Abstract:
An arbor system includes an arbor, a hole saw, a tightening feature and a tubular wrench. The arbor has a arbor coupling. A clamp body of the hole saw is sandwiched between the arbor coupling and the tightening feature in a pressed contact that is fully form fitting. Operational tilt and load torque are transmitted without affecting the tight-screwed interlocking between thread and tightening feature. Operational cutting vibrations are reduced by increased press contact facilitated by the tubular wrench that axially accesses the tightening feature from a direction opposite the power drill. The tubular wrench provides clearance to the pivot drill and the hole saw and safe handling protected against the hole saw&#39;s cutting teeth. Tightening feature and tubular wrench engage in a centering It manner such that the power drill may be used to quickly tighten or loosen the tightening feature while the tubular wrench is fixedly held.

Description:
CROSS REFERENCE  
       [0001]     The present application is a Continuation in Part of the U.S. patent application titled “Quick Release Arbor” of the same Inventor, application Ser. No. 11/022,417 filed Dec. 23, 2004. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention relates to arbor systems for rotary actuated and axially operating power tools. Particularly, the present invention relates to quick release arbor systems for hole cutting saws.  
       BACKGROUND  
       [0003]     Increasing use of wood and wood like structures in the field of architectural constructions creates a demand for specialized hole saws to cut holes for plumbing, piping and the like at the construction site. Special hole saws such as the cross referenced I-joist Hole Cutting Apparatus are invented to provide for on site fabrication of ever increasing hole diameters with common handheld power drills. The wheel like body of the I-joist Hole Cutting Apparatus has a solid rim that provides a relatively large momentum of inertia reducing the risk of sudden tool locking, which eventually causes the power drill to be ripped out of the operator&#39;s hands. The large momentum of inertia in turn causes relatively large gyroscopic forces opposing a tilting or wobbling of the rotating power tool.  
         [0004]     To reduce the operational torque necessary to cut large diameter holes, the I-joist Hole Cut Apparatus may be moved in a slight wobble movement around the pilot drill&#39;s centering hole. The peripherally rotating cutting blades thereby engage only partially in the cutting groove. This results on one hand in reduced friction between cutting blades and the side walls of the cutting groove and on the other hand in increased cutting pressure at the bottom of the cutting groove. Cutting pressure is ideally brought to a feasible maximum to increase the rate of chip removal. Unfortunately this causes, in combination with the wobble movement and the gyroscopic forces, a significant tilt torque that needs to be communicated between the power drill and the power tool.  
         [0005]     Hole saw bodies commonly provide a radial structural connection between the peripheral cutting elements and the central arbor, which in turn is chucked in a power drill. The central arbor needs to be made from high strength material such as steel or steel allow to match the mechanical properties of the power drill&#39;s chuck, to keep wear to a minimum and to withstand operational load torque and eventual tilt torque. The hole saw body has features that correspond with the arbor features to define an arbor system in which various diameter hole saw bodies are alternately connected with the arbor, without removing the arbor from the chuck. As hole saw diameters increase, material and fabrication costs of the hole saw body force the industry to select inexpensive low strength materials and fabrication techniques. This in turn increases discrepancies of mechanical properties of arbor and hole saw body.  
         [0006]     Prior art arbor systems commonly provide a connection between hole saw body and arbor via a central thread hole screwed onto a thread bolt of the arbor. The hole saw is operated in accordance with the thread orientation such that the torque transmitted via the chuck and the arbor causes the thread to tighten. To remove the power tool from the arbor, tool and arbor need to be rotated with respect to each other in direction opposite the operating torque. This requires usually additional hand tools to engage with the arbor and the power tool. Debris in the thread interlock, excessive operational torque eventually resulting from sudden tool locking and/or eventual corrosion in the thread interlock may cause thread locking. Thread locking may render a removal of the power tool from the arbor difficult if not impossible with conventional means.  
