JP5973304B2 - Drill and drilling method - Google Patents

Description

  The present invention relates to a drill suitable for deep hole processing of a thick plate material and drilling processing of a laminated plate material.

  For example, at the site of aircraft manufacturing, a number of holes are drilled manually on a structural material or a thick laminated plate material made of a high-hardness aluminum alloy for aircraft. In this case, a double-edged double margin drill with two blades is used as the drill. The double-blade double margin drill has a structure as shown in Patent Document 1, for example, and has the advantage that the presence of two margins provides high smoothness of the inner peripheral surface of the hole and excellent hole machining accuracy. It has been. In addition, the stepped type with a small diameter drill projecting at the tip must strictly eliminate the remaining cutting strain on the workpiece, especially in aircraft materials. It is necessary to gradually increase the hole diameter while reducing the cutting allowance (corresponding to the difference between the outer dimension of the small diameter part on the tip side and the outer dimension of the large diameter part on the base side) in the step drill. Because.

  However, since the stepped two-blade double margin drill inherently performs cutting with only two cutting blades, the cutting resistance is high and the cutting allowance for one drilling process cannot be increased. For this reason, many processing steps are required to finally reach a desired hole diameter. In addition, since a large cutting resistance also means a large amount of wear on the cutting blade, the tool life is short and the number of processed holes per drill cannot be increased.

  Furthermore, the double-edged drill has two twisted grooves for discharging chips, and the twisted grooves must be relatively deep to discharge chips of a predetermined volume. The shaft diameter becomes thinner. This means that the rigidity of the drill is lowered, and the drill is bent at the time of deep hole machining, and the possibility that the hole is slightly bent in the middle is increased. In addition, when machining an aluminum alloy, the double-edged drill has a long continuous chip and clogs in the torsion groove, scratches the inner peripheral surface of the hole and the surface of the workpiece, and relatively large burrs on the workpiece. There is also a problem that the hole machining accuracy is lowered.

  In order to solve these problems, it is conceivable to use a three-blade drill. However, using a three-blade drill for a workpiece of aluminum alloy with high hardness is a common sense for those skilled in the art in selecting a tool. Contrary. This is because a three-edged drill has a larger chisel at the tip where no cutting blade is provided, compared to a two-edged drill, so it does not bite against the workpiece, and a high-hardness aluminum alloy reduces the positional accuracy of drilling. There is a concern that the drill may tilt and enter. In addition, since aluminum alloys have a larger coefficient of thermal expansion than steel, smooth chip evacuation is essential.Three-blade drills do not have sufficient depth of twisted grooves for chip evacuation. This is because it is known that chip discharge is poor.

JP 2006-205272 A

  The present invention has been completed based on the above-described circumstances, and can be applied to drilling of a laminated plate or a thick material while reducing the number of processing steps until a required hole diameter is reached. An object is to provide a drill having a long life and excellent machining accuracy.

  The drill according to the present invention has a pilot shaft portion that is concentrically provided with a diameter smaller than that of the body at the tip of the body. The pilot shaft portion includes a shaft main portion, a tip flat surface located at the tip of the shaft main portion, and a tip tapered surface having a predetermined tip angle located between the outer peripheral surface and the tip flat surface of the shaft main portion. Prepare. On the other hand, the body has an odd number of twisted grooves on the outer peripheral surface and an odd number of adjacent grooves adjacent to the twisted groove on the front end surface of the body formed at a predetermined tip angle in the region extending from the outer peripheral surface to the pilot shaft portion. A blade is provided. The pilot shaft portion is formed with an auxiliary torsion groove connected to the torsion groove from the outer peripheral surface of the shaft main portion to the tip tapered surface, and an auxiliary cutting blade adjacent to the auxiliary torsion groove on the tip taper surface.

  According to the drill of the present invention, the drill has an odd number of cutting blades such as three or five and an odd number of twisted grooves corresponding thereto, a pilot shaft portion is provided at the tip of the drill, and the pilot The auxiliary cutting edge is provided on the tip tapered surface of the shaft portion. With a drill with an odd number of cutting blades, for example, with three blades, the margin positions are arranged at an angular interval of 120 °, and there is less fluctuation compared to an even blade drill with two blades, etc. A high-precision drilling process can be performed nearby. Also, since the number of torsion grooves that serve as chip discharge paths increases, the depth of the torsion grooves can be reduced, eventually increasing the axial rigidity of the drill, reducing the deflection and improving the straightness of the drill. As a result, drilling with good linearity is possible even in deep holes. Also, even if the workpiece is a high-hardness aluminum alloy, the chips are not separated into a series like conventional double-edged double margin drills, but are divided into pieces and discharged. It is possible to improve the drilling accuracy from the surface.

