Replaceable tip drill and drill head

Abstract

The present invention provides an interchangeable-tip drill and drill head that can stably supply coolant to the tip surface of the drill head, thereby improving cooling efficiency. [Solution] The system comprises a holder 20, a drill head 10, a clamp screw 30, and a coolant hole 105. The drill head 10 has a screw insertion hole 14 that penetrates the drill head 10 axially. The clamp screw 30 is inserted through the screw insertion hole 14 and is screwed into the female screw hole of the drill head mounting seat 106, with the clamp screw 30 in contact with a stepped portion 14d located on the inner circumferential surface of the screw insertion hole 14 from the axial tip side. The coolant hole 105 has a holder flow path extending inside the holder 20 and a head flow path 105b extending inside the drill head 10 and communicating with the holder flow path. The head flow path 105b is groove-shaped, recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole 14, and has a concave flow path 105c that extends along the screw insertion hole 14. The concave flow path 105c penetrates the drill head 10 axially.

Description

Technical Field

[0001] The present invention relates to an insertable drill and a drill head.

Background Art

[0002] As a conventional insertable drill, a configuration including a steel holder, a carbide drill head detachably attached to the tip of the holder, a clamp screw for fixing the drill head to the holder, and coolant holes extending inside the holder and inside the drill head is known (for example, Patent Document 1). In recent years, this type of insertable drill has attracted attention from the viewpoints of reducing tool costs by tungsten reduction and reducing environmental impact.

[0003] In an insertable drill, a plurality (for example, two) of clamp screws for fixing the drill head to the holder are provided, and thus the drill head can be firmly fastened to the holder. However, since a plurality of screw insertion holes for inserting the clamp screws are opened on the tip surface of the drill head, it is difficult to secure a space for opening the coolant hole on the tip surface of the drill head. If the coolant cannot be stably supplied to the tip surface of the drill head, there is a risk that the cutting heat generated during drilling cannot be efficiently removed (reduced).

[0004] Therefore, in Patent Document 1, oil holes that branch into two inside the cutting head are provided at the tool center of the tool body (holder) and the cutting head (drill head), and the branch portion of the oil hole communicates with the bolt hole (screw insertion hole), and the outlet of the oil hole is formed by the inlet portion of the bolt hole. According to Patent Document 1, the coolant can be supplied from the oil hole through the inlet portion of the bolt hole to the tip surface of the cutting head.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In recent years, there has been an increasing trend in the use of stainless steel and heat-resistant steel as workpiece materials. When drilling stainless steel and heat-resistant steel, cutting heat tends to increase more easily. Therefore, there is a need to stably supply coolant to the tip surface of the drill head to improve cooling efficiency. In this specification, stainless steel and heat-resistant steel may be replaced with stainless steel alloys and heat-resistant alloys.

[0007] The present invention aims to provide an interchangeable tip drill and drill head that can stably supply coolant to the tip surface of the drill head and improve cooling efficiency. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides the following means.

[0009] [Aspect 1 of the present invention] A replaceable-tip drill comprising: a holder extending axially along a rotation axis; a drill head detachably attached to a drill head mounting seat located at the axial end of the holder; a clamp screw for fixing the drill head to the drill head mounting seat; and coolant holes extending inside the holder and inside the drill head, wherein the drill head has a screw insertion hole that penetrates the drill head axially; the clamp screw is inserted through the screw insertion hole and is screwed into a female screw hole of the drill head mounting seat while in contact with a stepped portion located on the inner circumferential surface of the screw insertion hole from the axial end side; the coolant hole has a holder flow path extending inside the holder and a head flow path extending inside the drill head and communicating with the holder flow path, the head flow path is groove-shaped, recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole, and has a concave flow path extending along the screw insertion hole, the concave flow path penetrates the drill head axially.

[0010] In the replaceable-tip drill of the present invention, the head channel extending inside the drill head has a concave channel. The concave channel is groove-shaped, recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole, and is formed to penetrate the drill head in the axial direction. Coolant supplied from the holder channel to the head channel is ejected to the tip surface of the drill head through the concave channel.

[0011] The concave channel extends axially along the screw insertion hole. As a result, the coolant ejected from the concave channel to the tip surface of the drill head is supplied evenly over a wide area on the tip surface. Specifically, for example, in the case of a configuration where the branching portion of the oil hole extends radially outward as it approaches the tip side in the axial direction, as described in Patent Document 1 (Japanese Patent No. 4703940), the coolant ejected to the tip surface of the drill tends to flow radially outward due to the centrifugal force caused by the rotation of the drill, and is less likely to be supplied to the central part of the tip surface of the drill (especially near the chisel portion where cutting resistance is high).

[0012] On the other hand, in the present invention, the coolant ejected axially from the concave channel is also stably supplied to the central part of the drill tip surface. Therefore, even when drilling workpieces of materials that tend to generate a lot of cutting heat during drilling, such as stainless steel or heat-resistant steel, the cutting heat can be efficiently removed (reduced) and the cooling efficiency can be improved.

[0013] Furthermore, the concave channel opens to the drill tip surface while communicating with the screw insertion hole. Therefore, the coolant flows to the drill tip surface not only through the opening at the tip of the concave channel, but also through the opening at the tip of the screw insertion hole. For example, compared to a configuration like the one in Patent Document 1 above, which uses only the entrance of the bolt hole (the opening of the screw insertion hole) as the coolant outlet, the present invention allows both the opening of the concave channel and the opening of the screw insertion hole to be used as coolant outlets. Therefore, in the present invention, a large opening area of ​​the coolant outlet opening to the drill tip surface is secured. According to the present invention, the amount of coolant supplied to the drill tip surface can be increased, and a wider range of coolant supply can be secured.

[0014] As described above, the present invention makes it possible to stably supply coolant to the tip surface of the drill head and improve cooling efficiency. This extends tool life, reduces tool costs, and contributes to reducing environmental impact.

[0015] [Aspect 2 of the present invention] The replaceable tip drill according to embodiment 1, wherein a plurality of the concave flow channels are provided arranged around the central axis of the screw insertion hole.

[0016] In this case, since multiple concave channels are provided around the screw insertion hole, coolant is supplied to a wider area and in greater quantity onto the tip surface of the drill head from these multiple concave channels. As a result, cutting heat is efficiently removed from the vicinity of the cutting area during drilling (such as the bottom of the hole and the cutting edge of the workpiece), and the cooling efficiency of the coolant is improved.

[0017] [Aspect 3 of the present invention] The replaceable tip drill according to embodiment 1 or 2, wherein the concave channel is recessed from the inner circumferential surface of the screw insertion hole, at least in the direction of drill rotation around the rotation axis.

[0018] In this case, it is suppressed that the coolant supplied from the concave-shaped flow path to the tip surface of the drill head immediately flows out into the chip discharge groove adjacent to the counter-drilling rotation direction of the screw insertion hole. For this reason, the coolant tends to stay near the tip surface of the drill. Further, the coolant is jetted from the concave-shaped flow path to a position near the cutting edge on the tip surface of the drill head. Therefore, the cutting heat is efficiently removed by the coolant, and the cooling efficiency is enhanced.

