JP4723599B2 - Drilling tool - Google Patents

Description

  The present invention relates to a drilling tool.

  For drilling a printed wiring board (PCB), a drill composed of a body A having a blade portion C and a shank portion B as shown in FIG. 1 is used. Specifically, as shown in FIGS. 2 and 3, the blade C has a spiral chip discharge groove 22 formed on the outer periphery of the main body 20 from the tip of the drill toward the base end, and this chip discharge groove. A cutting edge 21 is formed at the intersecting ridge line portion between the rake face 22 and the first flank 24 provided at the tip (see Patent Document 1, etc.). In the figure, reference numeral 25 denotes a second flank that is connected to the rear side of the first flank 24 in the tool rotation direction, O 'is the center of rotation of the drill, and α' is the twist angle.

  By the way, recent printed wiring boards are required to have improved heat resistance, enhanced bending strength, and low thermal expansion in order to further improve reliability. The mechanical strength of glass cloth and resin constituting the PCB is required. Increasing the number of things that ensure high reliability.

  However, when the PCB having the above structure is considered as a work material for drilling, it is easy to promote wear of the drill by an amount corresponding to the increased mechanical strength, and is accompanied by breakage or excessive wear during drilling. It is easy to cause deterioration of hole quality such as hole position accuracy.

  Further, as the density of PCBs increases, the diameter of drills used is decreasing year by year, and most of them are drilling with a diameter of 0.4 mm or less. Further, in the hole drilling process, in consideration of the processing efficiency, it is common to perform drilling by stacking a plurality of PCBs having the same specifications.

  Therefore, in recent years, the first performance required for small-diameter drills for PCBs is the comparison as described above with respect to an attempt to increase the number of PCBs stacked for the purpose of reducing machining costs and to extend the drilling life of drills. Even in the processing of PCBs with poor workability, it is possible to drill holes without breaking.

JP-A-56-39807

  The present invention has been made in view of the current situation as described above, and it is difficult to break by changing the twist angle of the chip discharge groove on the way, and the chip discharge property is also good, and even a small-diameter drill is good. The present invention provides a drilling tool excellent in practicality that can realize drilling.

  The gist of the present invention will be described with reference to the accompanying drawings.

A drilling tool in which two spiral chip discharge grooves 2 are formed on the outer periphery of the tool body 1 from the tool front end to the base end side, and one of the two chip discharge grooves 2 is discharged. Only the groove 2 is provided with a cutting edge 5 on the tool tip side, and the chip discharge groove 2 having the cutting edge 5 is set as a main groove 2a formed from the tool tip to the base end of the blade part, The other chip discharge groove 2 not provided with the cutting edge is set to a sub-groove 2b shorter than the main groove 2a, and the groove depth at the tool tip of the main groove 2a and the sub-groove 2b is 20% to the tool diameter d. The main groove 2a and the sub-groove 2b are provided at asymmetrical positions with respect to the tool rotation center O in the tool tip view, and the tool tip has a chisel edge. and the tip flank is formed as but is formed, further, the main 2a, the first and helical region 3, the first being provided on the tool base side of the helical region 3 the first helix angle alpha ₁ is larger than the second twist having a first helix angle alpha ₁ A drilling tool comprising a second twist region 4 having an angle α ₂ , wherein the twist angle of the secondary groove 2 b is constant from the tip to the base .

Further, in the drilling tool according to claim 1, wherein the main groove 2a, the first twist angle alpha ₁ is set to 35 ° to 45 °, said second helix angle alpha ₂ is the first helix angle of the Chip is set to be 5 ° to 20 ° larger than α _1, and the connected portion 6 between the first twist region 3 and the second twist region 4 has a cutting edge 5 of 0.2 mm to the cutting edge 5 from the tool tip. The present invention relates to a drilling tool that is provided at a position that is ½ of the total length l of the groove 2.

Further, in the drilling tool according to claim 1, 2 or 1, wherein the twist angle alpha ₃ of the sub-grooves 2b in substantially the same angle as the twist angle alpha ₁ in the first helical region 3 of the main groove 2a The present invention relates to a drilling tool characterized by being set.

4. The drilling tool according to claim 3 , wherein the total length k of the secondary groove 2b is set to 0.2 mm from the tool tip to 1/2 of the total length 1 of the main groove 2a. It concerns tools.

Further, in the drilling tool according to any one of claims 3 and 4, the groove depth of the sub-groove 2b is set to be the same as the groove depth of the main groove 2a or shallower than the groove depth of the main groove 2a. The present invention relates to a drilling tool characterized by being made.

