JP2001328018A - Window hole forming cutting tool and window hole forming cutting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve production efficiency of machining of an annular first machining surface, a second machining surface crossing with the annular first machining surface and a third machining surface of a cylindrical surface orthogonal to the first machining surface. SOLUTION: A first arm 6, a second arm 7 and a third arm 8 are installed on a rotary shaft 5. The subject three surfaces can be machined and finished in one stroke by a first cutting blade row 2 installed on the first arm 6, a second cutting blade row 3 installed on the second arm 7 and a third cutting blade row 4 installed on the third arm 8. The first, second and third cutting blade rows 2, 3 and 4 are substantially arranged on the same circumference and substantially on the same diameter, and have at least two cutting blades for grinding cylindrical surfaces 38 and 36 and a surface 35 of a window hole 34. The two cutting blades of the first, second and third cutting blade rows 2, 3 and 4 are mutually positionally dislocated in the axis center line direction of the window hole 34, and are mutually positionally dislocated in the radial ray direction of the window hole 34 to perform highly accurate machining by a frictional guiding slide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool for forming a window hole and a cutting method for forming a window hole, and more particularly to a cutting tool for forming a window hole in a gas turbine casing with high precision. And a cutting method for forming a window hole.

[0002]

2. Description of the Related Art A large number of windows are provided in a gas turbine combustion chamber as shown in FIG. The inner surface of each of the windows needs to be machined and finished with high precision. As shown in FIG. 10, the processing surface of such a window 101 has an annular first processing surface 102, a second processing surface 103 crossing the first processing surface, and a direction substantially orthogonal to the first processing surface. There is a third processing surface 104 which is a cylindrical surface. Conventionally, the first processing surface 102
Is ground by the first rotary tool 105 (processed by a milling machine), and the second processing surface 103 is ground by the second rotary tool 1.
06, and the third processing surface 104 was ground by the third rotary tool 107. Such three grinding processes have been performed independently of each other. Such three independent processes hinder the improvement of the processing efficiency in the following two points. (1) Each of these tools is heavy and large,
In addition, the tool is heavy, and the work of installing and replacing the tool is complicated and difficult, which has prevented the series of processes from being unmanned. Such a series of steps is three steps, further preventing unmanned operation. (2) The first processing surface 102 is an inclined surface, and in the traversing process in which the first rotary tool 105 is traversed on a plane parallel to the inclined surface, there is a problem with the rigidity of the mechanical attachment.
Improvements in processing conditions and processing accuracy have been hindered.

An annular first processing surface 102, a second processing surface 103 intersecting with the first processing surface, and a cylindrical third processing surface 104 orthogonal to the first processing surface are formed, which are concentric. It is required that the production efficiency of the processing of the window surface arranged in can be improved.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an annular first processing surface 102, a second processing surface 103 intersecting the first processing surface, and a third cylindrical surface orthogonal to the first processing surface. To provide a window hole forming cutting tool and a window hole forming cutting method which are formed from the processing surface 104 and can improve the production efficiency of processing of a window surface on which these are concentrically arranged. is there.

[0005]

Means for solving the problem are described as follows. The technical items appearing in the expression are appended with numbers, symbols, and the like in parentheses (). The numbers, symbols, and the like are technical items that constitute at least one embodiment or a plurality of the embodiments of the present invention, in particular, the embodiments or the examples. Corresponds to the reference numerals, reference symbols, and the like assigned to the technical matters expressed in the drawings corresponding to the above. Such reference numbers and reference symbols clarify the correspondence and bridging between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are interpreted as being limited to the technical matters of the embodiments or the examples.

