JP4491538B1 - Manufacturing method of machined elbow - Google Patents

Abstract

An object of the present invention is to cut an elbow from a material that has no useless meat inside and whose cross-sectional shape perpendicular to the axis forms a circle at each part in the axial direction and the hole surface is gently bent along the axis. It is an issue to be able to manufacture by.
A step of forming a prepared hole with an undercut portion left on a hole surface in a material, a side cutter II having an outer diameter smaller than a finished hole diameter provided with an arcuate cutting edge, is revolved while rotating at a relatively inclined posture in the direction, the step of finishing the one end side of the inner diameter of the prepared hole 11 _-3 revolution at this time, is performed as the cutter is moved along the bore surface finish target ,
And to form a hole in the elbow through a step of finishing the other end of the inner diameter of the prepared hole 11 _-3 side cutter II by revolving while rotating.
[Selection] Figure 6

Description

  The present invention relates to a method for manufacturing a pipe cut-out elbow (curved pipe).

  For metal elbows for piping, welding is a casting elbow molded with a mold, an elbow with a straight pipe bent, and two halved bent pipes obtained by press-molding a metal plate. There are elbows cut out from elbows and metal materials.

Of these, the machined elbow is taken up in, for example, Patent Document 2 below. Patent Document 1 below describes a bending elbow and a welding elbow.

Japanese Examined Patent Publication No. 7-41315 Japanese Unexamined Patent Publication No. 2000-343136 (Japanese Patent No. 3352052)

  In a conventional shaving elbow, a hole is made in two directions with respect to a material, and the two holes are crossed inside to form an internal flow path. Therefore, for example, for a 90 ° elbow, the internal flow path is close to a right angle, and there is a drawback that the flow path resistance increases when used as part of a pipe. This is pointed out by Patent Document 2 in paragraph 0009.

  This problem of channel resistance can be solved by gently bending the hole, but it is a shaved elbow with a hole of such a shape, especially a bend angle of 90 ° or more and SUS (stainless steel) as the material. ), Titanium-based materials, nickel-base heat-resistant alloys {nickel-based alloys to which alloying elements such as iron, chromium, niobium and molybdenum are added, such as Special Metals Corporation trade name: Inconel} It was thought that elbows using materials could not be made using a 5-axis machine or a multi-axis multi-axis machine using the latest technology.

  If a processing machine with the most advanced functions is used, a bent hole can be processed to some extent. However, in a normal processing method, an undercut portion (uncut portion) that cannot be processed is formed on the hole surface at the inside of the bend, and this deteriorates the flow of fluid, so that a practical product cannot be obtained. Therefore, about this type of elbow, one manufactured by casting, bending, or welding has been adopted.

  However, casting elbows are prone to defects such as cast holes and it is difficult to ensure reliability in terms of quality. Moreover, the rigidity is low compared to other elbows.

  Further, the bending elbow does not have uniform thickness and strength at each part. There is a tendency that the wall thickness and strength of the pipe become smaller outside the bend where the wall thickness and strength are required rather than the inside of the bend, and the cross-sectional shape of the pipe is not highly accurate.

  In addition, the weld elbow is prone to stress corrosion cracking due to changes in the material structure of the weld joint, and large distortion due to welding is inevitable.

  For example, aircraft engine piping and nuclear facility piping are required to meet extremely strict conditions. In such applications, elbows with high quality, high accuracy, and low flow resistance are expected. .

  The machined elbow is an integrally processed product made of molten metal, and does not have a nest, weld defect or distortion, and has excellent reliability in terms of quality. It is also possible to increase dimensional accuracy and shape accuracy by using a high-precision machine. If this machined elbow hole can be machined well, the problem of flow resistance, which is a weak point of machined elbow, will be solved, and a metal elbow meeting the requirements of high quality, high accuracy, and low flow resistance will be obtained. Can be realized.

  Accordingly, the present invention cuts out an elbow having a hole in which there is no useless meat inside and the cross-sectional shape perpendicular to the axis forms a circle in each axial part, and the hole surface is gently bent along the axis. It is an issue to be able to manufacture by.