[0019] 〔Aspect 4 of the present invention〕 The concave-shaped flow path is a cutting-edge replaceable drill according to any one of Aspects 1 to 3, in which the groove depth dimension increases as it goes toward the tip side in the axial direction.

[0020] In this case, the cross-sectional area (opening area) of the flow path in the cross-section of the concave-shaped flow path (a cross-section perpendicular to the rotation axis) increases as it goes toward the tip side in the axial direction. For this reason, the coolant jetted from the opening at the tip side of the concave-shaped flow path to the tip surface of the drill head is supplied over a wider range on the tip surface.

[0021] 〔Aspect 5 of the present invention〕 The opening area where the concave-shaped flow path opens to the tip surface of the drill head is 20% or more and 100% or less of the area where the screw insertion hole opens to the tip surface, in the cutting-edge replaceable drill according to any one of Aspects 1 to 4.

[0022] When the opening area where the concave-shaped flow path opens to the tip surface of the drill is 20% or more of the area where the screw insertion hole opens to the tip surface of the drill, it is possible to sufficiently secure the amount of coolant jetting out from the concave-shaped flow path to the tip surface of the drill, and the cooling efficiency can be stably enhanced. Further, when the opening area where the concave-shaped flow path opens to the tip surface of the drill head is 100% or less of the area where the screw insertion hole opens to the tip surface of the drill head, while obtaining the above-described excellent effects by providing the concave-shaped flow path, the rigidity of the drill head can be maintained well.

[0023] 〔Aspect 6 of the present invention〕 The holder has a support surface facing the drill rotation direction around the rotation axis, the drill head has a supported surface facing the anti-drill rotation direction around the rotation axis and contacting the support surface, and the step portion is disposed at least at a portion of the inner peripheral surface of the screw insertion hole that is located in the anti-drill rotation direction relative to the central axis of the screw insertion hole. The cutting-edge replaceable drill according to any one of Aspects 1 to 5.

[0024] In this case, when the clamping screw is inserted into the screw insertion hole and screwed to the drill head mounting seat, the clamping screw contacts the step portion from the tip side in the axial direction and from the drill rotation direction. Since the clamping screw pushes the drill head in the anti-drill rotation direction by contacting the step portion during screwing, the supported surface of the drill head is pressed against the support surface of the holder. Thereby, the mounting state of the drill head with respect to the holder becomes more stable.

[0025] 〔Aspect 7 of the present invention〕 The coolant hole is disposed inside the holder and has a coolant reservoir chamber connected to the holder flow path. The cutting-edge replaceable drill according to any one of Aspects 1 to 6.

[0026] In this case, the coolant reservoir chamber is a hollow chamber formed inside the holder and stores the coolant. By providing such a coolant reservoir chamber, the ejection amount of the coolant can be stably increased, and the above-described operational effects by the concave flow path are more stably achieved.

[0027] 〔Aspect 8 of the present invention〕 A drill head detachably attached to a drill head mounting seat of a holder and rotated around a rotation axis together with the holder, the drill head having a screw insertion hole penetrating in the axial direction thereof through which a clamping screw is inserted, and a head flow path extending inside the drill head and communicating with a holder flow path extending inside the holder, the head flow path forming a groove shape recessed outward in the hole diameter direction from the inner peripheral surface of the screw insertion hole, and having a concave flow path extending along the screw insertion hole, the concave flow path penetrating the drill head in the axial direction.

[0028] According to the drill head of the present invention, the same excellent effects as those of the replaceable-tip drill of the present invention described above can be obtained. [Effects of the Invention]

[0029] According to the above-described aspect of the present invention, an interchangeable tip drill and drill head are provided that can stably supply coolant to the tip surface of the drill head and improve cooling efficiency. [Brief explanation of the drawing]

[0030] [Figure 1] Figure 1 is a perspective view showing a replaceable-tip drill according to this embodiment. [Figure 2] Figure 2 is a front view showing a replaceable-tip drill according to this embodiment. [Figure 3] Figure 3 is a side view showing a part of the replaceable-tip drill according to this embodiment. [Figure 4] Figure 4 is a cross-sectional view (longitudinal section) showing the section IV-IV in Figure 2. [Figure 5] Figure 5 is a cross-sectional view (longitudinal section) showing the VV section of Figure 2. [Figure 6] Figure 6 is a perspective view showing a part of the holder. [Figure 7] Figure 7 is a perspective view showing the drill head. [Figure 8] Figure 8 is a perspective view showing the drill head. [Figure 9] Figure 9 is a cross-sectional view (longitudinal section) showing a part of the drill head (near the screw insertion hole). [Figure 10] Figure 10 is a perspective view showing a modified drill head. [Figure 11] Figure 11 is a perspective view showing a modified drill head. [Figure 12] Figure 12 is a front view showing a modified example of the drill head. [Figure 13] Figure 13 is a cross-sectional view (longitudinal section) showing the XIII-XIII section of Figure 12. [Figure 14] Figure 14 is a cross-sectional view (longitudinal section) showing the XIV-XIV section of Figure 12. [Modes for carrying out the invention]

[0031] An interchangeable-tip drill 100 and drill head 10 according to one embodiment of the present invention will be described with reference to Figures 1 to 9. The interchangeable-tip drill 100 and drill head 10 of this embodiment are suitable for drilling holes in workpieces made of stainless steel, heat-resistant steel, etc., which tend to generate high cutting heat. In this embodiment, the interchangeable-tip drill 100 and drill head 10 may be simply referred to as a drill or a tool.

[0032] As shown in Figure 1, the replaceable tip drill 100 has a substantially cylindrical shape with a rotation axis O as its center. The replaceable tip drill 100 comprises a shank portion 101, a drilling portion 102, a flange portion 103, a chip evacuation groove 104, and a coolant hole 105. The shank portion 101, the drilling portion 102, and the flange portion 103 are arranged coaxially with respect to the rotation axis O as a common axis. The shank portion 101, the flange portion 103, and the drilling portion 102 are arranged in this order along the direction in which the rotation axis O extends.

[0033] The replaceable-tip drill 100 also includes a substantially cylindrical holder 20 centered on a rotation axis O, a drill head 10 that can be detachably attached to a drill head mounting seat 106 of the holder 20, and a clamp screw 30 that fixes the drill head 10 to the drill head mounting seat 106. The drill head 10 is made of, for example, cemented carbide and constitutes a part (the tip) of the effective drilling portion 102. The holder 20 is made of, for example, steel and constitutes the portion of the effective drilling portion 102 other than the aforementioned part, as well as the flange portion 103 and the shank portion 101.

[0034] [Definition of direction] In this embodiment, the direction in which the rotation axis O of the drill extends is called the axial direction. The rotation axis O is the central axis of the replaceable tip drill 100 and also the central axis of the drill head 10. Of the axial directions, the direction from the shank portion 101 toward the effective drilling portion 102 is called the axial tip side, or simply the tip side, and the direction from the effective drilling portion 102 toward the shank portion 101 is called the axial rear end side, or simply the rear end side.