         [0007]     The problem of thread locking has been addressed in the prior art by transmitting the operational torque via additional interlocking features such as driving pins that extend from the arbor commonly in an axial direction at an offset from the central thread bolt. The power tool features pin holes at an offset corresponding to that of the driving pins such that after screwing on of the power tool to the arbor, the driving pins may be aligned with corresponding pin holes at certain orientations of the power tool relative to the arbor. In the prior art arbor systems, the driving pins are commonly held axially moveable and circumferentially rigid with respect to the arbor&#39;s thread bolt and may be engaged with the pin holes once aligned with each other. Because the driving pins transmit the operational load torque from the arbor via the pin holes onto the power tool, the central thread connection remains relatively lose irrespective of the operational torque. Disassembly of the power tool is therefore easily accomplished by axially removing the driving pins from the driving holes, followed by unscrewing the central thread connection.  
         [0008]     A significant shortcoming of prior art arbors, having axially moveable driving pins and a central thread connection, is that due to the defined circumferential orientation between the arbor and the power tool and necessary tolerances between arbor and power tool, the assembled power tool remains loosely attached to the arbor&#39;s thread bolt. This prevents precise control of the power tool. More importantly, the above described tilting torque that may need to be transmitted onto the power tool via the thread connection is very limited due to the loose interlocking of both threads.  
         [0009]     Construction workers operate tools in a rough and fast paced manner. Exchanging hole saws may likely be performed without verification of a proper tightening of the tightening features and eventually even without use of tightening tools. A reliable arbor system may need a snap feature to prevent inadvertent loosening between the arbor and the hole saw during operation. Prior art quick release arbor systems utilize a number of relatively intricate elements to provide snap in and/or ratchet features that may be sensitive to debris, rough handling and that may be difficult to maintain and replace.  
         [0010]     For the reasons presented above, there exists a need for an arbor system that on one hand provides easy assembly and disassembly unaffected by the operationally transmitted torque. On the other hand an arbor system is needed with fully defined and rigid connection between the arbor and the power tool. The thread connection is thereby needed to remain substantially unaffected by tilting torque and/or operational load torque. The present invention addresses these needs.  
         [0011]     Further more, there also exists a need for an arbor system that provides a reliable form fitting of mechanically highly dissimilar materials of arbor and hole saw body. The present invention addresses this need as well.  
         [0012]     Also, there exists a need for a quick release arbor system that provides a simple, robust and easily replaceable snap feature to prevent unintentional loosening during hole saw operation. The present invention addresses also this need.  
         [0013]     In prior art hole saw systems there are commonly arbors employed that feature a central thread for loosely engaging with a corresponding central thread of a saw body. Once the arbor and saw body are loosely connected via thread and thread hole an arbor clutch is axially engaged with crown pins in corresponding holes circumferentially arrayed on the saw body around the central thread hole. Thread connection as well as clutch connection remain loosely form fitting whereby it is relied on a certain self centering action of the saw teeth to provide a smooth hole cutting. In cases, where holes need to be sawed into harder materials, or materials with low stiffness such as sheet metal, the engaging saw teeth likely cause vibrations. Such vibrations may prevent a smooth hole cutting even for small hole cutting diameters below 4 inches. The vibrations may cause a hammering action in the loose interface between anchor the saw body, which may loosen even more the form fit and may increase the vibrations. Therefore there exists a need for a rigid hole saw arbor system that is easily connected and disconnected with a hole saw body while providing substantially rigid interlocking between the arbor and the hole saw body. The present invention addresses this need.  
         [0014]     To increase the tight screwed interlocking between hole saw and arbor it is desirable to utilize a tightening tool that may be easily and ergonomically applied for externally applying a tightening torque and a loosening torque. Even more, and In case of the arbor  10  being chucked in a hand held power drill it is of particular interest to utilize the power drill&#39;s operational torque for applying the tightening torque and loosening torque for fastest and most convenient exchange of varying sizes hole saws while the arbor remains chucked in the power drill. The arbor system should at the same time be compact and light in weight. Therefore there exists a need for an arbor system that provides for an external tool access to a tightening feature of the arbor system for a save and eventually power drill assisted tightening and loosening of the hole saw on the chucked arbor. The present invention addresses also this need.  
