Abstract:
A match drilling tool comprising a body comprising a drilling leg and a fixing leg, said drilling leg being separated from said fixing leg by a gap, wherein said drilling leg defines a cutter guide opening, and wherein said fixing leg defines an alignment pin opening, said alignment pin opening being concentric with said cutter guide opening; and an alignment pin slideably received in said alignment pin opening.

Description:
FIELD 
     This application relates to tools and methods for match drilling and, more particularly, to tools and methods for drilling a hole in a first part (e.g., a non-metallic part) that will precisely align with a pre-drilled hole in a second part (e.g., a metallic part). 
     BACKGROUND 
     An aircraft fuselage is typically built in sections, which are then assembled to form the fuselage. The fuselage sections often are built at various locations and then transported to an assembly location for final assembly. 
     The tail-end of a fuselage is typically enclosed by the aft-pressure bulkhead (APB). In certain constructions, the aft-pressure bulkhead is fastened to the adjacent fuselage section using various mounting structures and mechanical fasteners. For example, metallic T-shaped angled brackets, commonly referred to as “T-clips,” are connected to the aft-pressure bulkhead, while composite brackets, commonly referred to as splice angles, are connected to the adjacent fuselage section. The aft pressure bulkhead-to-adjacent fuselage section connection is then made by mechanically fastening (e.g., with bolts) the T-clips to the slice angles. 
     Typically, the T-clips have pre-drilled bolt or rivet holes machined therein, whereas the splice angles do not. Holes in the splice angle must be machined on site at the time of assembly in order to account for slight variances in the alignment of the fuselage sections. Because the T-clips are mounted on the aircraft body, it is not possible to maneuver large precision drilling machines into place to drill the matching holes on the splice angle, so the holes must be hand-drilled. 
     No current solution supports automation of the fuselage APB join. Pilot holes in the T-clips are lined up with the slice angles, a power feed driller is used to drill full size holes through both parts, as well as through a carbon shim that has been placed therebetween. With a heavy power feed driller, it can be difficult to gauge whether the guide pin is accurately located prior to engaging the drill to operate. If the guide pin is slightly off, the cutter penetrates the material in the wrong location or direction, requiring that both parts be removed and replaced. 
     It is undesirable to hand-drill the splice angle holes by using the T-clip holes as a guide. The T-clip holes are machined to high precision. Hand drilling through the T-clip holes may result in the drill contacting the sides of the hole, altering the dimensions of the hole and, possibly, putting the T-clips out of specification and requiring re-approval. Correcting such a mis-drilling requires time-consuming de-burring and cleaning. 
     Accordingly, there is a need for drilling splice angle holes that perfectly align with T-clip holes, but without the drill coming into contact with the T-clip. 
     SUMMARY 
     In one embodiment, the disclosed match drilling tool may include a body having a drilling leg and a fixing leg, the drilling leg being separated from the fixing leg by a gap, wherein the drilling leg defines a cutter guide opening, and wherein the fixing leg defines an alignment pin opening, the alignment pin opening being concentric with the cutter guide opening; and an alignment pin slideably received in the alignment pin opening. 
     In one embodiment, the disclosed match drilling system may include a match drilling tool having a body that includes a drilling leg and a fixing leg, the drilling leg being separated from the fixing leg by a gap, wherein the drilling leg defines a cutter guide opening, and wherein the fixing leg defines an alignment pin opening, the alignment pin opening being concentric with the cutter guide opening, and an alignment pin extending at least partially through the alignment pin opening; a part assembly positioned in the gap, the part assembly including at least a pre-drilled part and a target part, the pre-drilled part including a pre-drilled hole, wherein the alignment pin extends into the pre-drilled hole; and a cutter extending through the cutter guide opening into engagement with the target part. 