Moreover, in the drilling tool according to any one of claims 1 to 5, a first cutting edge 5 is formed with the rake face of the main groove 2a so that the tip of the tool has a most pyramidal shape. The flank 11, the second flank 12 connected to the rear side of the first flank 11, and the flank surfaces 13, 14 respectively connected to the rear side of the rake face of the sub-groove 2 b are the tip of the tool. The present invention relates to a drilling tool characterized by being provided so as to escape at a predetermined angle .

The drilling tool according to any one of claims 1 to 6, wherein the tool diameter is 0.4 mm or less.

  Since the present invention is configured as described above, it is difficult to break by changing the twist angle of the chip discharge groove in the middle and the chip discharge property is also good, and a good drilling can be realized even with a small diameter drill. A drilling tool with extremely high practicality will be provided.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

By reducing the torsion angle α ₁ at the tool tip, the chips become thick and short instead of being thin and long, so that the tool body 1 can be prevented from being wound and the cutting edge angle of the cutting edge can be ensured to be large. It is possible to prevent chipping of the cutting edge and improve the hole position accuracy and make it difficult to break. Further, by increasing the twist angle alpha ₂ of the tool base side, the thick short chips produced at the tool distal end side by favorable pumping action can smoothly discharged, to prevent chip clogging, improved wall roughness This improvement in emissions also contributes to prevention of breakage.

  Specific embodiments of the present invention will be described with reference to FIGS.

The present embodiment is a drilling tool in which a plurality of spiral chip discharge grooves 2 extending from the tool front end to the base end side are formed on the outer periphery of the tool body 1, and the chip discharge grooves 2 A first twist region 3 having a twist angle α _1, and a first twist region α ₂ connected to the tool proximal end side of the first twist region 3 and having a _second twist angle α ₂ larger than the _first twist angle α ₁ . The second torsional region 4 is provided.

  Specifically, the present embodiment is a drill having a tool diameter d of 0.105 mm and a chip discharge groove 2 having a groove length l of 1.5 mm, and is used for drilling a PCB. More specifically, the tool shown in FIG. 2 is improved, and the first twist region 3 and the second twist region 4 are provided in the chip discharge groove 2 of the drill.

  Each part will be specifically described.

  Two chip discharge grooves 2 are provided, only one chip discharge groove 2 is provided with a cutting edge 5 on the tool tip side, and another chip discharge groove 2 is provided with a cutting edge on the tool tip side. It has no configuration.

  Specifically, as shown in FIGS. 4 and 5, the chip discharge groove 2 having the cutting edge 5 is formed in a main groove 2 a formed from the tip of the tool to the base end of the blade (C portion in FIG. 1). The chip discharge groove 2 that is set and is not provided with a cutting edge is set to a sub-groove 2b that is shorter than the main groove 2a.

  That is, the cutting edge 5 is provided at the crossing ridge line portion between the rake face of the main groove 2a and the first flank 11 provided at the tip of the tool (behind the rake face of the main groove 2a), and the rake of the auxiliary groove 2b. The cutting edge is not provided in the intersecting ridge line portion 10 between the surface and the flank surfaces 13 and 14 (behind the rake face of the auxiliary groove 2b) provided at the tool tip.

  Specifically, at least a portion corresponding to the cutting edge 5 in the intersecting ridge line portion 10 of the rake face of the sub-groove 2b and the flank faces 13 and 14 is immersed in the tool axis direction with respect to the cutting edge 5. It is configured not to exert a cutting action.

  In this embodiment, the tip flank is formed so that a chisel edge is formed at the tip of the tool. Specifically, the first flank 11 that forms the rake face of the main groove 2a and the cutting edge 5, the second flank 12 connected to the rear side of the first flank 11, and the auxiliary groove The flank faces 13 and 14 that are continuously provided on the rear side of the rake face 2b are configured so that each flank face escapes at a predetermined angle with respect to the tool tip so that the tip of the tool has the most protruding shape.

Further, the first twist angle alpha ₁ of the main groove 2a is set at 35 ° to 45 °. In consideration of chipping of the cutting edge, the twist angle should be 45 ° when an aluminum plate is placed on the upper surface of the work piece or when there are many copper foils on the inner and outer layers of the work piece. If it exceeds the maximum, the swarf of the cutting edge of the tool tip to be cut is generated with an angle of less than 45 ° because the swarf of the cutting edge of the cutting tool is marked. This is to shorten the length so that chips are not wound. In this embodiment, it is set to 38 °.

