Patent Publication Number: US-9839985-B1

Title: Fixture assembly

Description:
FIELD 
     The present disclosure relates to a fixture assembly, and more particularly, to a fixture assembly for holding a tool for a tool-sharpening operation. 
     BACKGROUND 
     This section provides background information related to the present disclosure and is not necessarily prior art. 
     Fixtures are commonly used for securing a workpiece during a machining operation. For example, a fixture may be used to hold a drill bit to sharpen the tip of the drill bit. Conventional fixtures for holding drill bits for sharpening operations must be realigned relative to a sharpening tool for drill bits having different diameters. That is, if drill bits of different diameters are to be sharpened, an operator must realign a conventional fixture relative to the sharpening tool for each drill bit diameter. Such repeated realignment of the fixture consumes substantial amounts of time, which substantially increases costs associated with sharpening numerous drill bits of a variety of different diameters. 
     The present disclosure provides a fixture that can hold drill bits (or other workpieces) of various diameters without having to realign the fixture relative to the sharpening tool for each diameter. That is, the fixture of the present disclosure can hold a drill bit having a first diameter for a sharpening operation before and/or after holding another drill bit having a second diameter for a sharpening operation without having to realign the fixture relative to the sharpening tool to account for the difference between the first and second diameters. Such capability can save substantial amounts of time, money and resources for a user that is sharpening many drill bits of various diameters. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     The present disclosure provides a fixture assembly that may include a housing, a clamp assembly, and a drive mechanism. The clamp assembly may be movably mounted to the housing and may include a first clamp member and a second clamp member. The first and second clamp members may be linearly movable relative to the housing toward and away from each other. The drive mechanism may be coupled to the clamp assembly and the housing and may drive the clamp assembly relative to the housing such that the first clamp member moves linearly toward the second clamp member at a first speed in a first direction and the second clamp member moves linearly toward the first clamp member at a second speed in a second direction that is opposite the first direction. The first speed may be different than the second speed. 
     In some configurations, the drive mechanism includes a central plate that engages the first and second clamp members. The central plate may be received in the housing and may be slidable within the housing in a third direction that is perpendicular to the first and second directions. 
     In some configurations, the central plate includes a first side having a first clamp slot formed therein and a second side having a second clamp slot formed therein. The first and second sides may be opposite each other. The first clamp member may be slidably received in the first clamp slot and the second clamp member may be slidably received in the second clamp slot. 
     In some configurations, the first and second clamp slots are disposed at acute angles relative to the third direction. 
     In some configurations, the first clamp slot is disposed at a first acute angle relative to the third direction, and the second clamp slot is disposed at a second acute angle relative to the third direction. The first acute angle may be different than the second acute angle. 
     In some configurations, the housing includes a first guide slot and a second guide slot. The first guide slot may slidably receive a first slider block attached to the first clamp member. The second guide slot may slidably receive a second slider block attached to the second clamp member. The first slider block may move within the second guide slot in the first direction as the central plate moves in the third direction. The second slider block may move within the second guide slot in the second direction as the central plate moves in the third direction. 
     In some configurations, the first clamp member includes a first flat gripping surface and a second flat gripping surface that is angled relative to the first flat gripping surface. The first and second flat gripping surfaces may both engage a workpiece (e.g., a drill bit or other tool) and cooperate with the second clamp member to fix the workpiece relative to the housing. 
     In some configurations, an angle between the first flat gripping surface and the second direction is equal to the first angle. An angle between the second flat gripping surface and the second direction may be equal to the first angle. The second angle may be less than the first angle. 
     In some configurations, the second clamp member includes cylindrical rod having a longitudinal axis that is perpendicular to the third direction. 
     In some configurations, the first clamp member includes a first clamp arm and a first clamp block. The first clamp arm may be slidably received in the first clamp slot in the central plate. The first clamp block may be mounted to an end of the first clamp arm and may be pivotable relative to the first clamp arm about a first rotational axis that is parallel to the third direction. The first and second flat gripping surfaces may be mounted on the first clamp block. 
     In some configurations, the second clamp member includes a second clamp arm and a second clamp block. The second clamp arm may be slidably received in the second clamp slot in the central plate. The second clamp block may be mounted to an end of the second clamp arm and may be pivotable relative to the second clamp arm about a second rotational axis that is parallel to the third direction. The cylindrical rod may be mounted on the second clamp block. 
     In some configurations, the first and second flat gripping surfaces are defined by first and second wear pads, respectively, that are mounted to the first clamp block. Edges of the first wear pad may be clamped to fix the first wear pad to the first clamp block, and edges of the second wear pad may be clamped to fix the second wear pad to the first clamp block. 
     The present disclosure also provides a fixture assembly that may include a base (or housing), a clamp assembly, and a drive mechanism. The clamp assembly is movably mounted on the base and includes a first clamp member and a second clamp member. The first and second clamp members may be linearly movable relative to the base toward and away from each other. The drive mechanism is coupled to the clamp assembly and drives the clamp assembly relative to the base. The drive mechanism may include a first link attached to the first clamp member and a second link attached to the second clamp member. The first and second links may be coupled to each other such that linear movement of the first link at a first speed and in a first direction causes corresponding linear movement of the second link at a second speed and in a second direction that is opposite the first direction. The first speed is different than the second speed. 
     In some configurations, the first clamp member includes a first flat gripping surface and a second flat gripping surface that is angled relative to the first flat gripping surface. The first and second flat gripping surfaces may simultaneously engage a workpiece (for example, a tool such as a drill bit) and cooperate with the second clamp member to fix the workpiece relative to the base. 
     In some configurations, the second clamp member includes cylindrical rod having a longitudinal axis that is parallel with an intersection of planes defined by the first and second flat gripping surfaces. 
     In some configurations, the first and second links are parallel to each other and move linearly relative to each other along parallel paths of motion. 
     In some configurations, the first and second clamp members are movable in the first and second directions along a common track. 
     In some configurations, each of the first and second clamp members includes a slider block, a gripping block, an adjuster block, and a resiliently flexible plate. The gripping block may be mounted to the slider block and may include a cavity and a first slot that is open to (i.e., extends through to) the cavity. The adjuster block may be mounted to the slider block and may be disposed at least partially within the cavity. The adjuster block may include a second slot. The resiliently flexible plate is received in the first slot of the gripping block and the second slot of the adjuster block. Clearances between the adjuster block and walls of the gripping block that define the cavity may allow for relative lateral movement between the gripping block and the adjuster block. The resiliently flexible plate may resist the relative lateral movement between the gripping block and the adjuster block and bias the gripping block toward a nominal position relative to the adjuster block. 