A window hole forming cutting tool according to the present invention comprises a rotating shaft (5), a first arm (6) attached to the rotating shaft (5), and a second arm (8) attached to the rotating shaft (5). ), A first cutting blade row (2) attached to the first arm (6), and a second cutting blade row (2) attached to the second arm (8).
A first cutting blade row (2) arranged substantially on the same circumference and on the same diameter to grind the cylindrical surface (38) of the window hole (34). The second row of cutting blades (4) are arranged on substantially the same circumference and on substantially the same diameter so that the window hole (3) is formed.
4) at least two cutting blades for grinding the surface (35), the two cutting blades of the first cutting blade row (2) being displaced from each other in the axial direction of the window (34), and Are displaced from each other in the radiation direction of the window hole (34), and the cylindrical surface (3) is displaced.
8) is ground prior to grinding the surface of the window hole (34).
Here, “second” in the component name is expressed as “third” in the embodiment.

The first and second cutting blade rows (2, 4) have at least two blade rows on one diameter, and each blade row has at least the two cutting blades (grinding blades) described above. . Since the first cutting blade row (2) and the second cutting blade row (4) share the rotating shaft (5), the cylindrical surface (38) and the surface (35) are moved in one reciprocating step of the rotating shaft. It will be turned. One of the two cutting blades of the first cutting blade row (2) is frictionally slidably guided with respect to the other, thereby correcting a run-out that tends to occur when both the blade rows rotate simultaneously. be able to.

The two cutting blades of the second cutting blade row (4) are displaced from each other in the axial direction of the window (34), and displaced from each other in the radiation direction of the window (34). Further, since the positions are shifted from each other in the circumferential direction of the window hole (34),
Corrections similar to those already described are possible. The first row of cutting blades (2) further comprises at least two other grinding elements arranged on substantially the same circumference as described above and on substantially another same diameter to grind the cylindrical surface of the window (34). A first cutting blade row (2) and two other cutting blades of the first cutting blade row (2).
The two cutting blades are displaced from each other in the axial direction of the window (34), and are displaced from each other in the radiation direction of the window (34). The first row of cutting blades (2) is thus arranged in a cross shape, thereby enabling more accurate cylindrical surface turning.

[0009] The second row of cutting blades (4) is further arranged at least about 2 on the same circumference and about another same diameter to grind the surface (35) of the window hole (34). Two cutting blades of the second cutting blade row (4) and two other cutting blades of the second cutting blade row (4) in the axial direction of the window hole (34). Are displaced from each other, and are displaced from each other in the radiation direction of the window hole.
Are displaced from each other in the circumferential direction. The second row of cutting blades (4) is thus arranged in a cross shape, and enables more accurate cylindrical surface turning.

A first cutting blade row (2) and a second cutting blade row (4)
Is greater than the axial length of the window hole (34). This condition allows grinding of the surface (35) in one step.

Further, a third arm (7) is added to the rotating shaft (5). A third cutting blade row (3) is attached to the third arm (7). The third arm (7) can be shared by the second arm (8). The third cutting blade row (3) is arranged on substantially the same circumference and substantially the same diameter, is connected to the cylindrical surface (38) of the window hole (34), and is rearward from the cylindrical surface (38). The located inclined surface (37) is ground, and the third cutting blade row (3) is disposed at an axially intermediate position between the first cutting blade row (2) and the second cutting blade row (4).
Such an arrangement allows processing of three surfaces in one reciprocating process, and can simultaneously process the slope (37) and the surface (35). As a geometric condition therefor, the axial distance between the first cutting blade row (2) and the third cutting blade row (3) is longer than the axial length of the window hole (34).

