rotary grinding member  9 , which includes a grindstone  8 , is mounted on a rotary shaft  7  of the motor  6  to rotate integrally with the rotary shaft  7 . The rotary grinding member  9  is secured to the rotary shaft  7  to rotate in a plane that is perpendicular to the rotary shaft  7 . 
     The housing  5  is formed to be inclined at a predetermined angle with respect to its bottom surface  10 , and the rotary shaft  7  is inclined at the same predetermined angle. In this embodiment, the inclination angle of the housing  5  and the rotary shaft  7  with respect to a vertical line is 35 degrees, but is not limited to this numerical value. The housing  5  includes an upper surface portion  11 , and the rotary grinding member  9  rotates above the upper surface portion  11 . The upper surface portion  11  prevents grinding water from entering inside the housing  5 . The upper surface portion  11  of the housing  5  is arranged to be perpendicular to an outer circumferential surface  57  of the housing  5 . The upper surface portion  11  has an outlet  12 , and a drain pipe  13  is attached to the outlet  12 . Thus, drained water received by the upper surface portion  11  is drained outside the housing  5 . The drainage container  4 , which stores drained water, is detachably mounted on the outer surface of the housing  5 . The drain pipe  13  constitutes a passage for draining water to the drainage container  4 . 
     The drainage container  4  has an opening  15  on its side surface, and the drain pipe  13  is inserted in the opening  15 . A protrusion (not shown) for hanging the container is formed on the outer surface of the grinder main body  2  that contacts the drainage container  4 , and a bore (not shown) that engages with the protrusion is formed in the drainage container  4 . The drainage container  4  is mounted on the grinder main body  2  by the engagement between the protrusion and the bore. The drainage container  4  is also formed to be inclined with respect to a bottom surface  16  at the same angle as the housing  5 . A detachable lid  17  is mounted on the drainage container  4 . Grinding of a cutting-tool is performed by inserting a blade in a guide groove  38  of the cover  3 . The drainage container  4  is mounted on the housing  5  on the opposite side of the cover  3  from the guide groove  38 . Thus, the drainage container  4  does not interfere with the grinding operation during grinding. A reference numeral  14  indicates part of an electrical cord. 
     As shown in  FIGS. 5 and 6 , the rotary grinding member  9  includes a circular substrate  18  and an annular grindstone  8 , which is adhered to the surface of the substrate  18  by an adhesive. A grinding surface  19  is formed by a conic surface. The substrate  18  is made of metal, and the grindstone  8  is formed of material in which water can penetrate. As material permeable to water, alumina-based abrasive grain is used in the present embodiment, but other material may be used such as a natural waterstone. The maximum diameter of the grindstone  8  is 135 mm, and the maximum thickness is 24 mm. The adhering method of the grindstone  8  is not limited to an adhesive, and other method, for example, a metal fitting such as a bolt may be used. 
     As shown in  FIG. 6 , the rotary grinding member  9  has a cavity  20  for storing the grinding water inside. The cavity  20  is surrounded by an inner wall  21 . The inner wall  21  is formed by an inclined surface, which is inclined inward, and the cavity  20  has a truncated-cone shape widened toward the end. An inlet  22  for the grinding water is formed in the upper center of the grindstone  8 . The grinding water is poured into the cavity  20  through the inlet  22 . Since the inner wall  21  is inclined inward, the inner diameter of the inlet  22  is smaller than the inner diameter of the bottom of the cavity  20 . In this embodiment, the inner diameter of the inlet  22  is 54 mm, and the inner diameter of the bottom of the cavity  20  is 88 mm. However, the inner diameters are not limited to these numerical values. 
     As shown in  FIG. 6 , the inclination angle of the conic surface configuring the grinding surface  19  of the grindstone  8 , that is, the inclination angle of the grinding surface  19  with respect to the substrate  18 , which configures a horizontal surface of the rotary grinding member  9  is 35 degrees. Also, as described above, the inclination angle of the housing  5  and the rotary shaft  7  with respect to the vertical line is also 35 degrees. As a result, a generating line  23  located at the highest position of the grinding surface  19  extends horizontally. When the blade is ground in the vicinity of this generating line  23 , the entire cutting-tool is ground while keeping the cutting-tool horizontal. This facilitates the operation. 
     The grinder  1  includes means for preventing the grinding water that has splashed from the grinding surface  19  from splashing to the outside. One example of the prevention means is an upper circumferential wall  25 , which extends circumferentially on the upper surface portion  11  of the housing  5 , as shown in  FIG. 4 . The upper circumferential wall  25  mainly prevents grinding water that splashes in the horizontal direction from splashing to the outside. Another prevention means is the cover  3 . The cover  3  mainly prevents the grinding water that splashes upward and in the horizontal direction from splashing to the outside. 
