Abstract:
A separation type hole saw, includes: a hole saw ( 3 ); a hole saw mounting metal fitting ( 2 ); a shank ( 5 ); a spherical body ( 13 ) inserted to the hole portion ( 12 ); an annular spring ( 14 ) inserted to the annular groove ( 15 ) and urging the spherical body ( 13 ) so that the spherical body ( 13 ) presses the fitting convex portion ( 2   a ) of the hole saw mounting metal fitting ( 2 ), thereby preventing the fitting recess portion ( 5   a ) of the shank ( 5 ) from being taken out from the fitting convex portion ( 2   a ) of the hole saw mounting metal fitting ( 2 ) due to the pressing operation of the spherical body ( 13 ); a center pin ( 6 ) inserted to a center portion of the shank ( 5 ) and guiding the hole saw ( 3 ) at a time of drilling a material in which a guide groove ( 19 ) is formed in an outer periphery of an end portion of the center pin ( 6 ) inserted to the shank ( 5 ); and a fitting member ( 22 ) provided in the shank ( 5 ). The fitting member ( 22 ) is fitted to and detached from the guide groove ( 19 ), whereby the center pin ( 6 ) is fixed to the shank ( 5 ) and is freely detached from the shank ( 5 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a separation type hole saw in which a hole saw can be, freely attached and detached and the hole saw can be easily replaced in a one-touch manner. 
     2. Description of the Related Art 
     Conventionally, the hole saw has had various kinds of drilling holes and has been required to be always provided with various kinds of hole saw mounting metal fittings being different in an effective length of a blade portion, a length of a center pin, a shape of a shank and the like. Accordingly, there has been a problem that a lot of time and labor is required for treating the hole saw and the treatment is troublesome, and the like. Therefore, a separation type hole saw tends to be increased in comparison with an integration type hole saw. 
     FIG. 1 shows a schematic view of a conventional separation type hole saw. In the drawing, a separation hole saw  1  is structured such that a hole saw  3  is integrally fixed to a mounting metal fitting  2  and is connected to a drilling portion of a working machine (not shown) by a detachable shank  5  and a screw portion  4 . Further, a center pin (or a center guide drill or the like)  6  used as a center guide at a time of drilling is provided in the shank  5  and is fixed by a fastening screw  7 . In this case, a spring  8  is inserted into a center pin  6 , and is structured such that one end forms a stationary end being fixed to the mounting metal fitting  2  and another end forms a free end so as to remove blanks (piercing refuses) during the drilling. 
     FIG. 2 shows an explanatory view of a using method of the separation type hole saw shown in FIG.  1 . In the drawing, the separation type hole saw is constituted by two kinds of large and small hole saws,  3 A and  3 B, mounting metal fitting  2 A and  2 B, shanks  5 A and  5 B, center guide drills  6 A and  6 B and an intermediate connection metal fitting  9 . As mentioned above, in the case that the sizes are different, the intermediate connection metal fitting  9  is frequently required. In this case, hexagonal fitting portions a and b fitting to each other are provided among the mounting metal fittings  2 A and  2 B, the shanks  5 A and  5 B and the intermediate connection metal fitting  9 , and are respectively fixed by a fastening screw  11 , so as to be prevented from falling off. 
     However, since a hexagonal wrench for fastening and loosening the fastening screw  7  is required for a replacing operation of the center pin (or the center guide drill or the like)  6 , and a tool such as a spanner or the like is required for a replacing operation of the hole saw  3 , there is a problem that a treatment thereof is troublesome and a working operability is reduced. 
     SUMMARY OF THE INVENTION 
     In order to solve the problems mentioned above, an object of the present invention is to provide a separation type hole saw in which a hole saw is replaced in a one-touch manner, is detachable, is easily treated and has an improved operation efficiency. 