       SUMMARY  
       [0015]     A releasable arbor system connects a chucked arbor to an axially operating power tool that operationally rotates around a rotation axis. The arbor system includes an arbor, a clamp body of the power tool, a tightening feature and an optional snap feature. The arbor has an arbor flanging feature and a first thread axially extending along the rotation axis. The arbor further includes at least one but preferably three driving pins extending from the arbor flanging feature at an offset to the rotation axis.  
         [0016]     The clamp body has a core with a tool flanging feature correspondingly shaped with the arbor flanging feature. The clamp body also features a pin hole for axially engaging with the arbor&#39;s driving pin, a clamp face opposite the tool flanging feature and a core shaft extending through the core axially along the rotation axis and aligned with the first thread.  
         [0017]     The tightening feature has a second thread corresponding to the first thread and a tightening face corresponding to the clamp face. While at least one of the first thread and the second thread extends through the core shaft and while the first thread and the second thread are tight-screwed interlocking, a pressed contact is established either between the flanging features together with the driving pin and pin hole or between at least three driving pins and three pin holes.  
         [0018]     The pressed contact provides a releasable fix that is axially, radially and circumferentially form fitting such that the tight-screwed interlocking remains substantially unaffected of operational tilt torque and operational load torque.  
         [0019]     The arbor may be a monolithic structure, preferably made of a high strength metal such as steel or steel alloy. The clamp body may also be a monolithic structure, preferably made of a light metal such as aluminum, aluminum alloy, and the like. The clamp body may also be made of plastic.  
         [0020]     The first thread may be an outside thread of a thread bolt and the tightening feature may be a nut with the second thread being an internal thread. The first thread may alternately be an internal thread and the tightening feature may be a screw with the second thread being an outside thread.  
         [0021]     The arbor flanging feature may include an arbor stud correspondingly shaped to the core shaft, both providing the radial form fitting. The arbor flanging feature may further include an arbor face facing substantially axially with respect to the rotation axis. In that case, the clamp flanging feature has a flange face correspondingly shaped to the arbor face, both providing the axial form fitting. The arbor flanging feature may alternately be provided by at least three driving pins and at least three pin holes, both preferably conical for a snug engaging, irrespective of fabrication tolerances and/or adverse operation influences such as debris deposits and/or corrosion. Driving pins and holes may be circumferentially arrayed with respect to the rotation axis.  
         [0022]     The tightening feature may have a profiled circumference for tool assisted actuation. The tightening feature may also have a snap serration interacting with a circumferentially rigid snap feature having an engaging position and a releasing position. At least during the tight-screwed interlocking, the engaging position is established by snap interlocking of the snap feature in the snap serration. The tightening feature is consequently prevented at least from unscrewing off the thread bolt. During the releasing position, the snap feature disengages the snap serration for intentional unscrewing the tightening feature.  
         [0023]     The snap feature is preferably held by a spring load in the engaging position and is movable against the spring load into the releasing position. The snap feature may be a spring loaded snap pin slidable along a snap axis. The snap axis may be parallel to the rotation axis. The snap pin may be guided within at least one driving pin extending through the clamp body. The driving pin, snap serration and snap axis may be positioned with respect to an outside circumference of the tightening feature such that the driving pin is accessible for moving to and holding in the releasing position while the profiled circumference is circumferentially actuated by either a tightening feature tool or by hand. The snap serration may be an integral part of the outside circumference.  
         [0024]     The snap feature may also be a resiliently suspended snap tongue having a suspended end and a free end with a snap profile correspondingly shaped and positioned with respect to the snap serration for snap interlocking with the snap serration. The snap tongue may be part of a washer sandwiched between the clamp body and the tightening feature. The washer may have a pin fit corresponding and interlocking with the driving pin extending through and above the clamp body&#39;s pin hole such that the washer is at least circumferentially rigid with respect to the arbor.  