The cutting tool for forming a window hole according to the present invention comprises a rotating shaft (5), a first arm (6) attached to the rotating shaft (5), and a second arm (6) attached to the rotating shaft (5). ), A third arm (8) attached to the rotating shaft (5), a first cutting blade row (2) attached to the first arm (6), and a second cutting blade row attached to the second arm (7).
The first cutting blade row (2) includes a cutting blade row (3) and a third cutting blade row (4) attached to the third arm (8).
The second cutting blade row (3) is provided with at least two cutting blades arranged on substantially the same circumference and substantially the same diameter to grind the first cylindrical surface (38) of the window hole (34). At least 2 grinding the second cylindrical surface (36) of the window hole (34) arranged substantially on the same circumference and substantially the same diameter.
The third row of cutting blades (4) are arranged on substantially the same circumference and on substantially the same diameter, and the window holes (3) are arranged.
4) At least two cutting blades for grinding the surface (35), the first cylindrical surface (38) is located axially forward of the second cylindrical surface (36), and the first cutting blade row (2). Is longer than the axial length of the window hole (34), and three surfaces can be machined in one reciprocation stroke. . The two cutting blades of the first cutting blade row (2) are displaced from each other in the axial direction of the window hole (34), and are displaced from each other in the radiation direction of the window hole (34). High precision processing is possible by the sliding guide. It is preferable that the friction sliding guide is also performed for the second cutting blade row (3) and the third cutting blade row (4).

[0013] In the cutting method for forming a window hole according to the present invention, the inner peripheral surface (38) of the window hole (34) is ground.
8) grinding the surface (35) of the window hole (34) after grinding, and grinding the inner peripheral surface (38) and grinding the surface (35) are performed by the same rotation axis ( The grinding of the inner peripheral surface (38), which is performed by the rotation of the rotary cutting blades (2, 4) sharing the rotation axis of 5), is performed by first grinding the inner peripheral surface (38). An inner peripheral surface grinding; and a second inner peripheral surface grinding subsequent to the first inner peripheral surface grinding with a radius larger than the radius of the first inner peripheral surface grinding. The movement is guided by friction sliding of the first inner peripheral surface grinding. Actually, the grinding is simultaneously performed by the plurality of blades as described above.

[0014] Grinding the surface (35) comprises removing the surface (3).
5) The first surface grinding, which is performed prior to the first surface grinding, and the second surface grinding, which is performed later, has a radius different from the radius of the first surface grinding, and is deeper in the axial direction of the window hole than the first surface grinding. A second surface grinding for grinding, wherein the frictional sliding of the second surface grinding is the first surface grinding.
Guided by friction sliding of surface grinding, more precise turning is performed.

After grinding the inner peripheral surface (38), the window hole (3
4) including grinding another inner peripheral surface (36), the other inner peripheral surface (36) having a larger diameter than the inner peripheral surface (38);
Moreover, the surface (3) of the window hole (34) is larger than the inner peripheral surface (38).
5), grinding the inner peripheral surface (36) and grinding the surface (35) are performed by the rotary cutting blades (3, 3) sharing the rotation axis of the same rotation axis (5). It is executed simultaneously by the rotation of 4).

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the drawings, an embodiment of a cutting tool for forming a window hole according to the present invention has three rotary cutting tools arranged coaxially. The three rotary cutting tools 1
As shown in FIG. 1, the first rotary grinding blade 2 and the second
It comprises a rotary grinding blade 3 and a third rotary grinding blade 4. The first rotary grinding blade 2, the second rotary grinding blade 3, and the third rotary grinding blade 4 are coaxially connected, share the same rotation axis L, and form a rotation shaft 5 having the rotation axis L. Are combined.

The rotary shaft 5 has a first arm 6, a second arm 7, and a third arm 8. The first arm 6 is arranged on the plane perpendicular to the axis at the first shaft end of the rotating shaft 5 and is formed in a cross shape, and four first arm radiating portions extending in the radial direction from the first arm first shaft end. 9 is provided. The four first arm radiating portions 9 extend in the radial direction orthogonal to each other.

The second arm 7 is arranged on the plane perpendicular to the axis at the second shaft end (the end opposite to the first shaft end) of the rotating shaft 5 and is formed in a cross shape. There are four second arm radiating portions 11 extending radially from the part. The four second arm radiating portions 11 extend in the radial direction orthogonal to each other.

