JP2014159095A - Drill bit for diameter expansion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill bit for diameter expansion which can cope with a small-diameter prepared hole by a simple structure.SOLUTION: A drill bit 10 for diameter expansion includes: a bit part 11 which has a plurality of cutting blade parts 21 for grinding a part of a prepared hole H, a cutting blade holding part 22 radially movably holding the plurality of cutting blade parts 21, and a shank part 23 supporting the cutting blade holding part 22; a bit support part 12 which supports the bit part 11; a shaft part 13 which is mounted to a power source-side rotary shaft 3a at its base end side and slidably and unrotatably mounted with the bit support part 12 at its tip side; and an operating rod part 14 which is connected to the shaft part 13 and engaged with the inside of the plurality of cutting blade parts 21, and expands the plurality of cutting blade parts 21 radially outward in accordance with the relative advancement of the shaft part 13 with respect to the bit support part 12.

Description

  The present invention mainly relates to a diameter expanding drill bit for expanding the diameter of a part of a pilot hole drilled in a housing such as concrete.

Conventionally, as this type of diameter expansion drill bit, an undercut drill device is known which is inserted into a straight-shaped prepared hole drilled in a concrete body or the like and expands the innermost part of the prepared hole. (See Patent Document 1).
This undercut drill device includes a hollow cylindrical cylindrical body that is inserted into a pilot hole, a contact member that sits on the opening edge of the pilot hole and rotatably supports the cylindrical body via a bearing, A shaft that slidably engages with the cylindrical body and rotates integrally with the cylindrical body, a truncated cone-shaped cone portion provided on the distal end side of the cylindrical body and having four guide grooves on the outer peripheral surface, and a distal end portion of the shaft Four arms that are attached and engage with each guide groove, and two cutting blades and two guide portions that are alternately provided on the outer surface of the front end of the four arms are provided.
The cutting blade and the guide part are located inside the cylindrical body with the shaft pulled up. When the cylindrical body and the shaft inserted into the prepared hole are integrally rotated and the shaft is moved downward, the four arms are opened outward while being moved downward by the guide groove of the cone portion. Thereby, a cutting blade grinds the internal peripheral surface of a pilot hole, and forms an enlarged diameter part in the bottom part (deepest part) of a pilot hole.

JP 2005-280243 A

  Such a conventional undercut drill device has a structure in which the arm having the cutting edge is guided by the outer peripheral surface of the cone portion, so the cone portion must be supported by the cylindrical body, and the structure is extremely complicated. There was a problem. In addition, since the arm, the cone portion, and the cylindrical body are arranged outside the shaft, the whole has a large diameter, and there is a problem that it cannot be used for a relatively small diameter pilot hole.

  An object of the present invention is to provide a drill bit for expanding the diameter that has a simple structure and can also accommodate a pilot hole having a small diameter.

  The diameter expansion drill bit of the present invention is used by being inserted into a pilot hole drilled in a housing, and is a diameter expansion drill bit for expanding a part of the pilot hole by grinding, and a part of the pilot hole A plurality of cutting edges, a cutting edge holding section for holding a plurality of cutting edges in a radial direction inside the plurality of cutting edges, and a bit portion having a shank portion for supporting the cutting edge holding section And a bit support portion for supporting the bit portion coaxially at the base portion, and a detachably mounted on the rotating shaft on the power source side on the base end side, and the bit support portion is slidably and non-rotatably mounted on the distal end side. The base end side is connected to the shaft portion on the same axis as the shaft portion, and the distal end side is engaged with the inside of the plurality of cutting blade portions. Actuating rod that expands the cutting edge radially outward Characterized by comprising a and.

