JP2008188682A - Boring drill for cast hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain high precision in hole position precision, hole diameter size, roundness, straightness and roughness on a finished surface by performing boring and finishing in a single step. <P>SOLUTION: A boring drill 1 for a cast hole equipped with cutting edges 2 at three points in the circumference with approximately equal intervals at the tip of a drill body and equipped with finishing edges 3 having a larger diameter than that of the edge 2 at three points in the circumference with approximately equal intervals at a distance from the cutting edges 2 backward around the axis O of the cutting edge 2. The drill 1 is characterized in that a land of each finishing edge has a margin. A radial rake angle &theta;1 of the cutting edge 2 is positive and that a radial rake angle &theta;2 of the finishing edge 3 is 0&deg; or negative. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  In particular, the present invention relates to a drill that is suitably used for machining a punched hole previously formed in a casting.

In order to reduce the amount of material used for casting, a pilot hole having a predetermined finishing allowance for a desired hole size may be formed by casting. This pre-formed core hole is often eccentric with respect to the hole reference of the finally obtained hole position. For this reason, it is necessary to perform a cutting process to correct this misalignment.
In such a punched hole machining, since a cutting process is performed on a pilot hole in a state shifted from the hole reference, in the cutting with a two-blade drill, only the cutting edge on one side of the drill is covered at the start of machining. It comes into contact with the cutting material and comes into contact with one edge, and the force pressed from the wall of the hole acts and the drill is shaken in the horizontal direction, easily following the core hole, hole diameter and roundness vary, and hole position accuracy May cause problems. In addition, the rotation of the drill is unstable and vibration is likely to increase, and not only the finish of the machined surface is deteriorated, but also there is a risk of damage to the blade and breakage of the tool.
Therefore, a smooth finished surface is obtained by first drilling a hole with the tool center aligned with the hole reference with a drill, re-opening the misaligned hole, and then finishing with a reamer. However, since the number of work processes increases, the production efficiency is poor and the production cost is increased.
In order to solve this problem, there has been proposed a drill in which three or more rough cutting blades arranged at substantially equal intervals in the circumferential direction are provided on the outer peripheral portion of the drill body, and a finishing blade is provided behind the rough cutting blade. (For example, refer to Patent Document 1 and FIG. 1).
Japanese Patent Laid-Open No. 2002-370113 (FIG. 1)

  However, in the invention of the above-mentioned Patent Document 1, the first rough cutting blade, the finishing blade, and the second rough cutting blade are arranged in this order from the front side in the rotation direction to the rear on the outer peripheral portion of the drill body. It is formed one by one. That is, roughing is performed with four rough cutting edges, and finishing is performed with two finishing edges. Therefore, since the number of cutting edges involved in cutting differs between the rough cutting edge and the finishing edge, the balance is poor, and the finishing edge is a two-blade cutting. As a result, the cutting state becomes unstable and the finished surface roughness and straightness may not be improved. Further, when the core thickness is small, the rigidity is low, and there is a problem that the target hole position accuracy cannot be obtained because it depends on the accuracy of the cast hole. Further, the rake angle in the radial direction of the drill is usually set to a positive angle, and there is a problem that it is not possible to expect an improvement in the finished surface roughness due to the burnishing action caused by the friction between the hole inner surface and the tool.

  The present invention has been made to solve the above problems, and can perform drilling and finishing at once, such as hole position accuracy, hole diameter size, roundness, straightness, finished surface roughness, etc. An object of the present invention is to provide a drill for punching holes with excellent hole accuracy.

In order to solve the above-described problems, the drill for drilling holes of the present invention employs the following means.
The present invention includes a drill body having a blade portion at a tip portion rotated around an axis, a groove formed on an outer peripheral portion of the drill body so as to extend from the tip side toward the rear end side, A rake face formed on the inner wall surface facing the front side of the drill rotation direction, a flank face formed on the tip face of the blade part, and a cutting edge formed at a cross ridge line part of the flank face and the rake face The cutting blades are provided at three locations at substantially equal intervals in the circumferential direction, and a finishing blade having a diameter larger than the cutting blade is disposed on the rear side in the axial direction of the cutting blade, Three are provided at substantially equal intervals with a gap from the cutting edge in the circumferential direction, and there is a margin in the land portion of each finishing blade, the rake angle in the radial direction at the cutting edge is positive, and the finishing The rake angle in the radial direction at the blade is 0 ° or And characterized in that.

  According to the present invention, the cutting edge provided on the front end side in the axial direction and the finishing blade having a slightly larger diameter than the cutting edge provided on the rear end side in the axial direction from the cutting edge are alternately arranged. Thus, drilling is first performed by the cutting blade, and then finishing is performed by the finishing blade. With such a configuration, even in the drilled hole machining where the center of the pilot hole and the axis of the drill are misaligned, it is not necessary to go through two steps of drilling and finishing with a reamer. It is possible to finish a smooth finished surface while re-opening the misaligned cast hole at an accurate position.

