Abstract:
A bolt cutting tool comprises a bolt engaging portion and a cutting blade. The bolt engaging portion has at least one bolt-receiving bore, which is adapted for receiving a portion of a bolt to be cut. The cutting blade is rotatably connected to the tool generally adjacent the bolt engaging portion. The cutting blade has a cutting surface with an arcuate peripheral cutting edge. The cutting blade is adapted for rotation relative to the bolt-receiving bore from a pre-cut starting position toward a post-cut finishing position. The blade is adapted to rotate in a manner so that the arcuate peripheral cutting edge of the blade cuts the bolt as the cutting blade is rotated toward the post-cut finishing position. The blade is configured so that an angle of incidence between the cutting surface of the blade and a center axis of the bolt-receiving bore is less than 15 degrees when the blade is in its pre-cut starting position.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention pertains to an apparatus for sizing a bolt to a desired length. In particular, the apparatus of the present invention shears a bolt to a desired custom length, producing lead threads on the end of the bolt that are ready for use. Although bolts are available in a variety of standard pre-cut lengths (e.g., ½″, ¾″, 1″, 1½″) and such standard lengths are usually suitable for most applications, the apparatus of the present invention allows sizing of a bolt to any desired custom length. The apparatus of the present invention also allows use of the bolt immediately after sizing, without the need for any secondary finishing process.  
           [0002]    It is generally known to use grinding wheels and other similar cutting tools to cut or otherwise size a bolt or other mechanical fastener to a desired length. However, such methods are not ideal solutions in all cases. Often times, heat generated in a grinding process may tend to anneal a hardened bolt, thereby degrading its strength. Although coolants may be used to control the amount of generated heat, such coolants must be contained. The use of fluid coolants also tends to be messy and not worth the trouble for small jobs. Also, both the bolt and the cut-off end may be dangerously hot from the grinding or other cutting operation, such that the bolt may not be safely usable for some period of time. Such processes may also cause undesirable discoloration of the bolt or potentially dangerous smoke and sparks.  
           [0003]    There are other inherent problems in using conventional cutting tools for sizing a bolt to length. Cutting operations can be relatively time consuming. For example, in grinding, the processing time can be influenced by several factors including the type and size of the grinding wheel, the speed of rotation of the grinding wheel, the speed of advancement of the grinding wheel through the cut, and the material of the bolt. Also, there is usually a fair amount of set-up time involved in preparing a cutting tool for a sizing operation. For instance, in the case of a conventional rotary cut-off tool, a suitable grinding wheel must be mounted and the bolt must be properly secured relative to the wheel to allow its proper sizing. In many cases, there is also a fair amount of skill involved in cutting a bolt to ensure that its end is square that its lead threads are not damaged. Additionally, in some cutting operations, burrs may be formed on the end of the bolt, which must be removed through a secondary finishing operation before use.  
           [0004]    As an alternative to using a grinding wheel, smaller diameter bolts may be sheared to a desired length with other conventional cutting tools. However, in shearing, care must be used to ensure the lead threads at the bolt end are not damaged. If lead threads are damaged, the user must either discard the damaged bolt entirely or use a special die to re-cut the threads, which takes some measure of skill. Also, in shearing, care must be used to ensure the cut is as clean as possible without producing burrs on the end of the bolt, which may interfere with the bolt&#39;s engagement in a tapped hole or nut. Typically, bolts are made from hardened steel material, and any burrs formed during a sizing process can be difficult and time consuming to remove in secondary finishing operations, such as filing, grinding or sanding. The prior art does include hand tools intended for use in shearing bolts. However, in many cases, such hand tools are difficult to use, because such bolt-shearing operations, by their very nature, require a fair amount of force and proper securement of the bolt to achieve a clean cut without causing deformation of the bolt or damage to the lead threads.  
           [0005]    Thus, there is a need for a hand held bolt cutting tool that can be used to shear a bolt to a desired custom length, producing lead threads on the end of the bolt that are ready for use, without the need for any secondary finishing process.  
         SUMMARY OF THE INVENTION  
         [0006]    It is therefore an object of the present invention to provide a device for quickly and easily producing a ready to use bolt at a desired custom length without causing deformation of the bolt or damage to its lead threads. The apparatus of the present invention avoids many of the problems found in conventional grinding, sawing and cutting operations and provides a means for cutting commonly sized bolts for most any type of job.  