     In one embodiment, the disclosed method for concentrically drilling a hole in a part assembly may include the steps of (1) providing a match drilling tool that includes a body having a drilling leg and a fixing leg, the drilling leg being separated from the fixing leg by a gap, wherein the drilling leg defines a cutter guide opening, and wherein the fixing leg defines an alignment pin opening, the alignment pin opening being concentric with the cutter guide opening, and an alignment pin slideably received in the alignment pin opening; (2) positioning the match drilling tool over the part assembly such that the part assembly is in the gap; (3) inserting the alignment pin into a pre-drilled hole in one member of the part assembly; (4) inserting a cutter into the cutter guide opening to drill a through hole in another member of the part assembly; (5) withdrawing the cutter from the cutter guide opening; and (6) withdrawing the alignment pin from the pre-drilled hole and removing the match drilling tool from the part assembly. 
     In another embodiment, the disclosed method for concentrically drilling a hole in a part assembly may include the steps of (1) fastening a target part and a pre-drilled part to one or more structures, wherein a gap remains between the target part and the pre-drilled part; (2) inserting a temporary shim in the gap between the target part and the pre-drilled part; (3) providing a match drilling tool having a body that includes a drilling leg and a fixing leg, the drilling leg being separated from the fixing leg by a gap, wherein the drilling leg defines a cutter guide opening, and wherein the fixing leg defines an alignment pin opening, the alignment pin opening being concentric with the cutter guide opening, and an alignment pin slideably received in the alignment pin opening; (4) positioning the match drilling tool over the part assembly such that the part assembly is in the gap; (5) inserting the alignment pin into the pre-drilled hole in the pre-drilled part; (6) inserting a cutter into the cutter guide opening to drill a through hole in the target part and a blind hole in the temporary shim concentric with the through hole; (7) withdrawing the cutter from the cutter guide opening; (8) withdrawing the alignment pin from the pre-drilled hole; (9) removing the match drilling tool from the part assembly; (10) removing the temporary shim from the gap between the target part and the pre-drilled part; and (11) installing a permanent shim into the gap between the target part and the pre-drilled part, wherein the permanent shim comprises a shim through hole concentric with the pre-drilled hole and the matching through hole, wherein the shim through hole has a diameter at least as large as the pre-drilled hole and the matching through hole. 
     Other embodiments of the disclosed match drilling tool, system and method will become apparent from the following detailed description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of the disclosed match drilling tool; 
         FIG. 2  is a front view of the match drilling tool shown in  FIG. 1 ; 
         FIG. 3  is a side view of the match drilling tool shown in  FIG. 1 ; 
         FIG. 3A  is a side view of an alternate embodiment of the disclosed match drilling tool; 
         FIG. 4  is a front view of the match drilling tool in use, with the part assembly in place; 
         FIG. 5  is a system view of the match drilling tool in use, with a partial cross-sectional view of the part assembly in place, and the cutter; 
         FIG. 6  is a cross-sectional view of the match drilling tool in use, with a partial cross-sectional view of the part assembly in place, and the cutter; 
         FIG. 7  is a partial cross-sectional view of the part assembly immediately after drilling; 
         FIG. 8  is a partial cross-sectional view of the part assembly in final form; and 
         FIG. 9  is a flow diagram depicting one embodiment of the disclosed match drilling method. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed match drilling tool, system and method may allow a user to drill a hole in a part assembly that achieves concentricity with a pre-drilled hole, but without making contact with the part defining the pre-drilled hole. The part assembly may include at least a pre-drilled part having a pre-drilled through hole therein, and a target part in which it is desired to have a matching, concentric hole that will align with the pre-drilled hole. 
     Referring to  FIGS. 5 and 6 , one embodiment of the disclosed match drilling system, generally designated  10 , may include a match drilling tool  100 , a part assembly  204  and a cutter  401 . The match drilling tool  100  may be positioned over the part assembly  204  such that the cutter  401  may precisely bore a hole in the part assembly  204 . 
     The match drilling tool  100  may include a body  20  and an alignment pin  301 . The body  20  may be rigid and generally U-shaped, and may include a drilling leg  101  and a fixing leg  102 . The drilling leg  101  may be connected to the fixing leg  102  by a central bridge  130 . A gap  120  may be defined between the drilling leg  101  and the fixing leg  102 . 