     As shown in  FIG. 4 , the cover  3  is detachably mounted on the upper circumferential wall  25  of the housing  5 . A circumferential wall  26  of the cover  3  is fitted to the outside of the upper circumferential wall  25  so that the cover  3  is mounted on the housing  5 . Means for preventing the cover  3  from being detached from the housing  5  is provided on the cover  3  and the housing  5 . As shown in  FIG. 11 , an engaging projection  27  for preventing detachment is provided on the inner surface of the circumferential wall  26  of the cover  3 . The engaging projection  27  has a locking groove  28 . 
     Also, as shown in  FIG. 10 , a recess  29  for preventing detachment is provided on the surface of the upper circumferential wall  25 , which extends along the circumference on the upper surface portion  11  of the housing  5 . The recess  29  includes an inlet  30  for introducing the engaging projection  27  of the cover  3 , and an engaging recess  31 , to which the engaging projection  27  is engaged. The engaging recess  31  has a locking protrusion  32 . 
     A retractable safety switch  33  is provided in the engaging recess  31 . When the safety switch  33  is protruding as shown in  FIG. 10 , power is not supplied to the motor  6  even if a drive switch  34  shown in  FIG. 1  is pressed, and the motor  6  does not rotate. When mounting the cover  3  on the housing  5 , the engaging projection  27  of the cover  3  is introduced into the recess  29  through the inlet  30  of the housing  5 , and the cover  3  is subsequently rotated in the direction toward the engaging recess  31 . 
     As the cover  3  is continuously rotated, the safety switch  33  sinks by the engagement with the cover  3 . When the drive switch  34  is pressed in this state, electric power is supplied to the motor  6 , and the motor  6  is rotated. Also, when the locking groove  28  of the cover  3  is engaged with the locking protrusion  32  of the housing  5 , the rotation of the cover  3  is stopped at this position, and reverse rotation of the cover  3  is prevented. The reference numeral  35  in  FIG. 10  and the reference numeral  36  in  FIG. 11  show positioning protrusions. When both the positioning protrusions  35 ,  36  entirely overlap, the operator can determine that the locking groove  28  of the cover  3  is engaged with the locking protrusion  32  of the housing  5 . The engagement structure that is the same as the above engagement structure is provided on the opposite side of the outer circumference portions of the cover  3  and the housing  5 , but the safety switch  33  and the positioning protrusions  35 ,  36  are not provided. 
     As shown in  FIGS. 1 to 4  and  7 , the cover  3  includes a conic surface  37  at part of its outer circumference. The inclination angle of the conic surface  37  is equal to the inclination angle of the grinding surface  19  of the grindstone  8 . A guide groove  38  is formed on the conic surface  37 . The guide groove  38  includes guide groove inner surfaces  40 ,  41  and an upper surface portion  42 . As shown in  FIG. 3 , the guide groove inner surfaces  40 ,  41  are located on both ends of the guide groove  38 . The guide groove inner surface  41 , which is located outward, is formed by the upper circumferential wall  25  of the housing  5 . Since the grinding surface  19  of the grindstone  8  is exposed from the guide groove  38 , the blade can be ground by the grinding surface  19  by inserting the blade through an insertion bore  39  of the guide groove  38 . The inner width of the insertion bore  39  is set to 7 mm, which is the size that prevents the fingers of the operator from being inserted. Since the guide groove  38  extends in the direction of the generating line of the conic surface  37  of the cover  3  as shown in  FIG. 3 , when grinding a blade  52 , a kitchen knife  51  is moved in the direction of the generating line of the conic surface  37  of the cover  3 , that is, in the direction of the generating line of the grinding surface  19  as shown in  FIG. 12  or  13 . The entire cover  3  or the upper surface portion  42  of the guide groove  38  may be formed to be transparent so that the grinding state can be visually checked. In the present embodiment, the guide groove  38  and a blade support  43  configure a guide for moving the cutting-tool that is being ground in the direction of the generating line of the grinding surface. 
     The blade support  43  is detachably mounted on the conic surface  37  adjacent to the insertion bore  39 . As shown in  FIG. 8 , the blade support  43  includes a blade support surface  44 , which is inclined at a predetermined angle. As shown in  FIG. 9 , the blade support  43  has a substantially semi-circular fitting portion  45 . As shown in  FIG. 7 , a receiving portion  46  for mounting the blade support  43  is formed on the conic surface  37  of the cover  3 . A substantially semi-circular recess  47  is formed in the receiving portion  46 . The blade support  43  is mounted on the cover  3  by fitting the fitting portion  45  of the blade support  43  in the recess  47 . 
