Abstract:
An adjustable drill microstop is employed with a drill and a drill bit to limit the depth of a hole drilled into an object surface by the drill bit. The apparatus is comprised of a housing and a nose piece that is mounted for reciprocating movement of a pre-selected distance in the housing. The nose piece projects from one end of the housing and is positioned adjacent the object surface to receive the drilled hole. The nose piece has an opening into which the drill bit is inserted and the nose piece has an engagement surface that engages with the object surface during the drilling operation. During the drilling operation, the drill pushes the nose piece into the housing as the drill bit performs the drilling operation. The pre-selected distance that the nose piece reciprocates in the housing limits the depth of the hole drilled by the drill bit into the object surface. The apparatus is globally adjustable to calibrate the predetermined stops. The downward force of the nosepiece provides pressure on one or more layers to be drilled so interlaminar burrs are eliminated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (1) Field of the Invention  
         [0002]     The present invention pertains to an adjustable drill bit stop apparatus that is employed with a drill and drill bit to limit the depth of a hole drilled into a surface by the drill bit. More specifically, the apparatus is comprised of a housing and a nose piece that is mounted for reciprocating movement of a pre-selected distance in the housing. The nose piece projects from one end of the housing and is positioned adjacent the surface to receive the drilled hole. The drill bit extends through the apparatus from the opposite end of the housing and the drill engages with or is secured to the opposite end of the housing. The nose piece has an opening through which the drill bit extends and the nose piece has an engagement surface that engages with the surface to receive the hole during the drilling operation.  
         [0003]     During the drilling operation, the drill pushing on the housing pushes the nose piece into the housing as the drill bit performs the drilling operation. The pre-selected distance that the nose piece reciprocates in the housing limits the depth of the hole drilled by the drill bit into the surface.  
         [0004]     (2) Description of the Related Art  
         [0005]     In drilling holes into surfaces in manufacturing goods, the precise control of the hole depth or countersink depth is often desirable. This is particularly true in the manufacturing of aircraft components where it is often necessary that the head of a fastener inserted into a hole drilled into a surface of the aircraft component be flush with the surface of the component.  
         [0006]     Fasteners employed in manufacturing aircraft components such as an aircraft fuselage or a control surface are often countersunk style rivets and screws. Many components require the use of multiple sizes and styles of fasteners. This often requires that an aircraft manufacturing workstation have multiple drills set up for drilling a different countersink depth for each different fastener used. Thus, a number of different hand drills with different countersink depth setups are required at each workstation. If this manufacturing process could be improved where only one drill is needed to drill several different countersink depth holes, the time and costs associated with the process would be reduced.  
       SUMMARY OF THE INVENTION  
       [0007]     The adjustable drill microstop of the present invention allows a single drill to be used in performing the functions of two to six separate drill set ups at a workstation to drill two to six different countersunk holes. The adjustable drill bit stop apparatus of the invention can be used with a single drill, and can be adjusted to control the single drill to countersink holes in a surface at a variety of different desired depths. The construction of the adjustable drill stop apparatus is inexpensive to manufacture, and is easily operated by the assembly line worker.  
         [0008]     The apparatus is basically comprised of a cylindrical housing. The housing has a first end that is adapted to be positioned adjacent the drill. A plurality parallel slots extend through a side wall of the housing. Each slot corresponds to an adjusted depth of a countersunk hole that is drilled using the drill bit stop apparatus. A plurality of anvil surfaces are provided in the interior of the housing.  
         [0009]     A nose piece is mounted in a second end of the housing, opposite the housing first end. The nose piece is received in the housing for reciprocating movement of the nose piece in opposite first and second directions relative to the housing. An engagement surface of the nose piece projects from the housing second end. A plurality of stop surfaces are provided on the nose piece. The nose piece is rotatable in the housing to selectively position each stop surface of the nose piece in alignment with an anvil surface of the housing. As the nose piece is moved in the first direction into the housing, the aligned stop surface and anvil surface will abut against each other, thus limiting the distance to which the nose piece can move into the housing. By rotating different stop surfaces in alignment with the anvil surfaces, the distance to which the nose piece can be moved in the first direction into the housing is adjusted.  
         [0010]     A pin on the nose piece projects through the slots of the housing to indicate the adjusted position of the nose piece relative to the housing, and guide the nosepiece stop surfaces onto the anvil.  
         [0011]     A spring is provided in the housing between the nose piece and the first end of the housing. The spring biases the nose piece back toward the second end of the housing.  