  According to this configuration, when the power source is driven to rotate with the bit portion inserted into the pilot hole, the shaft portion, the bit support portion, and the bit portion rotate integrally. In this state, when the shaft portion is moved forward relative to the bit support portion, the operation rod portion connected to the shaft portion causes the plurality of cutting blade portions to expand radially outward. That is, when the shaft portion is relatively advanced, a plurality of rotating cutting blade portions are expanded outward in the radial direction, and a part of the pilot hole is ground and expanded in diameter. In this case, since the plurality of cutting blade portions are held by the cutting blade holding portion and are expanded by the operating rod portion engaging inside, the operating rod portion may be directly connected to the shaft portion. And the structure can be simplified. In addition, the plurality of cutting blade portions, the cutting blade holding portion, and the operating rod portion that are inserted into the prepared holes can be arranged in a radial direction and do not require an outer cylinder as in the prior art. Therefore, it is possible to cope (expand the diameter) with a pilot hole with a small diameter.

  In this case, when the tip of the bit part is in contact with the bottom of the pilot hole, the shaft part is pushed through the rotating shaft, so that the shaft part can be moved forward relative to the bit support part. preferable.

  According to this configuration, the shaft portion and the operating rod portion can be advanced by pushing in the power source that is rotationally driven in the manner of a normal drilling operation, and the diameter expansion operation can be performed easily and quickly. In this case, the diameter of the prepared hole is increased by simply expanding the cutting edge portion of the bit portion. Therefore, it is preferable that the cutting blade in each cutting blade part is formed only on the outer peripheral surface.

  In this case, it is preferable that the cutting edge holding part has a spire part that is provided coaxially at the tip part and protrudes.

  According to this configuration, the innermost part of the pilot hole can be expanded in diameter by pressing the spire part against the hole bottom of the pilot hole and rotating it. In addition, during rotation, friction with the bottom of the hole can be reduced as much as possible, and rotational blurring of the bit portion can be suppressed.

  On the other hand, it is preferable to further include an adjustment attachment attached to the bit support portion and capable of adjusting the insertion depth of the bit portion into the prepared hole by contacting the opening edge of the prepared hole.

  According to this configuration, by adjusting the insertion depth of the bit portion into the prepared hole by the adjustment attachment, the diameter can be increased at an arbitrary depth position of the prepared hole.

  Further, the cutting blade holding portion is formed in a cylindrical shape and has a plurality of slit portions extending in the axial direction, and each cutting blade portion is provided along the outer peripheral surface of the cutting blade holding portion. And a rib portion that projects from the inside of the cutting blade body and engages with the slit portion in a slidable manner in the radial direction, and a retaining portion provided at the tip of the rib portion.

  According to this configuration, the cutting blade portion that moves radially outwardly slides with the rib portion guided by the slit portion of the cutting blade holding portion. In this case, since each rib part is engaged with the slit part extended in an axial direction so that sliding is possible in radial direction, a cutting-blade main body translates to radial direction outer side. Thereby, a pilot hole (part) can be ground uniformly. Moreover, since the moving end position of the cutting blade main body that moves radially outward is regulated by the retaining portion, the diameter expansion dimension of the pilot hole can be made constant. Each cutting blade body is preferably formed in a circular arc shape in cross section. If it does in this way, the grinding site | part of each cutting-blade main body will transfer to the intermediate part from the circular arc-shaped surrounding surface as expansion progresses. That is, as the grinding progresses, the frictional resistance of the cutting edge portion decreases, so that the grinding can proceed smoothly.

  Furthermore, the operating rod portion has a tapered portion that engages with the inside of the plurality of cutting blade portions, and the plurality of cutting blade portions expand when the taper portion that moves forward engages each retaining portion. It is preferable to do.

  According to this configuration, the plurality of cutting blade portions can be uniformly and easily expanded by the tapered portion of the operating rod portion. Further, the structure can be simplified by making the retaining portion also serve as the receiving portion of the tapered portion.

  Further, in order to supply the coolant to the tip of the bit part, the shaft part has an in-shaft flow path in the axial center part, and the operating rod part is in the rod communicating with the axial flow path in the shaft center part. It is preferable to have a flow path.