[0035] Furthermore, the direction perpendicular to the axis of rotation O is called the radial direction. Within the radial direction, the direction approaching the axis of rotation O is called the radially inward direction, and the direction moving away from the axis of rotation O is called the radially outward direction. Furthermore, the direction of rotation around the axis of rotation O is called the circumferential direction. Of the circumferential directions, the direction in which the drill is rotated during drilling is called the drill rotation direction T, and the direction opposite to this is called the opposite direction to the drill rotation direction T or the anti-drill rotation direction.

[0036] As shown in Figures 2 and 4, the drill head 10 has screw insertion holes 14 that penetrate the drill head 10 in the axial direction. Multiple screw insertion holes 14 are provided in the drill head 10, spaced apart from each other in the circumferential direction. The central axis C of each screw insertion hole 14 extends in the axial direction. That is, the central axis C of each screw insertion hole 14 and the rotation axis O of the drill extend parallel to each other.

[0037] In this embodiment, the direction perpendicular to the central axis C of the screw insertion hole 14 is called the diameter direction. Within the diameter direction, the direction approaching the central axis C is called the inside of the diameter direction, and the direction moving away from the central axis C is called the outside of the diameter direction. Furthermore, the direction that circumfers around the central axis C of the screw insertion hole 14 is called the circumferential direction of the hole.

[0038] [Holder] As shown in Figure 1, the holder 20 extends axially along the rotation axis O. The holder 20 includes a shank portion 101, a flange portion 103, and the portion of the effective drilling portion 102 other than the tip portion (drill head 10).

[0039] The shank portion 101 is columnar in shape, extending axially around the rotation axis O, and is specifically approximately cylindrical. The shank portion 101 is positioned at the rear end of the replaceable-tip drill 100. The shank portion 101 is detachably attached and held to, for example, the spindle of a machine tool (not shown) or the chuck of a drilling machine (hereinafter abbreviated as spindle, etc.). As the shank portion 101 is rotated in the drill rotation direction T by the spindle, etc., and moved toward the tip in the axial direction, the drill cuts into the workpiece and performs drilling.

[0040] The flange portion 103 is positioned in the axial direction between the shank portion 101 and the effective drilling portion 102. The flange portion 103 is the part of the replaceable tip drill 100 with the largest outer diameter. The end face of the flange portion 103 facing the rear end is a flat surface that extends in a direction perpendicular to the rotation axis O and contacts the tip surface of a spindle or the like (not shown). The surface of the flange portion 103 facing the tip is a tapered surface that decreases in diameter towards the tip.

[0041] The effective drilling portion 102 is columnar in shape, extending axially with respect to the rotation axis O. The effective drilling portion 102 includes the tip portion of the holder 20 and the drill head 10. The effective drilling portion 102 cuts into the workpiece by the drill head 10 to perform drilling, and is inserted into the drilled hole during machining.

[0042] The chip discharge groove 104 opens onto the tip surface (the tip surface 3 of the drill head 10, described later) and the outer circumferential surface of the effective drilling portion 102 and is groove-shaped, extending substantially in the axial direction. More specifically, the chip discharge groove 104 extends substantially spirally in the direction opposite to the drill rotation direction T as it moves from the tip surface of the effective drilling portion 102 toward the rear end. In this embodiment, the chip discharge groove 104 is arranged across the effective drilling portion 102 and the surface facing the tip side of the flange portion 103. Although not specifically shown, the chip discharge groove 104 may also be arranged on the outer circumferential surface of the flange portion 103. Note that the chip discharge groove 104 only needs to be arranged on the effective drilling portion 102 and does not need to be arranged on the flange portion 103.

[0043] The chip evacuation groove 104 has a head chip evacuation groove 104a located at the tip of the chip evacuation groove 104, and a holder chip evacuation groove 104b located in the part of the chip evacuation groove 104 other than the tip. The head chip evacuation groove 104a is the part of the chip evacuation groove 104 located in the drill head 10. The holder chip evacuation groove 104b is the part of the chip evacuation groove 104 located in the holder 20. In the following description, the head chip evacuation groove 104a or the holder chip evacuation groove 104b may be simply referred to as the chip evacuation groove 104.

[0044] Furthermore, multiple chip discharge grooves 104 are provided at intervals from each other in the circumferential direction. As shown in Figure 2, in this embodiment, a pair of chip discharge grooves 104 are provided at equal pitches in the circumferential direction.

[0045] As shown in Figure 6, the coolant hole 105 extends through the interior of the replaceable-tip drill 100. The coolant hole 105 extends through the interior of the holder 20 and the interior of the drill head 10. Although not specifically shown, the coolant hole 105 is provided through the replaceable-tip drill 100 in the axial direction. Coolant such as cutting fluid or compressed air is supplied to the coolant hole 105 via a spindle or the like (not shown). The detailed configuration of the coolant hole 105, other than those described above, will be described separately later.

[0046] As shown in Figures 3 to 6, the drill head mounting seat 106 is located at the axial end of the holder 20. The drill head mounting seat 106 has a mounting surface 107 facing the axial end, a support surface 108 that protrudes further towards the end than the mounting surface 107 and faces in the circumferential direction, a fitting hole 109 recessed toward the rear end in the axial direction from the mounting surface 107, and a female screw hole 110 that opens into the mounting surface 107. In other words, the holder 20 has a mounting surface 107, a support surface 108, a fitting hole 109, and a female screw hole 110.

[0047] The mounting surface 107 is planar in shape, extending in a direction perpendicular to the rotation axis O. Multiple mounting surfaces 107 are provided at intervals from each other in the circumferential direction. In this embodiment, a pair of mounting surfaces 107 are provided at equal pitches in the circumferential direction. The axial positions of each mounting surface 107 are the same.

[0048] The support surface 108 faces the drill rotation direction T in the circumferential direction around the rotation axis O. In this embodiment, the support surface 108 is planar. As shown in Figure 6, the support surface 108 extends radially outward toward the drill rotation direction T. Multiple support surfaces 108 are provided at intervals from each other in the circumferential direction. In this embodiment, a pair of support surfaces 108 are provided at equal pitches in the circumferential direction.

[0049] The fitting hole 109 is a bottomed hole centered on the rotation axis O, and is specifically a roughly circular hole. The fitting hole 109 is located radially inward from the mounting surface 107 and the support surface 108. A portion of the circumferential wall forming the inner surface of the fitting hole 109 is notched so as to penetrate radially. The fitting hole 109 and the holder chip discharge groove 104b are in communication with each other through the notch formed on the inner surface of the fitting hole 109.

[0050] The female screw hole 110 opens into the mounting surface 107 and extends from the mounting surface 107 toward the rear end in the axial direction. The central axis of the female screw hole 110 extends parallel to the rotation axis O. The female screw hole 110 has a female threaded portion on its inner circumferential surface. Multiple female screw holes 110 are provided spaced apart from each other in the circumferential direction. In this embodiment, a pair of female screw holes 110 are provided at equal pitches in the circumferential direction.

[0051] [Drill head] The drill head 10 is attached to a drill head mounting seat 106 located at the tip of the holder 20, and is rotated together with the holder 20 in the drill rotation direction T around the rotation axis O by a spindle (not shown).

