ROTARY CUTTING TOOL

Abstract

A rotary cutting tool includes a first cutting blade, a second cutting blade, a third cutting blade, a fourth cutting blade, and a fifth cutting blade on a circumference, in which a rotation angle from the first cutting blade to the second cutting blade is 60?1?, a rotation angle from the second cutting blade to the third cutting blade is 75?1?, a rotation angle from the third cutting blade to the fourth cutting blade is 60?1?, a rotation angle from the fourth cutting blade to the fifth cutting blade is 75?1?, and a rotation angle from the fifth cutting blade to the first cutting blade is 90?1?.

Claims

1. A rotary cutting tool comprising a first cutting blade, a second cutting blade, a third cutting blade, a fourth cutting blade, and a fifth cutting blade on a circumference, wherein a rotation angle from the first cutting blade to the second cutting blade is 60?1?, a rotation angle from the second cutting blade to the third cutting blade is 75?1?, a rotation angle from the third cutting blade to the fourth cutting blade is 60?1?, a rotation angle from the fourth cutting blade to the fifth cutting blade is 75?1?, and a rotation angle from the fifth cutting blade to the first cutting blade is 90?1?.

2. A rotary cutting tool comprising a first cutting blade, a second cutting blade, a third cutting blade, a fourth cutting blade, and a fifth cutting blade on a circumference, wherein a rotation angle from the first cutting blade to the second cutting blade is 60?1?, a rotation angle from the second cutting blade to the third cutting blade is 72?1?, a rotation angle from the third cutting blade to the fourth cutting blade is 60?1?, a rotation angle from the fourth cutting blade to the fifth cutting blade is 84?1?, and a rotation angle from the fifth cutting blade to the first cutting blade is 84?1?.

3. A rotary cutting tool comprising a first cutting blade, a second cutting blade, a third cutting blade, a fourth cutting blade, and a fifth cutting blade on a circumference, wherein a rotation angle from the first cutting blade to the second cutting blade is 72?1?, a rotation angle from the second cutting blade to the third cutting blade is 108?1?, a rotation angle from the third cutting blade to the fourth cutting blade is 90?1?, and a rotation angle from the fourth cutting blade to the first cutting blade is 90?1?.

4. A rotary cutting tool comprising: a base metal; and a first chip, a second chip, and a third chip provided on an outer circumference of the base metal and provided with a first cutting blade, a second cutting blade, and a third cutting blade, respectively, wherein a rotation angle from the first cutting blade to the second cutting blade is 126?1?, a rotation angle from the second cutting blade to the third cutting blade is 126?1?, and a rotation angle from the third cutting blade to the first cutting blade is 108=1?.

5. A rotary cutting tool in which three to five blades are arranged at unequal intervals on a circumference, wherein a rotation angle between each of the cutting blades and a cutting blade adjacent thereto is defined as an unequal flute spacing angle, and a greatest common divisor of the unequal flute spacing angles is 12, 15, or 18, a maximum angular difference of the unequal flute spacing angles is greater than or equal to 15? and less than or equal to 40?, and a value of F(?) represented by an expression of F(?)={X(?).sup.2+Y(?).sup.2}.sup.1/2 (here, when a maximum number of cutting blades is n and rotation angles of the first to n-th cutting blades are ?1 to ?n, X(?)=?2 cos ?1+?3 cos(?1+?2)+ . . . +?1 cos(?1+?2+ . . . +?n), Y(?)=?2 sin ?1+?3 sin(?1+?2)+ . . . +?1 sin(?1+?2+ . . . +?n) is greater than or equal to 5.5 and less than or equal to 29.

6. A rotary cutting tool comprising a first cutting blade, a second cutting blade, a third cutting blade, and a fourth cutting blade on a circumference, wherein a rotation angle from the first cutting blade to the second cutting blade is 105?1?, a rotation angle from the second cutting blade to the third cutting blade is 90?1?, a rotation angle from the third cutting blade to the fourth cutting blade is 90?1?, and a rotation angle from the fourth cutting blade to the first cutting blade is 75?1?.

7. A rotary cutting tool comprising a first cutting blade, a second cutting blade, a third cutting blade, and a fourth cutting blade on a circumference, wherein a rotation angle from the first cutting blade to the second cutting blade is 90?1?, a rotation angle from the second cutting blade to the third cutting blade is 90?1?, a rotation angle from the third cutting blade to the fourth cutting blade is 105?1?, and a rotation angle from the fourth cutting blade to the first cutting blade is 75?1?.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a front view of a reamer 100 as a rotary cutting tool according to an embodiment.