     In some configurations, the relative lateral movement between the gripping block and the adjuster block bends the resiliently flexible plate about an axis that is perpendicular to the first and second directions of the linear movement of the first and second links. 
     In some configurations, each of the first and second clamp members includes a post that extends from the slider block and slidably engages the adjuster block to allow for movement of the adjuster block and the gripping block relative to the slider block along a length of the post in a direction that is perpendicular to the first and second directions of the linear movement of the first and second links. 
     In some configurations, the fixture assembly includes a threaded fastener engaging the adjuster block. The threaded fastener is rotatable relative to the adjuster block in one direction to fix the adjuster block relative to the post and in another direction to allow movement of the adjuster block along the length of the post. 
     In some configurations, the first link engages the slider block of the first clamp member, and the second link engages the slider block of the second clamp member. 
     The present disclosure also provides a method of clamping a first tool and a second tool in a fixture assembly. The fixture assembly may include a housing, a first clamp member and a second clamp member. The first and second tools may have different outer diameters. The method may include simultaneously driving the first and second clamp members relative to the housing and toward each other to clamp the first tool therebetween such that a centerline of the first tool is disposed at a given location relative to the housing; unclamping the first tool; and simultaneously driving the first and second clamp members relative to the housing and toward each other to clamp the second tool therebetween such that a centerline of the second tool is disposed at the given location relative to the housing. 
     In some configurations, the first clamp member is disposed a first distance from the given location while the first tool is clamped between the first and second clamp members, and the second clamp member is disposed a second distance from the given location while the first tool is clamped between the first and second clamp members. The first clamp member is disposed a third distance from the given location while the second tool is clamped between the first and second clamp members, and the second clamp member is disposed a fourth distance from the given location while the second tool is clamped between the first and second clamp members. A difference between the third and first distances is different than a difference between the fourth and second distances. 
     In some configurations, simultaneously driving the first and second clamp members toward each other includes driving the first clamp member at a first speed while simultaneously driving the second clamp member at a second speed that is different from the first speed. 
     In some configurations, simultaneously driving the first and second clamp members toward each other includes driving the first and second clamp members in opposite linear directions. 
     In some configurations, simultaneously driving the first and second clamp members toward each other includes moving a plate within the housing in a direction perpendicular to the directions in which the first and second clamp members move toward each other. 
     In some configurations, the plate includes a first clamp slot that slidably receives the first clamp and a second clamp slot that slidably receives the second clamp. 
     In some configurations, the first clamp slot is disposed at a first acute angle relative to the direction in which the plate moves within the housing, and the second clamp slot is disposed at a second acute angle relative to the direction in which the plate moves within the housing. The first acute angle is different than the second acute angle. 
     In some configurations, the method includes adjusting positions of the first and second clamp members relative to the base in a direction perpendicular to the opposite linear directions. The positions of the first and second clamp members can be adjusted relative to the base in this manner independently of each other. 
     In some configurations, the method includes adjusting an angle between the first and second clamp members. 
     In some configurations, spring members resist adjustment of the angle between the first and second clamp members. 
     In some configurations, the first clamp member includes first and second gripping surfaces that are disposed at an angle relative to each other. Clamping the first tool may include contacting the first tool with the first and second gripping surfaces. Clamping the second tool may include contacting the second tool with the first and second gripping surfaces. 
     In some configurations, the second clamp member includes a cylindrical rod that is parallel with an intersection of the first and second gripping surfaces. Clamping the first tool may include contacting the first tool with the cylindrical rod. Clamping the second tool may include contacting the second tool with the cylindrical rod. 
     In some configurations, the method includes adjusting an angle between a longitudinal axis of the cylindrical rod and an intersection of planes defining the first and second flat gripping surfaces. 
     In some configurations, the first and second tools are drill bits. 
     In some configurations, clamping the first tool includes contacting the drill bit at only three locations (e.g., the first clamp member contacts the first tool at two locations, and the second clamp member contacts the first tool at only one location). 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a perspective view of another fixture assembly according to the principles of the present disclosure with a cover removed to more clearly depict certain aspects of the fixture assembly; 
         FIG. 2  is a partially exploded view of the fixture assembly of  FIG. 11 ; 
         FIG. 3  is a plan view of a drill bit and the fixture assembly in an unclamped position; 
         FIG. 4  is a plan view of the drill bit and the fixture assembly in a clamped position; 
         FIG. 5  is a side view of the drill bit and the fixture assembly in a clamped position; 
         FIG. 6  is a partial side view of the fixture assembly clamping a first drill bit (shown in solid lines) and clamping a second drill bit (shown in phantom lines); 
         FIG. 7  is a cross-sectional view of the fixture assembly; 
         FIG. 8  is a cross-sectional view of a portion of the fixture assembly; 
         FIG. 9  is a perspective view of another fixture assembly according to the principles of the present disclosure; 
         FIG. 10  is a perspective view of yet another fixture assembly according to the principles of the present disclosure; 
         FIG. 11  is a perspective view of yet another fixture assembly according to the principles of the present disclosure; 
         FIG. 12  is a perspective view of yet another fixture assembly according to the principles of the present disclosure; 
         FIG. 13  is an exploded view of the fixture assembly of  FIG. 12 ; 
         FIG. 14  is a plan view of a drill bit and the fixture assembly in a fully open (unclamped) position; 
         FIG. 15  is a plan view of the drill bit and the fixture assembly of  FIG. 12  in a partially closed position and clamping the drill bit; 
         FIG. 16  is a plan view of the fixture assembly of  FIG. 12  in a fully closed position; 
         FIG. 17  is a top view of the fixture assembly of  FIG. 12  and the drill bit; 
         FIG. 18  is a side view of the fixture assembly of  FIG. 12 ; 
         FIG. 19  is a plan view of a central plate of the fixture assembly of  FIG. 12 ; 
         FIG. 20  is a plan view of an outer plate of the fixture assembly of  FIG. 12 ; and 
         FIG. 21  is a plan view of another outer plate of the fixture assembly of  FIG. 12 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     With reference to  FIGS. 1-8 , a fixture assembly  10  is provided that can hold tools (e.g., drill bits) or workpieces of different diameters without having to realign the fixture assembly  10  relative to a drill-bit-sharpening tool (not show) for each drill bit diameter. That is, the fixture assembly  10  can clamp a first drill bit  18  having a first diameter for a sharpening operation before and/or after clamping a second drill bit  20  ( FIG. 6 ) having a second diameter that is different than the first diameter for a drill bit sharpening operation without having to realign the fixture assembly  10  relative to the sharpening tool to account for the difference between the first and second diameters. Such capability can save substantial amounts of time, money and resources for a user that is sharpening many drill bits of various diameters. 