In this case, these cutting blades and finishing blades are arranged alternately three by three so that six blades can be provided, so that the cutting resistance can be received in a well-balanced manner, and the cutting resistance per blade can be reduced. In addition to being reduced, the thickness of the core is increased and the tool rigidity is improved.
In addition, it is the three cutting edges that perform the drilling process substantially in connection with the cutting action. Therefore, unlike the conventional two-blade one, the three-point support can hold the axis of the drill body at a fixed position, and the rotation state of the drill is stabilized and vibration is reduced.

Further, since the rake angle in the radial direction of the cutting edge is set to be positive, the cutting edge is good and the cast hole can be re-opened at an accurate position. And generation | occurrence | production of chatter vibration can be suppressed by reduction of cutting resistance, and it can suppress that a part of chip | tip is welded to a blade edge | tip.
Further, in the finishing blade for finishing the hole formed by the cutting edge to a desired hole diameter, a margin is provided in the land portion, and the rake angle in the radial direction is set to 0 ° or negative. Therefore, the burnishing action is generated by the friction between the inner wall of the hole processed by the cutting edge and the drill body, and the finished surface roughness is improved.

  Therefore, highly accurate hole position accuracy, hole diameter dimensions, roundness, straightness, finished surface roughness, and the like can be obtained without being affected by the punched hole accuracy.

In the said invention, it is preferable that the rake angle of the radial direction in the said finishing blade shall be -10 degrees or more and 0 degrees or less.
By doing so, the friction between the inner wall of the hole machined by the cutting edge and the drill body causes a force to press the inner wall of the work hole against the drill body in the radial direction, that is, a burnishing action. Thus, the finish surface roughness can be further improved by the friction generated in the hole inner wall.

  Moreover, in the said invention, it is preferable that the core thickness of the drill on the basis of the said cutting edge shall be 40% or more and 60% or less of a drill diameter from a viewpoint of ensuring tool rigidity and reduction of cutting resistance.

Further, in the above invention, from the viewpoint of preventing only a part of the cutting edge from coming into contact with the work material at the start of machining and becoming a single edge contact state and following the punched hole, the biting portion in the cutting edge The angle formed by the line parallel to the inclination and the line parallel to the axis is preferably 60 ° or more and 90 ° or less.
Further, by reducing the substantial cutting thickness of the finishing blade 3 and reducing the cutting resistance, from the viewpoint of improving the hole position accuracy, hole diameter size, and roundness of the machining hole by the finishing blade 3, the erosion in the finishing blade 3 is improved. The angle formed by the line parallel to the inclination of the attached portion and the line parallel to the axis is preferably 40 ° or more and 50 ° or less.
Here, the biting portion refers to a portion that bites into the work material at the start of machining and mainly performs a cutting action.

  According to the drill for drilling holes of the present invention, drilling and finishing can be performed at once, and hole accuracy such as hole position accuracy, hole diameter size, roundness, straightness, and finish surface roughness can be achieved. Has the effect of being excellent in.

Hereinafter, a drilling hole drill according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.
As shown in FIG. 1, a drill 1 for drilling a hole according to an embodiment includes a drill body having a blade portion at a tip portion rotated about an axis O, and an outer peripheral portion of the drill body from the tip side. A groove formed so as to extend toward the rear end side, a rake surface formed on an inner wall surface facing the front side in the drill rotation direction of the groove, and a flank surface formed on a tip surface of the blade portion The cutting edge 2 is formed at the intersection ridge line between the flank and the rake face.

  The cutting edges 2 perform drilling mainly related to the cutting action. As shown in FIG. 2 (a), the cutting edges 2 are provided at three locations at equal intervals in the circumferential direction, and are raked in the radial direction. The angle θ1 is set to 20 °. In addition, an angle θ3 formed by a line parallel to the inclination of the biting portion 4 that bites the work material at the start of machining and mainly performs a cutting action and a line parallel to the axis O is set to 75 ° (FIG. 3).

A finishing blade 3 having a slightly larger diameter is formed on the rear side in the axis O direction from the cutting edge 2 so as to slightly protrude radially outward from the cutting edge 2.
The finishing blade 3 finishes the cutting hole 2 to a desired hole diameter, and as shown in FIG. 2 (a), the finishing blade 3 is equidistant from the cutting blade 2 in the circumferential direction. As shown in FIG. 2B, a margin 6 is formed on the land portion 7 on the front side in the drill rotation direction. The rake angle θ2 in the radial direction is set to 0 °. In addition, an angle θ4 formed by a line parallel to the inclination of the biting portion 5 and a line parallel to the axis is set to 45 ° (see FIG. 3).
These cutting blades 2 and finishing blades 3 are arranged alternately.