     When the blade support  43  is mounted on the cover  3 , a downward extension line of the blade support surface  44  extends to the insertion bore  39  of the guide groove  38 . When the blade is inserted in the guide groove  38  through the insertion bore  39  while being abut against the surface of the blade support surface  44 , the blade is abut against the grinding surface  19  at the grinding angle that is the same as the inclination angle of the blade support surface  44  and is ground. 
     In the present embodiment, the inclination angle of the blade support surface  44  with respect to the grinding surface  19  is 16 degrees, and the grinding angle is also 16 degrees. This angle is preferable for, for example, an usuba hocho used for cooking at home. Since both sides of the thin-bladed kitchen knife are ground, when both sides are ground at the grinding angle of 16 degrees, the cutting edge angle, which is the angle of the cross-section of the blade edge of the kitchen knife, will be 32 degrees. 
     A preferable grinding angle is obtained by replacing blade supports  43  having the blade support surfaces  44  with different inclination angles in accordance with the cutting-tool. For example, when the inclination angle of the blade support surface  44  is 22 degrees, a grinding angle preferable for a deba hocho (Japanese style kitchen carver) is obtained. Since only one side of the blade is ground for the deba hocho, when the grinding angle is 22 degrees, the cutting edge angle is also 22 degrees. The inclination angle of the blade support surface  44  is of course not limited to these numerical values, and an optimal cutting edge angle is obtained depending on the application by setting to other numerical values. Furthermore, the blade may be first ground by a grinding angle that is a relatively small acute angle, and then ground at a grinding angle that is a relatively large acute angle by replacing the blade support  43 . In this manner, the cutting edge angle in the vicinity of the blade edge can be changed, and sharpening of double beveled edge is possible. 
     A filler opening  48  for pouring the grinding water into the cavity  20  of the rotary grinding member  9  is provided at the center of the cover  3 . Ribs  49 , which extend in a radial pattern, and an annular rib are provided in the filler opening  48 . The ribs  49  minimize splashing of the grinding water from the filler opening  48  during grinding. As shown in  FIG. 4 , the grinding water poured through the filler opening  48  is poured into the cavity  20  via the inlet  22  of the rotary grinding member  9 . An inner wall  50  is provided on the inner side of the circumferential wall  26  of the cover  3 . The inner wall  50  is provided such that the splashed grinding water will adhere to the inner wall  50 . Thus, it is easy to wash off the splashed grinding water when the cover  3  is removed. 
     The grinding water stored in the cavity  20  of the rotary grinding member  9  collects at a low part of the cavity  20  since the rotary grinding member  9  is inclined. In this state, when the rotary grinding member  9  is rotated at high speed, centrifugal force is applied to the grinding water. Since the inner wall  21  of the cavity  20  that contacts the grinding water is rotated at high speed, the grinding water is rotated in a state adhered to the inner wall  21 . The grindstone  8  is formed of material permeable to water. Thus, the grinding water that penetrated through the inner wall  21  passes through the inside of the grindstone  8  by the centrifugal force and seeps out to the grinding surface  19 . The grinding water that has seeped out to the grinding surface  19  is rotated with the grindstone  8 , and moves gradually in the outer circumferential direction of the grinding surface  19  by the centrifugal force. However, even when the grinding water moves in the outer circumferential direction, the grinding water immediately contacts the blade edge of the blade. Thus, the movement amount of the grinding water in the outer circumferential direction is small. Therefore, the grinding water hardly splashes from the outer circumference of the grinding surface, and the grinding water necessary for grinding is efficiently supplied. In the present embodiment, the rotary grinding member  9 , which includes the cavity  20 , configures means for automatically supplying the grinding water to the grinding surface  19 . 
     The method for using the grinder  1  will now be described with reference to  FIGS. 12 and 13 . In the case with the usuba hocho for cooking, both sides of the blade, that is, the first blade surface and the second blade surface are ground. When grinding the blade of the cutting-tool such as a kitchen knife, the longitudinal direction of the cutting-tool is aligned with the direction of the generating line of the grinding surface  19 . 
     More specifically,  FIG. 12  shows the case in which the first blade surface of the blade is ground. When using the grinder  1 , the grinder  1  is arranged such that the insertion bore  39  of the guide groove  38  faces the operator. Then, the grinding water is poured into the filler opening  48  of the cover  3 , and stored in the cavity  20  of the rotary grinding member  9  by an appropriate amount. Subsequently, the operator grasps a handle  55  of the kitchen knife  51 , and presses the drive switch  34  on. In the present embodiment, the grindstone  8  is rotated at a 500 rpm, but the number of rotation is not limited to this. Furthermore, the number of rotation may be variable. 