     The fixture assembly  10  may include a base (or housing)  12 , a clamp assembly  14 , and a drive mechanism  16 . The base  12  may be a rigid plate having a plurality of mounting apertures  22  for mounting the fixture assembly  10  to a machining apparatus such as a drill-bit-sharpening tool, for example. 
     The clamp assembly  14  may include a track  24 , a first clamp member  26 , and a second clamp member  28 . The track  24  may be fixedly mounted to the base  12 . The first and second clamp members  26 ,  28  are slidable along the track  24  relative to the base  12  and each other. As will be described in more detail below, the first and second clamp members  26 ,  28  are slidable along the track  24  in opposite directions (toward and away from each other) at different speeds. 
     As shown in  FIG. 2 , the first and second clamp members  26 ,  28  may include first and second slider blocks  30 ,  31 , first and second gripping blocks  32 ,  33 , first and second adjuster blocks  34 ,  35 , and first and second spring members (e.g., resiliently flexible plates)  36 ,  37 , respectively. The first and second slider blocks  30 ,  31  may each include a channel  38  that slidably receives the track  24 . In some configurations, ball bearings (not shown) can be attached to the slider blocks  30 ,  31  within the channel  38  to facilitate smooth slidable motion of the slider blocks  30 ,  31  along the track  24 . Each of the slider blocks  30 ,  31  may include an aperture  40  extending at least partially therethrough in a direction parallel to a longitudinal axis of the track  24 . The aperture  40  of the first slider block  30  may be laterally offset from the track  24  in a first direction, and the aperture  40  of the second slider block  31  may be laterally offset from the track  24  in a second direction that is opposite the first direction. In other words, the track  24  is disposed laterally between the apertures  40  of the first and second slider blocks  30 ,  31 . Each of the slider blocks  30 ,  31  may also include a post  41  that extends upward (when viewed from the frame of reference of  FIG. 2 ) therefrom. 
     The first gripping block  32  is mounted to the first slider block  30  and may include a generally V-shaped recess  42 . The V-shaped recess  42  may extend laterally through the first gripping block  32  in a direction perpendicular to the longitudinal axis of the track  24  (i.e., perpendicular to the directions along which the first and second clamp members  26 ,  28  slide along the track  24 ). First and second gripping pads  44 ,  46  may be mounted to the first gripping block  32  within the V-shaped recess  42 . The gripping pads  44 ,  46  can be hard, flat blocks that define first and second gripping surfaces  48 ,  50 , respectively, that both contact the drill bit  18 ,  20  when the clamp assembly  14  is clamping the drill bit  18 ,  20 . 
     As shown in  FIG. 5 , the gripping surfaces  48 ,  50  are angled relative to each other. In some configurations, the angle between the gripping surfaces  48 ,  50  is 90 degrees. Each gripping surface  48 ,  50  may be angled 45 degrees (i.e., half of the angle between the gripping surfaces  48 ,  50 ) relative to a horizontal plane that is parallel to the directions in which the first and second clamp members  26 ,  28  slide along the track  24 . It will be appreciated that the angle between the gripping surfaces  48 ,  50  may be more or less than 90 degrees, and the angle between the horizontal plane and the gripping surfaces  48 ,  50  may be more or less than 45 degrees. 
     The first gripping block  32  may also include a first cavity  52  ( FIGS. 7 and 8 ) and a first slot  54  ( FIG. 7 ) that is open to (i.e., extends through to) the first cavity  52 . The first adjuster block  34  may be at least partially disposed within the first cavity  52 . The first spring member  36  may be at least partially disposed within the first slot  54 . 
     As shown in  FIGS. 7 and 8 , the second gripping block  33  is mounted to the second slider block  31  and may include a protrusion  56 , a second cavity  53 , and a second slot  55  that is open to (i.e., extends through to) the second cavity  53 . The protrusion  56  may extend generally toward the first gripping block  32  and may cooperate with a plate  58  to fixedly engage a hardened cylindrical wear pad (e.g., a cylindrical rod)  60 . A longitudinal axis of the cylindrical wear pad  60  may be parallel to and aligned with an intersection of planes defined by the first and second gripping surfaces  48 ,  50  of the first gripping block  32 . As shown in  FIGS. 5 and 6 , the cylindrical wear pad  60  and the first and second gripping surfaces  48 ,  50  contact the outer diameter of the drill bit  18 ,  20  to hold the drill bit  18 ,  20  in place when the clamp assembly  14  is in the clamped position. 
     The first and second adjuster blocks  34 ,  35  may be mounted to the first and second slider blocks  30 ,  31 , respectively, and may be at least partially received within the cavities  53  of the first and second gripping blocks  32 ,  33 , respectively. Each of the first and second adjuster blocks  34 ,  35  may include an aperture  62 , a clamping slot  64 , and a spring slot  66 . The posts  41  of the first and second slider blocks  30 ,  31  may be movably received within the apertures  62  of the first and second adjuster blocks  34 ,  35 , respectively. 
     The clamping slot  64  extends through three sides of the adjuster block  34 ,  35  and into the aperture  62 . Threaded fasteners  68  ( FIG. 5 ) extend through the clamping slot  64  and engage the adjuster block  34 ,  35  on both sides of the clamping slot  64 . The threaded fasteners  68  can be threadably tightened and loosened to contract and expand the aperture  62  to tighten and loosen the fit of the adjuster block  34 ,  35  on the post  41 . When the fit of the adjuster block  34 ,  35  on the post is loosened, the position of the adjuster block  34 ,  35  (and thus, the gripping block  32 ,  33 ) along the length of the post  41  can be adjusted, as shown in  FIG. 8 . When the fit of the adjuster block  34 ,  35  on the post is tightened, the position of the adjuster block  34 ,  35  (and thus, the gripping block  32 ,  33 ) along the length of the post  41  is fixed. 
     The spring slots  66  of the first and second adjuster blocks  34 ,  35  may receive the first and second spring members  36 ,  37 , respectively. In some configurations, fasteners may engage the adjuster blocks  34 ,  35  and the spring members  36 ,  37  to fix an end of each spring member  36 ,  37  relative to the corresponding adjuster block  34 ,  35 . 