In order to solve the above problems, in the present invention, a hole provided in the machined elbow,
A process of roughing a material from two directions with a rotary cutting tool and drilling a pilot hole in which an undercut portion is left on the surface of the material which is at least inside the elbow of the finished product,
Relative to the material in the direction in which the end face of the cutter is separated from the opening of the pilot hole inside the elbow bend, the side cutter having a smaller outer diameter than the finished hole diameter having an arcuate cutting edge on the outer periphery Revolves while rotating in a tilted position and cuts into the hole surface of the pilot hole, and the revolution at this time is performed so that the cutter moves along the hole surface of the finish target, and one end side of the pilot hole The process of finishing the inner diameter of
The side cutter is inserted into the pilot hole from the other end side of the pilot hole and revolved along the finishing target hole surface while rotating to finish the inner diameter on the other end side of the pilot hole. I did it. The side cutter is supported by an arbor and is inserted into the prepared hole.

  The revolution of the side cutter when finishing the pilot hole is the shape of the hole cut at each part in the axial direction when the hole to be finished is cut at right angles to the axis of the side cutter. If the cross section is parallel to the plane perpendicular to the cutter axis, the cross section is a perfect circle, and the cross section is an ellipse.) The revolution can be performed by moving the spindle of the processing machine according to a preset control program.

  If there is a lot of machining allowance by the side cutter, the machining is performed in several times.

  If the angle of the relative inclination between the material and the side cutter in the finishing process of the pilot hole is secured, for example, about 25 °, the undercut portion remaining in the pilot hole can be completely removed.

Further, the processing of the pilot hole by this method uses a milling cutter having an outer diameter having an arcuate cutting edge on the outer periphery of the tip and smaller than the inner diameter of the pilot hole,
The milling cutter is cut into two adjacent surfaces of the material while changing the cutting position and the cutting depth, and there is an undercut portion that intersects the elbow bending angle at the same angle as or close to the elbow bending angle. The outside of the elbow bend is a process of making a through hole having a shape substantially along the hole surface of the elbow hole,
The milling cutter is tilted in a direction in which the tip of the cutter approaches the inside of the elbow, and the undercut portion is shaved.This operation is repeated several times while changing the tilt angle of the milling cutter, and the undercut portion is It is preferable to carry out the process of reducing the remaining amount.

  Elbow outer diameter machining by this method can be performed by sequentially performing rough machining with a face mill or the like and finish machining with a ball end mill or the like. The outer diameter processing is preferably performed after drilling, but can also be performed before drilling.

  The present invention is particularly effective when applied to the production of a special elbow having a turning angle of 90 ° or more, which makes machining particularly difficult, but can also be used for the production of an elbow having a turning angle of 90 ° or less. Can do.

  In addition, this invention can be expected to have a particularly great effect when the material of the machined elbow is a metal, particularly difficult-to-cut materials such as SUS as described above. The effectiveness is also demonstrated when used. For example, if it is necessary to produce a small-diameter large-diameter special elbow made of resin, mold cost is high. In such a case, it is economically advantageous to cut out the elbow having the required shape and size from the resin material block.

  In addition, in the present invention, since an integral elbow is cut out from the material, the elbow hole is intentionally decentered in any direction with respect to the outer diameter of the elbow, or an integral connection flange is provided at the end of the pipe. It can also be formed.

  In the manufacturing method of the present invention, until the relative inclination angle between the side cutter and the material reaches the allowable upper limit, the side cutter and the material are relatively inclined according to the bent state of the hole at the position where the elbow hole is bent. It is also possible to finish the inner diameter on one end side by the above method by processing and fixing the relative inclination angle from the position where the relative inclination angle between the side cutter and the material reaches the allowable upper limit.

  The relative inclination of the material of the side cutter and the milling cutter may be performed by either a method of moving the material while fixing the cutter or a method of moving the cutter with respect to the material. For example, the rotation table can be rotated by setting the material on a rotary table having a rotary indexing function so that the center of the hole of the elbow to be machined is placed on a plane parallel to the table surface of the rotary table. For example, the material can be tilted in a necessary direction with respect to the milling cutter or the side cutter.