[0009] FIG. 2 is an enlarged view of a tip portion 106 of reamer 100 illustrated in FIG. 1.

[0010] FIG. 3 is a side view of four-blade reamer 100 as viewed from a direction indicated by an arrow III in FIG. 2.

[0011] FIG. 4 is a side view of five-blade reamer 100 according to another embodiment.

[0012] FIG. 5 is a side view of three-blade reamer 100 according to another embodiment.

[0013] FIG. 6 is a diagram illustrating a resultant force of cutting resistance.

DESCRIPTION OF EMBODIMENTS

Technical Problem

[0014] A rotary cutting tool in the related art has a problem that a feed mark is generated on a cut surface. Furthermore, there is a problem that circularity deteriorates.

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0016] FIG. 1 is a front view of a reamer 100 as a rotary cutting tool according to an embodiment. As illustrated in FIG. 1, reamer 100 according to a first embodiment includes a base metal 109. A base portion 107 of base metal 109 has a columnar shape, and has a larger diameter than a tip portion 106.

[0017] A hole 108 is provided along a rotation center axis of base metal 109. A coolant is supplied to hole 108. The coolant is discharged from tip portion 106 of reamer 100, and the coolant is supplied to a contact portion between a workpiece and reamer 100. Base metal 109 is made of, for example, a cemented carbide or a steel material.

[0018] FIG. 2 is an enlarged view of tip portion 106 of reamer 100 illustrated in FIG. 1. A first chip 121 and a third chip 123 are provided at tip portion 106 of reamer 100. Tip portion 106 is provided with other chips not illustrated in FIG. 2.

[0019] FIG. 3 is a side view of four-blade reamer 100 as viewed from a direction indicated by an arrow III in FIG. 2. As illustrated in FIG. 3, first chip 121 to a fourth chip 124 are provided on an outer circumference of base metal 109 of reamer 100.

[0020] First chip 121 to fourth chip 124 are provided with a first cutting blade 101 to a fourth cutting blade 104. First cutting blade 101 to fourth cutting blade 104 are portions that come into contact with the workpiece and process the workpiece. First chip 121 to fourth chip 124 are made of an ultra-hard tool material such as cemented carbide, diamond, or cubic boron nitride.

[0021] A rotation angle from first cutting blade 101 to second cutting blade 102 is 01, a rotation angle from second cutting blade 102 to third cutting blade 103 is ?2, a rotation angle from third cutting blade 103 to fourth cutting blade 104 is ?3, and a rotation angle from fourth cutting blade 104 to first cutting blade 101 is ?4. ?1 to ?4 are arranged along a rotation direction at the time of cutting in the order of ?1, ?2, ?3, and ?4.

[0022] Base metal 109 is provided with four flutes 131 to 134. Four flutes 131 to 134 extend along a longitudinal direction of base metal 109.

[0023] Flutes 131 to 134 are provided with coolant holes 111 to 114 connected to hole 108. Accordingly, the coolant is supplied from hole 108 to coolant holes 111 to 114.

[0024] As an example, ?1 is 72?1?, ?2 is 108?1?, ?3 is 90?1?, and ?4 is 90?1?.

[0025] As another example, ?1 is 105?1?, ?2 is 90?1?, ?3 is 90?1?, and ?4 is 75?1?.

[0026] As another example, ?1 is 90?1?, ?2 is 90?1?, ?3 is 105?1?, and ?4 is 75?1?.

[0027] FIG. 4 is a side view of five-blade reamer 100 according to another embodiment. As illustrated in FIG. 4, first chip 121 to a fifth chip 125 are provided on the outer circumference of base metal 109 of reamer 100. First chip 121 to fifth chip 125 are provided with first cutting blade 101 to a fifth cutting blade 105. First cutting blade 101 to fifth cutting blade 105 are portions that come into contact with the workpiece and process the workpiece. First chip 121 to fifth chip 125 are made of an ultra-hard tool material such as cemented carbide, diamond, or cubic boron nitride.

[0028] A rotation angle from first cutting blade 101 to second cutting blade 102 is ?1, a rotation angle from second cutting blade 102 to third cutting blade 103 is ?2, a rotation angle from third cutting blade 103 to fourth cutting blade 104 is ?3, a rotation angle from fourth cutting blade 104 to fifth cutting blade 105 is ?4, and a rotation angle from fifth cutting blade 105 to first cutting blade 101 is ?5.