[0052] As shown in Figures 7 and 8, the drill head 10 has a tip surface 3 facing the axial tip side, an outer peripheral surface 8 facing radially outward, a chip evacuation groove 104 opening on the tip surface 3 and the outer peripheral surface 8 and extending from the tip surface 3 towards the axial rear end, a rake surface 5, a relief surface 6, a cutting edge 7, a seating surface 9, a fitting portion 13, a screw insertion hole 14, and a supported surface 15. In this embodiment, the tip surface 3 may be referred to as the drill tip surface 3, etc.

[0053] The chip evacuation groove 104 of the drill head 10 is specifically the head chip evacuation groove 104a described above. The chip evacuation groove 104 (head chip evacuation groove 104a) extends in the direction opposite to the drill rotation as it moves from the tip surface 3 toward the rear end in the axial direction.

[0054] The chip discharge groove 104 has a thinning surface 11. The thinning surface 11 is located at the tip of the head chip discharge groove 104a. The thinning surface 11 is connected to the end of the tip surface 3 opposite to the drill rotation direction T. The thinning surface 11 extends axially toward the rear end as it is directed away from the drill rotation direction.

[0055] The rake face 5 is located at least at the tip of the chip evacuation groove 104 (head chip evacuation groove 104a) that faces the drill rotation direction T. That is, the chip evacuation groove 104 further has a rake face 5. As shown in Figure 3, the rake face 5 has a thinning rake face 51 and a main rake face 52.

[0056] The thinning rake face 51 is positioned at the radially inner end of the tip of the chip discharge groove 104. The thinning rake face 51 is connected to the radially inner end of the thinning face 11 and faces the drill rotation direction T. In this embodiment, the thinning rake face 51 has a substantially triangular planar shape.

[0057] The main rake face 52 is positioned radially outward from the thinning rake face 51. In this embodiment, the main rake face 52 has a concave curved portion. Of the main rake face 52, the concave curved portion described above has a concave curved shape that is recessed in the direction opposite to the drill rotation when viewed in a cross-sectional view perpendicular to the rotation axis O (i.e., a transverse view).

[0058] As shown in Figure 7, the relief surface 6 is positioned on the tip surface 3. That is, the tip surface 3 has a relief surface 6. The relief surface 6 has a first relief surface 61 and a second relief surface 62 positioned adjacent to the first relief surface 61 in the direction opposite to the drill rotation.

[0059] The first relief surface 61 extends toward the rear end in the axial direction as it is directed away from the direction of drill rotation. The second relief surface 62 also extends toward the rear end in the axial direction as it is directed away from the direction of drill rotation. The first relief surface 61 and the second relief surface 62 are each inclined as described above, thereby providing a relief angle. Furthermore, the second relief surface 62 has a larger relief angle than the first relief surface 61. That is, the amount of axial displacement per unit length along the circumferential direction of the second relief surface 62 (inclination corresponding to the relief angle) is greater than the amount of displacement of the first relief surface 61.

[0060] As shown in Figure 2, in a front view of the drill head 10 viewed from the tip side along the axial direction, the first relief surface 61 is a radially extending band (a roughly polygonal shape that is long in the radial direction), and the second relief surface 62 is roughly fan-shaped.

[0061] In this embodiment, an example was given in which the relief surface 6 has two inclined surfaces (a first relief surface 61 and a second relief surface 62) with different relief angles, but the configuration is not limited to this. The relief surface 6 may be formed by a single inclined surface, or it may have three or more inclined surfaces arranged in the circumferential direction.

[0062] As shown in Figure 7, the cutting edge 7 is positioned on the ridge where the surface of the chip evacuation groove 104 (head chip evacuation groove 104a) facing the drill rotation direction T connects to the tip surface 3. Specifically, the cutting edge 7 is positioned on the ridge where the rake surface 5 and the relief surface 6 connect. Multiple cutting edges 7 are provided on the drill head 10, spaced apart from each other in the circumferential direction. In this embodiment, two cutting edges 7 are provided at equal pitches in the circumferential direction. That is, the drill head 10 and the replaceable tip drill 100 in this embodiment are two-blade twist drills.

[0063] The cutting edge 7 has a thinning edge 71 and a main cutting edge 72. The thinning blade 71 is positioned at the radially inner end of the cutting edge 7. The thinning blade 71 is positioned on the ridge where the thinning rake face 51 and the first relief face 61 are connected. In a front view of the drill shown in Figure 2, the thinning blade 71 extends radially outward from near the rotation axis O, following approximately the radial direction. In this embodiment, the thinning blade 71 is linear. Also, as shown in Figure 3, the thinning blade 71 extends radially outward towards the axial rear end.

[0064] The main cutting edge 72 is positioned radially outward of the thinning edge 71. The main cutting edge 72 is positioned on the ridge where the main rake face 52 and the first relief face 61 are connected. In the front view of the drill shown in Figure 2, the main cutting edge 72 has a concave curved portion that is recessed in the direction opposite to the drill rotation.

[0065] As shown in Figure 3, the main cutting edge 72 extends radially outward towards the axial rear end. The radially inner end of the main cutting edge 72 connects to the radially outer end of the thinning edge 71. As shown in Figure 7, in this embodiment, the connection portion between the main cutting edge 72 and the thinning edge 71 has a convex curved shape that protrudes in the drill rotation direction T. This convex curved portion ensures a smooth connection between the main cutting edge 72 and the thinning edge 71.

[0066] Although not specifically shown in the illustrations, the cutting edge 7 may also have honing positioned at the cutting edge of the cutting edge 7. The honing extends along the direction in which the cutting edge 7 extends (the blade length direction). In this case, the honing may be round honing or chamfer honing.

[0067] The outer surface 8 has a margin 81 and a secondary bevel surface 82. The margin 81 is located at the end of the outer circumferential surface 8 in the drill rotation direction T and extends substantially in the axial direction. Specifically, the margin 81 extends in the direction opposite to the drill rotation direction as it approaches the rear end in the axial direction.

[0068] As shown in Figure 8, the margin 81 and the main rake face 52 are connected to each other via the ridge (leading edge 12). The margin 81 is positioned adjacent to the leading edge 12 in the direction opposite to the drill rotation. The margin 81 is located on a cylindrical rotation trajectory (not shown) obtained by rotating the leading edge 12 around the rotation axis O. In a cross-sectional view perpendicular to the rotation axis O, the margin 81 forms an arc shape centered on the rotation axis O. The leading edge 12 may also have a back taper. In this case, the leading edge 12 is positioned slightly radially inward as it approaches the rear end in the axial direction.

[0069] The secondary chamfering face 82 is positioned adjacent to the margin 81 in the direction opposite to the drill rotation. The secondary chamfering face 82 is positioned radially inward from the margin 81. During drilling, the secondary chamfering face 82 faces the inner circumferential surface of the machined hole in the workpiece with a radial gap between them.

[0070] The seating surface 9 faces the rear end in the axial direction. The seating surface 9 is planar, extending in a direction perpendicular to the axis of rotation O. Multiple seating surfaces 9 are provided at intervals from each other in the circumferential direction. In this embodiment, a pair of seating surfaces 9 are provided at equal pitches in the circumferential direction. The axial position of each seating surface 9 is the same as that of the others.