         [0012]     In use of the adjustable drill bit stop apparatus, the apparatus is first adjusted to limit the drilled depth of a hole by positioning the nose piece pin in the appropriate slot in the housing. A drill having a drill bit is then positioned relative to the apparatus with the drill bit extending through the housing and into the nose piece. The tip of the drill bit is positioned at the desired location of the countersunk hole on the surface of the component. The drilling operation is initiated, and the drill is moved toward the component surface, causing the drill to push the apparatus toward the component surface and causing the nose piece drill engagement surface to engage with the component surface, pushing the nose piece into the housing. The adjusted position of the nose piece in the housing causes one of the nose piece stop surfaces to move in the first direction toward and engage with the anvil surface in the housing. This limits the extent of the nose piece movement through the housing, and thereby determines the depth of the countersunk hole drilled into the component surface by the drill bit.  
         [0013]     By moving the nose piece to different adjusted positions in the housing, the length of the nose piece movement in the housing is adjusted and thereby the depth of the countersunk hole drilled into the surface of the component is adjusted.  
         [0014]     The individual positions and anvil offsets correspond to the variations in different countersink depths that the microstop is designed to drill. A mechanism and method of globally adjusting the drill depth of all positions in 0.001″ increments is integral to the design. In practice the drill depth of one position is adjusted to nominal with the global adjust feature and by design the drill depth of all of the positions will be correctly adjusted. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Further features of the invention are set forth in the following detailed description of the preferred embodiment of the invention and in the following drawing figures wherein:  
         [0016]      FIG. 1  is a housing end perspective view of the adjustable drill microstop apparatus of the invention;  
         [0017]      FIG. 2  is a side view of the apparatus;  
         [0018]      FIG. 3  is a side view of the apparatus rotated 90 degrees from  FIG. 2 ;  
         [0019]      FIG. 4  is a housing end view of the apparatus;  
         [0020]      FIG. 5  is a nose piece end view of the apparatus;  
         [0021]      FIG. 6  is an exploded side view of the component parts of the apparatus;  
         [0022]      FIG. 7  is an exploded housing end perspective view of the component parts of the apparatus; and,  
         [0023]      FIG. 8  is an exploded nose piece end perspective view of the component parts of the apparatus. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     The adjustable drill microstop apparatus of the invention is constructed of a minimum number of parts to facilitate its use at a workstation in limiting the depth of a hole drilled in the surface of a component being manufactured. The basic component parts of the apparatus include a housing and a nose piece that is mounted in the housing for reciprocating movement. The construction of the housing and nose piece limit the reciprocating movement of the nose piece in the housing to three, pre-selected distances in the illustrative embodiment of the invention. It should be understood that modifications to the apparatus are possible where the extent of movement of the nose piece in the housing can be adjusted to a plurality of different distances to adjust a hole being drilled using the apparatus to a plurality of different depths. In the preferred embodiment of the invention, each of the component parts of the apparatus is constructed of a metal. However, other materials may be used depending on the intended uses of the apparatus.  
         [0025]      FIG. 1  is a housing end perspective view of the apparatus  12  of the invention.  FIG. 7  is a view similar to that of  FIG. 1 , but with the component parts of the apparatus  12  disassembled. As stated above, the apparatus is basically comprised of a housing  14  and a nose piece  16  that is assembled into the housing for reciprocating movements in opposite first and second directions.  
         [0026]     The housing  14  has a cylindrical sidewall  22  having a center axis  24  and axially opposite first  26  and second  28  ends. The housing has a cylindrical threaded interior surface  32  that surrounds a center bore that extends entirely through the housing between the first  26  and second  28  ends.  
         [0027]     A plurality of anvils  34  project radially inwardly from the housing interior surface  32 . In the illustrative embodiment there are four anvils  34 . Each of the anvils  34  is positioned at the same axial distance on the housing interior surface  32  measured in a first direction extending through the housing interior bore from the housing second end  28  toward the housing first end  26 . The opposite direction through the housing interior bore, from the housing first end  26  toward the housing second end  28  is the opposite second direction through the housing interior bore. Each of the housing anvils  34  has an anvil surface  36  that faces toward the housing second end  28 .  
         [0028]     A plurality of axially extending slots  38 ( a )( b )( c ) are formed through the housing sidewall  22 . Each of the slots  38  extends parallel with the housing center axis  24 . Each of the slots  38  has a first end positioned adjacent the housing first end  26 , and an opposite second end positioned adjacent the housing second end  28 .  
         [0029]     A transverse slot  42  extends through the housing sidewall  22  and intersects the axial slots  38 ( a )( b )( c ). The transverse slot  42  intersects the axial slots  38  intermediate the opposite first and second ends of each axial slot.  