     With the first spring member  36  received within the spring slot  66  of the first adjuster block  34  and within the slot  54  of the first gripping block  32 , the resilient flexibility of the first spring member  36  allows the first gripping block  32  to move laterally and/or pivot about an axis that is perpendicular to directions of linear movement of the first and second clamp members  26 ,  28  along the track  24  and parallel to the longitudinal axis of the post  41 . Similarly, with the second spring member  37  received within the spring slot  66  of the second adjuster block  35  and within the slot  54  of the second gripping block  33 , the resilient flexibility of the second spring member  37  allows the second gripping block  33  to move laterally and/or pivot about an axis that is perpendicular to directions of linear movement of the first and second clamp members  26 ,  28  along the track  24  and parallel to the longitudinal axis of the post  41 . In this manner, an angle between the first and second gripping blocks  32 ,  33  can be adjusted to accommodate a tapered drill bit shaft  21  (having a taper angle α), as indicated by arrows A in  FIG. 7 . The spring members  36 ,  37  bias the gripping blocks  32 ,  33  toward a nominal position in which the gripping blocks  32 ,  33  are parallel to each other (e.g., to accommodate a constant diameter drill bit shaft). 
     As shown in  FIGS. 1-4 , the drive mechanism  16  may include an actuator  70 , a first link  72 , a second link  74 , and a lever  76 . The actuator  70  can be any type of actuator, including an electric motor, a hydraulic actuator, a pneumatic actuator (e.g., using a compressed air source), or a manual spring-loaded toggle switch, for example. 
     The first and second links  72 ,  74  may be elongated generally cylindrical rods, for example. A first end  80  of the first link  72  may engage an output shaft  78  ( FIG. 2 ) of the actuator  70 , and a second end  82  of the first link  72  may be attached to the first slider block  30  (e.g., clamped or otherwise fixedly received within the aperture  40  of the first slider block  30 ). An intermediate portion  84  of the first link  72  may be slidably and pivotably coupled to the lever  76 . A first end  86  of the second link  74  may be slidably and pivotably coupled to the lever  76 , and a second end  88  of the second link  74  may be attached to the second slider block  31  (e.g., clamped or otherwise fixedly received within the aperture  40  of the second slider block  31 ). 
     As shown in  FIG. 2 , the lever  76  may include a first slot  90  extending through one end of the lever  76  and a second slot  92  extending through the other end of the lever  76 . An aperture  94  may extend through the lever  76  at a location between the first and second slots  90 ,  92 . A lever pivot pin  96  may extend through the aperture  94  and engage the base  12  to allow the lever  76  to rotate relative to the base  12 . The lever  76  is rotatable relative to the base  12  about a rotational axis R ( FIGS. 1, 3, and 4 ) that is defined by the lever pivot pin  96  and the aperture  94 . The aperture  94  (and thus, the rotational axis R of the lever  76 ) may be located closer to the second slot  92  and the second link  74  than the first slot  90  and the first link  72 . In other words, the aperture  94  (and thus, the rotational axis R of the lever  76 ) may be off-center relative to a longitudinal center point of the lever  76 . 
     The intermediate portion  84  of the first link  72  and the first end  86  of the second link  74  may each include an aperture  97  ( FIG. 2 ) extending therethrough. Link pivot pins  98  may extend through the apertures  97  and corresponding ones of the first and second slots  90 ,  92  to rotatably couple the first and second links  72 ,  74  to the lever  76 . The first and second slots  90 ,  92  slide along the link pivot pins  98  as the lever  76  rotates relative to the base  12  about the lever pivot pin  96 , as shown in  FIGS. 3 and 4 . 
     A guide block  100  may be fixedly mounted to the base  12  and may include first and second apertures  102 ,  104  ( FIG. 2 ) that slidably receive the first and second links  72 ,  74 , respectively. The apertures  102 ,  104  in the guide block  100  extend longitudinally parallel to the length of the track  24  such that the guide block  100  supports the first and second links  72 ,  74  and guides the motion of the first and second links  72 ,  74  in linear directions parallel to the length of the track  24 . 
     In some configurations, a cover  106  ( FIGS. 1, 2 and 7 ) may be mounted to the base  12  to protect portions of the drive mechanism  16  from damage. The cover  106  may be disposed over the lever  76 , the guide block  100 , and portions of the first and second links  72 ,  74 . The first and second links  72 ,  74  may be movable through apertures  108 ,  110  in the cover  106 . 
     In operation, the actuator  70  can be selectively actuated by a user to move the clamp assembly  14  between an unclamped position ( FIG. 3 ) relative to the drill but  18 ,  20  and a clamped position ( FIG. 4 ) relative to the drill bit  18 ,  20  (in which the first and second clamp members  26 ,  28  clamp the drill bit  18 ,  20  in place). To move the clamp assembly  14  from the unclamped position to the clamped position, the actuator  70  may be operated to cause linear movement of the first link  72  in a first direction (i.e., to the right when viewed from the frame of reference of  FIG. 3 ) parallel to the length of the track  24 . Such movement of the first link  72  moves the first clamp member  26  linearly along the track  24  in the first direction (i.e., toward the second clamp member  28 ) and causes the lever  76  to rotate about rotational axis R (i.e., in a clockwise direction when viewed from the frame of reference of  FIG. 3 ). Such rotation of the lever  76  causes the second link  74  to move linearly in a second direction that is opposite the first direction, thereby moving the second clamp member  28  linearly along the track  24  in the second direction (i.e., toward the first clamp member  26 ). 
     Because the rotational axis R is located closer to the second link  74  than the first link  72 , linear movement of the first link  72  at a first speed results in the linear movement of the second link  74  at a second speed that is slower than the first speed. That is, operation of the actuator  70  causes movement of the first link  72  and the first clamp member  26  in one linear direction along the track  24  at a first speed and movement of the second link  74  and the second clamp member  28  in the opposite direction along the track  24  at a second speed that is slower than the first speed. 
     The positioning of the rotational axis R along the length of the lever  76  determines the difference between the first and second speeds (positioning the rotational axis R closer to the longitudinal center of the lever  76  decreases the difference between the first and second speeds, and positioning the rotational axis R further from the longitudinal center of the lever  76  increases the difference between the first and second speeds). The positioning of the rotational axis R may be selected to achieve a predetermined difference or a predetermined proportionality between the first and second speeds. The predetermined difference or proportionality between the first and second speeds will cause the first and second clamp members  26 ,  28  to clamp the first drill bit  18  at a location such that a longitudinal center C 1  of the first drill bit  18  is positioned at a predetermined location relative to the base  12  and will also cause the first and second clamp members  26 ,  28  to clamp the second drill bit  20  (which has a diameter that is larger than a diameter of the first drill bit  18 ) a location such that a longitudinal center C 2  of the second drill bit  20  is also positioned at the same predetermined location relative to the base  12 , as shown in  FIG. 6 . In other words, the predetermined difference or proportionality between the first and second speeds will cause the first and second clamp members  26 ,  28  to clamp any drill bit having any size diameter at the same predetermined location relative to the base  12  without making any adjustments to the positions of the gripping surfaces  48 ,  50  relative to the first slider block  30  or any adjustments of the position of the cylindrical wear pad  60  relative to the second slider block  31 . 