[0071] As shown in Figures 3 and 4, when the drill head 10 is attached to the drill head mounting seat 106, the seating surface 9 comes into contact with the mounting surface 107. This allows the drill head 10 to be supported by the drill head mounting seat 106 from the axial rear end side.

[0072] As shown in Figures 4 and 8, the fitting portion 13 protrudes from the seating surface 9 toward the rear end in the axial direction. The fitting portion 13 is columnar in shape with the rotation axis O as its center, and specifically, it is a substantially cylindrical shape extending in the axial direction. The fitting portion 13 is inserted into the fitting hole 109 of the drill head mounting seat 106. The fitting portion 13 and the fitting hole 109 fit together. This positions the drill head 10 radially on the drill head mounting seat 106.

[0073] As shown in Figures 5, 7, and 8, the screw insertion holes 14 penetrate the drill head 10 in the axial direction and open to the tip surface 3 and the seating surface 9. The screw insertion holes 14 are multi-stage circular holes that extend in the axial direction. The inner diameter of the screw insertion holes 14 decreases in stages from the drill tip surface 3 toward the rear end in the axial direction. Multiple screw insertion holes 14 are provided at intervals from each other in the circumferential direction. In this embodiment, a pair of screw insertion holes 14 are provided at equal pitches in the circumferential direction.

[0074] As shown in Figure 5, the screw insertion hole 14 has a large-diameter hole portion 14a located at the front end of the screw insertion hole 14, a small-diameter hole portion 14b located at the rear end of the screw insertion hole 14, and a tapered hole portion 14c located between the large-diameter hole portion 14a and the small-diameter hole portion 14b in the axial direction.

[0075] The large-diameter hole portion 14a is circular in shape and extends axially with respect to the central axis C of the screw insertion hole 14. The large-diameter hole portion 14a is the opening on the tip side of the screw insertion hole 14 and opens onto the second relief surface 62 of the drill tip surface 3.

[0076] The small-diameter hole 14b is circular in shape and extends axially around the central axis C of the screw insertion hole 14. The inner diameter of the small-diameter hole 14b is smaller than the inner diameter of the large-diameter hole 14a. The small-diameter hole 14b is the opening at the rear end of the screw insertion hole 14 and opens to the seating surface 9.

[0077] The tapered hole portion 14c has a tapered shape centered on the central axis C, and its inner diameter decreases (reduces in diameter) as it moves toward the rear end in the axial direction. The tip end of the tapered hole portion 14c is smoothly connected to the rear end of the large-diameter hole portion 14a. The rear end of the tapered hole portion 14c is smoothly connected to the tip end of the small-diameter hole portion 14b. The tapered hole portion 14c constitutes a stepped portion 14d located on the inner circumferential surface of the screw insertion hole 14. A part of the clamp screw 30 (the tapered portion 31b described later) contacts and is locked into the tapered hole portion 14c (stepped portion 14d).

[0078] In this embodiment, as shown in Figure 7, the concave flow channels 105c of the coolant hole 105, described later, are formed to cut out the inner circumferential surface of the screw insertion hole 14 outward in the diameter direction of the hole. Furthermore, multiple concave flow channels 105c are provided at intervals from each other in the circumferential direction of the hole. As shown in Figure 9, the tapered hole portion 14c is formed to be divided into multiple sections in the circumferential direction by multiple concave flow channels 105c arranged in that direction. Therefore, multiple stepped portions 14d, formed by the tapered hole portion 14c, are also provided at intervals from each other in the circumferential direction of the hole. Specifically, in this embodiment, six stepped portions 14d are provided at equal pitches in the circumferential direction of a single screw insertion hole 14.

[0079] The stepped portion 14d is positioned on the inner circumferential surface of the screw insertion hole 14, at least in a portion located in the direction opposite to the drill rotation relative to the central axis C of the screw insertion hole 14. In this embodiment, at least one of the multiple stepped portions 14d is located on the inner circumferential surface of the screw insertion hole 14 in the direction opposite to the drill rotation relative to the central axis C. Specifically, three of the six stepped portions 14d are located in the direction opposite to the drill rotation relative to the central axis C, and the remaining three are located in the drill rotation direction T relative to the central axis C (see Figure 2).

[0080] As shown in Figures 3, 7, and 8, the supported surface 15 is positioned in the circumferential direction between the chip discharge groove 104 (head chip discharge groove 104a) and the secondary beveling surface 82. The supported surface 15 faces the direction opposite to the drill rotation direction around the rotation axis O. In this embodiment, the supported surface 15 is planar. Specifically, the supported surface 15 is polygonal, and in the illustrated example, it is approximately trapezoidal. The supported surface 15 extends radially outward towards the drill rotation direction T.

[0081] Multiple support surfaces 15 are provided at intervals from each other in the circumferential direction. In this embodiment, a pair of support surfaces 15 are provided at equal pitches in the circumferential direction. As shown in Figure 3, the support surfaces 15 contact the support surface 108 of the drill head mounting seat 106, which faces the drill rotation direction T. As a result, the drill head 10 is supported by the drill head mounting seat 106 from the direction opposite to the drill rotation direction.

[0082] [Clamping screws] As shown in Figures 1, 2, 4, and 5, a clamp screw 30 is inserted into the screw insertion hole 14 to fasten the drill head 10 and the holder 20. The clamp screw 30 is inserted into the screw insertion hole 14 and, with its axial tip in contact with the stepped portion 14d located on the inner circumferential surface of the screw insertion hole 14, is screwed into the female screw hole 110 of the drill head mounting seat 106. In this way, the drill head 10 is detachably fixed to the drill head mounting seat 106.

[0083] When the clamp screw 30 is screwed into the female screw hole 110, the screw axis of the clamp screw 30 is approximately aligned with the central axis C of the screw insertion hole 14. However, this is not limited to this configuration; when the clamp screw 30 is screwed into the female screw hole 110, the screw axis of the clamp screw 30 may be positioned slightly in the anti-drill rotation direction relative to the central axis C of the screw insertion hole 14. In this case, the clamp screw 30 presses against the stepped portion 14d on the inner circumferential surface of the screw insertion hole 14 in the anti-drill rotation direction, thereby stabilizing the contact between the supported surface 15 of the drill head 10 and the support surface 108 of the drill head mounting seat 106. In other words, the mounting state of the drill head 10 to the drill head mounting seat 106 becomes more stable.

[0084] As shown in Figure 5, the clamp screw 30 has a substantially multi-stage cylindrical shape and extends in the axial direction. The clamp screw 30 has a screw head 31 located at the tip of the clamp screw 30 and a screw shaft portion 32 located on the part of the clamp screw 30 other than the tip.

[0085] The screw head 31 is roughly cylindrical and extends in the axial direction. The screw head 31 has the largest outer diameter among the clamp screws 30. The outer diameter of the screw head 31 is smaller than the inner diameter of the large diameter hole portion 14a of the screw insertion hole 14, and larger than the inner diameter of the small diameter hole portion 14b.

[0086] The screw head 31 has a locking hole 31a into which a work tool is locked, and a tapered portion 31b located on the rear end portion of the outer circumferential surface of the screw head 31. The locking hole 31a is concave, extending from the top surface facing the axial tip side of the screw head 31 toward the rear end. The tapered portion 31b decreases in outer diameter (reduces in diameter) as it extends toward the rear end in the axial direction. When the clamp screw 30 is inserted through the screw insertion hole 14 and screwed into the female screw hole 110, the tapered portion 31b contacts the stepped portion 14d (tapered hole portion 14c) from the axial tip side and from the inside in the diameter direction of the hole.