     The part assembly  204  may include a pre-drilled part  202 , a target part  201  and, optionally, a shim  203  positioned between the pre-drilled part  202  and the target part  201 . The part assembly  204  may be positioned in the gap  120  of the match drilling tool  100 . The drilling leg  101  is designed to abut the target part  201  and the fixing leg  102  is designed to abut the pre-drilled part  202 . The pre-drilled part  202  can be, but is not required to be, a metal part, such as a T-clip, and the target part  201  can be, but is not required to be, a composite or non-metallic part, such as a splice angle. 
     As shown in  FIGS. 1-3 , the drilling leg  101  of the match drilling tool  100  defines a cutter guide opening  111  that extends through the drilling leg  101 . The fixing leg  102  defines an alignment pin opening  112  that extends through the fixing leg  102 . The alignment pin opening  112  and cutter guide opening  111  are concentric and may have the same diameter. 
     The fixing leg  102  may further define a plurality of securing holes  113 . The securing holes  113  may be sized and shaped to receive securing screws  114  ( FIG. 5 ) in connection with an optional securing feature of the disclosed match drilling tool  100 .  FIGS. 1-3  show the securing holes  113  aligned with the alignment pin opening  112 , while  FIG. 3A  shows an alternate arrangement wherein the securing holes  113  are offset from the alignment pin opening  112 . 
     As shown in  FIG. 4 , the pre-drilled part  202  may include a pre-drilled hole  222 . In certain applications, this pre-drilled hole  222  may be precisely sized and should not be altered or damaged when the disclosed matched drilling tool  100  is used. The alignment pin  301  of the match drilling tool  100  may extend through the alignment pin opening  112  defined by the fixing leg  102 , and may be sized and shaped to engage the pre-drilled hole  222  to accurately align the match drilling tool  100  and the pre-drilled part  202 . The alignment pin  301  allows the operator to easily see when the match drilling tool  100  is lined up with the pre-drilled hole  222  of the pre-drilled part  202 . 
     Optionally, a biasing element  303 , such as a coil spring, may be operatively connected to the alignment pin  301  to bias the alignment pin  301  toward the drilling leg  101  and into the pre-drilled hole  222  of the pre-drilled part  202 . Therefore, as the pre-drilled hole  222  and alignment pin opening  112  align, the biasing element  303  may urge the alignment pin  301  into the pre-drilled hole  222 , thereby creating a concentric plane for the drilling leg  101 . Concentricity of the holes may be crucial in order for a fastener to fit appropriately. 
     Also optionally, a knob  302  may be connected to the alignment pin  301  to facilitate manually grasping the alignment pin  301  and moving the alignment pin  301  relative to the alignment pin opening  112 . For example, as shown in  FIG. 4 , prior to positioning the part assembly  204  into the gap  120  of the match drilling tool  100 , a pulling force (arrow F) may be applied (e.g., manually) to the knob  302  to withdraw the alignment pin  301  from the gap  120  (e.g., to move the alignment pin  301  to a retracted position). Then, when the knob  302  is released and the pulling force (arrow F) ceases, the biasing element  303  may urge the alignment pin  301  into the gap  120  (e.g., to an engaged position). When the alignment pin opening  112  is aligned with the pre-drilled hole  222  of the pre-drilled part  202 , the alignment pin  301  engages the pre-drilled hole  222 , thereby aligning the part assembly  204  relative to the match drilling tool  100 . A user may manually adjust the part assembly  204  relative to the match drilling tool  100  until the desired engagement of the pre-drilled hole  222  with the alignment pin  301  is achieved. 
     A securing feature may optionally be used to securely fasten the match drilling tool  100  to the part assembly  204  prior to employing the cutter  401 . As shown in  FIG. 5 , one example embodiment of the securing feature may include screws  114  in threaded engagement with the securing holes  113  in the fixing leg  102 . The screws  114  may pass through the fixing leg  102  and contact the part assembly  204 , specifically the pre-drilled part  202 . The screws  114  may be tightened, which may press the part assembly  204  against the drilling leg  101  in a vise-like arrangement, thereby preventing any of the components of the part assembly  204  from moving out of position. 