         [0030]     An interior groove  44  is formed around the interior surface  32  of the housing. The groove  44  is positioned adjacent the housing second end  28 .  
         [0031]     The nose piece  16  has a cylindrical head  52  with an outer cylindrical surface  54  that is received in the housing interior surface  32  for sliding, reciprocating movements in the opposite first and second directions. The annular end face of the nose piece head  52  is divided into four sets of three stop surfaces  56 ,  58 ,  62 . Each of the first stop surfaces  56  is set at the same position along the axial length of the nose piece  16 . Each of the second stop surfaces  58  is set at the same distance along the axial length of the nose piece  16 . Each of the third stop surfaces  62  is set at the same distance along the axial length of the nose piece  16 . Thus, each of the first stop surfaces  56  are positioned in one plane, each of the second stop surfaces  58  are positioned in one plane, and each of the third stop surfaces  62  are positioned in one plane, and each of the planes are axially spaced from each other and are positioned perpendicular to the center axis  24  of the housing.  
         [0032]     The nose piece outer surface  54  also mounts the nose piece  16  for rotary movement in the housing  14 . A pin hole  64  is provided in the nose piece outer surface  54  and a pin  66  is assembled into the pin hole  64 . With the nose piece  16  assembled into the housing  14 , the nose piece pin  66  projects outwardly into the slots  38 ( a )( b )( c ),  42  in the housing sidewall  22 . The pin  66  is dimensioned to move axially through each of the housing axial slots  38 ( a )( b )( c ) on reciprocating movement of the nose piece in the opposite first and second directions in the housing. The pin  66  is also dimensioned to move through the housing transverse slot  42  on rotary movement of the nose piece in the housing.  
         [0033]     With the nose piece head  52  assembled into the interior of the housing sidewall  22 , a snap ring  68  is assembled into the housing sidewall interior groove  44 . This limits the reciprocating movement of the nose piece head  52  between the anvils  34  and the snap ring  68  in the interior bore of the housing sidewall  22 . Furthermore, depending on the rotary adjusted position of the nose piece  16  in the housing  14 , the distance that the nose piece  16  can be moved through the interior of the housing  14  is adjusted between three separate preset distances. With the nose piece pin  66  in the first axial slot  38 ( a ), the nose piece  16  can be moved in the first direction through the housing  14  until the first stop surfaces  56  engage with the anvil surfaces  36 . With the first stop surfaces  56  projecting the greatest extent from the nose piece head  52 , the distance that the nose piece  16  travels in the first direction in the housing  14  with the nose piece pin  66  in the first slot  38 ( a ) is the smallest distance traveled.  
         [0034]     Moving the nose piece pin  66  to the second slot  38 ( b ) positions the nose piece stop surfaces  58  axially opposite the anvil surfaces  36 . Moving the nose piece  16  in the first direction will be limited by the engagement of the nose piece stop surfaces  58  against the anvil surfaces  36 . Thus, the nose piece with the nose piece pin  66  in the second axial slot  38 ( b ) moves a second distance in the first direction that is slightly greater than the first distance.  
         [0035]     With the nose piece pin  66  in the third slot  38 ( c ), the stop surfaces  62  are positioned axially opposite the anvil surfaces  36 . The nose piece  16  can now be moved in the first direction until the stop surfaces  62  engage with the anvil surfaces  36 . Thus, with the pin  66  in the third slot  38 ( c ), the nose piece can move its greatest distance in the first direction through the housing  14 .  
         [0036]     Two or more flanges  72  project axially from the nose piece head  52  out of the housing second end  28 . The flanges  72  extend to an annular orienting collar  74  on the nose piece  16 . The collar  74  has an engagement surface  76  at its axially outermost end. The engagement surface  76  surrounds a drill bit opening  78  through the collar. The drill bit opening  78  is dimensioned to provide clearance for a drill bit extending through the housing  14  and the nose piece  16 .  
         [0037]     A coil spring  82  is assembled into the interior of the apparatus housing  14 . The coil spring  82  is dimensioned to surround a drill bit inserted through the housing. The spring  82  extends through the housing and engages against the nose piece  16  at one end of the spring. In the preferred embodiment, the nose piece  16  is provided with an annular groove in the nose piece head  52  just inside of the stop surfaces  56 ,  58 ,  62  to receive the end of the spring  82 . Also in the preferred embodiment, the housing end sleeve  94  is provided with an annular groove in the housing end sleeve  94  outside of the cylindrical surface  104  to receive the opposite end of the spring  82 . The compressed axial length of the coil spring  82  is slightly less than the axial length of the distance between nosepiece groove  52  and groove in housing end sleeve  128 . The spring geometry such as length, number of coils, and wire diameter can be used to tailor the compressive load vs displacement of the nosepiece.  