  Furthermore, since there are more cutting blades compared to the conventional two-blade double margin drill, cutting can be performed efficiently, so that the expansion diameter of the hole diameter from the pilot hole can be increased, thereby Since the number of machining steps required to reach a required hole diameter can be reduced, and the amount of wear per cutting blade is reduced, the number of holes drilled per drill can be remarkably increased.

  As described above, the drill of the present invention exhibits superior cutting performance as compared to a double-edged double margin drill, while a multi-edged drill of three or more blades has a poor bite on a high-hardness workpiece. There is a concern that the position accuracy of the drilling process is lowered. However, since the tip of the drill of the present invention is a flat surface portion of the pilot shaft portion, it is completely different from a step drill and cannot perform the first drilling by itself, and a pilot hole is necessary. And This means that a double-edged drill with good biting is used for the pilot hole forming drill, and the pilot hole can be formed with high positional accuracy. Since the drill of the present invention has the pilot shaft portion at the tip, the pilot shaft portion is inserted into the pilot hole formed in advance with high precision, so that the drilling work is performed. The position accuracy can be kept high.

  In the present invention, it is preferable that the tip angle in the pilot shaft is set to be approximately the same as the tip angle in the body. This is because the drill can be easily manufactured. The tip angle of the tip tapered surface in the pilot shaft is most preferably 60 ° or more.

  On the other hand, when drilling a stacked plate formed by stacking a plurality of unit plates, the following operations can be performed using the drill of the present invention. First, a pilot hole having a predetermined diameter is formed in a stacked plate that is a workpiece (preparation process). In this case, it is preferable to use a drill that can form a pilot hole with high positional accuracy, instead of the drill of the present invention. In this pilot hole forming step, burrs may occur on the surface of each unit plate on the drill penetration destination side. Therefore, a deburring step for separating the stacked plates and removing the burrs on the unit plates is performed. Then, a stacked plate is formed in which the prepared holes formed by reassembling the unit plates after deburring are connected (restacking process), and the pilot shaft portion of the drill of the present invention is inserted into the prepared holes of the reassembled stacked plates Then, the hole is drilled by the cutting blade formed in the body (hole expanding process). At this time, if the position of each unit plate is shifted due to an assembly error in the re-stacking process, the inner peripheral surface of the pilot hole may be shifted in a stepped shape, but the pilot shaft portion of the drill of the present invention Since the auxiliary cutting edge is formed on the outer peripheral portion and the auxiliary torsion groove adjacent to the auxiliary cutting edge is connected to the torsion groove of the body, the stepped inner peripheral surface of the pilot hole is formed by the auxiliary cutting edge. There is no effect on the drilling operation by the pilot shaft through the pilot hole and by the body cutting blade, and the drilling operation can be completed without stopping in the middle.

  In addition, after performing the hole expansion process with the drill of the present invention, the deburring process and the re-stacking process are repeated, and the hole expansion process is repeated using the thicker drill of the present invention with the hole as a pilot hole. It is possible to open a hole with a necessary size by expanding the hole.

  As described above, according to the present invention, it is possible to reduce the number of processing steps required to reach a required hole diameter while being applicable to drilling of a laminated plate or a thick material, and the tool life is long and the processing accuracy is improved. It is also possible to provide a drill and a method for drilling a laminated plate that are excellent.

The side view which shows the drill of one Embodiment of this invention Enlarged side view of the drill tip Front view showing enlarged tip of drill Enlarged side view of the drill tip Sectional drawing which shows the pilot hole formation process of the punching method of the laminated board which concerns on this invention Sectional drawing which shows the state after completion of a pilot hole formation process Sectional view showing the deburring process Sectional view showing the hole expansion process Sectional drawing which shows the state after completion of a hole expansion process Sectional view showing the second hole expansion process Sectional view showing the status of unit plate misalignment in the hole expansion process

    An embodiment of the present invention will be described with reference to FIGS.

  The drill 1 of this embodiment is a round bar made of steel or cemented carbide with a shape in which a pilot shaft portion 20 smaller in diameter than the body 10 is concentrically provided at the tip of a body 10 having a predetermined diameter. It is manufactured by cutting.

  The body 10 has an odd number, for example, three twisted grooves 11 formed on the outer peripheral surface with predetermined leads, twist angles and groove lengths. The body distal end surface 12 connected to the base end portion of the shaft main body portion 21 of the pilot shaft portion 20 from the outer peripheral surface of the body 10 is positioned so as to surround the base end portion of the shaft main body portion 21 in an annular shape. It is in a state of being divided into three by the twisted groove 11. The body front end surface 12 has a tapered shape having a predetermined front end angle α (see FIG. 4). In this embodiment, the front end angle α is set to 118 °, for example. An appropriate value may be selected from the strength and cutting efficiency. A total of three cutting blades 13 are formed on the body front end surface 12 adjacent to each twist groove 11 and correspond to the outermost peripheral surface of the body 10 continuously to the outer peripheral surface side of the body 10. A margin 14 for determining the diameter is formed along the twisted groove 11.