The third arm 8 is formed on the above-described second shaft end of the rotary shaft 5 on a plane perpendicular to the axis, is formed in a cross shape, and has four third arms extending radially from the second shaft end. An arm radiating portion 12 is provided. Four third arm radiating portions 12
Extend radially perpendicular to one another.

As shown in FIG. 2, the first rotary grinding blade 2 forms an axial blade row 13 in which four blades are vertically arranged in a vertical direction. The axial blade row 13 is formed from four first independent blades 14. First cutting edge 1 of four first independent blades 14
5 is arranged on the surface of one first conical surface 16.
The slope of the first conical surface 16 is shown exaggerated.
Preferably, the four first cutting edges 15 are out of phase with each other in the circumferential direction. The first conical surface 16 is in the Z-axis direction which is the tool feed direction (the Z-axis coincides with the rotation axis L).
It is formed in a tapered shape.

Each first independent blade 14 uses a commercially available tool as a cartridge, and can be replaced for each independent blade. Each one first arm radiating part 9 has:
Four first independent blades 14 are arranged and fixed, the first cutting edges 15 of the first independent blades 14 are arranged on the same circumference, and the first independent blades 14 are circumferentially spaced between each other. A phase difference of 90 degrees is given to each other in the directions. A total of 16 first independent blades 14 form a row structure in which four single rows forming a row in the circumferential direction are arranged in the axial direction. 4 single row maximum outer diameters (first
(Double the radius R of the cutting edge).

As shown in FIG. 3, the second rotary grinding blades 3 form a single row in the circumferential direction, and each second arm radiating portion 1
1 has one second independent blade 17. 2nd independent blade 1
7 is a cutting edge line 19 included in the second conical surface 18.
Is formed. As the second arm radiating portion 11, a commercially available cartridge is used for each, and is exchangeable. A single circumferential row formed by the four second arm radiating portions 11, and a single circumferential single row 14 </ b> A in the axial direction of the first rotary grinding blade 2 (reverse Z-axis direction, −Z-axis direction). The approximate distance between is represented by D1.

As shown in FIG. 4, the third rotary grinding blade 4 has one third arm radiating portion 1 on the same plane perpendicular to the axis.
2, three third independent blades 21 are provided. FIG. 4 shows only two of the four third arm radiating portions 12. Each of the four third arm radiating portions 12 forms a single circumferential line. 16 thirds in total
The independent blades 21 form four sets of single rows in the circumferential direction.

The four third independent blades 21 of one third arm radiating portion 12 are shown in FIG. 5 as the third independent blades 21A, 21B, 21B.
21C and 21D. The four third independent blades 21A, 21B, 21C, 21D respectively have third cutting edges 22A, 22B, 22C, 22D facing in the radial direction. Four third cutting edges 22A, 22B, 22C,
22D are substantially straight lines, respectively, and the four straight lines are included in four third conical surfaces 23 slightly shifted from each other in the axial direction. The third conical surface 23 almost coincides with the plane perpendicular to the axis, and the inclination angle θ between the conical surface and the plane 24 perpendicular to the axis is extremely small. 16 third independent blades 21A, 2
For 1B, 21C, and 21D, tools that are commercially available as cartridges are used, and each can be exchanged. Four third independent blades 21A, 21B, 21C,
21D is slightly out of phase in the radial direction (radial direction), and is also slightly out of phase in the circumferential direction, as shown in FIG. The positions are shifted from each other.

FIG. 6 shows an embodiment of a cutting tool for forming a window hole according to the present invention. FIG. 7 shows a large number (2) opened in the conical surface forming portion 32 of the gas turbine fuel and pressure chamber 31.
A window hole 34 penetrating through (about 0) window forming portion 33 is shown. The window hole 34 is a processing target using the above-described window hole forming cutting tool. This processing includes boring (including cutting) and surface grinding. FIG. 8 shows shapes before and after processing. The dashed-dotted line portion is the volume portion to be cut. The finishing surface includes a first finishing surface 35 in front of the window and a second finishing surface 3 following the first finishing surface 35.
6, a third finished surface 37 following the second finished surface 36, and a fourth finished surface 38 following the third finished surface 37. The first finishing surface 35 is a conical surface having a gentle inclination angle with respect to the axis perpendicular surface 39, the second finishing surface 36 and the fourth finishing surface 38 are cylindrical surfaces, and the third finishing surface 37
Is a conical surface.