  According to this configuration, the coolant can be supplied from the power source side to the plurality of cutting blade portions of the bit portion via the shaft portion and the operating rod portion. For this reason, the diameter of the pilot hole can be smoothly and efficiently increased. In addition, it is preferable to use a cooling fluid, compressed air, cooling gas, etc. as a coolant.

It is an external view of the state which mounted | wore the drilling apparatus with the drill bit for diameter expansion which concerns on embodiment. It is a structural diagram of the drill bit for diameter expansion concerning a 1st embodiment. It is a perspective view around the bit part of the drill bit for diameter expansion. FIG. 4 is a structural diagram (a) and an exploded structural diagram (b) around a bit portion of a drill bit for diameter expansion. It is explanatory drawing which shows the diameter expansion operation | movement of the drill bit for diameter expansion. It is a structural diagram of the drill bit for diameter expansion concerning a 2nd embodiment.

  Hereinafter, a drill bit for diameter expansion according to an embodiment of the present invention will be described with reference to the accompanying drawings. This diameter-expanding drill bit mainly expands the deepest part of the pilot hole formed in the frame of concrete or stone to drive the anchor, and can increase the pullout strength of the anchor It is. A straight-shaped pilot hole drilled with a diamond core drill or the like is drilled on the side of the opening and narrowed on the back side by a minute axial blur, and has a substantially tapered shape. For this reason, if a large force due to an earthquake or the like is repeatedly applied to the anchor that has been driven in, the pullout strength decreases with time. The diameter-expanding drill bit expands a part of the pilot hole in the same manner as the pilot hole in order to prevent such a decrease in the pullout strength of the anchor over time.

  FIG. 1 is an external view of a state in which a drill bit for diameter expansion is mounted on a drilling device. As shown in the figure, the drilling device 1 has a hand-held electric drill 2 and a coolant attachment 3 attached to the electric drill 2, and a drill bit 10 for expanding the diameter is attached to the coolant attachment 3. . That is, the drill bit for diameter expansion 10 is used by being detachably mounted on the rotary shaft 3a in the coolant attachment 3 of the drilling device 1 (electric drill 2) constituting the power source.

  A coolant flow path is formed on the rotating shaft 3a, and a coolant supply device (not shown) is connected to the coolant attachment 3, and the coolant is supplied from the coolant supply device to the coolant attachment. 3 is supplied to the distal end portion of the diameter-expanding drill bit 10. In the drilling device 1 of the embodiment, a drill bit for drilling (for example, a diamond core bit) is mounted on the coolant attachment 3 to drill the pilot hole H, and then a drill bit 10 for expanding the diameter is mounted instead of the drill bit for drilling. In addition, the innermost portion Ha (hole bottom portion) of the prepared hole H is expanded in diameter.

  FIG. 2 is a structural diagram of the diameter-expansion drill bit 10 according to the first embodiment. As shown in the figure, the drill bit 10 for expanding the diameter includes a bit portion 11 that expands the diameter of the pilot hole H at the distal end portion, a bit support portion 12 that supports the bit portion 11 coaxially at the base portion, and a proximal end A shaft portion 13, which is detachably mounted on the rotating shaft 3 a of the drilling device 1 (coolant attachment 3) on the side, and on which the bit support portion 12 is slidably and non-rotatably attached on the distal end side. 13 and an operating rod portion 14 that extends from the tip of 13 and is inserted into the bit portion 11.

  The bit portion 11 includes a plurality of (two in the embodiment) cutting blade portions 21 for grinding the pilot hole H, and a cutting blade holding portion 22 that holds the plurality of cutting blade portions 21 movably in the radial direction. And a shank portion 23 that supports the plurality of cutting edge portions 21 via the cutting edge holding portion 22. In this diameter-expanding drill bit 10, with the bit portion 11 inserted into the pilot hole H, the operating rod portion 14 moves forward by pushing the diameter-expanding drill bit 10 while rotating it with the drilling device 1. The cutting blade portion 21 is expanded (see FIG. 5).