         [0038]     A circular hand ring  84 , with internal threaded surface is assembled over the exterior threaded surface  126  of the housing  14 . The hand ring  84  threaded configuration enables the hand ring to be rotated and retracted from the locking ring  94 . A plurality of dentil project radially outwardly from the peripheral edge of the housing end face  92  and engage in notches  102  around the periphery of the locking ring  94  in preventing the rotation of  98  relative to housing  14 . Retracting circular hand ring  84  and sliding back locking ring  94  unlocks the global drill depth adjustment. The locking ring  94  is assembled over the exterior surface of the housing  14  at the housing first end  26 . A pin  86  is employed in the locking ring  94  to prevent rotation of the locking ring  94  about the surface  22  of housing  14 .  
         [0039]     A housing end face  92  and a locking ring  94  are secured together and assembled to the first end  26  of the housing  14 . As seen in the drawing figures, the end face  92  is generally cylindrical and has an annular end surface  96 . The end surface  96  is positioned adjacent the drill in use of the apparatus.  
         [0040]     A cylindrical end face tube  104  projects from the housing end face  92  into the interior of the housing  14 . The tube  104  projects through the center of the spring  82  and into the cylindrical interior bore of the nose piece head  52 . A portion of the tube  104  reciprocates in the interior bore of the nose piece head  52  as the nose piece reciprocates through the housing  14 .  
         [0041]     With the adjustable drill stop apparatus  12  assembled as described above, the apparatus can be used in setting the depth of holes drilled into a component part surface by a drill. In use of the apparatus, the microstop assembly is removed from the drill by unthreading retaining ring  124  from housing end face  92  of tube  104 . A bit is then able to be inserted into the drill chuck  114 . drill. The microstop assembly is then reinstalled on the drill by threading retaining ring  124  onto housing end face  92  of tube  104  The drill extends through the interior of the housing  14  and through the nose piece opening  78  with the tip of the bit projecting into the nose piece opening  78  adjacent the nose piece engagement surface  76 . The apparatus is positioned at its desired position relative to the component surface to be drilled with the tip of the drill bit positioned adjacent the component surface at the site of the hole to be drilled. The drill is activated and moved toward the component surface, causing the drill to push the nose piece engagement surface  76  into contact with the component. Further movement of the drill and drill bit toward the component surface causes the drill bit tip to contact the surface begin the drilling operation. Further movement of the drill causes the nose piece  16  to move in the first direction through the interior of the apparatus housing  14 .  
         [0042]     A calibration of the microstop drill depth is then performed by checking the depth of the hole or countersink and comparing to one of the predetermined depths. Adjustments are made by unthreading circular hand ring  84  away form surface  114  of locking ring  94 . Locking ring  94  is moved away from surface  98  to disengage from surface  102 . The notches in surface  102  represent 0.001 inch change to all of the predetermined depths. By rotating the locking ring  94  clockwise or counterclockwise, the pin  86  which is engaged in slot  23  causes the cylindrical threaded interior surface  32  to move axially on the center axis  24  about the treaded surface  118  on tube  104 . The notches in surface  102  are counted as they rotate past the teeth in surface  98 . When the appropriate change has been made, locking ring is moved to engage surface  102  into surface  98 . Circular hand ring  84  is threaded towards surface  116  to lock locking ring in position.  
         [0043]     Pin  132  is used to break long strands of spinning drill chips to prevent a buildup of chips in the mechanism  
         [0044]     The distance that the nose piece  16  moves in the housing  14  determines the depth of the hole drilled into the surface of the component. Pin  66  in slot  38   abc  guides the nose piece  16  onto the anvil surface  36 . Depending on the rotary adjusted position of the nose piece  16  in the housing  14 , the apparatus  12  of the invention sets the depth of the hole drilled into the component at one of three pre-determined depths.  
         [0045]     As explained earlier, although the apparatus  12  is described above as having three stop surfaces for setting three, preset depths of countersunk holes, the apparatus can be modified with fewer or more stop surfaces on the nose piece and fewer or more axial slots in the housing to enable the apparatus to be used in controlling the drilling of holes at a plurality of preset depths. Slots  38  and pin  66  can be replaced by magnets to maintain alignment of anvil to stop surfaces to reduce chance of contaminants getting into interior mechanisms.  
         [0046]     Although the apparatus of the invention has been described above by reference to a specific embodiment, it should be understood that modifications and variations could be made to the apparatus described without departing from the intended scope of the appended claims.