  The feature of the method of the present invention is that the rough hole formed in the material is finished using a side cutter having an outer diameter smaller than the finished hole diameter provided with an arcuate cutting edge, The side cutter is revolved on the spiral trajectory while rotating in a posture in which the end surface of the cutter is inclined relative to the material in a direction away from the opening of the pilot hole inside the elbow bend. is there.

  The processing of the prepared hole in the material can be performed by a known method. However, in the conventional processing method, an undercut portion that cannot be processed is generated on the inner hole surface of the elbow. The undercut portion is scraped off using a side cutter having an arcuate cutting edge.

  In order that the revolution of the side cutter occurs in a plane substantially perpendicular to the axis of the elbow hole, the side cutter and the material are tilted relative to the bent state of the elbow at the position where the elbow hole is bent. If the inner diameter of the elbow hole can be finished by feeding the cutter, it is relatively easy to drill a perfect hole. However, in this method, for example, when trying to manufacture a 90 ° elbow, the side cutter and the material are at maximum relative to each other. Therefore, it is necessary to incline 45 °, and interference between the two is unavoidable.

  In the present invention, in order to avoid this problem, the relative inclination angle between the side cutter and the material is set to be small (an angle at which interference does not occur even if the pilot hole is machined in half in the axial direction). The angle varies depending on the difference between the inner diameter of the elbow hole and the outer diameter of the arbor holding the side cutter. However, since it is impossible to secure a 45 ° inclination angle in the manufacture of the 90 ° elbow, for example, 25 Set to about °.

  Assuming that the side cutter is tilted by 25 degrees relative to the material, the hole of the elbow finish target is cut at each part in the axial direction along a plane parallel to the end surface perpendicular to the axis of the tilted side cutter. The cut end of the hole becomes an ellipse in most places. The shape and size of the ellipse differ at each part of the cutting point, but if the cutter is moved along the cut shape at each part of the cutting point, the undercut part left in the pilot hole is removed cleanly and the elbow The hole is formed into a perfect circle at each part in the axial direction in the cross section perpendicular to the axis, and the hole surface is gently bent parallel to the axis.

  In order to enable hole finishing by the method of the present invention, a side cutter having an outer diameter smaller than the diameter of the elbow hole is used. Also, the larger the difference between the finished diameter of the elbow hole and the outer diameter of the arbor that supports the side cutter (which is naturally smaller than the side cutter), the greater the allowable angle of relative inclination between the side cutter and the material. However, if the outer diameter of the arbor is too thin, the tool rigidity will decrease and the cutter will become more chattered during machining, which will adversely affect machining stability and machining accuracy. Therefore, the outer diameter of the arbor is set in consideration of this point.

  Further, since the entire region of the elbow hole cannot be finished by machining from one end side of the prepared hole, the prepared hole is also finished by machining from the other end side of the prepared hole.

  As described above, according to the present invention, the finishing process of the pilot hole is performed while revolving the elliptical orbit using the side cutter having the circular arc blade, so that it has a circular shape that has been considered impossible in the past, and gently. A machined elbow having a bent hole can be produced.

  In addition, the elbow hole is eccentric with respect to the outer diameter of the elbow to increase the thickness and strength of the pipe outside the bend, and the elbow having a straight portion at least at one end, It is also possible to manufacture an elbow in which connecting flanges are integrally formed at both ends.