  The pilot shaft portion 20 has a right columnar shape and a base body portion 21 whose base end is integrally connected to the front end of the body 10, a distal end flat surface 22 positioned at the distal end of the shaft body portion 21, and the shaft body portion 21. A tip tapered surface 23 is provided between the outer peripheral surface and the tip flat surface 22. The tip angle β (see FIG. 4) of the tip tapered surface 23 is set to 90 ° as an example in this embodiment, but it is preferable to set the tip angle β to a range of 60 ° or more in consideration of machinability. Moreover, it is preferable on manufacture of a drill to make it the same grade as the front-end | tip angle (alpha) of the body front end surface 12 in the said body 10. FIG.

  The tip tapered surface 23 is positioned so as to surround the outer periphery of the tip flat surface 22 in an annular shape, but is divided into three portions by three auxiliary twist grooves 24 described later.

  The pilot shaft portion 20 has an auxiliary twist groove 24 formed on the outer peripheral surface of the shaft main body portion 21 continuously at the same twist angle as the twist groove 11 of the body 10. An auxiliary cutting edge 26 adjacent to the twist groove 24 is formed. Since the auxiliary torsion grooves 24 are continuous with the torsion grooves 11, three auxiliary torsion grooves 24 are formed. Accordingly, the auxiliary cutting blades 26 are formed in the same number as the cutting blades 13. The cutting margin of the auxiliary cutting blade 26 is set to be 0.3 mm, for example. The cutting allowance of the auxiliary cutting edge 26 can be set freely. However, if the auxiliary cutting edge 26 is set large, the effective dimension in the axial direction of the pilot shaft portion 20 is shortened and the guide performance by the pilot shaft portion 20 is deteriorated.

  Now, a method for drilling the laminated plate 30 made of, for example, a high-strength aluminum alloy for aircraft using the drill 1 will be described. The stacked plate 30 shown in FIG. 5 is a material in which two unit plates 31 are stacked in close contact with bolts (not shown). First, a pilot hole 33 having a predetermined size is formed on the overlap plate 30 with a pilot hole forming drill 32 as shown in FIG. 6 (preparation hole forming step). As the pilot hole forming drill 32, it is preferable to use a double-edged drill that has good biting and easily obtains positional accuracy.

  Next, the bolts are removed, the stacked plates 30 are separated as shown in FIG. 7, and the burrs 34 generated on the unit plates 31 are removed with an appropriate tool such as a counter cutter (deburring step). Then, after removing the burrs, the unit plates 31 are again aligned so that the pilot holes 33 are continuous, overlapped and fixed with bolts (re-stacking step), and the drill 1 of the present embodiment is used. Perform the hole expansion process. That is, in the drill 1, as shown in FIG. 8, the outer diameter of the pilot shaft portion 20 is substantially the same as the inner diameter of the pilot hole 33, and the pilot shaft portion 20 is fitted into the pilot hole 33 for drilling. Do work. When the drill 1 is rotated and pushed in, the inner peripheral surface of the prepared hole 33 is cut by the cutting blade 13 provided at the tip of the body 10, and the hole diameter is expanded to the outer diameter of the body 10.

  At this time, the cutting position of the drill 1 is surely determined by the pilot shaft portion 20, and the traveling direction is linearly guided by the fitting of the pilot shaft portion 20 and the pilot hole 33. As shown, a straight hole 35 can be drilled in the correct position. Further, since the drill 1 of the present embodiment is a so-called three-blade drill having three cutting blades 13, the positions of the margins 14 are arranged at an angular interval of 120 °, and the drill 1 is supported at three points. It will be in a state and will have less run-out than a double-edged drill. In the conventional double-edged double margin drill, there was a tendency for the drill to swing vertically due to the two-point support structure, and the hole tends to become an oval. Drilling could be done.

  Further, since there are as many as three torsion grooves 11 serving as chip discharge paths, the depth of the torsion grooves 11 can be made shallower. As a result, the axial rigidity of the drill 1 is increased, the bending is reduced, and the drill advances straight. As a result, drilling with good linearity is possible even in deep holes. Further, even when drilling a high-hardness aluminum alloy, chips do not continue in a series as in the conventional two-blade double margin drill, but are divided into pieces and discharged. There is little damage to the inner peripheral surface of the metal, and high-precision drilling can be performed from that surface.