           [0007]    In general, a bolt cutting tool of the present invention comprises a bolt engaging portion and a cutting blade. The bolt engaging portion has at least one bolt-receiving bore, which is adapted for receiving a portion of a bolt to be cut. The cutting blade is rotatably connected to the tool generally adjacent the bolt engaging portion. The cutting blade has a cutting surface with an arcuate peripheral cutting edge. The cutting blade is adapted for rotation relative to the bolt-receiving bore from a pre-cut starting position toward a post-cut finishing position. The blade is adapted to rotate in a manner so that the arcuate peripheral cutting edge of the blade cuts the bolt as the cutting blade is rotated toward the post-cut finishing position. The blade is configured so that an angle of incidence between the cutting surface of the blade and a center axis of the bolt-receiving bore is less than 15 degrees when the blade is in its pre-cut starting position.  
           [0008]    In another aspect of the invention, the arcuate peripheral cutting edge of the cutting blade has a cut initiating portion and a cut finishing portion. The cut initiating portion of the arcuate peripheral cutting edge is adapted for initial engagement with a bolt received in the bolt-receiving bore when the cutting blade is in its pre-cut starting position. The cut finishing portion of the arcuate peripheral cutting edge is adapted for engagement with the bolt when the cutting blade is rotated toward its post-cut finishing position. The arcuate peripheral cutting edge has a radius of curvature that increases as the cutting edge extends from its cut initiating portion toward its cut finishing portion. The radius of curvature of at least a portion of the arcuate peripheral cutting edge increases at a rate that is greater than a constant rate as the cutting edge extends toward its cut finishing portion.  
           [0009]    In still another aspect of the invention, a bolt cutting tool comprises a bolt engaging portion and a cutting blade rotatably connected to the tool generally adjacent the bolt engaging portion. The bolt engaging portion has at least one bolt-receiving bore with an internally threaded portion. The internally threaded portion is adapted for threaded engagement with an externally threaded bolt to be cut. The internally threaded portion of the bore defines a major inside diameter of the bore and a minor inside diameter of the bore. The major inside diameter is larger than the minor inside diameter. The cutting blade has a cutting surface with an arcuate peripheral cutting edge. The blade is adapted for rotation relative to the bolt-receiving bore from a precut starting position toward a post-cut finishing position. The blade is adapted for rotation in a manner so that the arcuate peripheral cutting edge of the blade cuts the bolt as the cutting blade is rotated toward the post-cut finishing position. The arcuate peripheral cutting edge lies within a plane that is generally perpendicular to an axis of rotation of the cutting blade. An end portion of the bore adjacent to the plane is counterbored to a diameter larger than the minor inside diameter.  
           [0010]    While the principal advantages and features of the present invention have been described above, a more complete and thorough understanding and appreciation of the invention may be attained by referring to the drawings and detailed description of the preferred embodiments, which follow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a front elevational view of a bolt cutting tool of the present invention;  
         [0012]    [0012]FIG. 2 is a rear elevational view of the bolt cutting tool of FIG. 1;  
         [0013]    [0013]FIG. 3 is a side elevational view of the bolt cutting tool of FIG. 1;  
         [0014]    [0014]FIG. 4 is a fragmented front elevational view of the bolt holding end of the tool of FIG. 1, with the cutting blade removed to show detail;  
         [0015]    [0015]FIG. 5 is an enlarged plan view of the cutting blade;  
         [0016]    [0016]FIG. 6 is an enlarged side cross-sectional view of the cutting blade taken along the plane of line  6 - 6  in FIG. 5;  
         [0017]    [0017]FIG. 7 is an enlarged side cross-sectional view of the cutting blade taken along the plane of line  7 - 7  in FIG. 5;  
         [0018]    [0018]FIG. 8 is an enlarged side cross-sectional view of the cutting blade taken along the plane of line  8 - 8  in FIG. 5;  
         [0019]    [0019]FIG. 9 is an enlarged cross-section view of one of the tapped holes taken along the plane of line  9 - 9  in FIG. 4;  
         [0020]    [0020]FIG. 10 is a front elevational view of the bolt cutting tool of FIG. 1 in use with a bolt held in one of the tapped holes of the bolt holding end of the tool, with a wrench in engagement with the cutting blade for turning the blade, and with the cutting blade in a pre-cut starting position;  
         [0021]    [0021]FIG. 11 is a front elevational view of the bolt cutting tool similar to FIG. 10, but with the cutting blade rotated toward a post-cut finishing position;  
         [0022]    [0022]FIG. 12 is a graph illustrating how the angle of incidence between the cutting surface of the blade and the center axis of the bolt-receiving bore increases as the blade is rotated from its pre-cut starting position toward its post-cut finishing position;  
         [0023]    [0023]FIG. 13 is a graph illustrating how the radius of curvature of the arcuate peripheral cutting edge of the blade increases as the cutting edge extends from its cut initiating portion toward its cut finishing portion; and  
         [0024]    [0024]FIG. 14 is a front elevational view of an alternative embodiment of a bolt cutting tool of the present invention incorporating a gear driven mechanism for rotating a cutting blade. 