The effect | action of the drill for core hole processing which concerns on this embodiment comprised in this way is demonstrated below.
According to the drill 1 for punching a hole according to the present embodiment, the cutting edge 2 on the tip side in the axis O direction first bites the work material and cuts the punched hole to a desired position and size. The finishing blade 3 on the rear end side in the axis O direction finishes the inner wall of the hole processed by the cutting edge 2 to a desired hole diameter.
Therefore, it is not necessary to go through two steps of drilling with a drill and finishing with a reamer, and it is possible to finish a cast hole whose position is shifted at a time to a smooth finished surface while re-opening it at an accurate position.

With such a configuration, the cutting edge 2 performs cutting prior to the finishing edge 3, so that the punching process is substantially performed by the three cutting edges 2.
Therefore, the three-point support of these three cutting edges 2 keeps the axis of the drill body in a fixed position even in the drilling hole processing where the center of the pilot hole and the axis of the drill are displaced. The rotation state of the drill can be stabilized. In other words, unlike the conventional two-blade one, only the biting part of one of the cutting edges comes into contact with the outer peripheral edge of the punched hole at the start of machining and comes into contact with the single edge, and the force pressed from the hole wall surface is extremely high. The drill is shaken in the radial direction by acting on the unbalance, and the axial center of the drill is not displaced following the cast hole. This enables stable drilling with less vibration, so that the desired hole position accuracy and hole diameter can be obtained without being affected by the punched hole accuracy, roundness, straightness, Excellent cylindricity and finished surface roughness. Moreover, there is no fear of damage to the blade part, breakage of the tool, or the like. Even when the finishing blade 3 performs finish cutting following the cutting edge 2, it is prevented from following the punched hole, so that the roundness, straightness, cylindricity and finished surface roughness of the processed hole are reduced. Excellent.

In this case, in the punched hole drill 1 according to the present embodiment, the cutting edges 2 and the finishing edges 3 are alternately arranged three by three, so that the cutting resistance can be received in a well-balanced manner, and Cutting resistance per blade is reduced.
Further, since the cutting edge 2 and the finishing edge 3 are combined to form 6 blades, the core thickness is large, and the core thickness of the drill 1 based on the cutting edge 2 is 60% of the drill diameter. Because it is set, it has excellent tool rigidity and low cutting resistance.
Therefore, it is possible to perform the drilling process without being influenced by the accuracy of the punched hole while suppressing the copying to the punched hole at the time of processing, so that the hole position accuracy and the hole diameter are excellent. Furthermore, since the occurrence of chatter vibration can be suppressed by reducing the cutting resistance, the finished surface roughness, roundness, straightness, cylindricity, etc. are excellent. And damage to a blade part, tool breakage, etc. can be prevented.

Further, since the rake angle θ1 in the radial direction of the cutting edge 2 which performs drilling mainly in connection with cutting is set to 20 °, the sharpness is good and the cutting resistance is small.
Therefore, it is possible to re-open the cast hole at an accurate position while suppressing the occurrence of chatter vibration while suppressing the welding of the chip to the cutting edge and the component cutting edge, and the excellent hole position accuracy, hole diameter dimension, Roundness, straightness, and finished surface roughness can be obtained.

  Further, a margin 6 is formed on the front side of the land portion 7 in the drill rotation direction of the finishing blade 3 that mainly performs finishing, and the rake angle θ2 in the radial direction of the finishing blade 3 is set to 0 °. Therefore, the friction between the inner wall of the hole machined by the cutting edge 2 and the drill body causes a force to press the work material radially outward of the drill body, that is, a burnishing action, thereby improving the finished surface roughness. .

In addition, since the angle θ3 formed by the line parallel to the inclination of the biting portion 4 and the line parallel to the axis of the cutting edge 2 is set to 70 °, the force with which the drill is pressed radially inward during cutting is set. It becomes smaller against the force acting in the axial direction of the drill, and at the start of machining, only a part of the cutting edges 2 can come into contact with the work material and come into contact with the one edge to prevent following the core hole. it can.
Further, the angle θ4 formed by the line parallel to the inclination of the biting portion 5 in the finishing blade 3 and the line parallel to the axis is smaller than the angle θ3 of the cutting blade 2 and is set to 45 °. Compared to 2, the actual cutting thickness of the finishing blade 3 is reduced, and the cutting resistance is reduced. Therefore, there is an advantage that the hole position accuracy, the hole diameter dimension, and the roundness of the processed hole by the finishing blade 3 are improved.