Also the second helix angle alpha ₂ of the main groove 2a is set larger first helix angle alpha ₁ than 5 ° to 20 °. This is to reduce the contact area with the work material by increasing the groove region, and to obtain a better pumping action than the first twist region 3 in which the twist angle is made smaller in order to shorten the chips, The reason why the angle is set to 20 ° or less is that if it exceeds 20 °, there is a concern that the torsional rigidity of the tool may be lowered due to an excessively strong helix angle. In this embodiment, the angle is set to 55 °.

Further, in order to satisfactorily discharge the chips, it is desirable to vary as much as possible the tool distal end side to the second helix angle alpha _2, generally drill for PCB use again sharpening the tip after use For this reason (re-grinding), the connecting portion 6 between the first twisted region 3 and the second twisted region 4 is 0.2 mm from the tip of the tool to 1 / of the groove length l of the main groove 2a in consideration of the polishing amount. The position 2 is preferably set. In the present embodiment, the change point between the first twist angle α ₁ and the second twist angle α ₂ is set to a position (C ₁ ) of 20% of the groove length l from the tool tip.

  Further, as described above, when only one cutting edge is provided at the tool tip and two (or more) chip discharge grooves are provided, the tip of the drill is caused by the presence of a chip discharge groove (sub-groove 2b) that does not form a cutting edge. It becomes possible to reduce the cutting resistance in and to obtain good straightness of the drill. Moreover, since the sub-groove 2b has the effect of improving the hole quality such as the hole position accuracy and the inner wall roughness when the full length of the main groove 2a is increased, the chip discharging performance is improved accordingly. , The rigidity of the hole is lowered, and the accuracy of the hole position is deteriorated, resulting in breakage.

  Therefore, in the present embodiment, the total length k of the sub-groove 2b is set to 0.2 mm from the tool tip to ½ of the total length l of the main groove 2a in consideration of regrindability described later. When the length is longer than ½ of the total length l, a better inner wall roughness can be obtained. In this embodiment, it is set to 0.35 mm.

  By the way, there is a possibility that the drill base end side of the sub-groove 2b is connected (communication) with the middle part of the main groove 2a and the rigidity is lowered at the connection part (communication part). In the range of / 2, there are many cases where the breakage condition is not greatly affected, and a configuration in which the breakage condition is provided may be employed. In this case, the chip dischargeability is improved, and a good inner wall roughness can be obtained.

Further, the main groove 2a and the sub-groove 2b are provided at asymmetrical positions with respect to the tool rotation center O in the tool tip view. Specifically, the land portion 15 behind the main groove 2a is set to be larger than the land portion 16 behind the sub-groove 2b. In the present embodiment, the line connecting the outer peripheral side end of the cutting edge 5 of the main groove 2a and the drill rotation center, and the outer peripheral end of the surface opposite to the wall surface facing the drill rotation direction of the sub groove 2b and the drill. a line connecting the rotational center angle theta ₁ is set to be 40 ° or more less than 180 °, and the size of the rear land portion 15 of the main groove 2a large enough.

That is, the land portion 15 behind the main groove 2a serves as a backup for the cutting edge 5. If the land portion 15 is too small, sufficient backup cannot be secured, the straightness of the drill is lowered, and the hole position accuracy is deteriorated. To do. On the other hand, if it is too large, depending on the processing conditions, the inner wall surface of the hole may be roughened due to an increase in the contact area with the inner wall of the processed hole, or breakage may occur due to an increase in cutting resistance (torque resistance). For this reason, the angle θ ₁ is set to be within the numerical range.

  In this embodiment, a single chip discharge groove (sub-groove 2b) that does not exhibit cutting action and has a shorter overall length than the main groove 2a is provided. However, the cutting action is not exhibited and is shorter than the main groove 2a. It is good also as a structure which provides two or more chip discharge grooves.

For example, as shown in FIG. 6, a configuration may be adopted in which a sub-groove 2c that is shallower than the sub-groove 2b and has a length that is 1/2 or less of the main groove 2a is provided in the center of the land portion 15 behind the main groove 2a (main (It is provided so as to leave the L ₁ and L ₂ portions of the land portion 15 behind the groove 2a, that is, not to communicate with the main groove 2a and the sub groove 2b at the tool tip). In this case, depending on the machining conditions, the contact area with the inner wall of the machined hole is optimized without reducing the rigidity of the drill as much as possible and without reducing the backup effect of the cutting edge 5, thereby improving the hole quality and breakage resistance. Can be planned. Further, for example, as shown in FIG. 7, the land 15 located behind the main groove 2a communicates with the sub-groove 2b and is provided with a clearance X that is shallower than the sub-groove 2b and has a length that is ½ or less of the main groove 2a. In this case, the hole quality and breakage resistance can be improved as in the case of the configuration shown in FIG. In this case, L ₁ portion of the land portion 15 is set larger than the guide width G of the land portion 16.