         [0025]     The snap serration may have a sliding face configured to force the snap feature into the releasing position while the tightening feature is rotated in a free rotation direction, which is preferably a tightening direction in which the nut is screwed on the first thread towards the clamp body.  
         [0026]     The snap tongue may be suspended inward and tangential such that the snap tongue operates in conjunction with the snap serration as a ratchet. The ratchet provides the free rotation direction and a locking rotation direction.  
         [0027]     The power tool is preferably a hole saw. The arbor system provides a simple and reliable attachment and quick release of varying size hole saws while the arbor preferably remains chucked in a power drill. For smaller diameter hole saw bodies an arbor system may include a tubular socket wrench tool that extends axially beyond a hole saw body height and the pilot drill while axially engaging with the tightening feature. In that way, the anchor may be easily tightened and loosened also in cases of small hole saw body diameters. The tubular socket wrench externally engages in an axially opposing direction of an power drill in which the arbor may be chucked. In that way the tubular socket wrench may be conveniently rigidly held while the tightening torque or loosening torque is applied by via the power drill. Due to the axial alignment of the socket wrench and the preferably centering encompassing of the tightening feature, a tool slip off may be avoided and the power assisted tightening and loosing performed in a save and ergonomic fashion.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0028]      FIG. 1  is a first perspective exploded view of the arbor system according to a first embodiment of the invention.  
         [0029]      FIG. 2  is the first perspective view of the assembled arbor system of  FIG. 1 .  
         [0030]      FIG. 3  is the first perspective view of the arbor of the first embodiment having a central recess face.  
         [0031]      FIG. 4  is the first perspective view of the arbor according to a second embodiment.  
         [0032]      FIG. 5  is the first perspective exploded view of the arbor system according to a third embodiment of the invention.  
         [0033]      FIG. 6  is the first perspective view of the assembled arbor system of  FIG. 5 .  
         [0034]      FIG. 7  is the first perspective exploded view of the arbor system according to a fourth embodiment of the invention.  
         [0035]      FIG. 8  is a second perspective view of the assembled arbor system of  FIG. 7 .  
         [0036]      FIG. 9  shows a third perspective view of a nut having serrations with sliding faces.  
         [0037]      FIG. 10  is the second perspective view of an arbor system including a snap pin and the nut of  FIG. 9 .  
         [0038]      FIG. 11  is the second perspective view of an arbor system with a ratchet tongue washer and the nut of  FIG. 9  shown in disassembled spacing.  
         [0039]      FIG. 12  is the arbor system of  FIG. 11  with the nut of  FIG. 9  in assembled position.  
         [0040]      FIG. 13  is fourth perspective exploded view of a fifth embodiment of the invention including a tubular socket wrench.  
         [0041]      FIG. 14  is a front view of the fifth embodiment without tubular socket wrench.  
         [0042]     FIG. AA is a cut view of  FIG. 14  as indicated in  FIG. 14  by section line A-A.  
         [0043]      FIG. 15  is a front view of the fifth embodiment with tubular socket wrench.  
         [0044]     FIG. BB is a cut view of  FIG. 15  as indicated in  FIG. 15  by section line B-B.  
     
    
     DETAILED DESCRIPTION  
       [0045]     As in  FIGS. 1 and 2 , an arbor system  1  includes an arbor  10 , a clamp body  20  and a tightening feature  30 . The arbor  10  has an arbor body  12  having an arbor flanging feature, which includes according to a first embodiment an arbor face  13  and an arbor stud  14 . From the arbor stud  14  extends a first thread  16  in the exemplary form of an outside thread of a thread bolt. The first thread  16  extends at least axially with respect to a rotation axis RA. Arbor stud  14  and first thread  16  are preferably also concentric with respect to the rotation axis RA. At least one but preferably three driving pins  15  extend from the arbor body  12  in an offset to the rotation axis RA. Opposite the driving pin(s)  15  extends a well known chucking stud  11  for concentrically chucking the arbor  1  with respect to the rotation axis RA in a well known chuck of a power drill or the like. From the arbor body  12  extends a well known pilot drill  17  concentric with respect to the rotation axis RA. The arbor  10  is preferably monolithically fabricated from high strength metal such as steel or steel alloy. While the arbor  1  is chucked in the power drill, the arbor  1  is operationally rotated around the rotation axis RA.  