     The first and second clamp members  26 ,  28  move at different speeds because they move different distances to clamp a drill bit at the predetermined location relative to the base  12 . As shown in  FIG. 6 , when the first drill bit  18  is clamped in the clamp assembly  14 , a given point on the first clamp member  26  is disposed at a first distance D 1  from the center C 1  of the first drill bit  18  (the center C 1  is at the predetermined location relative to the base  12 ) and a given point on the second clamp member  28  is disposed a second distance D 2  from the center C 1 . When the second drill bit  20  is clamped in the clamp assembly  14 , the given point on the first clamp member  26  is disposed at a third distance D 3  from the center C 2  of the second drill bit  20  (the center C 2  is at the predetermined location relative to the base  12 ) and the given point on the second clamp member  28  is disposed a fourth distance D 4  from the center C 2 . The difference between the third and first distances D 3 , D 1  is greater than the difference between the fourth and second distances D 4 , D 2 . Therefore, the drive mechanism  16  moves the first clamp member  26  at a faster speed than the second clamp member  28  so that the first and second clamp members  26 ,  28  will both come into contact with the outer diameter of the drill bit at the same time and at locations at which the center of the drill bit will be at the predetermined location relative the base  12 , regardless of the size of the diameter of the drill bit. 
     The ability of the fixture assembly  10  to clamp any drill bit having any size diameter at the same predetermined location relative to the base  12  eliminates the need for a user to realign the fixture assembly  10  relative to a drill bit sharpening tool for drill bits of different diameters. Such capability can save substantial amounts of time, money and resources for a user that is sharpening many drill bits of various diameters. 
     With reference to  FIG. 9 , another fixture assembly  210  is provided that may include a base (or housing)  212 , a clamp assembly  214 , and a drive mechanism  216 . The structure and function of the base  212  and the clamp assembly  214  may be similar or identical to that of the base  12  and the clamp assembly  14  described above, and therefore, will not be described again in detail. 
     The drive mechanism  216  may include an actuator  270 , a first link  272 , a second link  274 , and a lever  276 . The structure and function of the actuator  270  can be similar or identical to that of the actuator  70 . Like the first link  72 , one end of the first link  272  may engage an output shaft of the actuator  270  and the other end of the first link  272  may engage a slider block of a first clamp member  226  of the clamp assembly  214 . An intermediate portion  284  of the first link  272  may include a slot  285  that slidably and pivotably engages a first end  290  of the lever  276 . One end of the second link  274  may include a slot  275  that slidably and pivotably engages a second end  292  of the lever  276 . The other end of the second link  274  may engage a slider block of a second clamp member  228  of the clamp assembly  214 . The lever  276  also includes an aperture (like the aperture  94  described above) through which a pivot pin  296  extends. The pivot pin  296  engages the base  212  and defines a rotational axis (like the rotational axis R described above) about which the lever  276  is rotatable. 
     In a similar manner as described above, the actuator  270  may be operated to cause linear movement of the first link  272  in a first direction parallel to the length of a track  224  mounted to the base  212 . Such movement of the first link  272  moves the first clamp member  226  linearly along the track  224  in the first direction and causes the lever  276  to rotate about rotational axis defined by the pivot pin  296 . Such rotation of the lever  276  causes the second link  274  to move linearly in a second direction that is opposite the first direction, thereby moving the second clamp member  228  linearly along the track  224  in the second direction. Because the rotational axis defined by the pivot pin  296  is disposed closer to the second end  292  of the lever  276  than the first end  290  of the lever  276 , linear movement of the first link  272  at a first speed results in linear movement of the second link  274  at a second speed that is slower than the first speed. In this manner, operation of the drive mechanism  216  results in movement of the clamp assembly  214  in substantially the same manner as operation of the drive mechanism  16  causes movement of the clamp assembly  14 , as described above. Accordingly, like the fixture assembly  10 , the fixture assembly  210  can clamp drill bits of various diameters at the same predetermined location relative to the base  212 , as described above. 
     With reference to  FIG. 10 , another fixture assembly  310  is provided that may include a base (or housing)  312 , a clamp assembly  314 , and a drive mechanism  316 . The structure and function of the base  312  and the clamp assembly  314  may be similar or identical to that of the base  12  and the clamp assembly  14  described above, and therefore, will not be described again in detail. 
     The drive mechanism  316  may include an actuator  370 , a first link  372 , a second link  374 , and a gear set  376  disposed between the first and second links  372 ,  374 . The structure and function of the actuator  370  can be similar or identical to that of the actuator  70 . Like the first link  72 , one end of the first link  372  may engage an output shaft of the actuator  370  and the other end of the first link  372  may engage a slider block of a first clamp member  326  of the clamp assembly  314 . One end of the second link  374  may engage a slider block of a second clamp member  328  of the clamp assembly  314 . The first and second links  372 ,  374  both include a linear arrangement of gear teeth  375  spanning at least a portion of the lengths of the first and second links  372 ,  374 . 
     The gear set  376  may include a first gear  377 , a second gear  379 , and a third gear  381 . The first, second and third gears  377 ,  379 ,  381  are rotatably mounted to the base  312 . The first gear  377  meshingly engages the gear teeth  375  of the first link  372  and meshingly engages the second gear  379 . The third gear  381  meshingly engages the gear teeth  375  of the second link  374  and meshingly engages the second gear  379 . The third gear  381  may have a larger diameter than the first and second gears  377 ,  379 . 
     The actuator  370  may be operated to cause linear movement of the first link  372  in a first direction parallel to the length of a track  324  mounted to the base  312 . Such movement of the first link  372  moves the first clamp member  326  linearly along the track  324  in the first direction and causes rotation of the first gear  377 . Such rotation of the first gear  377  is transmitted to the second and third gears  379 ,  381 , which causes the second link  374  to move linearly in a second direction that is opposite the first direction, thereby moving the second clamp member  328  linearly along the track  324  in the second direction. Because the third gear  381  has a larger diameter than the first and second gears  377 ,  379 , linear movement of the first link  372  at a first speed results in linear movement of the second link  374  at a second speed that is slower than the first speed. In this manner, operation of the drive mechanism  316  results in movement of the clamp assembly  314  in substantially the same manner as the movement of the clamp assembly  14  described above. Accordingly, like the fixture assembly  10 , the fixture assembly  310  can clamp drill bits of various diameters at the same predetermined location relative to the base  312 , as described above. 