     
    
       [0025]    Reference characters used in these Figures correspond to reference characters used throughout the detailed description of the preferred embodiments, which follows.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    FIGS.  1 - 3  show a bolt cutting tool  20  of the present invention comprising a generally flat elongated tool shank  22  with a bolt holding end  24  and opposite handle  26 . The tool shank  22  is preferably made from a tool steel material that is hardenable and wear and impact resistant. Such tool steel materials may include AISI 4140 hardened to 55 Rockwell C. Preferably, the tool shank  22  is of sufficient length to enable the user to generate the necessary amount of leverage and torque to enable shearing of a bolt. The handle  26  may be provided with a hole  28  on its end to allow a user to hang the bolt cutting tool  20  on a hook for storage or from a tool belt. The bolt holding end  24  is provided with a cam shaped cutter  30  for cutting the bolt to a desired custom length. As will be described below in greater detail, the cam shaped cutter  30  is rotatably attached to the tool shank  22  and extends outward from a cutting side  32  of the tool shank.  
         [0027]    With reference to FIG. 4, the bolt holding end  24  is provided with a center cutter hole  34  for rotatably attaching the cam shaped shear cutter  30  to the tool shank, and a plurality of bolt receiving bores  36  are intermittently spaced about the center cutter hole for accommodating the bolt to be sized. Each of the bolt receiving bores  36  is preferably tapped for a different diameter size and thread style. For example, the bolt receiving bores may be tapped for #10-24 and #10-32, ¼″-20 and ¼″-28, {fraction (5/16)}″-18 and {fraction (5/16)}″-24, and ⅜″-16 and ⅜″-24. The bolt receiving bores  36  may also be tapped for standard metric sizes. The bolt receiving bores  36  are preferably arranged about the center cutter hole  34  in a manner to accommodate their number and size without degrading the strength of the tool shank. Preferably, the bolt receiving bores are spaced from the center cutter hole in a manner whereby the cutter acts upon the bolt as the cutter  30  rotates through at least 270°.  
         [0028]    As shown in FIGS.  5 - 8 , the cam shaped cutter  30  has a hexagonally shaped driver  38  that extends outward from the cutting side  32  of the tool shank that allows the cam shaped cutter to be rotated by using a standard wrench. Opposite the driver  38 , the cam shaped cutter  30  is formed with a bushing  40  that is received in the cutter hole  34  on the bolt holding end  24  (FIGS.  6 - 8 ). A tapped hole  42  is provided internal to the bushing  40  to allow the cam shaped cutter  30  to be rotatably secured in the center cutter hole  34  of the tool shank with a mechanical fastener  44  as shown in FIG. 3. Preferably, the driver  38 , cam shaped cutter  30 , and bushing  40  are formed monolithically from a hardened tool steel that can withstand impact and wear. AISI 4140 hardened to 55 Rockwell C is a suitable material for the cam shaped cutter, driver and bushing. The cam shaped cutter  30  has a cutting surface with a peripheral cutting edge  46  between the driver  38  and the bushing  40  that passes over the bolt receiving bores  36  as the cam shaped cutter is rotated. The peripheral edge  46  of the cutter engages the bolt in the bolt receiving bore to shear the bolt to the desired length.  