     The screws  114  may be non-marring so as not to damage or mark the part assembly  204  (e.g., the pre-drilled part  202 ) when the screws  114  are tightened. The exact non-marring feature of the screws  114  is not critical, and various non-marring features may be used. Non-limiting examples of non-marring features suitable for use with the screws  114  include a ball bearing tip, a rubber tip, and a swivel foot. In addition, one or both of the legs  101 ,  102  of the match drilling tool  100  can be treated or surfaced with a non-marring material. 
     As shown in  FIG. 6 , the cutter  401  may be inserted into the cutter guide opening  111  of the drilling leg  101  of the match drilling tool  100 , thereby machining a through hole  221  ( FIG. 7 ) in the target part  201 . The cutter  401  may by be powered by a motor  402 , and may tunnel through the target part  201  and at least partially through the temporary shim  203 , thereby creating a blind hole  233  ( FIG. 7 ) in the temporary shim  203 . As used herein, “cutter” can encompass any mechanical device capable of machining or milling a hole in a material, and includes, but is not limited to, drills, routers, knives, and grinders. 
     As shown in  FIG. 5 , the cutter  401  may be elongated along a longitudinal axis A, and may include a shoulder  404  and a tip  405 . The tip  405  of the cutter  401  may be axially opposed from the shoulder  404 , thereby defining the length L of the cutter  401 . When the cutter  401  is fully inserted into the match drilling tool  100  (by way of the cutter guide opening  111 ), the shoulder  404  of the cutter  401  may abut the drilling leg  101 , thereby preventing the cutter  401  from penetrating further into the part assembly  204 . Therefore, the thickness T 1  of the drilling leg  101  and the length L of the cutter  401  may define the maximum depth to which the cutter  401  plunges into the part assembly  204 . 
     As note herein, in certain applications it may be important that the cutter  401  not contact the pre-drilled part  202  of the part assembly  204 . Therefore, the thickness T 1  of the drilling leg  101  and the length L of the cutter  401  may be sized such that the tip  405  of the cutter  401  plunges no deeper than the temporary shim  203 . In other words, the length L of the cutter  401  may be greater than the combined thickness (T 1 +T 2 ) of the drilling leg  101  (thickness T 1 ) and the target part  201  (thickness T 2 ), but less than the combined thickness (T 1 +T 2 +T 3 ) of the drilling leg  101  (thickness T 1 ), the target part  201  (thickness T 2 ) and the shim  203  (thickness T 3 ). 
     Optional, a drill stop  403  may be connected to the drilling leg  101 , as shown in  FIG. 6 . The drill stop  403  may be received over, and aligned with, the cutter guide opening  111  such that the shoulder  404  of the cutter  401  engages the drill stop  403  rather than the drilling leg  101 , directly. Therefore, the drill stop  403  may effectively increase or decrease (or keep the same) the thickness T 1  of the drilling leg  101 , thereby modifying the depth to which the cutter  401  plunges into the part assembly  204 . The drill stop  403  may be adjustable, such as by way of a threaded engagement between the drill stop  403  and the drilling leg  101 , which may facilitate adjusting the effective thickness T 1  of the drilling leg  101  and, thus, the depth to which the cutter  401  plunges into the part assembly  204 . 
     Once the through hole  221  has been formed, the cutter  401  may be backed out through the cutter guide opening  111 , the securing screws  114  may be loosened, the alignment pin  301  may be withdrawn to the retracted position, and the match drilling tool  100  may be removed from the part assembly  204 . The resulting through hole  221  will be precisely aligned with the pre-drilled hole  222 . As one option, the temporary shim  203 , which may only have a blind hole  233  formed therein, may be removed and replaced with a permanent shim  203 A, which may have a through hole  223  formed therein, as shown in  FIG. 8 . As another option, the blind hole  233  may be hand bored (e.g., with a reamer) to provide a through hole in the shim  203 , which may render the temporary shim  203  a permanent shim  203 A without the need for swapping shims. 
     Thus, as shown in  FIG. 8 , the pre-drilled hole  222  in the drilled part  202  may be aligned with the through hole  221  formed in the target part  201  and the through hole  223  in the shim  203 A, thereby forming a concentric through hole through the part assembly  204 . If desired, a mechanical fastener, such as a bolt, may be inserted through the through hole in the part assembly  204  to connect the target part  201  with the drilled part  202 . 