(A): Perspective view showing an example of a machined elbow manufactured by the method of the present invention, (b): A cross-sectional view perpendicular to the axis of the elbow. (A): perspective view showing half of elbow cutting area of material, (b) plan view of half cutting area (A)-(d): The figure which shows the process of the front | former stage of pilot hole processing (A)-(e): The figure which shows the process of the latter stage of pilot hole processing (A): The figure which shows the attitude | position of the raw material and side cutter when finishing one end side of a prepared hole, (b): The perspective view which shows the half of the prepared hole which finished one end side (A-1)-(a-3): The figure which shows the revolution movement of the side cutter in the finishing process of the one end side of a pilot hole, (b-1)-(b-3): The revolution movement of a side cutter ( View from above corresponding to (a-1) to (a-3) (A): perspective view showing an unfinished state of the other end side of the pilot hole, (b) perspective view showing a finished state of the other end side of the pilot hole (A): Perspective view showing another example of a machined elbow manufactured by the method of the present invention, (b): A cross-sectional view perpendicular to the axis of the elbow of the above. The perspective view which shows the further another example of the shaving elbow manufactured with the method of this invention The perspective view which shows the further another example of the shaving elbow manufactured with the method of this invention (A): Perspective view showing an example of a rotary cutting tool used for rough machining of a hole and an outer diameter by the method of the present invention mounted on an arbor, (b): Side view of the above cutting tool (A): Perspective view showing an example of a side cutter used for hole finishing by the method of the present invention, (b): Side view of a state in which the above cutter is mounted on an arbor Side view showing an example of a ball end mill used for finishing the outer diameter by the method of the present invention

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for manufacturing a machined elbow according to the present invention will be described below with reference to the accompanying drawings.

  First, an example of the rotary cutting tool used by the method of this invention is shown in FIGS. The cutting tool shown in FIG. 11 is a commercially available cutting edge-exchangeable milling cutter (front milling cutter) I in which a plurality of arc-shaped cutting edges 2 are provided on the outer periphery of the cutter body 1 at intervals in the circumferential direction. In the elbow material, rough machining of the prepared hole and the outer diameter of the elbow is performed. The roughing is preferably performed by attaching the illustrated milling cutter I having the cutting edge 2 made of a detachable round piece chip to the arbor 3 so that high-efficiency machining can be performed. However, a milling cutter other than a face mill, for example, radius It is also possible to use an end mill or a ball end mill.

  FIG. 12 shows a side cutter II in which a plurality of arc-shaped cutting edges 5 are provided on the outer periphery of the cutter body 4 at intervals in the circumferential direction, and finish processing of the prepared hole provided in the material of the elbow is performed. The side cutter II shown in the figure is an improved version of a commercially available cutter that has a cutting edge 5 made of a detachable round piece chip, so that it can be firmly fixed to the arbor, and is attached to the tip of a custom-made arbor 6. And use it. The side cutter II has an outer diameter smaller than the diameter of the pilot hole to be finished. The outer diameter of the arbor 6 is further smaller than the outer diameter of the side cutter II.

  FIG. 13 shows a commercially available blade edge replaceable ball end mill III. In the illustrated method, the outer diameter of the elbow is finished with this blade edge replaceable ball end mill III or a solid ball end mill instead.

  An example of a machined elbow manufactured by the method of the present invention is shown in FIG. The illustrated elbow 10 is a 90 ° elbow without a flange, and has a hole 11 whose axis is smoothly bent with a predetermined curvature.

  The following description will be given by taking as an example the production of the 90 ° elbow 10 of FIG. 1 using the above cutting tool. 2 of FIG. 2 is an elbow material processed into a square block shape. In order to facilitate understanding of the processing situation, the material 12 is cut in half and the cutter is also simplified.

  Here, the center 12 of the hole of the elbow 10 to be machined is a table surface of the rotary table (this is perpendicular to the axis of the rotation center). The cutter and the material 12 are inclined relative to each other by rotating the rotary table.

A milling cutter I is set on the main spindle (not shown) of the processing machine, and the milling cutter I is rotated while changing the cutting position and the cutting depth with respect to the A surface of the material 12 as shown in FIG. was cut over the feed direction, in the outer bend open the blind hole 11 _-1 as shown in FIG. 3 is small undercut of the hole surface (b).

Next, as shown in FIG.3 (c), the B surface orthogonal to the A surface of the raw material 12 was made to face the front-end | tip of the milling cutter I, and the milling cutter I was pierced in the A surface in this state In the same way as in the case of changing the cutting position and the cutting depth, the B surface is fed in the axial direction and cut, and the hole generated in this process is communicated with the blind hole that has been machined in advance to the inside of the bend in the hole radial direction. obtaining a through hole _{11 -2} undercut portion 13 raised there.