[0029] Base metal 109 is provided with five flutes 131 to 135. Five flutes 131 to 135 extend along a longitudinal direction of base metal 109.

[0030] Flutes 131 to 135 are provided with coolant holes 111 to 115 connected to hole 108. Accordingly, the coolant is supplied from hole 108 to coolant holes 111 to 115. Coolant holes 111 to 115 may not be provided. Hole 108 may be opened or may not be opened at the tip of base metal 109.

[0031] As an example, ?1 is 60?1?, ?2 is 75?1?, ?3 is 60?1?, ?4 is 75?1?, and ?5 is 90=1?.

[0032] As another example, ?1 is 60?19, ?2 is 72?1?, ?3 is 60?1?, ?4 is 84?1?, and ?5 is 84=1?.

[0033] FIG. 5 is a side view of three-blade reamer 100 according to another embodiment. As illustrated in FIG. 4, first chip 121 to third chip 123 are provided on the outer circumference of base metal 109 of reamer 100. First chip 121 to third chip 123 are provided with first cutting blade 101 to third cutting blade 103. First cutting blade 101 to third cutting blade 103 are portions that come into contact with the workpiece and process the workpiece. First chip 121 to third chip 123 are made of an ultra-hard tool material such as cemented carbide, diamond, or cubic boron nitride.

[0034] A rotation angle from first cutting blade 101 to second cutting blade 102 is 01, a rotation angle from second cutting blade 102 to third cutting blade 103 is ?2, and a rotation angle from third cutting blade 103 to first cutting blade 101 is ?3.

[0035] Base metal 109 is provided with three flutes 131 to 133. Three flutes 131 to 133 extend along a longitudinal direction of base metal 109.

[0036] Flutes 131 to 133 are provided with coolant holes 111 to 113 connected to hole 108. Accordingly, the coolant is supplied from hole 108 to coolant holes 111 to 113.

[0037] As an example, ?1 is 126?1?, ?2 is 126?1?, and ?3 is 108?1?.

[0038] FIG. 6 is a diagram illustrating a resultant force of cutting resistance. A rotation track 102a of second cutting blade 102 is indicated by an arc.

[0039] The magnitude of the cutting resistance (thrust force) of second cutting blade 102 at a contact point with the workpiece is represented by F1. In a case where an x axis and a y axis are determined as illustrated in FIG. 6 by setting first cutting blade 101 as the x axis of a reference axis and setting an axis perpendicular to the x axis as the y axis, second cutting blade 102 forms an angle ?1 from the x axis that is the reference axis. An x-component force of F1 is ?F1 cos ?1, and a y-component force is ?F1 sin ?1.

[0040] The magnitude of the cutting resistance (thrust force) of third cutting blade 103 at a contact point with the workpiece is represented by F2. Third cutting blade 103 forms an angle ?1+?2 from the x axis that is the reference axis. The x-component force of F2 is ?F2 cos(?1+?2), and the y-component force is ?F2 sin(?1+?2).

[0041] The magnitude of the cutting resistance (thrust force) of n-th cutting blade at a contact point with the workpiece is represented by Fn?1. The n-th cutting blade forms an angle ?1+?2+ . . . +?n?1 from the x axis that is the reference axis. The x-component force of Fn?1 is ?Fn?1 cos(?1+?2+ . . . +?n?1), and the y-component force is ?Fn?1 sin(?1+?2+ . . . +?n?1).

[0042] The magnitude of the cutting resistance (thrust force) of first cutting blade 101 at a contact point with the workpiece is represented by Fn. First cutting blade 101 forms an angle ?1+?2+ . . . +?n from the x axis that is the reference axis. The x-component force of Fn is ?Fn cos(?1+?2+ . . . +?n), and the y-component force is ?Fn sin(?1+?2+ . . . +?n).

[0043] The resultant force of the x component is ?F1 cos 01?F2 cos(?1+?2)? . . . ?Fn?1 cos(?1+?2+ . . . +?n?1)?Fn cos(?1+?2+ . . . +?n).

[0044] The resultant force of the y component is ?F1 sin 01?F2 sin(?1+?2)?. . . ?Fn?1 sin(?1+?2+ . . . +?n?1)?Fn sin(?1+?2+ . . . +?n).

[0045] It is assumed that the magnitudes of the cutting resistance F1 to Fn are proportional to cutting lengths ?1 to ?n, and when an arbitrary constant is F, F1=F.Math.?2, F2=F.Math.?3, Fn?1=F.Math.?n, and Fn=F.Math.?1.