As shown in FIG. 6, the rotary shaft 5 has advanced a certain distance in the axial direction, and the first rotary grinding blade 2 has already finished most of the fourth finished surface 38. The first finished surface 35, the second finished surface 36, and the third finished surface 37
No work has yet begun. The axial length of the window hole is indicated by D2. When the rearmost first independent blade 14 of the first rotary grinding blade 2 passes through the window forming portion 33 and the distance D1 as defined above becomes greater than the distance D2,
The fourth finished surface 38 is completely finished. At the moment when the fourth finished surface 38 is completely finished, the second rotary grinding blade 3
Has not yet reached the window forming surface (plane perpendicular to the axis) 39 before processing.

The rotating shaft 5 further advances a little distance in the axial direction, the distance D1 further increases, and the second independent blade 17 of the second rotary grinding blade 3 starts working. The distance D3 is the approximate axial distance between the edge of the third independent blade 21 of the third rotary grinding blade 4 or the third conical surface 23 and the second independent blade 17. First
After the rotary grinding blade 2 starts processing, the rotary shaft 5 is moved a distance (D
When the movement further proceeds about 1 + D3), the third rotary grinding blade 4 starts processing. The third rotary grinding blade 4 cuts and grinds the surface of the window forming portion 33 by the width ΔL in the axial direction.

The rotation locus of the cutting edge of the set of four third independent blades 21 of the third rotary grinding blade 4 forms one conical surface 23. The third rotary grinding blade 4 progresses by about ΔL through the processing to finish the first finished surface 35. The surfaces finished by the second rotary grinding blade 3 at the time of finishing the first finished surface 35 are a second finished surface 36 and a third finished surface 37. Therefore,
First finished surface 35, second finished surface 36, and third finished surface 3
At 7, the finishing is completed almost at the same time.

As shown in FIG. 6, the first rotary grinding blade 2
The circumferential single row including the preceding first independent blade 14 forms a cylindrical surface having a smaller diameter than the circumferential single row located at the back. The circumferential single row including the rearmost first independent blade 14 forms a cylindrical surface with the largest diameter to form the fourth finished surface 38.
Finish. The cutting step formed by the first independent blade 14 at the front and the frictional sliding between the first independent blade 14 and the first independent blade 14 guide the cutting of the first independent blade 14 at the rear to guide the first independent blade 1 at the rear.
4 stabilizes the frictional sliding. In this way, the friction sliding at the front position successively guides the friction sliding at the rear position, and the fourth finished surface 38 as the final finished surface is finished to the required accuracy.

As shown in FIG. 6, the first rotary grinding blade 2
The circumferential single row including the preceding first independent blade 14 of
Next, a cylindrical surface having a diameter smaller than that of the single circumferential row at the rear position is formed. The circumferential single row including the rearmost first independent blade 14 forms a cylindrical surface with the largest diameter to form the fourth finished surface 38.
Finish. The cutting step formed by the first independent blade 14 at the front and the frictional sliding between the first independent blade 14 and the first independent blade 14 guide the cutting of the first independent blade 14 at the rear to guide the first independent blade 1 at the rear.
4 stabilizes the frictional sliding. In this way, the friction sliding at the front position successively guides the friction sliding at the rear position, and the fourth finished surface 38 as the final finished surface is finished to the required accuracy.