  In the present embodiment, the core thickness of the drill 1 with respect to the cutting edge 2 is set to 60% of the drill diameter, but can be set to an arbitrary core thickness. In this case, it is preferable that the angle is 40 ° or more and 70 ° or less from the viewpoint of securing the tool rigidity and reducing the cutting resistance.

In the present embodiment, the rake angle θ1 in the radial direction of the cutting edge 2 is set to 20 °, but can be set to an arbitrary positive angle. In this case, the angle is preferably set to 10 ° or more and 30 ° or less from the viewpoint of improvement of sharpness and reduction of cutting resistance.
In the present embodiment, the rake angle θ2 in the radial direction of the finishing blade 3 is set to 0 °, but can be set to any negative angle. In this case, it is preferable to set it to −10 ° or more and 0 ° or less. When the rake angle θ2 in the radial direction of the finishing blade 3 is set to be negative, it is difficult for chips to be welded to the cutting edge, the constituent cutting edge can be suppressed, and the hole diameter dimension, finished surface roughness, etc. are excellent. Even if a negative rake angle θ2 is applied in the radial direction of the finishing blade 3, the cutting edge 2 cuts prior to the finishing blade 3 at the time of machining. Cutting resistance at the time of attachment can be reduced. And since the core thickness is thick and the tool rigidity is excellent, cutting resistance can be reduced.

In the present embodiment, the angle θ3 formed by the line parallel to the inclination of the biting portion 4 and the line parallel to the axis of the cutting edge 2 is 75 °, but is set within a range of 60 ° to 90 °. be able to. If it is within this range, it is possible to suppress the copying of the punched hole during processing.
Further, the angle θ4 formed by the line parallel to the inclination of the biting portion 5 and the line parallel to the axis of the finishing blade 3 is 45 °, but can be set within a range of 40 ° to 50 °. If it is within this range, the cutting thickness of the finishing blade 3 is smaller than the cutting blade 2 and the cutting resistance is reduced, so that the hole position accuracy, hole diameter dimension, and roundness of the machining hole by the finishing blade 3 are improved. The effect that can be obtained.

Further, in this embodiment, the margin 6 is provided at one place on each of the finishing blades 3 on the front side of the land portion 7 in the drill rotation direction. However, the position and the number of the margins 6 are not limited thereto. Further, a margin 6 may be provided on the land portion 7 of the cutting edge 2 in order to improve the finished surface roughness.
In addition, it is good also as providing a guide pad in the heel part of a drill for the purpose of improving guide property.

It is a front view which shows the drill for cast hole processing which concerns on one Embodiment of this invention. It is a figure which shows the drill for punching holes shown in FIG. 1, (a) is a left view, (b) is an enlarged view which shows the front-end | tip part of the finishing blade in Fig.2 (a). It is an enlarged view which shows the front-end | tip part of the drill for drilling holes of FIG.

Explanation of symbols

1 Drilling hole drill 2 Cutting edge 3 Finishing blade 6 Margin 7 Land part θ1 Cutting edge radial rake angle θ2 Finishing blade radial rake angle

Claims (5)

A drill body having a blade at the tip rotated around the axis, a groove formed on the outer periphery of the drill body so as to extend from the tip side toward the rear end, and a forward direction of the groove in the drill rotation direction A drill having a rake face formed on an inner wall surface facing the side, a flank face formed on a tip face of the blade part, and a cutting edge formed at a cross ridge line part of the flank face and the rake face. There,
The cutting edges are provided at three locations at approximately equal intervals in the circumferential direction,
A finishing blade having a diameter larger than the cutting edge is disposed on the rear side in the axial direction of the cutting edge, and is provided at three positions at approximately equal intervals in the circumferential direction with a gap from the cutting edge.
There is a margin in the land portion of each finishing blade,
The rake angle in the radial direction at the cutting edge is positive,
A drill for drilling holes, wherein a rake angle in a radial direction of the finishing blade is 0 ° or negative. The rake angle of the radial direction in the said finishing blade is -10 degrees or more and 0 degrees or less, The drill for cast hole processing of Claim 1 characterized by the above-mentioned. 2. The core hole drill according to claim 1, wherein a core thickness of the drill with respect to the cutting edge is 40% or more and 60% or less of a drill diameter. 4. The punched hole machining according to claim 1, wherein an angle formed by a line parallel to the inclination of the biting portion in the cutting edge and a line parallel to the axis is 60 ° or more and 90 ° or less. 5. Drill. 5. The angle formed by a line parallel to the inclination of the biting portion and a line parallel to the axis of the finishing blade is 40 ° or more and 50 ° or less. 5. Drill for drilling holes described in 1.

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