       FIGS. 7 and 8  show in more detail how two shims may be used: a sacrificial temporary shim  203  ( FIG. 7 ) and a precision machined permanent shim  203 A ( FIG. 8 ), which has through hole  223  machined to match the pre-drilled part  202  pre-drilled hole  222  and the target part  201  through hole  221 . The temporary shim  203  is used as a buffer to keep the cutter  401  from contacting the pre-drilled part  202 . After the through hole  221  is drilled through the target part  201 , the temporary shim  203  is removed and discarded or recycled, and the permanent shim  203 A having a shim through hole  223  is installed between the pre-drilled part  202  and the target part  201 , with all three holes  221 ,  222 ,  223  concentrically aligned. The diameter of the shim through hole  223  can be the same as the other two holes  221 ,  222 , or it can be larger. 
     Also disclosed is a method for drilling an opening in a target part concentrically with an existing through hole in a pre-drilled part. One embodiment of the disclosed match drilling method, generally designated  1000 , is shown in  FIG. 9 . The method  100  may begin at Block  1002 . 
     At Block  1002 , the target part  201  and the pre-drilled part  202  may optionally be fastened to one or more structures. A gap  120  may remain between the target part  201  and the pre-drilled part  202 . Therefore, as shown at Block  1004 , a temporary shim  203  may be inserted into the gap between the target part  201  and the pre-drilled part  202 . 
     At Block  1006 , a match drilling tool  100  may be provided. The match drilling tool  100  may be positioned over the part assembly (Block  1008 ) and the alignment pin  301  of a match drilling tool  100  may be inserted into the pre-drilled hole  222  in the pre-drilled part  202  (Block  1010 ). Optionally, at Block  1012 , one or more securing screws  114  may be tightened against the pre-drilled part  202  to clamp the target part  201 , the temporary shim  203 , and the pre-drilled part  202  within the match drilling tool  100 . 
     At Block  1014 , a cutter guide opening  111  in the drilling leg  101  of the match drilling tool  100  may be used as a guide for drilling a matching through hole  221  in the target part  201 , wherein the cutter guide opening  111  in the drilling leg  101  of the match drilling tool  100  is concentric with the alignment pin  301  of the match drilling tool  100 . Optionally, a drill stop  403  of the match drilling tool  100  may be used to ensure the desired plunge depth of the cutter. 
     With the through hole  221  formed, the cutter  401  may be withdrawn from the cutter guide opening  111  (Block  1016 ). Then, the alignment pin  301  may be withdrawn (Block  1018 ) and the match drilling tool  100  may be removed from the part assembly  204  (Block  1020 ). 
     Optionally, the temporary shim  203  may be removed from the gap  120  between the target part  201  and the pre-drilled part  202  (Block  1022 ), and a permanent shim  203 A may be installed (Block  1024 ). The permanent shim  203 A may include a shim through hole  223  concentric with the pre-drilled hole  222  in the pre-drilled part  202  and the through hole  221  in the target part  201 . The shim through hole  223  may have a diameter at least as large as the pre-drilled hole  222  and the through hole  221 . 
     Accordingly, the disclosed match drilling tool, system and method may be used to form a precisely concentric through hole in a part assembly that includes at least a first member and a second member, wherein one of the members has a pre-drilled through hole formed therein. Significantly, the precisely concentric through hole may be formed without passing a cutter through the pre-drilled through hole and without contacting the member with the pre-drilled through hole. 
     Thus, the disclosed match drilling tool, system and method may save time and cost by allowing machinists to keep components fastened, without removal, while assembling components. This may reduce labor hours in production as well as costs associated with rework and non-conforming material. This may allow an operator to keep surrounding components installed while being able to drill through only one material without needing a cleaning and de-burring processes for the pre-drilled part. The part assembly is not limited to composite parts and metallic parts, and would work with any delicate or precision part that requires drilling or machining to concentrically align with an existing hole in a part. 
     Although various embodiments of the disclosed match drilling tool, system and method have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.