     As the grindstone  8  is rotated, the grinding water seeps out to the grinding surface  19 . In this state, a heel  53  of the blade  52  is inserted in the guide groove  38  from a blade edge  54 . At this time, the blade  52  is abut against the blade support surface  44  of the blade support  43  so that the grinding angle is determined, and the longitudinal direction of the blade  52  is aligned with the direction of the generating line of the grinding surface  19 . The surface of the blade edge  54  is ground by the grinding surface  19  while drawing the kitchen knife  51  in the direction of the arrow. The kitchen knife becomes stable by placing the left hand on the blade  52  during grinding. If the kitchen knife  51  is ground while slowly drawing the kitchen knife  51 , the blade is ground in a suitable manner by drawing the kitchen knife only once in the arrow direction. The kitchen knife  51  may of course be ground by reciprocating a number of times. 
     After completing grinding the first blade surface of the blade  52 , the kitchen knife  51  is switched to the left hand as shown in  FIG. 13 , and the second blade surface is arranged with respect to the grinding surface  19  in the same manner as the first blade surface of the blade  52 . Then, the second blade surface of the blade  52  is ground while drawing the kitchen knife  51  in the direction of the arrow. At this time, the kitchen knife becomes stable by placing the right hand on the blade  52 . When switching the kitchen knife to the other hand, the drive switch  34  may be left on, or the drive switch  34  may be turned off and then turned on again. 
     In the above-mentioned method for using the grinder  1 , the insertion bore  39  for the blade faces the operator as shown in  FIG. 2 . As apparent from  FIG. 2 , in the grinder  1  arranged on a flat surface such as a table, the blade insertion bore  39  and the blade support  43  are located at the highest region, the upper surface  56  of the cover  3  is inclined downward to the right, and the outer circumferential surface  57  of the housing  5  is inclined downward to the left. 
     Since the kitchen knife  51  is held horizontally during grinding of the kitchen knife  51 , when grinding the kitchen knife  51  holding it in the right hand as shown in  FIG. 12 , a triangular space is generated between the handle  55  of the kitchen knife  51 , which extends horizontally, and the upper surface  56  of the cover  3  as viewed from the front of  FIG. 2 . Thus, the right hand that grasps the kitchen knife  51  during grinding does not interfere with the upper surface  56  of the cover  3 , and the grinding operation is easy to perform. At this time, the left hand is preferably placed on the blade  52  to stabilize the kitchen knife  51 . The left hand does not interfere with the outer circumferential surface  57  on the left side of the housing  5 . 
     Also, when grinding the kitchen knife  51  holding it in the left hand as shown in  FIG. 13 , a triangular space is generated between the handle  55  of the kitchen knife  51 , which extends horizontally, and the outer circumferential surface  57  on the left side of the housing  5  as viewed from the front of  FIG. 2 . Thus, the left hand that grasps the kitchen knife  51  during grinding does not interfere with the outer circumferential surface  57  on the left side of the housing  5 , and the grinding operation is easy to perform. At this time, the right hand is preferably placed on the blade  52  to stabilize the kitchen knife  51 . The right hand does not interfere with the upper surface  56  of the cover  3 . That is, since the housing  5  and the cover  3  do not interfere with the hand and the handle  55 , the grinding operation is smoothly performed even when the kitchen knife  51  is ground while held in either of the left and right hands. 
     In the present embodiment, the guide groove  38  and the grinding surface  19 , which is exposed in the guide groove  38 , configure means for permitting the cutting-tool to be aligned with the direction of the generating line of the grinding surface  19  and permitting the blade to be abut against the grinding surface without the handle  55  of the cutting-tool and the hand that holds the cutting-tool being interfered by the grinder  1  in the case in which the blade is ground with the tip of the blade of the cutting-tool such as the kitchen knife  51  facing the extending direction of either end of the generating line of the grinding surface  19 . 
     The present invention may be embodied in various manners. For example, in the above-mentioned embodiment, an usuba hocho having a double-ground edge is described as an example, but a single-edged kitchen knife such as a deba hocho may be ground. Also, other cutting-tools such as a knife or a pair of scissors, which is a single-edged cutting-tool, may be ground. 
     For example, since a deba hocho is a single-edged knife generally for right-handers, when grinding the blade, there is no problem with the grinder of Patent Document 1. However, a deba hocho for left-handers has an inclined surface along the blade edge on the blade surface opposite to the knife for right-handers. Thus, when grinding the deba hocho for left-handers, it is the same as grinding the deba hocho for right-handers in a state in which the distal end of the blade and the handle are flipped over and the kitchen knife is turned over. Thus, in the grinder of Patent Document 1, the handle of the kitchen knife and the hand that holds the kitchen knife are interfered by the grinder. In contrast, in the grinder of the present embodiment, such interference does not occur. There are also scissors for left-handers, and for grinding of such scissors, the blades are flipped over and ground in the same manner as the deba hocho. However, there is no interference in the grinder of the present embodiment. When grinding a cutting-tool different from the usuba hocho, the blade support  43  corresponding to the cutting-tool may be prepared.