     A first aspect of the present invention provides a separation type hole saw comprising: a hole saw ( 3 ) a hole saw mounting metal fitting ( 2 ), in which one end of the hole saw mounting metal fitting ( 2 ) is integrally mounted to the hole saw ( 3 ), and a polygonal fitting convex portion ( 2   a ) is formed in another end of the hole saw mounting metal fitting ( 2 ); a shank ( 5 ), in which a polygonal fitting recess portion ( 5   a ) is formed in one end of the shank ( 5 ), the fitting convex portion ( 2   a ) of the hole saw mounting metal fitting ( 2 ) is inserted to the fitting recess portion ( 5   a ), another end of the shank ( 5 ) is attached to a rotational shaft portion of a working machine, a hole portion ( 12 ) extending through the fitting recess portion ( 5   a ) from an outer peripheral surface of the shank ( 5 ) is provided, and an annular groove ( 15 ) is formed in an outer periphery at a position of the hole portion ( 12 ) of the shank ( 5 ); a spherical body ( 13 ) inserted to the hole portion ( 12 ); an annular spring ( 14 ) inserted to the annular groove ( 15 ), the annular spring ( 14 ) urging the spherical body ( 13 ) so that the spherical body ( 13 ) presses the fitting convex portion ( 2   a ) of the hole saw mounting metal fitting ( 2 ), thereby preventing the fitting recess portion ( 5   a ) of the shank ( 5 ) from being taken out from the fitting convex portion ( 2   a ) of the hole saw mounting metal fitting ( 2 ) due to the pressing operation of the spherical body ( 13 ); a center pin ( 6 ) inserted to a center portion of the shank ( 5 ) and guiding the hole saw ( 3 ) at a time of drilling a material, in which a guide groove ( 19 ) is formed in an outer periphery of an end portion of the center pin ( 6 ) inserted to the shank ( 5 ); and a fitting member ( 22 ) provided in the shank ( 5 ), the fitting member ( 22 ) being fitted to and detached from the guide groove ( 19 ), whereby the center pin ( 6 ) is fixed to the shank ( 5 ) and is freely detached from the shank ( 5 ). 
     A second aspect of the present invention, as it depends from the first aspect, provides a separation type hole saw, in which the guide groove ( 19 ) is an inclined groove structured such that a depth of the groove is increased along a rotational direction of the center pin ( 6 ). 
     According to the separation type hole saw of the first and second aspects mentioned above, since a replacing operation of the hole saw can be simply performed with one action and a treatment thereof is easy, an operation efficiency can be improved. 
     A third aspect of the present invention provides a separation type hole saw comprising: a hole saw ( 103 ); a hole saw mounting metal fitting ( 114 ), in which one end of the hole saw mounting metal fitting ( 114 ) is integrally mounted to the hole saw ( 103 ), a fitting convex portion ( 114   a ) is formed in another end of the hole saw mounting metal fitting ( 114 ), and a first annular groove ( 118 ) is formed in an outer periphery of the fitting convex portion ( 114   a ); a shank ( 115 ), in which a polygonal fitting recess portion ( 115   a ) is formed in one end of the shank ( 115 ), the fitting convex portion ( 114   a ) of the hole saw mounting metal fitting ( 114 ) is inserted to the fitting recess portion ( 115   a ), another end of the shank ( 115 ) is attached to a rotational shaft portion of a working machine, a first hole portion ( 116 ) extending through the fitting recess portion ( 115   a ) from an outer. peripheral surface of the shank ( 115 ) is provided, a second annular groove ( 121 ) is formed in an outer periphery at a position of the first hole portion ( 116 ) of the shank ( 115 ), a center pin insertion hole ( 127 ) if formed in the shank ( 115 ), a second hole portion ( 123 ) extending through the center pin insertion hole ( 127 ) from an outer peripheral surface is further formed in the shank ( 115 ), and a third annular groove ( 125 ) is formed in an outer