[0087] The screw shaft portion 32 is roughly cylindrical and extends in the axial direction. The outer diameter of the screw shaft portion 32 is smaller than the outer diameter of the screw head 31. Also, the outer diameter of the screw shaft portion 32 is smaller than the inner diameter of the small diameter hole portion 14b of the screw insertion hole 14. The axial tip of the screw shaft portion 32 is connected to the axial rear end of the screw head 31. The screw shaft portion 32 has a male thread on its outer circumferential surface. The screw shaft portion 32 is screwed into the female screw hole 110.

[0088] [Coolant holes] Here, the coolant hole 105 of this embodiment will be described in detail. The coolant hole 105 has a holder channel 105a extending inside the holder 20 and a head channel 105b extending inside the drill head 10 and communicating with the holder channel 105a.

[0089] As shown in Figure 6, the holder channel 105a is located in at least the portion of the holder 20 that constitutes the effective drilling portion 102 (in other words, the portion of the effective drilling portion 102 other than the drill head 10). The holder channel 105a is located between a pair of circumferentially adjacent chip discharge grooves 104 (holder chip discharge groove 104b) in the effective drilling portion 102.

[0090] The holder channel 105a extends in the direction opposite to the drill rotation as it approaches the rear end in the axial direction. Although not specifically shown, in this embodiment the holder channel 105a extends across the effective drilling portion 102, the flange portion 103, and the shank portion 101, that is, along the entire axial length of the holder 20. The holder channel 105a is provided to penetrate the holder 20 in the axial direction.

[0091] The holder channel 105a has, for example, multiple (e.g., two) linear channels that extend in a straight line. The multiple linear channels are arranged side by side in the axial direction and are connected to each other. Of the multiple linear channels, one linear channel located at the front end opens to the mounting surface 107 of the drill head mounting seat 106. Of the multiple linear channels, another linear channel located at the rear end opens to the rear end surface of the shank portion 101. One linear channel and the other linear channels extend in different directions (i.e., they have different inclinations). In addition, the inner diameter of one linear channel is smaller than the inner diameter of the other linear channels.

[0092] The holder channel 105a may, for example, have multiple curved channels that extend in a curved shape. The multiple curved channels are arranged in a line in the axial direction and connected to each other. Alternatively, the holder channel 105a may be formed by combining straight channels and curved channels.

[0093] As shown in Figure 6, multiple holder channels 105a are provided at intervals from each other in the circumferential direction. In this embodiment, a pair of holder channels 105a are provided at equal pitches in the circumferential direction.

[0094] As shown in Figures 7 to 9, the head channel 105b is provided, penetrating the drill head 10 in the axial direction. The head channel 105b is positioned adjacent to the outer side of the screw insertion hole 14 in the diameter direction and is connected to the screw insertion hole 14. The tip end of the head channel 105b opens to the second relief surface 62 of the drill tip surface 3. The rear end of the head channel 105b opens to the seating surface 9.

[0095] The opening area at the front end of the head flow path 105b (the area opening around the large-diameter hole 14a of the screw insertion hole 14) is larger than the opening area at the rear end of the head flow path 105b (the area opening around the small-diameter hole 14b of the screw insertion hole 14). The opening area (flow path cross-sectional area) of the head flow path 105b in a cross-section perpendicular to the central axis C gradually increases towards the front end in the axial direction. Multiple head channels 105b are provided in the circumferential direction, spaced apart from each other. In this embodiment, a pair of head channels 105b are provided at equal pitches in the circumferential direction.

[0096] The head channel 105b has a concave channel 105c that is recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole 14. The concave channel 105c penetrates the drill head 10 in the axial direction. In this embodiment, multiple concave channels 105c are provided arranged around the central axis C of the screw insertion hole 14. That is, each head channel 105b has multiple concave channels 105c.

[0097] The multiple concave channels 105c are arranged at intervals from each other in the circumferential direction of the hole. Specifically, in this embodiment, each head channel 105b has six concave channels 105c arranged at equal pitches in the circumferential direction of the hole. In addition, at least one of the multiple concave channels 105c is formed as a recess from the inner circumferential surface of the screw insertion hole 14 toward the drill rotation direction T. That is, at least one of the multiple concave channels 105c opens to the drill tip surface 3 between the screw insertion hole 14 (clamp screw 30) and the cutting edge 7 in the circumferential direction.

[0098] The concave channel 105c is groove-shaped and extends in the axial direction. The concave channel 105c extends along the screw insertion hole 14. Both axial ends (tip and rear end) of the concave channel 105c open to the second relief surface 62 and the seating surface 9 of the drill tip surface 3. The shape of the cross-section of the concave channel 105c perpendicular to the central axis C is a semicircular shape that is recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole 14.

[0099] The groove bottom of the concave channel 105c extends outward in the diameter direction of the hole as it approaches the axial tip. That is, the groove depth dimension (the dimension recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole 14) increases as it approaches the axial tip of the concave channel 105c. The opening area at the tip end of the concave channel 105c is larger than the opening area at the rear end of the concave channel 105c. The groove width dimension along the circumferential direction of the hole at the tip end of the concave channel 105c is larger than the groove width dimension along the circumferential direction of the hole at the rear end of the concave channel 105c. Also, the groove depth dimension along the diameter direction of the hole at the tip end of the concave channel 105c is larger than the groove depth dimension along the diameter direction of the hole at the rear end of the concave channel 105c.

[0100] The opening area of ​​the concave channel 105c that opens onto the tip surface 3 of the drill head 10 is set to be between 20% and 100% of the opening area of ​​the screw insertion hole 14 that opens onto the tip surface 3. More specifically, in this embodiment, a plurality (six) of concave channels 105c are provided on the inner circumference of one screw insertion hole 14, and the sum of the opening areas of the plurality (six) of concave channels 105c that open onto the drill tip surface 3 is set to be between 20% and 100% of the opening area of ​​one screw insertion hole 14 that opens onto the drill tip surface 3, with the opening area of ​​one screw insertion hole 14 being the standard (100%).

[0101] As shown in Figures 4 to 6, the coolant hole 105 further has a connecting passage 105d that connects the holder passage 105a and the head passage 105b. In this embodiment, the connecting passage 105d is located on the drill head mounting seat 106 of the holder 20. Multiple connecting passages 105d are provided spaced apart from each other in the circumferential direction. In this embodiment, a pair of connecting passages 105d are provided at equal pitches in the circumferential direction.

[0102] The connecting channel 105d is concave, recessed in the axial direction towards the rear end from the mounting surface 107 of the drill head mounting seat 106. In this embodiment, the connecting channel 105d is groove-shaped, extending in the circumferential direction. The groove width dimension (i.e., the cross-sectional area of ​​the connecting channel 105d) increases as it moves toward the drill rotation direction T. The tip of the holder channel 105a is connected to the end of the connecting channel 105d in the direction opposite to the drill rotation direction. The rear end of the head channel 105b (each of the rear ends of the multiple concave channels 105c) is connected to the end of the connecting channel 105d in the drill rotation direction T.