As described above, the set of four third independent blades 21 are displaced from each other in the circumferential direction a as shown in FIG. Direction) also to each other
The position is shifted by L ′, and as shown in FIG. 9B, the positions are shifted from each other in the radiation direction R by ΔR. The third independent blade 21 </ b> A that precedes in the circumferential direction scrapes the surface portion of the window forming portion 33 most shallowly. The third independent blade 21D, which is the last in the circumferential direction, shallowly cut away the portion left behind by the preceding third independent blade 21C and cut the portion that has not been ground at all deepest. The surface ground by the last third independent blade 21D is the first finished surface 35.

The third part of the blade 21A cuts off the third
The sliding friction when the independent blade 21A slides is the third independent blade 2
1B guides the sliding friction at the time of grinding, and thus the sliding friction at the rear portion is sequentially guided to the sliding friction at the front. With such a chained guide relationship,
The first finished surface 35 is finished with required accuracy.

Such three-dimensional displacements in the axial, circumferential, and radial directions are given for one third arm radiating portion 12, but are distributed to four first conical surfaces 16. In addition, a total of 16 third independent blades 21 can be sequentially provided on a spiral line that spirals four times. The displacement of the eight third arm radiating portions 12 arranged in one diametrical direction is given spirally, and the other
The displacement of the other eight diametrically aligned third arm radiating portions 12 can be given helically, in which case 8
The positional shift relationship between the third arm radiating portions 12 is the other 8
It is preferable for the stability of rotation that the phase is shifted by 90 degrees with respect to the other positional shift relationships. Other combinations of such positional deviations can be freely designed.

[0034]

The cutting tool for forming a window hole and the cutting method for forming a window hole according to the present invention can reduce the number of steps with high accuracy.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a window hole forming cutting tool according to the present invention.

FIG. 2 is a plan view showing a cutting blade row.

FIG. 3 is a plan view showing another cutting blade row.

FIG. 4 is a plan view showing still another cutting blade row.

FIG. 5 is a plan view showing still another cutting blade row.

FIG. 6 is a plan view showing still another cutting blade row.

FIG. 7 is an axial projection view showing a grinding target.

FIG. 8 is a cross-sectional view showing an embodiment of a window hole forming cutting method according to the present invention.

FIG. 9 is a plan view showing another embodiment of the cutting method for forming a window hole according to the present invention.

FIG. 10 is a plan view showing a known window-hole forming cutting tool.

[Explanation of symbols]

 2 1st cutting blade row 3, 4 2nd cutting blade row 4 3rd cutting blade row 5 ... rotating shaft 6 1st arm 7, 8 ... 2nd arm 8 ... 3rd arm 34 ... window hole 35 ... Surface 36: cylindrical surface (second cylindrical surface) 37: slope 38: cylindrical surface (first cylindrical surface)

Claims (12)