Further, the twist angle α ₃ of the sub-groove 2 b is set to an angle (38 °) that is substantially the same as the twist angle α ₁ in the first twist region 3 of the main groove 2 a. This is because good rectilinearity is exhibited by setting the same angle as the first twist angle of the main groove 2a, which makes it possible to obtain good hole position accuracy.

The groove depth Y _s of the sub-groove 2b is shallower set than the groove depth Y _m of the same or main groove 2a and the groove depth Y _m of the main groove 2a. This minor groove 2b has no cutting action in drilling tip, since this chip to be discharged into the minor groove 2b is made the small amount compared to the main groove 2a, the groove depth Y _s of the sub-groove 2b This is because it can be shallower than the groove depth Y _m of the main groove 2a. If groove depth of the main groove 2a and minor groove 2b is set substantially the same, in which the groove depth Y _s of the sub-groove 2b is set shallower than the groove depth Y _m of the main groove 2a in the present embodiment In this case, it is possible to secure the wall thickness and increase the rigidity of the drill as much, and the hole position accuracy can be improved without impairing the chip discharging property, and the drill is not easily broken.

Further, as shown in FIG. 8, the main groove 2a and the first inclined region 7 the groove depth Y _m is shallower gradually toward the tool base side, base end side of the first inclined region 7 And a second inclined region 8 having a smaller degree of inclination than the first inclined region 7. Also, minor groove 2b is configured so as tilt degree of the groove depth Y _s and groove depth is substantially the same as the first inclined region 7 of the main groove 2a.

  Specifically, the groove depth at the tool tip of the main groove 2a and the sub groove 2b is set to be 20% to 40% of the tool diameter d. This is because if it is less than 20%, a smooth chip flow cannot be obtained at the tip of the tool and there is a concern about the deterioration of the hole inner wall roughness. This is because the hole position accuracy deteriorates because it is easily worn away by processing and an appropriate rigidity cannot be obtained. In this embodiment, it is set to 29%. The sub groove 2b may be set shallower than the main groove 2a.

  The inclination of the groove depth in the first inclined region 7 of the main groove 2a is set to 0.040 mm / mm, and the inclination of the groove depth in the second inclined region 8 is 0.004 mm / mm. Is set to

Further, the first inclined region 7 and the second connecting portion 9 of the inclined region 8, i.e., the change point of the first inclined region 7 change point C ₂ of the second inclined region 8 torsion angles C It is desirable to be at the tool proximal side from ₁ . In the present embodiment, a change point C ₂ of the first inclined region 7 and the second inclined region 8 is set to be 30% of the position of the groove length l from the tool tip.

If the length of the _secondary groove 2b is longer than the length from the tool tip to the change point C2, the degree of inclination of the groove depth of the secondary groove 2b is set in the same manner as the main groove 2a in order to ensure appropriate rigidity. It may be changed.

Since the present embodiment is configured as described above, by reducing the twist angle α ₁ at the tip of the tool, the chips become thick and short instead of thin and long, so that the tool body 1 can be prevented from being wound and further cut. Since a large blade angle of the blade can be secured, chipping of the cutting blade can be prevented, and the hole position accuracy is improved and breakage is difficult. Further, by increasing the twist angle alpha ₂ of the tool base side, the thick short chips produced at the tool distal end side by favorable pumping action can smoothly discharged, to prevent chip clogging, improved wall roughness This improvement in emissions also contributes to prevention of breakage.

  Further, by providing the main groove 2 a with the second inclined region 8 on the tool base end side of the first inclined region 7, the rigidity of the tool body 1 is ensured and also on the base end side of the chip discharge groove 2 to some extent. The groove volume can be secured, and the chips can be discharged smoothly accordingly.

Further, the connecting portion 9 between the first inclined region 7 and the second inclined region 8 of the main groove 2 a is connected to the tool base end from the connecting portion 6 between the first twisted region 3 and the second twisted region 4. by providing shifted to the side, can be shifted a change point C ₁ of the groove depth change point C ₂ and the torsion angle of inclination degree of inhibiting the discharge of the chip, chip discharge performance is deteriorated rapidly Therefore, it is possible to improve both the hole position accuracy and the hole inner wall roughness without reducing the chip dischargeability as much as possible.