     With reference to  FIG. 11 , another fixture assembly  410  is provided that may include a base (or housing)  412 , a clamp assembly  414 , and a drive mechanism  416 . The structure and function of the base  412  and the clamp assembly  414  may be similar or identical to that of the base  12  and the clamp assembly  14  described above, and therefore, will not be described again in detail. 
     The drive mechanism  416  may include an actuation assembly  470 , a first link  472 , and a second link  474 . The actuation assembly  470  may include an actuator  476 , a first drive block  478 , a second drive block  480 , and a drive link  482 . The structure and function of the actuator  476  can be similar or identical to that of the actuator  70 . An output shaft of the actuator  476  may be coupled to the drive link  482  and may move the drive link  482  linearly up and down (relative to the frame of reference of  FIG. 11 ). 
     The first and second drive blocks  478 ,  480  may be similar to first and second slide blocks  430 ,  431  (which may be similar or identical to slide blocks  30 ,  31 ) of the first and second clamp member  426 ,  428 . The drive blocks  478 ,  480  and the slide blocks  430 ,  431  are slidable along a track  424  mounted to the base  412 . One end of the first link  472  may engage the first drive block  478  and the other end of the first link  472  may engage the first slide block  430  such that the first drive block  478  and the first slide block  430  move together along the track  424 . One end of the second link  474  may engage the second drive block  480  and the other end of the second link  474  may engage the second slide block  431  such that the second drive block  480  and the second slide block  431  move together along the track  424 . 
     The first and second drive blocks  478 ,  480  may include first and second guide plates  484 ,  486 , respectively. The first and second guide plates  484 ,  486  may include first and second slots  490 ,  492 , respectively. The drive link  482  may slidably engage both of the slots  490 ,  492 . The first slot  490  is angled relative to the track  424  (i.e., angled relative to the directions in which the drive blocks  478 ,  480  slide along the track  424 ) such that the first slot  490  extends vertically upward as the first slot  490  extends horizontally toward the first and second clamp members  426 ,  428 . The second slot  492  is angled relative to the track  424  (i.e., angled relative to the directions in which the drive blocks  478 ,  480  slide along the track  424 ) such that the second slot  492  extends vertically downward as the second slot  492  extends horizontally toward the first and second clamp members  426 ,  428 . The angle of the second slot  492  relative to the track  424  is a steeper angle than the angle of the first slot  490  relative to the track  424 . 
     The actuator  476  can be operated to move the drive link  482  vertically up and down (i.e., toward and away from the track  424 ). Movement of the drive link  482  causes the drive blocks  478 ,  480  (and thus, the clamp members  426 ,  428 ) to move in opposite directions as the drive link  482  slides along the slots  490 ,  492 . That is, linear downward movement of the drive link  482  causes the first drive block  478  to move along the track  424  away from the second clamp member  428  and causes the second drive block  480  to move along the track toward the first clamp member  426 , which moves the first and second clamp members  426 ,  428  away from each other. Linear upward movement of the drive link  482  causes the first drive block  478  to move along the track  424  toward the second clamp member  428  and causes the second drive block  480  to move along the track away from the first clamp member  426 , which moves the first and second clamp members  426 ,  428  toward each other. 
     Since the angle of the second slot  492  relative to the track  424  is a steeper angle than the angle of the first slot  490  relative to the track  424 , upward and downward movement of the drive link  482  along the slots  490 ,  492  causes the first drive block  478  (and thus, the first clamp member  426 ) to move at a faster speed along the track  424  than the second drive block  480  (and thus, the second clamp member  428 ). Therefore, like the fixture assembly  10 , the fixture assembly  410  can clamp drill bits of various diameters at the same predetermined location relative to the base  412 , as described above. 
     Referring now to  FIGS. 12-21 , another fixture assembly  510  is provided that can clamp drill bits of various diameters at the same predetermined location relative to the housing  512 , as described above. That is, the fixture assembly  510  can hold drill bits (or other tools or workpieces) of different diameters without having to realign the fixture assembly  510  relative to a drill-bit-sharpening tool (not show) for each drill bit diameter. That is, the fixture assembly  510  can clamp the first drill bit  18  having a first diameter for a sharpening operation before and/or after clamping the second drill bit  20  having a second diameter that is different than the first diameter for a drill bit sharpening operation without having to realign the fixture assembly  510  relative to the sharpening tool to account for the difference between the first and second diameters, as described above. When the first drill  18  is clamped in the fixture assembly  510 , the longitudinal centerline of the first drill bit  18  is in the same location relative to the housing  512  (and the sharpening tool) as the longitudinal centerline of the second drill bit  20  when the second drill bit  20  is clamped in the fixture assembly  510 . 
     The fixture assembly  510  may include a housing (or base)  512 , a drive mechanism  514 , and a clamp assembly  516 . The housing  512  may include a first outer plate  518 , a second outer plate  520 , an end plate  522 , and a pair of side plates  524 . The plates  518 ,  520 ,  522 ,  524  cooperate to define a cavity  526  having an opening  525 . The plates  518 ,  520 ,  522 ,  524  may be fixedly attached to each other by fasteners, for example. In some configurations, one or more of the plates  518 ,  520 ,  522 ,  524  could be integrally formed with another one or more of the plates  518 ,  520 ,  522 ,  524 . One or more of the plates  518 ,  520 ,  522 ,  524  may include mounting apertures  527  for mounting the fixture assembly  510  to a drill bit sharpening tool (not shown), for example. As shown in  FIG. 20 , the first outer plate  518  may include a first guide slot  528 . As shown in  FIG. 21 , the second outer plate  520  may include a second guide slot  530 . As shown in  FIGS. 14-16 , the first and second guide slots  528 ,  530  extend in directions that are parallel to each other (i.e., longitudinal axes of the guide slots  528 ,  530  are parallel to each other). The first and second guide slots  528 ,  530  are formed in surfaces of the first and second outer plates  518 ,  520  that face each other and define the cavity  526 . 