         [0029]    As shown in FIG. 5, the peripheral cutting edge  46  has the general form of a tear drop with a radius of curvature that increases from a cut initiating portion  50  of the cutter  30  to a cut finishing portion  52  of the cutter. To allow optimal positioning of the bolt relative to the cut initiating portion  50  of the cutter, a starting relief  54  is provided in the peripheral cutting edge  46  between the cut initiating portion  50  and the cut finishing portion  52 . Moving in a counter-clockwise direction (as viewed in FIG. 5), the rate at which the radius of curvature of the cutting edge  46  increases is preferably substantially constant from the cut initiating portion  50  of the cutting edge  46  to a point  56 , which is approximately 270 degrees (the 270° point) away from the start of the cut initiating portion  50 . After the 270° point, the radius of curvature preferably increases at a rate greater than a constant rate. FIG. 13 is a graphical representation (not necessarily to scale) of the rate of increase of the radius of curvature of the cutting edge  46  of the cam shaped cutter  30 . By increasing the radius gradually from the cut initiating portion to the 270° point, the speed of the cutter rotation relative to the bolt is kept relatively low and a large amount of torque can be generated to start the cut. By increasing the radius at a rate greater than a constant rate for the portion of the peripheral edge after the 270° point, the rate of movement of the cutting edge  46  through the bolt is increased, which ensures a cleaner cut with fewer burrs. Although a larger radius of curvature after the 270° point necessarily results in less torque, finishing the cut generally requires less torque than starting the cut. Thus, the radius of curvature can be dramatically increased, preferably after the 270° point, to accelerate the speed of the cut and prevent the formation of burrs on the end of the bolt. Preferably, the bolts are positioned in their bolt receiving bores at a distance from the cutter which enables the cut finishing portion  52  of the cutter  30  (after the 270° point) to pass through the bolt to complete the cut.  
         [0030]    To further enhance the efficiency of the cutter  30 , the peripheral cutting edge  46  has an incident angle  48 . Preferably, the incident angle  48  changes from the cut initiating portion  50  of the cutter  30  to the cut finishing portion  52 . Referenced from an axis of rotation  58  of the cam shaped cutter, the incident angle  48  of the peripheral cutting edge at the cut initiating portion is preferably shallow, being no more than 10-15 degrees, to ensure the user can attain the proper amount of leverage and torque for starting a smooth, shearing cut. More preferably, the incident angle  48  is about 7 degrees at the start of the cut. As the radius of curvature of the cam cutter  30  increases, the incident angle  48  also preferably increases or flattens outs where less leverage and shearing force is needed to complete the cut that has already been started. The higher incident angle towards the cut finishing portion  52  of the cutter also ensures a clean finish with fewer burrs. Moving in a counter-clockwise direction (as viewed in FIG. 5), the incident angle preferably increases at a substantially constant rate from the cut initiating portion  50  to about the 270° point, and after the 270° point, the rate of increase is preferably greater than a constant rate. FIGS.  6 - 8  provide further illustration of the increasing incident angles  48 ,  48   i ,  48   ii ,  48   iii ,  48   iv ,  48   v  along the peripheral cutting edge  46 . FIG. 12 provides a graphical representation of the rate of increase of the incident angle of the cam cutter, showing a greater than constant rate of increase for the incident angle after the 270° point. As stated previously, the bolts are preferably positioned in the bolt receiving bores at a distance from the cutter which enables the cut finishing portion of the cutter after the 270° point to pass through the bolt to cleanly and smoothly finish the cut.  
         [0031]    With reference to FIG. 9, on the cutting side  32  of the tool shank, each of the bolt receiving bores  36  preferably has a counterbore  60  with a diameter approximately equal to the major diameter of the thread of the bolt and a depth equal to the spacing of at least one to three threads. With the counterbore  60  in the bolt receiving bore, the force and stress exerted by the threads of the bolt against the tool in the bolt receiving bore during cutting is borne by substantially the entire internally threaded portion of the bolt receiving bore, rather than by the rim at the surface of the bolt receiving bore. The counterbore  60  in effect relieves a stress concentration point on the tool shank, thereby preventing chipping of the tool shank adjacent the bolt receiving bore during cutting.  