[0103] [Effects of this embodiment] In the replaceable tip drill 100 and drill head 10 of this embodiment described above, the head channel 105b extending inside the drill head 10 has a concave channel 105c. The concave channel 105c is groove-shaped, recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole 14, and is formed to penetrate the drill head 10 in the axial direction. Coolant supplied from the holder channel 105a to the head channel 105b is ejected through the concave channel 105c onto the tip surface 3 of the drill head 10.

[0104] The concave channel 105c extends axially along the screw insertion hole 14. Therefore, the coolant ejected from the concave channel 105c onto the tip surface 3 of the drill head 10 is supplied evenly over a wide area on the tip surface 3. Specifically, for example, in the case of a configuration where the branching portion of the oil hole extends radially outward as it approaches the tip side in the axial direction, as described in Patent Document 1 (Japanese Patent No. 4703940) above, the coolant ejected onto the drill tip surface tends to flow radially outward due to the centrifugal force caused by the rotation of the drill, and is less likely to be supplied to the central part of the drill tip surface (especially near the chisel portion where cutting resistance is high).

[0105] On the other hand, in this embodiment, the coolant ejected axially from the concave channel 105c is also stably supplied to the vicinity of the center of the drill tip surface 3. Therefore, even when drilling workpieces of materials that tend to generate a lot of cutting heat during drilling, such as stainless steel or heat-resistant steel, the cutting heat can be efficiently removed (reduced) and the cooling efficiency can be improved.

[0106] Furthermore, the concave channel 105c opens to the drill tip surface 3 while communicating with the screw insertion hole 14. Therefore, the coolant flows out to the drill tip surface 3 not only through the opening at the tip of the concave channel 105c, but also through the opening at the tip of the screw insertion hole 14. For example, compared to a configuration like the one in Patent Document 1 above, which uses only the entrance of the bolt hole (the opening of the screw insertion hole) as the coolant outlet, in this embodiment, both the opening of the concave channel 105c and the opening of the screw insertion hole 14 can be used as coolant outlets. Therefore, in this embodiment, a large opening area of ​​the coolant outlet opening to the drill tip surface 3 is secured. According to this embodiment, the amount of coolant supplied to the drill tip surface 3 can be increased, and a wider range of coolant supply can be secured.

[0107] As described above, according to this embodiment, coolant can be stably supplied to the tip surface 3 of the drill head 10, thereby improving cooling efficiency. This extends tool life, reduces tool costs, and contributes to reducing environmental impact.

[0108] In this embodiment, multiple concave flow channels 105c are provided arranged around the central axis C of the screw insertion hole 14. In this case, since multiple concave channels 105c are provided around the screw insertion hole 14, coolant is supplied to a wider area and in a larger quantity onto the tip surface 3 of the drill head 10 from the multiple concave channels 105c. As a result, cutting heat is efficiently removed from the vicinity of the cutting area during drilling (such as the bottom of the machined hole in the workpiece and the cutting edge 7), and the cooling efficiency by the coolant is improved.

[0109] In this embodiment, the groove depth dimension of the concave flow channel 105c increases as it moves toward the tip side in the axial direction. In this case, the cross-sectional area (opening area) of the flow path in the cross-section of the concave flow path 105c (the section perpendicular to the axis of rotation O) increases as it moves towards the tip side in the axial direction. As a result, the coolant ejected from the opening at the tip side of the concave flow path 105c onto the tip surface 3 of the drill head 10 is supplied over a wider area on the tip surface 3.

[0110] In this embodiment, the opening area of ​​the concave flow channel 105c that opens onto the tip surface 3 of the drill head 10 is 20% to 100% of the opening area of ​​the screw insertion hole 14 that opens onto the tip surface 3.

[0111] If the opening area of ​​the concave channel 105c that opens onto the drill tip surface 3 is 20% or more of the opening area of ​​the screw insertion hole 14 that opens onto the drill tip surface 3, then a sufficient amount of coolant can be ejected from the concave channel 105c onto the drill tip surface 3, thereby stably increasing the cooling efficiency. Furthermore, if the opening area of ​​the concave channel 105c that opens to the drill tip surface 3 is 100% or less of the opening area of ​​the screw insertion hole 14 that opens to the drill tip surface 3, then by providing the concave channel 105c, the above-mentioned excellent effects can be obtained while maintaining good rigidity of the drill head 10.

[0112] In this embodiment, the stepped portion 14d is positioned on the inner circumferential surface of the screw insertion hole 14 at least in the direction opposite to the drill rotation direction from the central axis C of the screw insertion hole 14. In this case, when the clamp screw 30 is inserted through the screw insertion hole 14 and screwed into the drill head mounting seat 106, the clamp screw 30 contacts the stepped portion 14d from the axial tip side and from the drill rotation direction T. As the clamp screw 30 contacts the stepped portion 14d during screwing, it pushes the drill head 10 in the opposite direction of drill rotation, causing the supported surface 15 of the drill head 10 to be pressed against the support surface 108 of the holder 20. This makes the mounting state of the drill head 10 to the holder 20 more stable.

[0113] In this embodiment, the coolant hole 105 also has a connecting passage 105d that connects the holder passage 105a and the head passage 105b. In this case, the connecting channel 105d ensures stable communication between the holder channel 105a and the head channel 105b. The interposition of the connecting channel 105d between the holder channel 105a and the head channel 105b increases the degree of freedom in the shape and layout of each channel in the holder channel 105a and the head channel 105b.

[0114] [Other components included in the present invention] The present invention is not limited to the embodiments described above, and modifications to the configuration, etc., are possible without departing from the spirit of the invention, as described below. In the illustrations of modified examples, the same reference numerals are used for the same components as in the embodiments described above, and the main differences will be described below.

[0115] Figures 10 to 14 show a modified drill head 10A, which is a modified version of the drill head 10 described in the above-described embodiment. Although not specifically shown, the drill head 10A is detachably attached to the drill head mounting seat 106 of the holder 20. The drill head 10A constitutes the tip of the effective drilling portion 102 of the replaceable tip drill 100. As shown in Figures 10 to 14, the modified drill head 10A differs from the drill head 10 of the above-described embodiment in the configuration of the head flow path 105b of the coolant hole 105.

[0116] Specifically, in this modified example, each of the pair of head channels 105b has one concave channel 105c that penetrates the drill head 10A in the axial direction. The concave channel 105c is formed recessed outward in the diameter direction of the hole, at least toward the drill rotation direction T, from the inner circumferential surface of the screw insertion hole 14. The shape of the cross-section of the concave channel 105c perpendicular to the central axis C is approximately oval, recessed outward in the diameter direction of the hole from the inner circumferential surface of the screw insertion hole 14, and extending in the circumferential direction of the hole.

[0117] The concave channel 105c is groove-shaped and extends parallel to the central axis C of the screw insertion hole 14 (i.e., along the axial direction). The circumferential dimension of the concave channel 105c (groove width dimension) is larger than the radial dimension of the concave channel 105c (groove depth dimension). In this modified example, the opening area at the leading end of the concave channel 105c and the opening area at the rear end of the concave channel 105c are approximately the same.