  Therefore, in this embodiment, by changing the twist angle of the chip discharge groove in the middle, it is difficult to break and the chip discharge property is also good, and even with a small diameter drill, it is possible to realize a good hole drilling and extremely practical. It will be excellent.

  An experimental example supporting the effect of the present embodiment will be described.

  As shown in FIG. 2, each chip length is 1 with two grooves and two blades having two chip discharge grooves (the twist angle is constant at 45 °) and having a cutting edge at the tip side of each chip discharge groove. 4 mm, the main groove 2a shown in FIG. 4 (twisting angles are 38 ° and 55 °, changing at a position 0.35 mm from the tip of the drill), and the secondary groove 2b (twisting angle is 38 °). The breakage life of the drill of this example in which the groove length of the main groove 2a is 1.5 mm and the groove length of the sub-groove 2b is 0.35 mm was evaluated. In both cases, the drill diameter is 0.105 mm.

  9 and 10, it was confirmed that the drill of this example had a large number of hits until breakage, and the anti-breakability was improved.

  In addition, it has confirmed that the structure of a present Example is suitable for a small diameter drill, especially a drill with a tool diameter of 0.4 mm or less.

It is a schematic explanatory side view of the drill for PCB. It is an expansion schematic explanatory drawing of the principal part of a prior art example. It is a schematic explanatory front view of a conventional example. It is an expansion outline explanatory side view of the principal part of a present Example. It is a schematic explanatory front view of a present Example. It is a schematic explanatory front view of another example. It is a schematic explanatory front view of another example. It is an expansion schematic explanatory drawing of the principal part of a present Example. It is a table | surface which shows an experimental result. It is a graph which shows an experimental result.

DESCRIPTION OF SYMBOLS 1 Tool main body 2 Chip discharge groove 2a Main groove 2b Subgroove 3 1st twist area | region 4 2nd twist area | region 5 Cutting edge 6 Connection part (alpha) ₁ 1st twist angle (alpha) ₂ 2nd twist angle (alpha) ₃ ( Twist angle l (sub groove 2b) l Total length (main groove 2a) k Total length (sub groove 2b) O Tool rotation center d Tool diameter

Claims (7)

A helical chip-evacuating flutes are two formed drilling tool toward the base end side from the tool tip to the outer periphery of the tool body, only one of the chip flutes of the two chip flutes A cutting edge is provided on the tool tip side, and the chip discharge groove having this cutting edge is set to a main groove formed from the tool tip to the base end of the blade part, and the other cutting edge is not provided. The chip discharge groove is set to a sub-groove shorter than the main groove, and the groove depth at the tool tip of the main groove and the sub-groove is set to be 20% to 40% of the tool diameter. The main groove and the sub-groove are provided at asymmetrical positions with respect to the tool rotation center in the tool tip view, and a tip flank is formed on the tool tip so that a chisel edge is formed. the main groove includes a first helical region with a first helix angle of, The first being provided on the tool base side of the helical region and a second helical region with the first helix angle larger than the second twist angle of the twist angle of the sub-groove is proximal from the distal end of the A drilling tool characterized by being constant up to . 2. The drilling tool according to claim 1 , wherein the main groove has a first twist angle of 35 ° to 45 °, and the second twist angle is 5 ° to 20 ° larger than the first twist angle. Is set, and the connecting portion between the first twist region and the second twist region is provided at a position that is 0.2 mm from the tool tip to a half of the total length of the chip discharge groove having the cutting edge. A drilling tool characterized by 3. The drilling tool according to claim 1, wherein the twist angle of the sub-groove is set to be substantially the same as the twist angle in the first twist region of the main groove. Drilling tool. 4. The drilling tool according to claim 3 , wherein the total length of the sub-groove is set to 0.2 mm from the tool tip to 1/2 of the total length of the main groove. The drilling tool according to any one of claims 3 and 4, wherein the groove depth of the sub-groove is set to be equal to or shallower than the groove depth of the main groove. A featured drilling tool. In the drilling tool according to any one of claims 1 to 5, a first flank that forms a cutting edge with a rake face of the main groove so as to be a pyramid shape in which the tool tip protrudes most, A second flank surface continuously provided on the rear side of the first flank surface and a flank surface continuously provided on the rear side of the rake face of the auxiliary groove are provided so as to escape at a predetermined angle with respect to the tool tip. A drilling tool characterized by The drilling tool according to any one of claims 1 to 6, wherein the tool diameter is 0.4 mm or less.

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