periphery at a position of the second hole portion ( 123 ) of the shank ( 115 ); a first spherical body ( 117 ) inserted to the first hole portion ( 116 ); a first annular spring ( 120 ) inserted to the second annular groove ( 121 ), the first annular spring ( 120 ) urging the first spherical body ( 117 ):so that the first spherical body ( 117 ) presses the fitting convex portion ( 114   a ) of the hole saw mounting metal fitting ( 114 ), thereby preventing the fitting recess portion ( 115   a ) of the shank ( 115 ) from being taken out from the fitting convex portion ( 114   a ) of the hole saw mounting metal fitting ( 114 ) due to the pressing operation of the first spherical body ( 117 ); a center pin ( 6 ) inserted to a center portion of the shank ( 115 ):and guiding the hole saw ( 103 ) at a time of drilling a material, in which a circular arc groove ( 126 ) is formed in an outer peripheral surface of an end portion of the center pin ( 6 ) inserted to the shank ( 115 ); a second spherical body ( 124 ) inserted to the second hole portion ( 123 ); a second annular spring ( 122 ) inserted to the third annular groove ( 125 ), the second annular spring ( 122 ) urging the second spherical body ( 124 ) so that the second spherical body ( 124 ) presses the circular arc groove ( 126 ) of the center pin ( 6 ), thereby preventing the center pin ( 6 ) from being taken out from the center pin insertion hole ( 127 ) due to the pressing operation of the second spherical body ( 124 ); and an outer peripheral ring ( 113 ) provided in an outer periphery of the shank ( 115 ). in which the first annular spring ( 120 ) and the second annular spring ( 122 ) rotate at a desired rotational angle and a pressing force applied to the first spherical body ( 117 ) and the second spherical body ( 124 ) by the first annular spring ( 120 ) and the second annular spring ( 122 ) is changed when the outer peripheral ring ( 113 ) is rotated around a shaft of the shank ( 115 ), whereby a locking and canceling operation of the center pin ( 6 ) with respect to the center pin insertion hole ( 127 ) and a locking and canceling operation between the fitting recess portion ( 115   a ) of the shank ( 115 ) and the fitting convex portion ( 114   a ) of the hole saw mounting metal fitting ( 114 ) are simultaneously performed. 
     A fourth aspect of the present invention, provides a separation type hole saw according to the third aspect, wherein a third hole portion ( 141 ) extending through the center pin insertion hole ( 127 ) is formed in the outer peripheral surface of the shank ( 115 ), a third spherical body ( 143 ) is inserted to the third hole portion ( 141 ), the third spherical body ( 143 ) presses the annular arch groove ( 126 ) of the center pin ( 6 ) so as to prevent the center pin ( 6 ) from being taken out from the center pin insertion hole ( 127 ), and the locking and canceling operation of the center pin ( 6 ) with respect to the center pin insertion hole ( 127 ) is performed by rotating the outer peripheral ring ( 113 ) at a desired rotational angle. 
     A fifth aspect of the present invention provides a separation type hole saw according to the third or fourth aspect, wherein a guide groove ( 129 ) is formed in an inner surface of the outer peripheral ring ( 113 ), a fourth spherical body ( 131 ) is inserted between the guide groove ( 129 ) and the shank ( 115 ), and the guide groove ( 129 ) is formed such that a rotational angle of the outer peripheral ring ( 113 ) is kept 60 degrees. 
     A sixth aspect of the present invention provides a separation type hole saw according to the third aspect, the fourth aspect or the fifth aspect, wherein the first hole portion ( 116 ) is uniformly separated into three sections in a direction of extending through the fitting recess portion ( 115   a ) from the outer peripheral surface of the shank ( 115 ), and three first spherical bodies ( 117 ) are respectively inserted to the three first hole portions ( 116 ). 