         [0046]     The clamp body  20  may be part of a power tool that preferably operates axially with respect the rotation axis RA. Such a power tool is preferably the cross referenced I-Joist Hole Cutting Apparatus. The clamp body  20  has a core  22  with a core shaft  24  and pin hole(s)  25 . Either the first thread  16  or a second thread  36  of a tightening feature  30  extends through the core  22  to screw on and interlock across the core  22 . In the exemplary Figures, the first thread  16  as part of the thread bolt extends through core  22 , moreover the tightening features  30 ,  40 ,  60  are nuts. The clamp body  20  may be monolithically fabricated from light metals such as aluminum, aluminum alloy and the like. The clamp body  20  may also be made of plastic.  
         [0047]     The axial, radial and circumferential form fitting provides for low peak stresses in the pressed contact areas and consequently for a combination of arbor material and clamp body material with highly dissimilar mechanical properties. This again contributes advantageously to a cost effective fabrication of a compact arbor  10  from expensive high strength material and at the same time a cost effective fabrication of a voluminous power tool body with integral clamp body  20  of a low cost and/or lightweight material. The arbor systems  1 - 4  as in the Figures are preferably configured to be chucked in a conventional hand held power drill having a common chucking capacity of up to about ½ inch and to releasable fix a power tool for cutting holes into wood and wood like material with hole diameter of up to about 12 inches.  
         [0048]     The pin hole(s)  25  are positioned and shaped for axially engaging with the driving pin(s)  15 . On the clamp body&#39;s  20  side away from the arbor  10  is a clamp face  27 . On the clamp body&#39;s  20  side towards the arbor  10  is a flange face  23 . Flange face  23  and core shaft  24  may be part of a tool flanging feature correspondingly shaped to the arbor flanging feature. In particular and in reference to  FIGS. 1, 2 ,  FIGS. 4-7  and  FIGS. 9-11 , the flange face  23  corresponds to arbor face  13  providing an axial form fitting while the clamp body  20  is releasable fixed on the arbor  10 . Likewise and also in reference to  FIGS. 1, 2 ,  FIGS. 4-7  and  FIGS. 9-11 , the core shaft  24  corresponds to the arbor stud  14  providing a radial form fitting while the clamp body  20  is releasable fixed on the arbor  10 . Also in reference to  FIGS. 1, 2 ,  FIGS. 4-7  and  FIGS. 9-11 , the engaging of the driving pin(s)  15  in corresponding pin hole(s)  25  provides a circumferential form fitting while the clamp body  20  is releasable fixed on the arbor  10 . Tolerances and eventual gaps between driving pin(s)  15  and pin hole(s)  25  may be selected sufficiently large that radial form fitting between arbor shaft  14  and shaft fit  24  are not compromised. An operational torque received by the arbor  1  from the power drill, causes the driving pin(s)  15  to circumferentially contact the pin holes  25  such that the operational load torque LT may be coupled onto the clamp body  20  and the power tool. In the case of rotationally symmetric driving pins  15 , the operationally forced pin/hole contact may additionally contribute to a radial centering of the clamp body  20  relative to the arbor  10  as may be well appreciated by anyone skilled in the art.  
         [0049]     Arbor face  13  and arbor stud  14  may be combined into a first cone. In that case, the flange face  23  and the core shaft  24  may be a second cone correspondingly shaped to the first cone. The pressed contact between the first and the second cone provides simultaneously the axial and the radial form fitting.  