  The shaft portion 13 is integrally formed of a large diameter portion 31 on the proximal end side and a small diameter portion 32 on the distal end side. Further, an in-shaft flow path 33 for the coolant that communicates with the coolant attachment 3 is formed in the shaft center portion of the shaft portion 13.

  A female thread part 35 is recessed and formed in the small diameter portion of the large diameter part 31, and this female thread part 35 is screwed into a male thread part (see FIG. 1) of the rotating shaft 3 a of the coolant attachment 3. By screwing the shaft portion 13 to the rotating shaft 3a of the coolant attachment 3, the rotating shaft 3a and the shaft portion 13 are located on the same axis, and the rotational power of the rotating shaft 3a is transmitted to the shaft portion 13, while The coolant can be passed from the coolant attachment 3. Although not shown in the drawing, a tool hooking portion for a spanner is formed in the large-diameter portion 31, and the shaft portion 13 is detachably attached to the coolant attachment 3, that is, the perforating apparatus 1 at the female screw portion 35.

  The narrow-diameter portion 32 has a spline structure and is mutually engaged with the bit support portion 12, and spline teeth 36 that are engaged with spline grooves 38 of the bit support portion 12 described later are formed on the outer peripheral surface. . Thereby, the shaft portion 13 supports the bit support portion 12 so as to be slidable in the axial direction and non-rotatable. In addition, the shaft part 13 and the bit support part 12 can be made into a slidable and non-rotatable joining form such as a serration, a sliding key, and a polygonal cross section in addition to engagement by a spline. Further, it is preferable to provide a click mechanism (for example, a click ball) for regulating the home position of the bit support portion 12 between the shaft portion 13 and the bit support portion 12.

  The bit support portion 12 is formed in a cylindrical shape having an end wall 37 on the distal end side, and a spline groove 38 that engages with the spline teeth 36 of the shaft portion 13 is formed on the inner peripheral surface thereof. The end wall 37 is formed with an insertion hole 39 through which the operating rod portion 14 is inserted. Thereby, the bit support part 12 rotates with the rotation of the shaft part 13 and allows the operation rod part 14 to move forward together with the shaft part 13.

  As shown in FIGS. 2, 3 and 4, the bit portion 11 includes a shank portion 23 extending from the tip of the bit support portion 12, a cylindrical cutting blade holding portion 22 provided at the tip of the shank portion 23, and a cutting portion. And two cutting blade portions 21 held on the outer peripheral portion of the blade holding portion 22. In this case, the outer diameters of the two cutting edge portions 21 are slightly smaller than the inner diameter of the pilot hole H. In addition, the outer diameter of the cutting blade holding portion 22 is slightly smaller than the outer diameter of the two cutting blade portions 21, and the outer diameter of the shank portion 23 is smaller than the outer diameter of the cutting blade holding portion 22. Has been.

  The shank portion 23 is formed in a cylindrical shape, and the inside thereof communicates with the insertion hole 39 of the bit support portion 12. That is, the operating rod portion 14 is inserted inside the shank portion 23. Similarly, the cutting blade holding portion 22 is also formed in a cylindrical shape, and the operating rod portion 14 is inserted through the inside thereof.

  The cutting blade holding part 22 has a holding part main body 41 that holds the two cutting edge parts 21 along the outer peripheral surface, and a holding part receiver 42 to which the holding part main body 41 is attached. The holding portion receiver 42 is connected to the shank portion 23 at the base end side, and a female screw 44 into which the holding portion main body 41 is screwed is formed on the distal end side inner peripheral surface. In the embodiment, the holding portion receiver 42, the shank portion 23, and the bit support portion 12 are integrally formed. However, the holding portion receiver 42, the shank portion 23, and the bit support portion 12 may be appropriately separated and joined by screws or welding. Further, the holding portion receiver 42 is formed with a diameter larger than that of the shank portion 23, and the operating rod portion 14 faces the inside including a female screw 44 portion.