     According to the separation type hole saws of the third to sixth aspects mentioned above, since a replacing operation of the hole saw can be simply performed with one action and a treatment thereof is easy, an operation efficiency can be improved. Further, a concentricity of the members on the basis of the respective elements, that is, an accuracy at which the centers of the elements coincide with each other can be improved and a quality can be improved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a conventional separation type hole saw attaching and detaching apparatus; 
     FIG. 2 is an explanatory view of a using method of a separation type hole saw attaching and detaching apparatus; 
     FIG. 3 is a schematic view of an embodiment corresponding to a main portion of the present invention; 
     FIG. 4 is a horizontal cross sectional view of FIG. 1; 
     FIG. 5A is a front elevational view of a summary of an annular spring; 
     FIG. 5B is a plan view of the same; 
     FIG. 6 is a schematic view of an annular groove provided in an outer periphery of a shank; 
     FIG. 7 is a schematic view of center pin fitting means corresponding to another main portion of the present invention; 
     FIG. 8 is a horizontal cross sectional view of FIG. 7; 
     FIG. 9 is a schematic view of a working process of a guide groove in a center guide drill; 
     FIG. 10 is a bottom elevational view of FIG. 9; 
     FIG. 11 is an explanatory view of another structure of center pin fitting means; 
     FIG. 12 is an explanatory view of the other structure of the center pin fitting means; 
     FIG. 13 is a schematic view showing a second embodiment of a separation type hole saw in accordance with the present invention; 
     FIG. 14 is a cross sectional view taken along a line XIV—XIV in FIG. 13, showing a lock cancel state of a hole saw mounting metal fitting attaching and detaching portion; 
     FIG. 15 is a horizontal cross sectional view taken along XV—XV in FIG. 14; 
     FIG. 16 is a view showing a lock state of the hole saw mounting metal fitting attaching and detaching portion; 
     FIG. 17 is a cross sectional view taken along XVII—XVII in FIG. 13, showing a lock cancel state of a center pin attaching and detaching portion; 
     FIG. 18 is a view showing a lock state of the center pin attaching and detaching portion; 
     FIG. 19A is a front elevational view of a summary of an annular spring; 
     FIG. 19B is a plan view of the same; 
     FIG. 20 is a schematic view of an annular groove provided in an outer periphery of a shank; 
     FIG. 21 is a schematic view showing another embodiment of the center pin attaching and detaching portion in accordance with the present invention; 
     FIG. 22 is a view of a lock cancel state of FIG. 21; and 
     FIG. 23 is a schematic view showing the other embodiment of the hole saw mounting metal fitting attaching and detaching portion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description will be in detail given below of embodiments in accordance with the present invention with reference to the accompanying drawings. 
     FIG. 3 is a schematic view of an embodiment corresponding to a main portion of the present invention, and FIG. 4 shows a horizontal cross sectional view of FIG.  3 . In FIGS.  3  and  4 , a hole saw mounting metal fitting attaching means  10  for constructing a separation type hole saw is constituted by fitting portions  2   a  and  5   a  formed between another end of a hole saw mounting metal fitting  2  and one end of a shank  5  so as to form a polygonal shape (a hexagonal shape in the present embodiment), thereby being fitted to each other, a spherical body  13  inserted to an inclined hole  12  provided in a direction of the hole saw mounting metal fitting portion  2   a  from the shank fitting portion  5   a , and an annular spring  14  inserted into an annular groove  15  provided along an outer periphery of the shank  5 . The annular spring  14  holds a spherical body  13  within the inclined hole  12  by a notch portion  14   a  having an angle of about 60 degrees so as to apply a pressing pressure. In this case, reference numeral  17  denotes an insertion hole of a center guide drill  6  inserted to the shank  5 . 
     As shown in FIGS. 5A,  5 B and  6 , when setting an outer diameter d 1  of an applied shank  5  to, for example, 25 mm, a reference size of a groove diameter d 2  is set to 23.9 mm, a reference size of a groove width m is set to 1.35 mm, a reference size of a spring inner diameter d 3  of the annular spring  14  is set to 23.4 mm, a reference size of a spring width b is set to 2 mm and a reference size of a thickness t is set to 1.2 mm, so that these sizes are made standards. 