  In order to further widen the hole diameter after drilling the hole 35 with the drill 1 as described above, the deburring process, the re-stacking process, and the hole expanding process using the larger-diameter drill 1 are performed step by step. If it repeats, it can be expanded to a desired hole diameter. In this case, the drill 1 of the present embodiment has three cutting blades 13 that are more than the conventional two-blade double margin drill, so that the cutting in one drilling operation is performed efficiently. be able to. As a result, the hole diameter expansion allowance at each step can be further increased, and as a result, the number of processing steps required to reach the required hole diameter can be reduced as compared with the prior art, and the work efficiency is high. Moreover, in the drill 1 of this embodiment, since the number of the cutting blades 13 corresponds to 1.5 times that of the conventional drill, the wear amount of the drill 1 per step is reduced, and the number of holes processed per drill is reduced. Can be increased significantly.

  Now, in the re-stacking process, a shift occurs in the stacking position of each unit plate 31, and the inner peripheral surface of the pilot hole 33 may shift in a stepped manner as shown in FIG. In the laminated plate 30 described in the present embodiment, an assembly error (tolerance) of, for example, 0.2 mm is planned, and when such a deviation occurs, an auxiliary cutting edge 26 is provided on the pilot shaft portion 20. Otherwise, the tip of the pilot shaft 20 may abut against the stepped portion 36 of the pilot hole 33, and further progress of the drill 1 may be hindered.

  On the other hand, in this embodiment, the tip tapered surface 23 is provided on the outer peripheral portion of the tip flat surface 22 of the pilot shaft portion 20 and the auxiliary cutting edge 26 is formed here. Even if the resulting stepped portion 36 is generated, the stepped portion 36 is scraped off by the auxiliary cutting edge 26 and can continue to be drilled straight as it is. Accordingly, the unit plate 31 is formed by sequentially performing the pilot hole forming step, the deburring step, the re-stacking step, and the hole expanding step on the stacked plate 30 configured by stacking a plurality of unit plates 31. Even in the drilling work where the deviation is inevitable, the drilling work can be completed without hindrance.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) The tip angle α in the body 10 and the tip angle β in the pilot shaft 20 illustrated in the above embodiment are examples, and the present invention is not limited to these.

  (2) Although the three-blade drill 1 is illustrated in the above embodiment, a five-blade may be used. This is because if the number of teeth is an odd number, the margin is evenly arranged with an odd number with respect to the entire circumference, which is effective for steadying.

  (3) In the above embodiment, the punching operation of the stacked plate is exemplified, but the workpiece is not limited to the stacked plate in the drill of the present invention. For example, even when deep hole machining of about 5D or more is performed, the linearity of the hole is important, and the drill of the present invention having high axial rigidity and less deflection is optimal for it.

DESCRIPTION OF SYMBOLS 10 ... Body 11 ... Twist groove | channel 12 ... Body tip surface 13 ... Cutting blade 14 ... Margin 20 ... Pilot shaft part 21 ... Shaft main part 22 ... Tip flat surface 23 ... Tip taper surface 24 ... Auxiliary twist groove 26 ... Auxiliary cutting blade 30 ... Laminated plate 31 ... Unit plate

Claims (3)

Having a pilot shaft that is concentrically projected at a tip of the body smaller in diameter than the body,
The pilot shaft portion includes a shaft main portion, a tip flat surface located at the tip of the shaft main portion, and a tip tapered surface having a predetermined tip angle located between the outer peripheral surface of the shaft main portion and the tip flat surface. Has
The body has an odd number of twisted grooves on the outer peripheral surface, and an odd number of cutting blades adjacent to the twisted groove on the front end surface of the body formed at a predetermined tip angle in a region extending from the outer peripheral surface to the pilot shaft portion. Is provided,
The pilot shaft portion is formed with an auxiliary torsion groove connected to the torsion groove from the outer peripheral surface of the shaft main portion to the tip tapered surface, and an auxiliary cutting blade adjacent to the auxiliary torsion groove on the tip tapered surface. Drill. The drill according to claim 1, wherein the tip angle of the pilot shaft is set to 60 ° or more. A method of drilling a hole in a stacked plate in which a plurality of unit plates are stacked,

A pilot hole forming step of forming a pilot hole of a predetermined diameter in the stacked plate;
A deburring step for separating the stacked plate after the formation of the pilot hole and removing the burr of the unit plate;
A re-stacking step of reassembling the unit plate to constitute the stacked plate;
A hole expanding step of drilling a hole using the drill of claim 1 in the pilot hole of the reassembled stack;
A method for drilling a laminated board that sequentially executes and.

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