[Claims] A rotating arm; a first arm attached to the rotating shaft; a second arm attached to the rotating shaft; a first cutting blade row attached to the first arm; A second cutting blade row attached, wherein the first cutting blade row includes at least two cutting blades arranged on substantially the same circumference and substantially the same diameter to grind the cylindrical surface of the window hole. The second cutting blade row comprises at least two cutting blades arranged on substantially the same circumference and substantially the same diameter to grind the surface of the window hole, The two cutting blades are displaced from each other in the axial direction of the window hole, and are displaced from each other in the radiation direction of the window hole. The cylindrical surface is ground prior to grinding the surface. Cutting tool for forming window holes. 2. The method according to claim 1, wherein the two cutting blades of the second cutting blade row are displaced from each other in an axial direction of the window hole, and are mutually displaced in a radial direction of the window hole. A cutting tool for forming a window hole, which is misaligned and further misaligned in the circumferential direction of the window hole. 3. The method according to claim 1, wherein the first cutting blade row is further arranged on substantially the same circumference and substantially on another same diameter to grind a cylindrical surface of the window hole. Two other cutting blades, the two cutting blades of the first cutting blade row and the other two cutting blades of the first cutting blade row are displaced from each other in the axial direction of the window hole, In addition, a cutting tool for forming a window hole, which is displaced from each other in the radiation direction of the window hole. 4. The window row according to claim 3, wherein the second row of cutting blades is further arranged on substantially the same circumference and substantially on another same diameter to grind the surface of the window hole. Two other cutting blades, wherein the two cutting blades of the second cutting blade row and the two other cutting blades of the second cutting blade row are mutually positioned in the axial direction of the window hole. A window hole forming cutting tool which is shifted and displaced from each other in a radial direction of the window hole, and further displaced from each other in a circumferential direction of the window hole. 5. The axial distance between the first cutting blade row and the second cutting blade row is longer than the axial length of the window hole. Cutting tool for forming window holes. 6. The apparatus according to claim 1, further comprising: a third arm attached to the rotating shaft; and a third cutting blade row attached to the third arm. The three cutting blade rows are arranged on substantially the same circumference and substantially the same diameter, are connected to the cylindrical surface of the window hole, and grind a slope positioned behind the cylindrical surface, and the third cutting is performed. A cutting tool for forming a window hole, wherein the blade row is disposed axially intermediate between the first cutting blade row and the second cutting blade row. 7. The cutting tool according to claim 6, wherein an axial distance between the first cutting blade row and the third cutting blade row is longer than an axial length of the window hole. 8. A rotating shaft, a first arm attached to the rotating shaft, a second arm attached to the rotating shaft, a third arm attached to the rotating shaft, and a second arm attached to the first arm. A first cutting blade row, a second cutting blade row attached to the second arm, and a third cutting blade row attached to the third arm, wherein the first cutting blade row is substantially on the same circumference. And at least two cutting blades arranged on substantially the same diameter to grind the first cylindrical surface of the window hole, wherein the second cutting blade row is substantially on the same circumference and substantially on the same diameter. And at least two cutting blades arranged to grind the second cylindrical surface of the window hole, wherein the third cutting blade row is arranged on substantially the same circumference and substantially on the same diameter as the window. At least two cutting blades to grind the surface of the hole The first cylindrical surface is located axially forward of the second cylindrical surface, and the distance between the peripheral area of the first cutting blade row and the peripheral area of the third cutting blade row is: A cutting tool for forming a window hole that is larger than the axial length of the window hole. 9. The two cutting blades of the first cutting blade row,
A cutting method for forming a window hole, wherein the positions of the window holes are shifted from each other in the axial direction of the window holes and the positions of the window holes are shifted from each other in the radial direction of the window holes. 10. Grinding the inner peripheral surface of the window hole, grinding the surface of the window hole after grinding the inner peripheral surface, grinding the inner peripheral surface and removing the surface Grinding is performed by rotation of a rotary cutting blade sharing the same rotation axis of the same rotation axis, and grinding the inner peripheral surface is performed by first grinding the inner peripheral surface in advance. Surface grinding; and a second inner peripheral surface grinding that follows the first inner peripheral surface grinding and has a larger radius than the radius of the first inner peripheral surface grinding. The friction of the second inner peripheral surface grinding is provided. The sliding is a window hole forming cutting method guided by friction sliding of the first inner peripheral surface grinding. 11. The grinding of the surface according to claim 10, wherein the grinding of the surface comprises: a first surface grinding for grinding the surface in advance; and a radius of the first surface grinding after the first surface grinding. And a second surface grinding for grinding deeper in the axial direction of the window hole than the first surface grinding, and the friction sliding of the second surface grinding is the friction of the first surface grinding. Window hole forming cutting method guided by sliding. 12. The method according to claim 11, further comprising: grinding another inner circumferential surface of the window hole after grinding the inner circumferential surface, wherein the other inner circumferential surface has a diameter larger than that of the inner circumferential surface. It is arranged on the side of the surface of the window hole larger than the inner peripheral surface, and the grinding of the inner peripheral surface and the grinding of the surface share a rotation axis of the same rotation axis. Window forming method simultaneously performed by the rotation of the rotating cutting blade.