  The holding portion main body 41 includes a flange-shaped tip flange portion 51, a cylindrical holding portion 52 that is connected to the tip flange portion 51 and holds the two cutting blade portions 21, and a cylindrical screw portion 53 that is connected to the cylindrical holding portion 52. Have. The holding portion main body 41 includes a spire portion 54 provided at the front end of the center portion of the front end flange portion 51, and a plurality (two) slit portions 55 formed in the cylindrical holding portion 52 and the cylindrical screw portion 53. Have. In this case, it is preferable that the front-end | tip flange part 51, the cylindrical holding | maintenance part 52, the cylindrical screw part 53, and the spire part 54 are integrally formed. Note that the tip of the operating rod portion 14 faces the inside of the cylindrical holding portion 52 and the cylindrical screw portion 53.

  The front end flange portion 51 and the holding portion receiver 42 are formed to have the same diameter, and are arranged so as to sandwich the cutting blade portion 21 held by the cylindrical holding portion 52 in the axial direction with a minute gap. Although details will be described later, each cutting blade portion 21 is held by the cylindrical holding portion 52 via the slit portion 55, and in this state, the cylindrical screw portion 53 is screwed into the female screw 44 of the holding portion receiver 42. . In addition, in order to screw the holding part main body 41 into the holding part receiver 42, it is preferable to provide a tool hook part on the tip flange part 51 (not shown).

  The cylindrical screw portion 53 is formed to have the same diameter as the cylindrical holding portion 52, although a male screw is formed on the outer peripheral surface. The two slit portions 55 are formed so as to cut from the proximal end of the cylindrical screw portion 53 toward the cylindrical holding portion 52. Further, the two slit portions 55 are formed at point-symmetric positions in the circumferential direction of the cylindrical holding portion 52 and the cylindrical screw portion 53. Therefore, each cutting blade portion 21 is attached to the cylindrical holding portion 52 so as to slide from the proximal end of the cylindrical screw portion 53, that is, from the small edge. Further, the holder main body 41 is attached to the holder receiver 42 after the two cutting blade portions 21 are mounted.

  Each of the cutting blade portions 21 is provided at the cutting blade main body 61 provided along the outer peripheral surface of the cutting blade holding portion 52, the rib portion 62 protruding from the inside of the cutting blade main body 61, and the tip of the rib portion 62. And a retaining portion 63. The cutting blade body 61 and the retaining portion 63 have a substantially ¼ arc cross-sectional shape, and the rib portion 62 engages with the slit portion 55 so as to be slidable in the radial direction. That is, the cutting blade main body 61 is located outside the cutting blade holding portion 52 (holding portion main body 41), and the retaining portion 63 is located inside, and in this state, the rib portion 62 is slidable with respect to the slit portion 55. Is engaged.

  Further, the rib portion 62 and the retaining portion 63 are formed shorter in the axial direction than the cutting blade body 61, and these protrude from the intermediate portion in the axial direction of the cutting blade body 61. And the taper part 72 of the action | operation rod part 14 mentioned later engages with the inner side of the retaining part 63. FIG. The inner surface of the retaining portion 63 is preferably a surface (complementary) that follows the peripheral surface of the tapered portion 72.

  In this way, the two cutting blade portions 21 held by the cutting blade holding portion 22 expand outward in the radial direction by the advancement of the operating rod portion 14. That is, the inner surface of the cutting blade body 61 is in contact with the outer peripheral surface of the cylindrical holding portion 52 in the initial state of the diameter expansion, and the outer surface of the retaining portion 63 is the inner periphery of the cylindrical holding portion 52 in the completed state of the diameter expansion. Contact the surface (see FIG. 5). In addition, since the diameter expansion of the pilot hole H in the embodiment is intended to prevent the anchor from coming off, the diameter expansion dimension may be minute. Therefore, it is preferable that the sliding movement of the cutting edge portion 21 is about 0.1 to 2 mm.

