JP2012086286A - Thread milling cutter for machining high hardness material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a newly shaped thread milling tool capable of reducing a cutting resistance and provided with edge strength enduring machining of a high hardness material in order to stabilize internal threading of the high hardness material of HRC50 or more.SOLUTION: The thread milling cutter includes thread cutting edges on an outer circumference and helically fed to a workpiece in a relative manner as well as automatically driven. The thread cutting edge has a plurality of threads. Of the thread cutting edges, a leading edge is formed lower than a finishing edge in height of threads, and a thread angle of the leading edge is smaller than that of the finishing edge. The shape of the leading edge is designed to be included within that of the finishing edge when the former is graphically overlapped on the latter with reference to a thread bottom. The thread milling cutter is provided with a bottom edge at a bottom thereof, the bottom edge being a cutting edge for forming a pilot hole in the workpiece.

Description

  The present invention relates to a thread milling machine, and in particular, when a work material having a work material hardness of HRC 50 or higher (preferably HRC 60 or higher) is processed, a separate tool is used as a pre-process for thread cutting. The present invention relates to a thread milling cutter for high-hardness materials that does not require pilot hole machining.

  In recent years, the hardness of materials has been increasing for the purpose of extending the life of dies and parts. For example, as a typical steel used for the mold and parts, a high-hardness material of HRC50 or higher such as high-speed tool steel or cold tool steel such as SKD11 is often used. Accordingly, there is an increasing need for cutting tools for cutting such hard materials. Conventionally, when manufacturing molds and parts for female threads, it has been the mainstream to process the internal threads before quenching these workpieces. Along with this, there is an increasing need for female thread processing from the state of becoming a high hardness material after quenching of the work material.

  As a tool for forming a female thread, there is a conventional thread milling machine. Thread milling cutters have a cutting edge without a lead with a cross-sectional shape corresponding to the thread groove of the female thread to be formed on the outer periphery, and are attached to an NC machining center etc. to form a female thread by helical feeding. It is a tool to do. However, most of these conventional threading mills are directed to work materials with low hardness, which are different from the present invention in use.

  In view of this, several proposals have been made as a thread milling machine that performs machining without preparing a pilot hole for the purpose of performing female thread machining on a high-hardness material, which is the subject of the present invention.

  In Patent Document 1, a thread cutting blade is provided at the side of the tip of the tool body, a recess is formed at the bottom, and a bottom blade is provided. Further, at the bottom of the recess, the inner peripheral portion is more than 90 ° from the bottom blade. A threading mill that continuously performs pilot hole formation and thread formation is described as a shape in which an outer peripheral blade that is continuous at a large angle and is provided at the outer peripheral portion with an angle that matches the thread cutting blade is provided. Yes.

  In Patent Literature 2, an end mill-shaped bottom blade for forming the bottom portion of the screw pilot hole and an outer peripheral blade forming the inner peripheral surface of the screw pilot hole are provided at the tip end in the tool axis direction, and the thread cutting blade in the outer peripheral blade is provided. Describes an end mill type tap having a rough blade, a medium rough blade, and a finishing blade, which continuously perform pilot hole formation and thread formation.

  Patent Document 3 describes a thread milling cutter for a high-hardness material that continuously performs pilot hole formation and thread formation by improving the cutting edge strength by setting the rake angle of a thread cutting milling blade to a negative value. .

JP-A-9-225743 JP 2004-322285 A Japanese Patent Laid-Open No. 11-156539

However, the conventional threading mill as described above has the following problems.
As apparent from the object and effect of the invention, the threading mill described in Patent Document 1 mainly aims to reduce cutting resistance and improve chip discharge, and is particularly intended for cutting high-hardness materials. It was n’t. Since this thread cutting miller has a shape in which the bottom blade and the outer peripheral blade are continuous at an angle of 90 ° or more, the bottom blade to which a load is applied can have a certain edge strength, but the present invention is intended as a work material. When a high hardness material of HRC50 or higher is cut, the strength is insufficient, and as a result, the cutting edge wear proceeds and the cutting resistance increases, so that the threading miller is bent and uncut material is generated. For this reason, there is a problem that offset (adjustment of cutting amount) is frequently required as the number of processed holes increases.

  The thread milling cutter described in Patent Document 2 is an end mill type tap, and an end mill-shaped bottom blade is provided to form a screw pilot hole. Due to this bottom blade shape, there are some important points in threading a high-hardness material. Problems arise. In other words, when the end mill-shaped bottom blade is ball-shaped, the peripheral speed of the ball tip is the slowest, and this is the process that places the most load on the ball tip that is not sharp. It is easy to produce. Moreover, since cutting resistance is also large, there exists a problem that a thread cutting milling bends and screw accuracy is bad. When the end mill-shaped bottom blade is a square shape or a radius shape, the angle of the outer peripheral portion of the bottom blade becomes an acute angle, so that the strength of the blade tip is reduced, and the chipping at the outer peripheral corner portion of the bottom blade is likely to occur during drilling of the prepared hole.