         [0050]     The tightening feature  30  has an outside circumference  31 , a tightening face  37  and an internal thread  36  with which it may be screwed on and tightened on the first thread  16 . The outside circumference  31  may be profiled to engage with and be actuated by a well known nut tool and/or to ergonomically assist a manual actuation.  
         [0051]     During a tight-screwed interlocking of the first thread  16  and the second thread  36 , either the arbor flanging feature is in pressed contact with the tool flanging feature, according to  FIGS. 1 -3 , or at least three driving pins  15  are in pressed contact with correspondingly shaped pin holes  25 , according to  FIG. 4 . The pressed contact warrants a releasable fix that is axially, radially and circumferentially form fitting such that the tight-screwed interlocking remains substantially unaffected by an operational tilt torque TT and an operational load torque LT.  
         [0052]     The operational tilt torque TT may result from a wobbling motion induced by an operator onto a hand held power drill in the chuck of which the arbor  1  is chucked. The wobbling motion may be induced with respect to a pilot hole drilled with the pilot drill  17  to partially lift the rotating cutting teeth out of the a cutting groove for the purpose of clearing the cutting groove from cutting debris, for reducing cutting friction and/or for reducing contact area between cutting teeth and cut material as may be well appreciated by anyone skilled in the art.  
         [0053]     Reducing the cut contact area provides for a cut contact pressure at a level necessary for material removal at a limited feed force. The feed force may be limited by an operator&#39;s physical strength. The rotating cutting teeth may be part of the rotating power tool in the preferred configuration of the cross referenced I-joist Hole Cutting Apparatus. The operational load torque LT results from rotating the power tool via the power drill&#39;s chuck against a cutting resistance of the power tool&#39;s engaging teeth as may be well appreciated by anyone skilled in the art. The wobbling motion contributes substantially to simple, inexpensive and fast cutting of holes into wood and wood like materials with diameters of 12 inch and above at the construction site by merely utilizing a freely hand held power drill in combination with the I-joist Hole Cutting Apparatus.  
         [0054]     Referring to  FIG. 3 , the arbor flanging feature may have a recess face  19  such that the axial form fitting between arbor face  13  and flange face  23  is ring shaped along the outer circumference of the arbor body  12 . As a favorable result, the pressed contact is established primarily along the arbor body&#39;s  12  circumference. This again provides for reduced stress peaks from tilt torque TT and for a reduced pressed contact as may be well appreciated by anyone skilled in the art. Consequently, the pressed contact may be established by merely hand tightening the tightening features  30 ,  40 ,  60 , which greatly simplifies exchange of power tools on the arbor  10 . The ring shaped axial form fit may be provided alternately or in combination with the arbor recess face  19  by any well known recess feature fabricated into the core  22 .  
         [0055]     In  FIG. 4 , the arbor flanging feature may be omitted and the pressed contact established between at least three driving pins  15  snuggly engaging with correspondingly shaped pin holes  25 . In that case, the driving pins  15  may be conical to warrant the releasable fix. The driving pins  15  are preferably evenly circumferentially arrayed with respect to the rotation axis RA to evenly distribute the contact pressure, operational pressure from tilt torque TT and operational load torque LT.  
         [0056]      FIGS. 5-12  pertain to embodiments that include a circumferentially rigid snap feature  18 ,  57 ,  77  having an engaging position and a releasing position. The engaging position is established at least while the tightening feature  40 ,  60  is tightly screwed on the first thread  16 . In the engaging position, the snap feature is snap interlocking in a snap serration of the tightening feature  40 ,  60  and at least prevents it from unscrewing the first thread  16 . In the releasing position, the snap feature  18 ,  57 ,  77  disengages the snap serration for unscrewing the tightening feature  40 ,  60  from the first thread  16 . The snap feature is preferably held by a spring load in the engaging position and is movable against the spring load into the releasing position. The spring load may result from a natural resilience of the snap feature  57 ,  77  or, as in the case of the snap feature  18 , from an additional spring member such as a well known coil spring.  