     In order to attach the hole saw mounting metal fitting  2  to the shank  5 , when combining the fitting portions  2   a  and  5   a  so as to insert them to the shank  5  and aligning the spherical body  13  with a recess groove  16  in the fitting portion  2   a  of the hole saw mounting metal fitting  2 , the hole saw mounting metal fitting  2  is prevented from being fallen down from the shank  5  by holding the spherical body  13  within the recess groove  16  due to an elastic force of the annular spring  14 . 
     FIG. 7 is a schematic view of center pin fitting means corresponding to another main portion of the present invention, FIG. 8 is a horizontal cross sectional view of FIG. 7, FIG. 9 is a schematic view of a working process of a guide groove in a center guide drill in FIG. 7, and FIG. 10 is a bottom elevational view of FIG.  9 . In FIGS. 7 to  10 , center pin fitting means  18  is constituted by a guide groove  19  provided near a shank insertion end of the center guide drill  6 , and a center guide fitting member with an elastic member fitted to a guide groove  19  provided in the shank  5 , in the present embodiment, a spherical body with an urethane member  20 . The spherical body with the urethane member  20  is structured such that a spherical body (a ball)  22  is fitted to the guide groove  19  so as to engage the center guide drill  6  with the shank  5 , thereby freely attach and detach the center guide drill  6  with respect to the shank  5 . In this case, reference numeral  23  denotes an urethane rubber applying a pressing pressure to the spherical body  22 , and reference numeral  24  denotes a pressing force adjusting screw engaged with the shank  5 . 
     In this case, there is a risk that the drill  6  can not rotate when the spherical body  22  is completely drawn back from the guide groove  19 . Accordingly, the guide groove  19  is formed in an inclined groove having a depth increasing toward a rotational direction of the drill  6 , in which a groove diameter is set so as to satisfy the relation k 1 &lt;k 2 . Accordingly, the spherical body  22  receives a pressing force in a rotational direction (a direction of k 2 ), is always brought into contact with an inner portion of the guide groove  19 , prevents the drill  6  from not rotating, and keeps a fitting state between the guide groove  19  and the spherical body  18 . In this case, the urethane rubber is used as the elastic member, however, a spherical body with a spring  25  may be employed as shown in FIG. 11. A spherical body  27  and a spring  28  are integrally received within an adjusting screw  26 . 
     Further, as shown in FIG. 12, a plunger with a spring  29  may be employed. A plunger  31  and a spring  32  are integrally received within an adjusting screw  30 . 
     In FIGS. 9 and 10, attention should be paid so that a length l of the spherical body with the spring  25  or the plunger with the spring  29  does not increase as protruding to an outer portion of the shank  5  because the shank  5  is a rotational body. 
     As mentioned above, the hole saw  3  is simply replaced in a one-touch manner, is detachable, is easily treated and has an improved operation efficiency since the hole saw mounting metal fitting attaching means  10  and the engaging member with the elastic member, the spherical body with the urethane member  18  in the present embodiment are provided as the separation type hole saw. 
     A description will be in detail given below of a second embodiment in accordance with the present invention with reference to the accompanying drawings. 
     FIG. 13 is a schematic view showing a second embodiment of a separation type hole saw in accordance with the present invention, FIG. 14 is a cross sectional view taken along a line XIV—XIV in FIG. 13, showing !a lock cancel state of a hole saw mounting metal fitting attaching and detaching portion, FIG. 15 is a horizontal cross sectional view taken along XV—XV in FIG. 14, FIG. 16 is a view showing a lock state of the hole saw mounting metal fitting attaching and detaching portion, FIG. 17 is a cross sectional view, taken along XVII—XVII in FIG. 13, showing a lock cancel state of a center pin attaching and detaching portion, and FIG. 18 is a view showing a lock state of the center pin attaching, and detaching portion. In FIGS. 13 to  18 , a separation type hole saw  110  in accordance with the present invention is mainly constituted by a hole saw mounting metal fitting attaching and detaching portion  111 , a center pin attaching and detaching portion  112  and an outer peripheral ring  113 . 