  Further, in the thread cutting mill described in Patent Document 3, in order to perform high-hardness material processing, the rake angle of the thread cutting milling blade is made negative to improve the cutting edge strength, but pilot hole formation and thread formation are performed. In thread milling performed continuously and simultaneously, the cutting resistance increases and the tool bends only by making the rake angle negative. Therefore, there is a problem that offset (adjustment of cutting amount) is frequently required as the number of processed holes increases.

  The present invention has been made in view of the above problems, and in order to perform stable internal thread machining of a high-hardness material, a new shape of thread cutting with a cutting edge strength that can reduce cutting resistance and withstand high-hardness material processing. The purpose is to provide milling.

  The thread milling cutter of the present invention optimizes the shape of the connecting part between the bottom blade and the leading blade, which is the most loaded, for the purpose of threading a high hardness material of HRC50 or higher, and can maintain the accuracy of the female thread for a long period of time. It optimizes the mutual shape of the leading blade and the finishing blade.

  That is, the threading mill of the present invention is a threading mill that includes a threading blade on the outer periphery, is driven to rotate and is helically fed relative to the workpiece, and the threading blade has a plurality of threads. Among the thread cutting blades, at least one screw thread on the tip side of the milling cutter is a leading blade that performs rough cutting of a screw shape on a workpiece, and the other is a finishing blade, and the leading blade is more threaded than the finishing blade. The height of the thread of the leading edge is smaller than the angle of the thread of the finishing edge, and the shape of the leading edge is graphically superimposed on the finishing edge with respect to the valley bottom. The leading edge is included in the finishing edge, and the bottom of the threaded milling mill is provided with a bottom edge that is a cutting edge for forming a pilot hole in the workpiece. You High hardness material processing thread milling cutter.

  Furthermore, the threading mill of the present invention is a threading mill that includes a threading blade on the outer periphery, is driven to rotate and is helically fed relative to the workpiece, and the threading blade has a plurality of threads. Among the thread cutting blades, at least one screw thread on the tip side of the milling cutter is a leading blade that performs rough cutting of a screw shape on a workpiece, and the other is a finishing blade, and the leading blade is more threaded than the finishing blade. The angle of the thread of the leading edge is smaller than the angle of the thread of the finishing edge, and the angle of the leading edge of the leading edge is that of the leading edge of the finishing edge. 2 ° to 5 ° smaller than the angle, and the shape of the leading blade is such that the leading blade is included in the finishing blade when it is graphically superimposed on the finishing blade based on the valley bottom. The screw A threaded milling cutter for machining a high-hardness material, characterized in that a bottom blade, which is a cutting blade for forming a pilot hole in a workpiece, is provided at the bottom of the cutting miller.

  More preferably, the thread cutting mill of the present invention has a thread cutting blade on the outer periphery, is a screw cutting mill that is driven to rotate and is helically fed relative to the workpiece, and the thread cutting blade has a plurality of screw threads. Among the thread cutting blades, at least one thread on the tip side of the milling cutter is a leading blade that performs rough cutting of a screw shape on the workpiece, and the other is a finishing blade, and the leading blade is threaded from the finishing blade. The angle of the thread of the leading edge is smaller than the angle of the thread of the finishing edge, and the angle of the leading edge of the leading edge is the leading edge of the finishing edge. 2 ° to 5 ° smaller than the angle of the blade, and the angle formed by the valley bottom and the trailing edge of each of the leading blade and the finishing blade is the same, and the shape of the leading blade is the finish based on the valley bottom. On the blade A bottom blade that is a cutting edge for forming a pilot hole in a workpiece is provided at the bottom of the threaded milling cutter so that the preceding blade is included in the finishing blade when they are overlapped graphically. A threaded milling cutter for machining a high hardness material.

  According to the present invention, a thread cutting blade is provided on the outer peripheral portion of the tip end portion of the tool body, a bottom blade is provided on the bottom portion of the tip end portion, and the angle of the thread of the preceding blade in the thread cutting blade is set to the angle of the thread of the finishing blade. By making it smaller than this, the angle formed by the leading side cutting edge and the bottom edge of the leading edge can be made more obtuse. As a result, the strength of the cutting edge is improved, and stable threading can be performed even when there is no pilot hole machining by another tool as a previous process in threading cutting of a hard material having HRC50 or higher. Further, in particular, the total cutting edge length is shortened by making the angle of the leading edge of the leading edge 2 ° to 5 ° smaller than the angle of the leading edge of the finishing blade. As a result, cutting resistance is reduced, There is an effect that processing with high screw accuracy can be performed.