         [0032]    In operation, the bolt  62  to be sized is threaded into the applicable bolt receiving bore  36  such that the length desired to be removed extends from the bolt receiving bore on the cutting side  32  of the tool shank. The cam shaped cutter  30  may be rotated as necessary by hand to align the bolt in the starting relief  54 . As shown in FIGS.  10 - 11 , a box end wrench  64  or other suitable style wrench is engaged on the driver, and the cam shaped cutter  30  is rotated clockwise to move the starting relief  54  away from the bolt  62  and to force the peripheral cutting edge  46  into the bolt. To provide proper leverage, both the tool shank handle  26  and the driving wrench  64  are held on their respective distal ends with the bolt holding end  24  positioned away from the user. Preferably, the driver  38  extends axially away from the cutting side  32  of the tool shank a distance sufficient to ensure that the user&#39;s hand on the handle  26  remains clear of the driving wrench  64  when the driving wrench is rotated past the handle. Safety goggles should be used. Preferably, the driving wrench is rotated 360° to move the entire peripheral edge  46  of the cutter  30  through the bolt. By rotating the driving wrench, the cam shaped cutter  30  engages the bolt  62 , shearing it to the desired custom length. After shearing the bolt, the bolt may be unscrewed from its threaded hole and used as desired.  
         [0033]    Again, FIGS. 10 and 11 show the use of a box end wrench  64  or other suitable style wrench for rotating the driver  38  relative to the tool shank  22 . However, alternatively, the hexagonally shaped driver  38  could be secured in a vice, and the tool shank  22  then rotated relative to the vice-secured driver  38  to accomplish the same cutting operation. For heavy-duty cutting jobs, this manner of use may actually be preferred.  
         [0034]    [0034]FIG. 14 shows an alternative embodiment of the invention, which utilizes gear-driven multiplication to provide leverage, rather than relying on the length of the tool shank to provide the needed leverage. As shown in FIG. 14, a bolt cutting tool of this embodiment of the invention comprises a generally flat elongated tool shank  82  with a bolt holding end  84  and opposite handle  86 . Preferably, the tool shank  82  is of sufficient length to enable the user to comfortably grip the tool, but the length of the shank is not as important in this embodiment because the necessary leverage is provided by a gear mechanism that creates a mechanical advantage, as described hereinafter.  
         [0035]    The bolt holding end  84  is similar in most respects to the embodiment of FIGS.  1 - 4  and contains a plurality of bolt receiving bores (not shown). The bolt holding end  84  is provided with a cam shaped cutter  90 , which is similar in virtually all respects to the cutter  30  described above. However, as shown in FIG. 14, the present embodiment of the invention further comprises a drive gear  92  and a driven gear  94 . Preferably, the drive gear and the driven gear are each rotatably connected to the bolt holding end  84  of the tool generally adjacent one another and in operative engagement with one another so that rotational motion of the drive gear  92  is transmitted into rotational motion of the driven gear  94 . Preferably, the drive gear  92  is configured for manual operation by a user. The drive gear  92  may include a hand-operable handle (not shown) for manual rotation of the drive gear  92  by a user or, alternatively, may include a hexagonally shaped driver (not shown), similar to the driver  38  described above, adapted for engagement by a box end wrench or other suitable style wrench for rotating the drive gear  92  relative to the tool shank  82 . The driven gear  94  is preferably fixed relative to the cutter  90 , and may be formed monolithically therewith. Thus, in operation of this embodiment of the tool, the user rotates the drive gear  92 , which causes rotation of the driven gear  94 , which in turn cases rotation of the cutter  90 .  
         [0036]    As shown in FIG. 14, the radius of the driven gear  94  is preferably larger than the radius of the drive gear  92 , so that the two gears create a mechanical advantage through gear-driven multiplication, which provides leverage that assists the user in cutting a bolt with the tool. Preferably, the radius of the driven gear  94  is at least three times the radius of the drive gear  92 .  
         [0037]    While the present invention has been described by reference to specific embodiments and specific uses, it should be understood that other configurations could be constructed and other uses could be made without departing from the scope of the invention as set forth in the following claims.