  The cutting blade body 61 is constituted by a diamond cutting blade having an arc cross section, and the diamond for grinding is provided only on the outer peripheral surface. Thereby, the innermost peripheral surface Ha of the pilot hole H is ground and diameter-expanded to a predetermined dimension. Since the cutting blade main body 61 has an arc shape, as the spreading progresses, the grinding portion shifts from the entire arc-shaped peripheral surface to the intermediate portion (see FIG. 5). That is, as the grinding progresses, the frictional resistance of the cutting blade body 61 decreases, so that the grinding can proceed smoothly. Moreover, in order to reduce the grinding resistance in the initial stage of grinding, it is preferable that the circumferential front end side (front end side in the rotation direction) of the cutting blade body 61 is chamfered. In the circumferential direction, the diameter of this portion where the two cutting edge portions 21 are in the initial state is formed to be smaller than the diameter of the pilot hole H by about 0.5 to 1.0 mm. The insertion into the hole H can be performed smoothly.

  As shown in FIG. 2, the actuating rod portion 14 is connected to the shaft portion 71 extending from the tip of the shaft portion 13 and the shaft portion 71 and engages with the retaining portion 63 when the two cutting blade portions 21 are expanded. The tapered taper portion 72 and the initial engagement portion 73 that is continuous with the taper portion 72 and engages with the retaining portion 63 in an initial state are integrally formed. Further, an in-rod flow path 74 communicating with the above-described in-shaft flow path 33 is formed in the axial center portion of the operating rod portion 14. Then, the coolant introduced into the in-rod channel 74 is discharged into the pilot hole H from the two slit portions 55 toward the two cutting blade portions 21. Note that compressed air or cooling gas can be used instead of the cooling liquid (details will be described later).

  In the initial state (non-expanded state) in which the plurality of cutting blade portions 21 are closed, the initial engaging portion 73 of the operating rod portion 14 is engaged with the retaining portion 63, and the operating rod portion 14 moves forward. Eventually, the tapered portion 72 engages with the retaining portion 63, and the two cutting blade portions 21 expand outward. The actuating rod portion 14 may be formed integrally with the shaft portion 13 as shown, or may be fixed to the shaft portion 13 by screwing (separately).

  Next, with reference to FIG. 1 and FIG. 5, the diameter expansion operation | work of the pilot hole H by the drill bit 10 for diameter expansion is demonstrated. In this diameter expansion work, it is assumed that a pilot hole H is formed in advance in a target concrete frame A or the like. In addition, the concrete frame A in this case includes a foundation, a beam, and the like in addition to a concrete outer wall, an inner wall, and a slab. The pilot hole H is formed by, for example, a drilling operation in which a diamond core bit is mounted on the drilling device 1 described above.

  In the diameter expansion operation, first, the diameter expansion drill bit 10 is mounted on the drilling device 1, and the bit portion 11 is inserted into the pilot hole H (see FIG. 5A). When the spire portion 54 of the bit portion 11 is inserted so as to abut against the bottom of the pilot hole H, the electric drill 2 is driven to rotate the diameter expanding drill bit 10. At the same time or before and after, the coolant is supplied to the cutting edge portion 21 via the in-shaft channel 33 and the rod-inside channel 74. Here, as in the case of drilling, the handled electric drill 2 is pushed in while continuing the rotation.

  When the electric drill 2 is pushed in, the shaft portion 13 and the actuating rod portion 14 are opposed to the bit portion 11 and the bit support portion 12 that have come into contact with the hole bottom due to the mutual spline engagement between the shaft portion 13 and the bit support portion 12. Will move forward. As the working rod portion 14 advances, the tapered portion 72 of the working rod portion 14 engages with the retaining portion 63 of each cutting blade portion 21, and the two cutting blade portions 21 expand outward ( (Refer FIG.5 (b)). Thereby, the rotating cutting edge part 21 grinds the inner surface of the pilot hole H, and the innermost part Ha of the pilot hole H is expanded in diameter. When the innermost portion Ha is expanded in diameter to a predetermined dimension, the retaining portion 63 is regulated by the holding portion main body 41 and the diameter expansion is completed.