     The hole saw mounting metal fitting attaching and detaching portion  111  is constituted by fitting portions  114   a  and  115   a  formed between another end of a hole saw mounting metal fitting  114  and one end of a shank  115  so as to form a polygonal shape (a hexagonal shape in the present embodiment), thereby being fitted to each other, a hole portion  116  drilled from an outer peripheral surface of the shank fitting portion  115   a  in a direction of the fitting portion  114   a  of the hole saw mounting metal fitting  114 , a spherical body  117  inserted to the hole portion  116 , a recess circular arc shaped annular groove  118  (a first annular groove  118 ) engaged with the spherical body  117  on an outer peripheral surface of the fitting portion  114   a  of the hole saw mounting metal fitting  114 , an annular groove  121  (a second annular groove  121 ) provided along an outer peripheral surface of the fitting portion  115   a  of the shank  115  via the hole portion  116 , and annular spring  120  inserted into the annular groove  121 , applying a pressing force to the spherical body  117  and attach the hole saw mounting metal fitting  114  to the shank  115 . 
     Further, the center pin attaching and detaching portion  112  is constituted by an annular arc groove  126  provided near an insertion end of the center pin with respect to the shank  115 , a hole portion  123  drilled toward the circular groove  126  provided in the shank  115 , two spherical bodies  124  inserted to the hole portion  123 , an annular groove  125  (a third annular groove  125 ) provided along an outer peripheral surface of the shank  115  via the hole portion  123 , and an annular spring  122  inserted into the annular groove  125  and applying a pressing force to the spherical body  124  so as to attach the center pin  6  to the shank  115 . In the present embodiment, the annular spring  120  and  122  have absolutely the same size capable of being commonly used. 
     In this case, reference numerals  127  and  127   a  denotes an insertion hole of the center pin  6  provided in the shank  115  and the hole saw mounting metal fitting  114 . 
     As shown in FIGS. 19 and 20, when setting an outer diameter of the annular springs  120  and  122  to be the same as the outer diameter d 1  of an applied shank  115 , for example, 25 mm, a reference size of a groove diameter d 2  is set to 23.9 mm, a reference size of a groove width m is set to 1.35 mm, a reference size of a spring inner diameter d 3  is set to 23.4 mm, a reference size of a spring width b is set to 3.1 mm and a reference size of a height ‘a’ of a protruding portion  130  provided in a gap portion  129  is set to 4.3 mm, so that these sizes are made standards. 
     As shown in FIGS. 14 and 17, the outer peripheral ring  113  is rotatably provided in an outer periphery of the shank  115 , and has a receiving portion  132  receiving a projection portion  130  of the annular springs  120  and  122  in an inner surface thereof. Further, in order to keep a desired angle, a rotational angle of about 60 degrees in the present embodiment, in the outer peripheral ring  113 , an annular groove  129  having an angle of about 60 degrees and a spherical body  131  attached to the shank  115  surface are provided in an inner surface of the outer peripheral ring  113 . Accordingly, the outer peripheral ring  113  can rotate the annular springs  120  and  122  by the receiving portion  132  and simultaneously perform a locking operation or a lock canceling operation between the hole saw mounting metal fitting attaching portion  111  and the center pin attaching portion  112  in a one-touch manner. 
     Since the spherical body  117  is under an easily attached and detached state (a lock canceled state) capable of escaping in an outer direction when the gap portion  129  of the annular spring  120  is placed on the spherical body  117 , the hole saw mounting metal fitting  114  can be prevented from falling down from the shank  115  by aligning the hexagonal fitting portions  114   a  and  115   a  with each other so as to insert, aligning the spherical body  117  with the annular groove  118  of the hole saw mounting metal fitting  114  and holding the spherical body  117  within the annular groove  118  due to an elastic force of the annular spring  120 . 