[0118] In this modified example, there is one concave channel 105c provided within the screw insertion hole 14. The shape of the inner circumferential surface of the screw insertion hole 14, which is divided in the circumferential direction by the concave channel 105c, is approximately C-shaped when viewed from the tip side in the axial direction of the drill, as shown in Figure 12. Therefore, the tapered hole portion 14c of the screw insertion hole 14 is approximately C-shaped when viewed from the front of the drill, and extends in the circumferential direction of the hole around the central axis C, extending radially inward, in the direction opposite to the drill rotation, and radially outward from the central axis C.

[0119] Furthermore, the stepped portion 14d, which is formed by the tapered hole portion 14c, also extends in the circumferential direction of the hole, extending radially inward from the central axis C, in the direction opposite to the drill rotation, and radially outward. In other words, in this modified example as well, the stepped portion 14d is positioned on the inner circumferential surface of the screw insertion hole 14, at least in the direction opposite to the drill rotation from the central axis C of the screw insertion hole 14.

[0120] The modified drill head 10A and the replaceable-tip drill 100 equipped therewith described above also provide the same excellent effects as those of the previously described embodiment.

[0121] In this modified form, the concave flow channel 105c is recessed from the inner circumferential surface of the screw insertion hole 14, at least in the direction of drill rotation T around the rotation axis O. In this case, the coolant supplied from the concave channel 105c to the tip surface 3 of the drill head 10A is prevented from immediately flowing out into the adjacent chip discharge groove 104 (head chip discharge groove 104a) in the direction opposite to the drill rotation of the screw insertion hole 14. As a result, the coolant is more likely to remain near the tip surface 3 of the drill. In addition, the coolant is ejected from the concave channel 105c to the part of the tip surface 3 of the drill head 10A that is close to the cutting edge 7. Therefore, the cutting heat near the cutting edge 7 is efficiently removed by the coolant, and the cooling efficiency is improved.

[0122] Furthermore, in cases where the head channel 105b has a plurality of concave channels 105c arranged in the circumferential direction of the hole, as described in the above embodiment, at least one of the plurality of concave channels 105c is recessed from the inner circumferential surface of the screw insertion hole 14 toward the drill rotation direction T, thereby obtaining the same effects as the modified example described above.

[0123] Furthermore, although not specifically shown in the figures, the coolant hole 105 may have a coolant storage chamber located inside the holder 20 and connected to the holder flow path 105a. In this case, the coolant storage chamber is a hollow chamber formed inside the holder 20, which stores the coolant. Specifically, the coolant storage chamber can be, for example, a cylindrical chamber that is located inside the shank portion 101 and extends in the axial direction. By providing such a coolant storage chamber, the amount of coolant ejected can be stably increased, and the effects described above by the concave flow path 105c are more stably achieved.

[0124] Furthermore, in the embodiments and modifications described above, the connecting passage 105d of the coolant hole 105 is located on the mounting surface 107 of the drill head mounting seat 106 of the holder 20, but the configuration is not limited to this. For example, the connecting passage 105d may be located on the seating surface 9 of the drill heads 10, 10A, and may have a concave shape that is recessed toward the tip in the axial direction from the seating surface 9. Alternatively, the connecting passage 105d may be provided on both the mounting surface 107 and the seating surface 9.

[0125] In the embodiments and modifications described above, the replaceable tip drill 100 is given as an example of a two-flute twist drill, but it is not limited to this. The replaceable tip drill may be a one-flute drill or a drill with three or more flutes. Accordingly, the number of screw insertion holes 14, head flow paths 105b, and clamp screw sets 30 may be changed as appropriate. However, the number of sets is not limited to the same number as the number of cutting edges 7 of the drill.

[0126] The present invention may be combined in any way that does not depart from the spirit of the invention, as described in the above embodiments and modifications, and the configurations may be added, omitted, substituted, or otherwise modified. Furthermore, the present invention is not limited by the above embodiments, but is limited only by the claims. [Industrial applicability]

[0127] The replaceable-tip drill and drill head of the present invention enable a stable supply of coolant to the tip surface of the drill head, thereby improving cooling efficiency. Therefore, it has industrial applicability. [Explanation of Symbols]

[0128] 10,10A…Drill head 14…Screw insertion hole 14d...Double part 15…Supported surface 20... Holder 30... Clamp screws 100... Replaceable tip drill 105... Coolant hole 105a...Holder flow path 105b... Head channel 105c…Concave channel 106... Drill head mounting base 108…support surface 110...Female screw hole C...Central axis of the screw insertion hole O... Rotation axis T...Drill rotation direction

Claims

1. A holder extending axially along the axis of rotation, A drill head is detachably attached to a drill head mounting seat located at the axial end of the holder, A clamp screw for fixing the drill head to the drill head mounting base, The holder and the drill head are equipped with coolant holes extending from the inside of the holder and the inside of the drill head, The drill head has a screw insertion hole that penetrates the drill head in the axial direction, The clamp screw is inserted through the screw insertion hole and screwed into the female screw hole of the drill head mounting seat, while in contact with the stepped portion located on the inner circumferential surface of the screw insertion hole from the axial end side. The coolant hole is A holder channel extending inside the holder, It has a head channel that extends inside the drill head and communicates with the holder channel, The head channel has a groove-like shape that is recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole, and has a concave channel that extends along the screw insertion hole. The aforementioned concave channel penetrates the drill head in the axial direction. Replaceable tip drill.

2. Multiple concave channels are provided, arranged around the central axis of the screw insertion hole. The replaceable tip drill according to claim 1.

3. The concave channel is recessed from the inner circumferential surface of the screw insertion hole, at least in the direction of drill rotation around the rotation axis. The replaceable tip drill according to claim 1 or 2.

4. The groove depth of the aforementioned concave channel increases as it approaches the tip in the axial direction. The replaceable tip drill according to claim 1 or 2.

5. The opening area of ​​the concave channel that opens to the tip surface of the drill head is 20% to 100% of the area of ​​the screw insertion hole that opens to the tip surface. The replaceable tip drill according to claim 1 or 2.

6. The holder has a support surface that faces the direction of drill rotation around the rotation axis, The drill head has a supported surface that faces in the opposite direction of drill rotation around the rotation axis and contacts the support surface, The stepped portion is positioned on the inner circumferential surface of the screw insertion hole, at least in the portion located in the direction opposite to the drill rotation direction relative to the central axis of the screw insertion hole. The replaceable tip drill according to claim 1 or 2.

7. The coolant hole is located inside the holder and has a coolant storage chamber connected to the holder flow path. The replaceable tip drill according to claim 1 or 2.

8. A drill head that is detachably attached to the drill head mounting seat of a holder and rotates together with the holder around a rotation axis, The drill head has a screw insertion hole through which a clamp screw is inserted, The drill head has a head channel that extends inside the drill head and communicates with a holder channel that extends inside the holder, The head channel has a groove-like shape that is recessed outward in the diameter direction from the inner circumferential surface of the screw insertion hole, and has a concave channel that extends along the screw insertion hole. The aforementioned concave channel penetrates the drill head in the axial direction. Drill head.

Images