         [0057]     Referring to  FIGS. 5, 6  and  10 , the arbor system  2 ,  3  includes the snap feature  18  in the configuration of a snap pin  18 . A coil spring or the like may be internally pushing against the snap pin  18 . The snap pin  18  is spring loaded and slidable along a snap axis SA, which is preferably parallel to the rotation axis RA. The snap pin  18  is preferably part of the arbor  10  and is guided within at least one of the driving pin(s)  15 , which interlocks with a pin hole  25  extending through the core  22 . The snap pin  18  has a natural snap height SH larger than a flange height  20 H such that it extends through the clamp body  20  and snap interlocks with a snap serration  48 ,  68  at least while the serration nut  40  is tightly screwed on the first thread  16 . The snap interlocking is preferably spring loaded. The snap pin  18 , the snap serration  48 ,  68  and the snap axis SA are preferably positioned with respect to an outside circumference of the tightening feature  40 ,  60  such that the snap pin  18  is accessible for being moved into and held in the releasing position while the outside circumference of the tightening feature  40 ,  60  is circumferentially actuated either manually or by a well known tightening feature tool. The snap serration is preferably an integral part of the outside circumference.  
         [0058]     In  FIGS. 7, 8  and  11 ,  12 , the snap feature is a resiliently suspended snap tongue  57 ,  77  along the free end of which a snap profile  58 ,  78  is correspondingly shaped and positioned with respect to the snap serrations  48 ,  68 . The snap tongue  57 ,  77  is naturally in the engaging position and snap interlocking with the snap serration  48 ,  68 . The snap tongue  57 ,  77  may be forced into the releasing position. The snap tongue  57 ,  77  may be part of a washer  50 ,  70  sandwiched between the clamp body  20  and the tightening feature  40 ,  60 . The washer  50 ,  70  may be positioned at least circumferentially rigid by a driving pin  15  extending through and above the corresponding pin hole  25  and interlocking with a corresponding pin fit  55 ,  75  of the washer  50 ,  70 .  
         [0059]     Referring to  FIGS. 9-12 , the snap serration  68  may have a sliding face  681  configured for forcing the snap feature  18 ,  57 ,  77  into the releasing position while the tightening feature  60  is rotated in a free rotation direction FR. The free rotation direction FR is preferably the direction in which the tightening feature  60  is screwed on. A number of snap serrations  68  may be placed along the outer circumference of the tightening feature  60  and rotationally symmetric with respect to the tightening axis TA, which is the center axis for the second thread  66 . The tightening axis TA preferably coincides with the rotation axis RA. The snap serration  60  may also have a resting face  682  and a stopping face  683  against which the snap feature  18 ,  57 ,  77  presses with spring load. The stopping face  683  is configured to inhibit inadvertent movement of the tightening feature  40 ,  60  out of the engaging position.  
         [0060]     According to  FIGS. 11, 12 , the snap tongue  77  is configured to additionally assist the ratchet operation of the snap serration(s)  68 . The snap tongue  77  extends substantially inward and tangential with respect to the rotation path of the snap serration  48 ,  68 . The ratchet has a free rotation direction FR and an opposite locking rotation direction.  
         [0061]     To provide the a maximum of interlocking threads while keeping the height of the tightening feature  30 ,  40 ,  60  and/or the eventual thread bolt to a minimum above the clamp face  27 , the arbor stud  14  may be substituted by a similarly operating cylindrical protrusion axially protruding off the tightening face  37 ,  47 ,  67  in case of a thread bolt, the first thread  16  in the configuration of an outside thread may extend all the way to the arbor face  13  providing more threads for the tightening feature to engage  30 ,  40 ,  60  with. While the tightening feature  30 ,  40 ,  60  is tightened, the cylindrical protrusion centers within the core shaft  24  contributing to the radial form fitting. In case of the first thread  16  being an internal thread, the arbor stud  14  may be substituted by an arbor shaft inward extending from the arbor face  13  followed by the first thread  16 . The cylindrical protrusion may thereby simultaneously center in the core shaft  24  and the arbor shaft while the tightening feature  30 ,  40 ,  60  is in the tight-screwed interlocking with the arbor  10 . The present invention includes embodiments in which driving pins  15  are provided by the clamp body  20  and the pin holes  25  provided by the arbor  10 .  