     In the same manner, since the spherical body  124  slightly escapes in an outer direction so as to be under an easily attached and detached state (a lock canceled state) when the gap portion  129  of the annular spring  122  is on the spherical body  124  as shown in FIG. 17, the hole saw mounting metal fitting  102  can be prevented from being fallen down from the shank  115  by aligning the spherical body  124  within the hole portion  123  of the shank  115  with the circular arc groove  126  of the center pin  6  and holding the spherical body  117  within the annular groove  118  due to the elastic force of the annular spring  122 . in this case, reference numeral  128  denotes a cushion member interposed between two spherical bodies  124  and  124 . 
     As shown in FIGS. 16 and 18, at a position satisfying the elation rotational angle α of the outer peripheral ring  113 =about 60 degrees, since the respective spherical bodies  117  and  124  are not in the gap portion  129  between the annular springs  120  and  122 , the spherical bodies are prevented from escaping in an outer direction so as to be held in a lock state, and can not be removed. 
     FIG. 21 is a schematic view showing another embodiment of the center pin attaching and detaching portion. In the drawing, a center pin attaching and detaching portion  140  is constituted by a circular arc groove  126  provided near an insertion end of the shank  115  of the center pin  6 , a hole portion  141  (a third hole portion  141 ) drilled toward the circular arc groove  126 , and two spherical bodies  143  and  143  (third spherical bodies  143 ) applying a pressing force to the circular arc groove  126  via an elastic member inserted to the hole portion  141 , for example, a coil spring  142  so as to attach the center pin  6  to the shank  115 . 
     In this case, a portion ‘m’ having an interval with respect to the spherical body  143  and a portion ‘n’ having an interval ‘a’ being set to be almost 0 are provided in the inner periphery of the outer peripheral ring  133 , an annular groove  129  having an angle of about 60 degrees and a spherical body  131  inserted between the shank  115  and the outer peripheral ring  113  are provided in an inner periphery of the outer peripheral ring  133  in order to keep the outer peripheral ring  133  in a desired angle, a rotational angle of about 60 degrees in the present embodiment, and it is possible to simultaneously perform a locking operation and a lock canceling operation between the hole saw mounting metal fitting attaching portion  111  and the center pin attaching portion  140 . FIG. 21 shows a lock state and FIG. 22 shows a lock cancel state. In this case, reference numeral  1 . 44  denotes a cover foreclosing the insertion hole after assembling the spherical body  143 , the spring  141  and the spherical body  131 . 
     FIG. 23 is a schematic view showing the other embodiment of the hole saw mounting metal fitting attaching and detaching portion. In the drawing, the same reference numerals are attached to the elements having the same functions as those in FIGS. 14 and 16. The hole saw mounting metal fitting attaching and detaching portion  111  has three hole portions  116  obtained by uniformly separating and drilling the circumference into three portions at every  120  degrees toward the fitting portion  114   a  of the hole saw mounting metal fitting  114  from the outer peripheral surface of the fitting portion  115   a  of the shank  115 , and three spherical bodies  117  inserted to the hole portion  116 . As mentioned above, by providing three spherical bodies  116 , it is easy to improve a concentricity between the shank  115  and the hole saw mounting metal fitting  114 . 
     As mentioned above, in comparison with the conventional hole saw, the separation type hole saw  110  in accordance with the present invention can be replaced in a one-touch manner, is detachable, is easily treated, has an improved operation efficiency, and has an increased concentricity. 
     The entire contents of Japanese Patent Applications P11-186822 (filed Jun. 30, 1999), P11-222645 (filed Aug. 5, 1999) and P2000-22368 (filed Jan. 31, 2000) are incorporated herein by reference. 
     Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.