[0046] Thus, the x resultant force is calculated as ?F.Math.?2 cos ?1?F.Math.?3 cos(?1+?2)? . . . ?F.Math.?n cos(?1+?2+ . . . +?n?1)?F.Math.?1 cos(?1+?2+ . . . +?n)=?F{?2 cos ?1+?3 cos(?1+?2)+ . . . +?n cos(?1+?2+ . . . +?n?1)+?1 cos(1+2+ . . . +?n)}.

[0047] When X(?)=?2 cos ?1+?3 cos(1+?2)+ . . . +?n cos(?1+?2+ . . . +?n?1)+?1 cos(?1+?2+ . . . +?n), x resultant force=?F.Math.X(?) . . . . Expression (1) is obtained.

[0048] The y resultant force is calculated as ?F.Math.?2 sin ?1?F.Math.?3 sin(?1+?2)? . . . ?F.Math.?n sin(?1+?2+ . . . +?n?1)?F.Math.?1 sin(?1+?2+ . . . +?n)=?F{?2 sin ?1+?3 sin(?1+?2)+ . . . +?n sin(?1+?2+ . . . +?n?1)+?1 sin(?1+?2+ . . . +?n)}.

[0049] When Y(?)=?2 sin ?1+?3 sin(?1+?2)+ . . . +?n sin(?1+?2+ . . . +?n?1)+?1 sin(?1+?2+ . . . +?n), y resultant force=?F.Math.Y(?) . . . . Expression (2) is obtained.

[0050] When the resultant force is calculated from two Expressions (1) and (2), the resultant force is expressed by the following expression.

[00001]$\begin{array}{cc}\mathrm{Resultant}\mathrm{Force}=F{\left\{{X\left(?\right)}^2+{Y\left(?\right)}^2\right\}}^{1/2}& \mathrm{Expression}\left(3\right)\end{array}$$\begin{array}{cc}F\left(?\right)={\left\{{X\left(?\right)}^2+{Y\left(?\right)}^2\right\}}^{1/2}& \mathrm{Expression}\left(4\right)\end{array}$

[0051] In the rotary cutting tool of the present disclosure, three to five cutting blades are arranged at unequal intervals on the circumference. A rotation angle between each cutting blade and a cutting blade adjacent thereto is defined as an unequal flute spacing angle. The greatest common divisor of the unequal flute spacing angles is 12, 15, or 18, the maximum angular difference of the unequal flute spacing angles is greater than or equal to 15? and less than or equal to 40?, and a value of F(?) represented by the expression of F(?)={X(?).sup.2+Y(?).sup.2}.sup.1/2 (here, when the maximum number of cutting blades is n, and the rotation angles of the first to n-th cutting blades are ?1 to ?n, X(?)=?2 cos ?1+?3 cos(?1+?2)+ . . . +?1 cos(?1+2+ . . . +?n), Y(?)=?2 sin ?1+?3 sin(?1+?2)+ . . . +?1 sin(?1+?2+ . . . +?n) is greater than or equal to 5.5 and less than or equal to 29.

[0052] The unequal flute spacing angle means that a certain flute spacing angle among a plurality of flute spacing angles of the plurality of cutting blades is different from another flute spacing angle. For example, in a case where the flute spacing angles are 90?, 90?, 70?, and 110? in four blades, the flute spacing angles are unequal flute spacing angles.

First Example

[0053] First, three-blade reamers (refer to FIGS. 1, 2, and 5) of sample numbers 1 to 8, 6-1, and 6-2 listed in Table 1 were prepared. The unit of ? is ?. Sample number 6-1 is obtained by changing angles ?1 to ?3 of sample number 6 within a range of ?1?. Sample number 6-2 is obtained by changing angles ?1 to ?3 of sample number 6 within a range of ?2?.

TABLE-US-00001 TABLE 1 Maximum Greatest Angular Sample Common Difference Number ?1 ?2 ?3 F(?) Divisor (?) 1 120 120 120 0 120 0 2 105 130 125 23.2 5 25 3 135 105 120 29.7 15 30 4 120 100 140 37.4 20 40 5 110 130 120 19.1 36 20 6 126 126 108 18.6 18 18 7 120 108 132 22.8 12 24 8 105 135 120 28.3 15 30 6-1 127 126 107 20 1 20 6-2 128 126 106 21.4 2 22

[0054] ?1 to ?3 in Table 1 are ?1 to ?3 in FIG. 5. F(?) is a value represented by Expression (4). A greatest common divisor is the greatest common divisor of ?1 to ?3. A maximum angular difference is the maximum angular difference of ?1 to ?3.