         [0062]     Arbor stud  14 , arbor face  13 , driving pins  15  may also be seen as parts of an arbor coupling and flange face  23 , core shaft  24  and pin holes  25  may also be seen as parts of a tool coupling correspondingly shaped to the arbor coupling. As shown in  FIGS. 13-15 , the clamp body  20  may also be part of a well known conventional hole saw having a saw rim  28  with saw teeth  29  as is well known in the art for sawing holes of up to about 4 inches diameter.  
         [0063]     The rigid combination between the arbor coupling and the chucking stud  11  is a significant contribution for the axially, radially and circumferentially rigid hold of the hole saw  20  against operational tilt torque, operational load torque and operational sawing vibrations. A tubular wrench  80  may be additionally employed for externally applying a tightening torque and/or loosening torque onto a torque receiving feature of the tightening feature  30 . The torque receiving feature may be in case of a well known hex nut its outside circumference  31 . The tubular wrench  80  may have a tightening feature mating end  81  corresponding to the torque receiving feature. While the first thread  16  or the second thread  36  is extending through the core shaft  24  and while the first thread  16  and the second thread  26  are in screwed engagement, the tightening feature  30  is externally accessible preferably by the tubular wrench  80  from a direction substantially axially opposite the chucking stud  11 . Also while the first thread  16  or the second thread  36  is extending through the core shaft  24  and in a tight-screwed interlocking a pressed contact is established between the tool coupling and the arbor coupling on one side and between said clamp face  27  and said tightening face  37  on the other side. The tubular wrench  80  has an inner clearance including an inner clearance diameter  80 DI and an inner clearance height  80 HI. The inner clearance is larger than the pilot drill  17  while the tubular wrench  80  is engaging with the torque receiving feature  31  via the tightening feature mating end  81 . The tubular wrench  80  has an outer clearance including an outer clearance diameter  80 DA and an outer clearance height  80 HA. The outer clearance is fitting within the saw rim  28  while the tubular wrench  80  is engaging with the torque receiving feature  31  via the tightening feature mating end  81 . Part of the tubular wrench  80  is also an access feature for externally rigidly holding the tubular wrench  80 . The access feature may include a cross pin  85  as indicated in the  FIGS. 13 -15 .  
         [0064]     The tightening feature mating end  81  is preferably self centering engaging with the tightening feature  31  and substantially concentric with respect to the chucking stud  11 . In case of the tightening feature  30  being a hex nut, the tubular wrench  80  may be a tubular socket wrench  80 .  
         [0065]     The tubular wrench  80  may further include a teeth guard  87  radially extending from the body  83  of the tubular wrench  80  in the outer clearance height  80 HA from a stop face  82  of said tubular wrench  80  such that the cutting teeth  29  are shielded by the teeth guard  87  while the tightening feature mating end  81  is engaging with the torque receiving feature  31 . The teeth guard  87  may have an outer diameter sufficiently large to reliably shield the teeth  29  of a maximum diameter hole saw  20 . The teeth guard  87  prevents harmful contact of the teeth  29  with an operators hand holding the tubular wrench around the access feature  85 . Particularly in the case where a hand held power drill is rotating the chucked arbor  10  and the hole saw  20  while the tubular wrench  20  is hand held for a power drill assisted tightening or loosening of the tightening feature  30 , high rotational speeds and fast teeth  29  movements are safely kept away from the operators hand.  
         [0066]     Accordingly, the scope of the invention described in the specification above is set forth by the following claims and their legal equivalent.