     The drive mechanism  514  may include a central plate  532  and an actuator  534  drivingly connected to the central plate  532 . The central plate  532  may be slidably received in the cavity  526  of the housing  512  and may include a first clamp slot  536  and a second clamp slot  538  (see  FIGS. 14-16 and 19 ). As shown in  FIG. 19 , the first and second clamp slots  536 ,  538  are formed in opposite sides of the central plate  532 . That is, the first clamp slot  536  is formed in a first side of the central plate  532  that faces the first outer plate  518 , and the second clamp slot  538  is formed in a second side of the central plate  532  that faces the second outer plate  520 . The central plate  532  may also include a cutout  540  having an opening that faces the end plate  522 . 
     The actuator  534  can be any suitable type of actuator that can move the central plate  532  within the cavity  526  of the housing  512 , as shown in  FIGS. 14-16 . For example, the actuator  534  could be an electromechanical actuator, a pneumatic actuator, or a hydraulic actuator. The actuator  534  may include an actuator housing  542  and a piston  544 . The piston  544  may engage the cutout  540  in the central plate  532  and may extend through an aperture in the end plate  522 . The actuator housing  542  could include a hydraulic cylinder containing hydraulic fluid, a pneumatic cylinder containing compressed air, a solenoid, or an electric motor, for example, that may selectively move the piston  544  relative to the housing  512  back and forth in actuation directions AD ( FIGS. 14-16 ). Such movement of the piston  544  drives the central plate  532  in the actuation directions AD relative to the housing  512 . 
     As shown in  FIGS. 14-16 , the first clamp slot  536  is disposed at a first acute angle A 1  relative to the actuation directions AD, and the second clamp slot  538  is disposed at a second acute angle A 2  relative to the actuation directions AD. That is, a longitudinal axis of the first clamp slot  536  extends at the first acute angle A 1  relative to the actuation directions AD, and a longitudinal axis of the second clamp slot  538  extends at the second acute angle A 2  relative to the actuation directions AD. The first acute angle A 1  may be different angle than the second acute angle A 2 . The first acute angle A 1  may be a larger angle than the second acute angle A 2 . For example, the first acute angle A 1  may be 45 degrees and the second acute angle A 2  may be 35 degrees. 
     As shown in  FIGS. 14-16 , the clamp assembly  516  may include a first clamp member  546  and a second clamp member  548  that are movable relative to the housing  512  and each other in first and second opposite directions D 1 , D 2  between a fully open position ( FIG. 14 ) and a fully closed position ( FIG. 16 ). As shown in  FIG. 15 , the first and second clamp members  546 ,  548  can clamp the drill bit  18 ,  20  at any position between the fully open and fully closed positions. The first and second directions D 1 , D 2  are perpendicular to the actuation directions AD. 
     The first clamp member  546  may include a first clamp arm  550  and a first clamp block (or gripping block)  552  disposed on an end of the first clamp arm  550 . The second clamp member  548  may include a second clamp arm  554  and a second clamp block (or gripping block)  556  disposed on an end of the second clamp arm  554 . As shown in  FIG. 17 , the first clamp block  552  may be fastened to the first clamp arm  550  by a single pin or fastener  558 , and the second clamp block  556  may be fastened to the second clamp arm  554  by another single pin or fastener  558 . In this manner, the position of the clamp blocks  552 ,  556  on the clamp arms  550 ,  554  can be adjusted by rotating the clamp blocks  552 ,  556  relative to the clamp arms  550 ,  554  about rotational axes RA ( FIG. 14 ) that are parallel to the actuation directions AD. The rotational axes may be defined by the pins  558 . Accordingly, an angle between the first and second clamp blocks  552 ,  556  can be adjusted to accommodate the tapered drill bit shaft  21  ( FIG. 17 ). 
     The first clamp block  552  may include a generally V-shaped recess  560 . The V-shaped recess  560  may extend laterally through the first clamp block  552  in a direction perpendicular to the first and second directions D 1 , D 2  and perpendicular to the actuation directions AD. First and second gripping pads  562 ,  564  may be mounted to the first clamp block  552  within the V-shaped recess  560 . The gripping pads  562 ,  564  can be hard, flat blocks that define first and second flat gripping surfaces  566 ,  568 , respectively, that both contact the drill bit  18 ,  20  when the clamp assembly  516  is clamping the drill bit  18 ,  20 , as shown in  FIG. 15 . 
     As shown in  FIGS. 14-16 , the gripping surfaces  566 ,  568  are angled relative to each other. In some configurations, the angle between the gripping surfaces  566 ,  568  is 90 degrees. Each gripping surface  566 ,  568  may be angled 45 degrees (i.e., half of the angle between the gripping surfaces  566 ,  568 ) relative to the first and second directions D 1 , D 2 . It will be appreciated that the angle between the gripping surfaces  566 ,  568  could be more or less than 90 degrees, and the angle between the gripping surfaces  566 ,  568  and the first and second directions D 1 , D 2  may be more or less than 45 degrees. 
     As shown in  FIGS. 14-17 , the gripping pads  562 ,  564  may be secured to the first clamp block  552  by a plurality of clamps  570  mounted to the first clamp block  552  by fasteners  572 . That is, a pair of the clamps  570  contact and clamp against opposing edges of the first gripping pad  562  (as shown in  FIG. 17 ), and another pair of the clamps  570  contact and clamp against opposing edges of the second gripping pad  564 . Clamping the gripping pads  562 ,  564  to the first clamp block  552  may allow for more accurate placement of the gripping pads  562 ,  564  than other methods of fixing the gripping pads  562 ,  564  to the first clamp block  552  such as adhesive bonding (since it can be difficult to apply a layer of adhesive having a uniform thickness, and a layer of adhesive having a non-uniform thickness would change the relative angles of the gripping pads  562 ,  564  relative to each other and relative to the first and second directions D 1 , D 2 ). 
     The second clamp block  556  may include a protrusion  574  that extends generally toward the first clamp block  552  and may cooperate with a plate  576  to fixedly engage a hardened cylindrical wear pad (e.g., a cylindrical rod)  578 . As shown in  FIG. 15 , the cylindrical wear pad  578  and the first and second gripping surfaces  566 ,  568  contact the outer diameter of the drill bit  18 ,  20  to hold the drill bit  18 ,  20  in place when the clamp assembly  516  is in the clamped position. An angle between a longitudinal axis of the cylindrical wear pad  578  and an intersection of planes defined by the first and second gripping surfaces  566 ,  568  can be adjusted by rotating the clamp blocks  552 ,  556  relative to the clamp arms  550 ,  554  about rotational axes RA, as described above. 