[0055] Using the reamers of sample numbers 1 to 8, 6-1, and 6-2, a processing test was conducted in which a pilot hole having an inner diameter of 11.2 mm was processed with the reamer to an inner diameter of 12 mm. Processing conditions are as follows.

[0056] Material of chip: polycrystalline diamond [0057] Material of base metal: cemented carbide [0058] Tool diameter D: 12 mm [0059] Tool protrusion length L: 70 mm [0060] Material of workpiece: ADC 12 (aluminum die casting) [0061] Dimension and shape of pilot hole: blind hole having inner diameter of 11.2 mm and depth of 20 mm [0062] Number of processes: 5 [0063] Peripheral speed: 249 m/min [0064] Feed (mm/rev): 0.6 (3 blades), 0.8 (4 blades), 1 (5 blades) [0065] Rotation speed: 6600 min-1 [0066] Machining depth: 18 mm [0067] Equipment: vertical machining center (spindle BT30) [0068] Cutting oil: emulsion-based water-soluble coolant dilution rate 10%

[0069] As a result of the cutting, the presence or absence of a feed mark on a cut surface was visually examined. Furthermore, a circularity of the processed hole was examined with a circularity/cylinder shape measuring machine. The circularity is a difference between radii of two concentric circles in a case where an interval between two concentric circles is minimized when a circular body is interposed between two concentric geometric circles in accordance with JIS B 0621-1984. The results are listed in Table 2.

TABLE-US-00002 TABLE 2 Machining Surface Sample Presence or Absence Circularity Number of Feed Mark (?m) 1 Absent 6.3 2 Present 3.0 3 Present 1.6 4 Present 2.6 5 Present 3.3 6 Absent 1.6 7 Absent 2.0 8 Absent 1.9 6-1 Absent 1.9 6-2 Absent 3.0

[0070] In Table 2, circularity is an average value of circularity of processed holes. The circularity was measured at the inlet, middle part, and inner part of each hole, and the largest value was taken as the circularity of the hole. In sample numbers 6 to 8 and 6-1, there was no feed mark, and the circularity showed a good value.

Second Example

[0071] Four-blade reamers (refer to FIGS. 1, 2, and 3) of sample numbers 11 to 30, 51 to 53, and 29-1 to 29-3 listed in Table 3 were prepared. Sample numbers 29-1 and 29-2 are obtained by changing angles ?1 to ?4 of sample number 29 within a range of ?1?. Sample number 29-3 is obtained by changing angles ?1 to ?4 of sample number 29 within a range of ?2?.

TABLE-US-00003 TABLE 3 Maximum Greatest Angular Sample Common Difference Number ?1 ?2 ?3 ?4 F(?) Divisor (?) 11 90 90 90 90 0 90 0 12 95 65 115 85 22.5 5 50 13 80 110 60 110 6 10 50 14 105 60 110 85 9.5 5 50 15 90 105 60 105 12.9 15 45 16 90 80 90 100 16.2 10 20 17 95 100 60 105 17.4 5 45 18 100 90 75 95 19.2 5 25 19 60 100 100 100 22.4 20 40 20 65 95 105 95 27.4 5 40 21 60 100 105 95 28 5 45 22 60 95 110 95 34.1 5 50 23 118 98 60 90 40.9 5 55 24 120 90 60 90 48 30 60 25 96 72 108 84 13.5 12 36 26 60 108 84 108 8.4 12 48 27 72 108 90 90 20 18 36 28 80 100 85 95 5.6 5 20 29 105 90 90 75 16.7 15 30 30 90 90 105 75 18.1 15 30 51 90 108 72 90 21.9 18 36 52 84 108 84 84 22.8 12 24 53 96 108 72 84 28.2 12 36 29-1 104 91 90 75 16.3 1 29 29-2 104 91 91 74 15.8 1 30 29-3 103 92 90 75 16 1 28

[0072] ?1 to ?4 in Table 3 are ?1 to ?4 in FIG. 3 F(?) is a value represented by Expression (4). A greatest common divisor is the greatest common divisor of ?1 to ?4. A maximum angular difference is the maximum angular difference of ?1 to ?4. Using the reamers of sample numbers 11 to 30, 51 to 53, and 29-1 to 29-3, a processing test was conducted in which a pilot hole having an inner diameter of 11.2 mm was processed with the reamer to an inner diameter of 12 mm. Processing conditions are as described in the first example.