  In this situation, the remaining amount of the undercut portion 13 is too large, and the side cutter II in FIG. 12 cannot completely remove the undercut portion in the finishing process. Therefore, as shown in FIG. 4A, the material 12 is inclined by θ ° with respect to the milling cutter I in the direction in which the tip of the cutter I approaches the inner side of the elbow bending, and the cutting position of the milling cutter I is cut in this state. While changing the position, the sheet is fed in the axial direction to cut off a part of the undercut portion 13.

  This operation is repeated several times while gradually increasing the relative inclination angle between the milling cutter I and the material 12 to sufficiently reduce the remaining amount of the undercut portion 13. The relative inclination angle of the material 12 and the milling cutter I in this processing is set so that the cutting burden on the cutter does not become excessive according to the material of the material. In the evaluation test, θ in FIG. 4A is set to 15 °, θ1 in FIG. 4B is set to 25 °, θ2 in FIG. 4C is set to 35 °, and θ3 in FIG. 4D is set to 45 °. However, the present invention is not limited to this.

The undercut portion 13 may be removed from both ends of the through hole _11-2 .
Answer the purpose only machining from one end of the bore _11-2 through in many cases, this requires less working steps.

Through the above steps, a pilot hole _11-3 as shown in FIG. Therefore, the tool mounted on the spindle of the processing machine is replaced with the side cutter II of FIG. 12, and the side hole II is used to finish the _prepared hole _11-3 .

Its finishing is a side cutter II, as shown in FIG. 5 (a), with respect to the material 12 in the direction of the end face of the side cutter II is away from the opening of the prepared hole 11 _-3 inside bend of the elbow 10 to be cut out relatively angle θ4 inclined Te, thereby cut into the bore surface of the prepared hole 11 _-3 by revolving while rotating the side cutter II in this posture. Then, the revolution of the side cutter II at this time is performed so that the cutter moves along the spiral track along the finishing target hole surface. Here, it is considered that the angle θ4 of the relative inclination between the side cutter II and the material is always kept constant, but this is not an essential requirement.

  (A-1) to (a-3) and (b-1) to (b-3) in FIG. 6 show a state in which the side cutter II revolves counterclockwise while being fed in the axial direction while rotating. Represents. Since the revolution is a revolution while feeding, the side cutter II moves along the spiral trajectory.

  In addition, the position perpendicular to the axis of the elbow 10 before being cut is parallel to the end surface (the end surface of the side cutter inclined at an angle θ4) perpendicular to the axis of the side cutter II with respect to the material 12 (FIG. 5A). At the position along the Y-Y line}, the cut of the elbow hole 11 becomes a perfect circle, and at other positions along the XX line or the Z-Z line in FIG. The cut in the cross section perpendicular to the axis of the hole 11 becomes an ellipse. In addition, the cut edge of the ellipse is different in size and shape at each portion of the hole 11 perpendicular to the axis. The side cutter II causes the revolving movement along the hole surface of the finish target, that is, along the hole cross section of the cut portion in each axial direction.

  In the case of the example processing method, finishing at the position beyond the ZZ line (the other end side of the hole) is performed by moving the cutter along the hole cross section of the cut portion in each axial direction only outside the bending of the hole. The arbor 6 is prevented from interfering with the material. Since the finishing process from one end side of the pilot hole only needs to be able to process half of the hole, it is not necessary to force the cutter to follow the hole cross section of the cut inside the bend.

  If the machining allowance at this time is large, the machining is performed in several times to reduce the machining burden per time. If a method is adopted in which the uncut portion is divided into several portions and is gradually cut and finished to the target inner diameter in the final processing, the cutting load does not become excessive, and the stability and accuracy of processing increase.

By processing with the side cutter with this movement control, most of the undercut portion left in the pilot hole _11-3 is removed, and the inner diameter of one end side of the pilot hole is finished.