     As shown in  FIGS. 14-16 , the first and second clamp arms  550 ,  554  of the first and second clamp members  546 ,  548  may be elongated members that are slidably received in the first and second clamp slots  536 ,  538 , respectively, of the central plate  532 . The first clamp arm  550  includes a first slider block  580  attached thereto and extending therefrom. The first slider block  580  is slidably received in the first guide slot  528  formed in the housing  512 . The second clamp arm  554  includes a second slider block  582  attached thereto and extending therefrom. The second slider block  582  is slidably received in the second guide slot  530  formed in the housing  512 . 
     The first and second guide slots  528 ,  530  are perpendicular to the actuation directions AD (i.e., longitudinal axes of the guide slots  528 ,  530  are perpendicular to the actuation directions AD and parallel to each other and the first and second directions D 1 , D 2 ). Therefore, as shown in  FIGS. 14-16 , when the drive mechanism  514  causes the central plate  532  to move relative to the housing  512  in one of the actuation directions AD, the slider blocks  580 ,  582  move linearly along the guide slots  528 ,  530  in the first and second opposite directions D 1 , D 2 , thereby causing the first and second clamp members  546 ,  548  to slide within the clamp slots  536 ,  538  and move linearly relative to the housing  512  toward each other or away from each other in the first and second directions D 1 , D 2 . That is, when the central plate  532  moves away from the end plate  522 , the slider blocks  580 ,  582  move away from each other in the first and second directions D 1 , D 2  along their respective guide slots  528 ,  530  and the clamp blocks  552 ,  556  move toward each other in the first and second directions D 1 , D 2 . When the central plate  532  moves toward the end plate  522 , the slider blocks  580 ,  582  move toward each other in the first and second directions D 1 , D 2  along their respective guide slots  528 ,  530  and the clamp blocks  552 ,  556  move away from each other in the first and second directions D 1 , D 2 . 
     Since the first clamp slot  536  is disposed at a larger angle (i.e., the first acute angle A 1 ) relative to the actuation directions AD than the angle at which the second clamp slot  538  is disposed (i.e., the second acute angle A 2 ), movement of the central plate  532  in the actuation directions AD will cause the first clamp block  552  to move linearly relative to the housing  512  at a first speed that is faster than a second speed at which the second clamp block  556  will move linearly relative to the housing  512 . 
     The predetermined difference or proportionality between the first and second speeds will cause the first and second clamp blocks  552 ,  556  to clamp the first drill bit  18  at a location such that the longitudinal center C 1  of the first drill bit  18  is positioned at a predetermined location relative to the housing  512  and will also cause the first and second clamp blocks  552 ,  556  to clamp the second drill bit  20  (which has a diameter that is larger than a diameter of the first drill bit  18 ) a location such that the longitudinal center C 2  of the second drill bit  20  is also positioned at the same predetermined location relative to the housing  512 , as shown in  FIG. 6  and described above with reference to the fixture assembly  10 . In other words, the predetermined difference or proportionality between the first and second speeds will cause the first and second clamp blocks  552 ,  556  to clamp any drill bit having any size diameter at the same predetermined location relative to the housing  512  without making any adjustments to the positions of the gripping surfaces  566 ,  568  relative to the first clamp block  552  or any adjustments of the position of the cylindrical wear pad  578  relative to the second clamp block  556 . 
     The first and second clamp blocks  552 ,  556  move at different speeds because they move different distances to clamp a drill bit at the predetermined location relative to the housing  512 . As shown in  FIG. 6  with reference to the fixture assembly  10 , when the first drill bit  18  is clamped in the clamp assembly  516 , a given point on the first clamp member  546  is disposed at a first distance D 1  from the center C 1  of the first drill bit  18  (the center C 1  is at the predetermined location relative to the housing  512 ) and a given point on the second clamp member  548  is disposed a second distance D 2  from the center C 1 . When the second drill bit  20  is clamped in the clamp assembly  516 , the given point on the first clamp member  546  is disposed at a third distance D 3  from the center C 2  of the second drill bit  20  (the center C 2  is at the predetermined location relative to the housing  512 ) and the given point on the second clamp member  548  is disposed a fourth distance D 4  from the center C 2 . The difference between the third and first distances D 3 , D 1  is greater than the difference between the fourth and second distances D 4 , D 2 . Therefore, the drive mechanism  514  moves the first clamp member  546  at a faster speed than the second clamp member  548  so that the first and second clamp members  546 ,  548  will both come into contact with the outer diameter of the drill bit at the same time and at locations at which the center of the drill bit will be at the predetermined location relative the housing  512 , regardless of the size of the diameter of the drill bit. 
     The ability of the fixture assembly  510  to clamp any drill bit having any size diameter (within the range or capacity of a given fixture assembly  510 ) at the same predetermined location relative to the housing  512  eliminates the need for a user to realign the fixture assembly  510  relative to a drill bit sharpening tool for drill bits of different diameters. Such capability can save substantial amounts of time, money and resources for a user that is sharpening many drill bits of various diameters. 
     The configuration of the first and second clamp blocks  552 ,  556  described above (i.e., the first clamp block  552  having the gripping pads  562 ,  564  that cooperate to form a V-shape, and the second clamp block  556  having the cylindrical wear pad  578 ) and the manner in which the first and second clamp blocks  552 ,  556  grip the drill bit  18 ,  20  (i.e., the gripping pads  562 ,  564  and wear pad  578  cooperate to grip the drill bit  18 ,  20  at three locations) allow the fixture assembly  510  to grip drill bits (or other workpieces) of a wider range of diameters relative to other prior-art fixture assemblies. For example, unlike the fixture assemblies  10 ,  210 ,  310 ,  410 ,  510  of the present disclosure, a fixture assembly that grips a drill bit (or other workpiece) using two V-shaped grippers (such as the fixture assembly disclosed in U.S. Pat. No. 4,647,097) or three flat grippers (such as the fixture assembly disclosed in U.S. Pat. No. 4,399,639) cannot grip very small-diameter workpieces. That is, when a fixture assembly that grips a workpiece using two V-shaped grippers or three flat grippers is in a fully closed position (i.e., where the two V-shaped grippers are in contact with each other or where the three flat grippers are in contact with each other), very small-diameter workpieces cannot be gripped by these grippers. On the other hand, when the fixture assemblies  10 ,  210 ,  310 ,  410 ,  510  of the present disclosure are in the fully closed position (as shown in  FIG. 16 , for example), the cylindrical wear pad  578  and the gripping pads  562 ,  564  are able to securely grip very small-diameter workpieces since the cylindrical wear pad  578  is able to get much closer to the intersection of the gripping pads  562 ,  564 . This configuration of the fixture assemblies  10 ,  210 ,  310 ,  410 ,  510  also allows for gripping of very large-diameter workpieces. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.