[0073] As a result of the cutting, the presence or absence of a feed mark on a cut surface was visually examined. Furthermore, a circularity of the processed hole was examined with a circularity/cylinder shape measuring machine. The results are listed in Table 4.

TABLE-US-00004 TABLE 4 Machining Surface Sample Presence or Absence Circularity Number of Feed Mark (?m) 11 Absent 4.7 12 Present 2.5 13 Absent 2.8 14 2.6 15 Present 3.1 16 3.1 17 2.8 18 2.9 19 3.1 20 3.0 21 3.1 22 3.2 23 3.4 24 4.4 25 Absent 2.0 26 Present 2.5 27 Absent 1.6 28 5.4 29 1.8 30 1.7 51 1.9 52 1.7 53 1.8 29-1 2.0 29-2 2.0 29-3 3.5

[0074] In Table 4, circularity is an average value of circularity of processed holes. In sample numbers 25, 27, 29, 30, 51 to 53, 29-1, and 29-2, there was no feed mark, and the circularity showed a good value.

Third Example

[0075] Five-blade reamers (refer to FIGS. 1, 2, and 4) of sample numbers 31 to 46, and 40-1 to 40-3 listed in Table 5 were prepared. Sample numbers 40-1 and 40-2 are obtained by changing angles ?1 to ?5 of sample number 40 within a range of ?1?. Sample number 40-3 is obtained by changing angles ?1 to ?5 of sample number 40 within a range of ?2?.

TABLE-US-00005 TABLE 5 Maximum Greatest Angular Sample Common Difference Number ?1 ?2 ?3 ?4 ?5 F(?) Divisor (?) 31 72 72 72 72 72 0 72 0 32 90 90 60 60 60 33.1 30 30 33 60 85 60 80 75 1.8 5 25 34 60 80 75 65 80 3.5 5 20 35 70 65 85 60 80 3.8 5 25 36 60 80 80 60 80 7.4 20 20 37 75 60 90 60 75 7.8 15 30 38 60 90 65 70 75 11 5 30 39 60 84 60 84 72 5.5 12 24 40 60 75 60 75 90 17.5 15 30 41 60 72 60 84 84 18.5 12 24 42 60 78 78 60 84 1.6 6 24 43 60 72 72 72 84 9.7 12 24 44 60 60 84 72 84 14.9 12 24 45 60 75 75 75 75 8.1 15 15 46 60 60 75 90 75 26 15 30 40-1 61 74 60 75 90 18.1 1 30 40-2 61 74 60 74 91 18.9 1 31 40-3 62 73 60 75 90 18.8 1 30

[0076] ?1 to ?5 in Table 5 are ?1 to ?5 in FIG. 4. F(?) is a value represented by Expression (4). A greatest common divisor is the greatest common divisor of ?1 to ?5. A maximum angular difference is the maximum angular difference of ?1 to ?5. Using the reamers of sample numbers 31 to 46, and 40-1 to 40-3, a processing test was conducted in which a pilot hole having an inner diameter of 11.2 mm was processed with the reamer to an inner diameter of 12 mm. Processing conditions are as described in the first example.

[0077] As a result of the cutting, the presence or absence of a feed mark on a cut surface was visually examined. Furthermore, a circularity of the processed hole was examined with a circularity/cylinder shape measuring machine. The results are listed in Table 6.

TABLE-US-00006 TABLE 6 Machining Surface Sample Presence or Absence Circularity Number of Feed Mark (?m) 31 Absent 5.6 32 Present 2.6 33 Absent 2.5 34 4.1 35 3.4 36 3.2 37 1.9 38 Present 2.7 39 Absent 2.0 40 1.5 41 1.6 42 2.5 43 1.9 44 1.7 45 1.8 46 1.7 40-1 1.9 40-2 2.0 40-3 4.0

[0078] In Table 6, circularity is an average value of circularity of two processed holes. In sample numbers 37, 39 to 41, 43 to 46, 40-1, and 40-2, there was no feed mark, and the circularity showed a good value.

[0079] It was confirmed that the same effect was obtained not only in the reamer but also in other rotary cutting tools such as a drill and an end mill.

[0080] It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

REFERENCE SIGNS LIST

[0081] 100: reamer, 101: first cutting blade, 102: second cutting blade, 102a: rotation track, 103: third cutting blade, 104: fourth cutting blade, 105: fifth cutting blade, 106: tip portion, 107: base portion, 108: hole, 109: base metal, 111-115: coolant hole, 121: first chip, 122: second chip, 123: third chip, 124: fourth chip, 125: fifth chip, 131-135: flute