  Here, the operator stops the electric drill 2 and shifts to an operation of pulling out the bit portion 11 from the prepared hole H. In the initial pulling-out operation, the shaft portion 13 and the operating rod portion 14 move backward with respect to the bit portion 11 and the bit support portion 12. When the operating rod portion 14 is retracted, the tapered portion 72 of the operating rod portion 14 is detached from the retaining portion 63 and returns to the initial state so that the two cutting blade portions 21 are closed. Subsequently, the bit portion 11 is pulled out together with the bit support portion 12.

  As described above, in the first embodiment, the innermost portion Ha of the pilot hole H can be simply and quickly expanded in diameter by simply pushing the electric drill 2 while inserting and rotating the bit part 11 into the pilot hole H. be able to. Moreover, since it is the structure expanded by the action | operation rod part 14 which has arrange | positioned the some cutting blade part 21 in the inner side, an apparatus structure can be simplified. Further, since the plurality of cutting blade portions 21, the cutting blade holding portion 22, and the operating rod portion 14 can be arranged in the radial direction, appropriate diameter expansion is performed even for the small-diameter prepared hole H. be able to.

  Next, with reference to FIG. 6, about the diameter-expansion drill bit 10A which concerns on 2nd Embodiment, a different part from 1st Embodiment is mainly demonstrated. As shown in the figure, the diameter-expanding drill bit 10A is different from the diameter-expanding drill bit 10 of the first embodiment in which the innermost portion Ha of the prepared hole H is expanded, and has an arbitrary depth of the prepared hole H. It is intended to expand the position. For this reason, 10 A of diameter expansion drill bits of 2nd Embodiment are further provided with the adjustment attachment 80 which can adjust the insertion depth to the pilot hole H of the bit part 11. FIG.

  The adjustment attachment 80 is provided at a cylindrical attachment main body 81 that is screwed to the bit support portion 12, a set screw portion 82 that is screwed to the bit support portion 12 adjacent to the attachment main body 81, and a distal end portion of the attachment main body 81. And an annular rotation receiving portion 83.

  A male screw is formed on the outer peripheral surface of the bit support portion 12, and a female screw is formed on the inner peripheral surface of the attachment main body 81 and the inner peripheral surface of the set screw portion 82 correspondingly. After the set screw portion 82 is screwed deeply into the bit support portion 12, the attachment body 81 is screwed to adjust the insertion depth of the bit portion 11 into the pilot hole H. When the adjustment is completed, the set screw portion 82 is returned and tightened so as to be in contact with the attachment main body 81 so that the attachment main body 81 is not loosened. In addition, it is preferable to form a scale indicating the insertion depth on the outer peripheral surface of the bit support portion 12.

  The rotation receiving portion 83 is constituted by a thrust bearing, for example, and comes into contact with the opening edge portion of the pilot hole H. The attachment main body 81 and the set screw portion 82 rotate together with the bit support portion 12, but the rotation is received by the rotation receiving portion 83 so that the rotational power is not transmitted to the opening edge portion of the pilot hole H.

  In such a configuration, the insertion depth of the bit portion 11 into the prepared hole H can be adjusted by the screwing depth of the attachment main body 81. That is, an enlarged diameter portion can be formed at an arbitrary depth position of the pilot hole H.