The processing from one end of the prepared hole, it is impossible to finish the entire area of the lower hole as shown in FIG. 5 (b) occurs machining regulations hole shape, after which, from the other end of the prepared hole 11 _-3 Also finish the hole by processing. The side cutter II located on the other end of the prepared hole 11 _-3 As shown in FIG. 7 (a), by performing the same operation as described above (to perform the movement control of the same condition is not always necessary) The remaining part of the undercut part 13 is scraped off.

  As described above, the elbow hole 11 is formed into a perfect circle at each axial portion in the cross section perpendicular to the axis, and the hole surface is gently bent parallel to the axis.

  In the illustrated manufacturing method, the outer diameter of the elbow is then roughly processed using the milling cutter I shown in FIG. 11, and then the outer diameter is further processed using the ball end mill III shown in FIG. Thus, the desired shaving elbow is completed.

  The outer diameter processing of the elbow is preferably performed after drilling, since it is easy to improve the holding stability of the material during drilling and can prevent damage to the outer diameter surface, but can also be performed before drilling.

  Further, the relative inclination of the milling cutter I and the side cutter II with respect to the material 12 can be performed by a method of inclining the main axis of the processing machine equipped with the cutter.

Furthermore, the control of the processing machine is a little more complicated, so cut the side cutter II to the prepared hole 11 _-3 to revolve while rotating, substantially perpendicular to the axis of the bore in which the mobile is provided to the finished product of the elbow one end of the inner diameter of the prepared hole 11 _-3 from one end side of the hole while relatively inclined according to the state bent hole side cutter II and material 12 to occur in a plane at a position where the hole 11 of the elbow is bent processed halfway toward the other end, the one end of the prepared hole 11 _-3 from the position relative tilt angle of the side cutter II and material 12 reaches the allowable upper limit to fix the angle of the relative tilt The object of the invention can also be achieved by performing the inner diameter finishing step.

This method of addition, the present invention, since the machining shaving, increasing the thickness and strength of the outwardly tube bending center O ₁ of the hole 11 of the elbow is made eccentric with respect to the outer diameter center O ₂ of the elbow The elbow 10 as shown in FIGS. 8 (a) and 8 (b), the elbow as shown in FIG. 9 having the straight portion 14 at least at one end, or the connecting flange 15 at both ends are integrally processed. It is also possible to manufacture an elbow as shown in FIG.

  A 90 ° elbow having an inner diameter of φ190 mm, a center bending radius of φ200 mm, and a wall thickness of 10 mm was prototyped by the method of the present invention. Since the elbow material is a test to demonstrate the processing method, wood was used.

  Further, the rotary cutting tool is a milling cutter I of FIG. 11 having an outer diameter of φ50 mm, an R radius of an arc cutting edge of 8 mm, and a number of four-blade chip-attached cutting edge replaceable face mills as a side cutter II of FIG. A ball end mill having an outer diameter of φ30 mm was used as the ball end mill III shown in FIG.

As the processing machine, a CNC horizontal center grinder owned by the applicant was used. The CNC horizontal center grinder is equipped with the world's highest level rotary table with a division index accuracy of 1/10000 degrees. The material is set on the rotary table, and the relative inclination of the material and cutter is set on the rotary table. The method was controlled by

  The processing was performed according to the procedure described in FIGS. For the finishing process of the pilot hole by the side cutter, a method was used in which the remaining cutting area was processed in increments of 2 mm and finally finished with 0 remaining. As a result, the uncut part is completely inside the hole, the hole is a perfect circle, the hole surface is parallel to the axis of the elbow, and the thickness of each part of the pipe {each part of the cross section of FIG. 1 (b) An elbow with a uniform thickness t} was obtained.

  By using a processing machine equipped with a rotary table having a high indexing accuracy as described above, the revolution of the side cutter occurs in a plane substantially perpendicular to the axial center of the hole provided in the elbow of the finished product until halfway. The inner diameter of the pilot hole is finished while relatively tilting the side cutter and the material according to the bending state of the elbow hole, and the relative inclination angle between the side cutter and the material reaches the allowable upper limit. High-precision machining can be performed without problems by fixing the angle of inclination and revolving on an elliptical orbit.

I Milling cutter
II Side cutter
III Ball end mill 1, 4 Cutter body 2, 5 Cutting edge 3, 6 Arbor 10 Elbow 11 Hole 11 _-1 Blind hole 11 _-2 Through hole 11 _{-3 Pilot} hole 12 Material 13 Undercut part 14 Straight part 15 Flange A, B Material orthogonal plane t Tube thickness

Claims (6)

The hole (11) provided in the machined elbow (10)
A rough hole in which the undercut portion (13) is left on the hole surface on the inner side of the bending of the elbow of the finished product after roughing the material (12) from two directions with a rotary cutting tool. The step of opening ( _11-3 ),
The side cutter (II) having a smaller outer diameter than the finished hole diameter provided with an arcuate cutting edge (5) on the outer periphery is the opening of the _pilot hole (11 _-3 ) at the end face of the elbow inside the elbow bending. And revolving while rotating in a posture inclined relative to the material (12) relative to the material (12) in a direction away from the material (12), and cutting into the hole surface of the pilot hole ( _11-3 ). When the elbow hole (11) is perpendicular to the plane perpendicular to the axis of the side cutter (II), the cutter trajectory is a perfect circle. A step of finishing the inner diameter on one end side of the pilot hole (11 ₋₃ ) by making the cutter into an ellipse and moving along the hole surface to be finished;
The side cutter (II) is inserted into the pilot hole ( _11-3 ) from the other end side of the pilot hole, and revolved along the finishing target hole surface while rotating to prepare the pilot hole ( _11-3 ). A method for manufacturing a machined elbow that is formed through a step of finishing the inner diameter of the other end of the steel. Wherein the side cutter (II) is revolved while rotating by cut into the pilot hole (11 _-3), the so its place movement in substantially perpendicular planes to the axis of the hole provided in the finished product of the elbow While the side cutter (II) and the material (12) are relatively inclined according to the bending state of the hole at the position where the hole of the elbow is bent, the inner diameter of one end side of the elbow hole is changed from the opening side of the hole to the middle. Processed
Finishing the inner diameter of one end of the _pilot hole ( _11-3 ) by fixing the relative inclination angle from the position where the relative inclination angle of the side cutter (II) and the material (12) has reached the allowable upper limit. The manufacturing method of the shaving elbow of Claim 1 which performs a process. Processing of the _pilot hole ( _11-3 ),
Using a milling cutter (I) having an outer diameter with an arcuate cutting edge (2) on the outer periphery of the tip is smaller than the inner diameter of the pilot hole,
The milling cutter (I) is cut into two adjacent surfaces (A, B) of the material (12) while changing the cutting position and the cutting depth, and the elbow bending angle is the same as or equal to the elbow bending angle. There is an undercut portion (13) that intersects at an approximate angle, and the outside of the elbow bend is formed with a through hole ( _11-2 ) having a shape substantially along the hole surface of the elbow hole (11);
The milling cutter (I) is tilted in a direction in which the tip of the cutter approaches the inside of the elbow, and the undercut portion (13) is shaved. This operation is performed while changing the tilt angle of the milling cutter (I). Reducing the remaining amount of the undercut part (13) by repeating several times,
The manufacturing method of the shaving elbow of Claim 1 or 2 performed through this.   The material (12) is set on a rotary table having a rotary indexing function so that the center of the hole of the elbow to be machined is placed on a plane parallel to the table surface of the rotary table, and the rotary table is rotated. The method for manufacturing a machined elbow according to any one of claims 1 to 3, wherein the material (12) is tilted in a necessary direction with respect to the milling cutter (I) and the side cutter (II).   The method for manufacturing a machined elbow according to any one of claims 1 to 4, wherein the material (12) is a metal difficult-to-cut material.   The method for manufacturing a machined elbow according to any one of claims 1 to 5, wherein the hole (11) of the elbow is decentered in a direction in which the thickness of the elbow increases outside the elbow with respect to the outer diameter of the elbow. .

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