In the present embodiment, the bit portion 11 is expanded by pushing the electric drill 2, but the bit portion 11 may be expanded by hydraulic pressure or air pressure. In such a case, an actuator such as a cylinder is incorporated in the coolant attachment 3, and the shaft portion 13 and the operating rod 14 are moved forward and backward by hydraulic pressure or air pressure.
Moreover, in this embodiment, although the number of the cutting blade parts 21 was two, three or more may be sufficient.
Further, when compressed air or cooling gas is used instead of the cooling liquid, a compressed air supply device (compressor or the like) is connected to the cooling liquid attachment 3 instead of the cooling liquid supply device, or the cooling liquid attachment 3 is connected to the cooling liquid attachment 3. Instead, a cooling gas attachment capable of mounting a gas cylinder such as a liquefied gas is used.

  DESCRIPTION OF SYMBOLS 1 Drilling device, 2 Electric drill, 3 Coolant attachment, 3a Rotating shaft, 10, 10A Diameter expansion drill bit, 11 bit part, 12 bit support part, 13 Shaft part, 14 Actuation rod part, 21 Cutting edge part, 22 Cutting blade holder, 23 Shank, 33 Shaft channel, 36 Spline teeth, 38 Spline groove, 41 Holder body, 42 Holder holder, 51 Tip flange, 52 Cylindrical holder, 53 Cylindrical screw, 54 Spire Part, 55 slit part, 61 cutting blade body, 62 rib part, 63 retaining part, 71 shaft part, 72 taper part, 74 flow path in rod, 80 adjustment attachment, A concrete frame, H pilot hole, Ha innermost part

Claims (7)

A drill bit for expanding the diameter, which is used by being inserted into a prepared hole drilled in a housing, for expanding a part of the prepared hole by grinding,
A plurality of cutting blade portions for grinding a part of the prepared hole, a cutting blade holding portion for holding the plurality of cutting blade portions movably in the radial direction inside the plurality of cutting blade portions, and the cutting blade holding portion A bit part having a shank part for supporting
A bit support portion that coaxially supports the bit portion at a base portion;
A shaft portion that is detachably mounted on the power source side rotation shaft on the base end side, and the bit support portion is slidably and non-rotatably attached on the distal end side;
A base end side is connected to the shaft portion on the same axis, and a tip end side is engaged with the inside of the plurality of cutting blade portions, and a plurality of the shaft portions are advanced as the shaft portion advances relative to the bit support portion. A drill bit for expanding a diameter, comprising: an operating rod portion that expands a cutting blade portion radially outward.   In a state where the tip of the bit portion is in contact with the bottom of the pilot hole, the shaft portion is pushed through the rotating shaft, whereby the shaft portion is advanced relative to the bit support portion. The drill bit for diameter expansion according to claim 1 characterized by things.   The diameter-expanding drill bit according to claim 2, wherein the cutting edge holding part has a spire part that is coaxially positioned and protrudes from the tip part.   The adjustment attachment which is attached to the said bit support part, contact | abuts the opening edge part of the said pilot hole, and can adjust the insertion depth to the said pilot hole of the said bit part is further provided. The drill bit for diameter expansion as described in 1. The cutting blade holding part is formed in a cylindrical shape and has a plurality of slit parts extending in the axial direction,
Each of the cutting blade portions is provided with a cutting blade body provided along the outer peripheral surface of the cutting blade holding portion;
A rib portion protruding from the inside of the cutting blade body and slidably engaged with the slit portion in a radial direction;
The drill bit for diameter expansion according to any one of claims 1 to 4, further comprising a retaining portion provided at a tip of the rib portion. The operating rod portion has a tapered portion that tapers into the inside of the plurality of cutting blade portions,
The diameter-expanding drill bit according to claim 5, wherein the plurality of cutting blade portions are expanded by the taper portion that moves forward engaging each retaining portion.   In order to supply the coolant to the tip of the bit portion, the shaft portion has an in-shaft channel in the axial center portion, and the operating rod portion communicates with the in-shaft channel in the axial center portion. The drill bit for diameter expansion according to any one of claims 1 to 6, further comprising a flow path in the rod.

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