  In particular, the leading blade is formed with a thread height lower than that of the finishing blade, and the angle of the thread of the leading blade is smaller than the angle of the thread of the finishing blade, and the leading side of the leading blade The angle of the cutting edge is 2 ° to 5 ° smaller than the angle of the leading edge of the finishing blade, and the angle formed between the bottom edge of each of the leading edge and the finishing edge and the trailing edge is the same, and the leading edge If the blade is shaped so as to be included in the finishing blade, the wear of the finishing blade can be greatly reduced.

  Since the thread cutting mill of the present invention can improve the edge strength at the corner of the intersection between the bottom edge and the leading edge of the preceding edge, the edge wear is suppressed. Further, rough cutting of the thread groove is performed by the leading edge, so that the wear of the edge of the finishing edge is suppressed and cutting resistance is reduced as compared with the conventional threading milling cutter.

  According to the thread cutting mill of the present invention, it is possible to suppress the bending and uncut material of the thread cutting tool, which is a particular problem in the conventional thread cutting mill that performs processing by helical feed, so that there is no pilot hole machining by another tool. Thus, there is an effect that offset (adjustment of cutting amount) is not necessary even when the number of processed holes increases.

It is a front view which shows the outline of the whole thread cutting mill which is an example of this invention example. It is a left view of FIG. It is the figure which expanded the thread cutting blade of the example of this invention shown in FIG. It is explanatory drawing of the processing form performed using the thread cutting mill of the example of this invention. It is a figure which shows the difference in the magnitude | size of a preceding blade and a finishing blade when a preceding blade and a finishing blade are piled up on the basis of the valley bottom. It is a figure which shows the shape which made the angle of the follower side cutting edge of a preceding blade smaller than the angle of the follower side cutting edge of a finishing blade as other embodiment of this invention. In still another embodiment of the present invention, the angle of the trailing edge of the finishing blade and the angle of the trailing edge of the leading edge are the same, but the trailing edge of the leading edge is the trailing edge of the finishing edge. It is a figure which shows the shape provided inside rather than.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a front view showing an outline of an entire thread cutting mill as an example of the present invention. FIG. 2 is a left side view of FIG. FIG. 3 is an enlarged view of the thread cutting blade of the present invention shown in FIG. FIG. 4 is an explanatory view of a machining state performed using the thread cutting mill of the present invention. FIG. 5 is a diagram showing a difference in size between the leading blade and the finishing blade when the leading blade and the finishing blade are overlapped with respect to the valley bottom. FIG. 6 is a view showing a shape in which the angle of the trailing edge of the leading edge is made smaller than the angle of the trailing edge of the finishing edge as another embodiment of the present invention. FIG. 7 shows another embodiment of the present invention, in which the angle of the trailing edge of the finishing blade is the same as the angle of the trailing edge of the leading edge, but the trailing edge of the leading edge is the trailing edge of the finishing edge. It is a figure which shows the shape provided inside the side cutting edge.

  Reference numeral 1 in FIG. 1 indicates a thread milling cutter. The thread milling cutter 1 has a gripping portion 2, a neck portion 3, and a tip portion 13. The neck diameter of the neck portion 3 is smaller than the root diameter of the thread cutting blade 4 at the tip portion 13. It is formed to become. The number of blades of the thread cutting mill 1 is appropriately selected according to the diameter of the thread cutting mill. For example, when the diameter of the thread cutting mill is 12 mm or less, the number of blades is preferably 4 blades, and when the diameter of the thread cutting mill is larger than 12 mm, the number of blades is preferably 6 blades. 1 and 2 show examples of four blades.

  The gripping portion 2 in the thread cutting mill 1 is held by a main shaft of an NC machine tool such as a machining center or a milling machine capable of helical feeding, and the shape thereof may be formed so as to match the holder.

  A screw cutting blade 4 is provided on the outer peripheral portion of the tip 13 of the thread cutting mill 1, and the screw cutting blade 4 has a shape divided by a chip discharging portion 8.

  The thread cutting blade 4 has a plurality of threads, and at least one thread on the tip side of the thread cutting blade 4 is a leading blade that performs rough cutting of the workpiece on the workpiece, and the other threads are finished blades. Is formed. In the thread cutting mill 1 shown in FIG. 1, one thread on the tip side is the leading blade 5, and the remaining two threads are finished blades 6 and 7 having the same shape as the thread of the female thread formed on the workpiece. It is. Furthermore, it can be seen from FIGS. 1 and 3 that the thread height of the leading blade 5 is formed lower than the thread height of the finishing blades 6 and 7. The height of the thread in the present invention refers to the height of the top of the peak when measured from the bottom of the leading edge or the finishing edge when the thread milling cutter is arranged so that the tool axis O is horizontal. Yes. In the present invention, all the threads having a thread height lower than the height of the thread of the finishing blade are all leading blades.

  In the thread milling cutter of the present invention, the leading edge 5 and the finishing blade 6 on the tip side adjacent to the leading blade 5 perform main cutting, but a predetermined thread groove shape cannot be obtained due to cutting edge wear of the finishing blade 6 on the tip side. In order to prevent this, it is desirable to provide two or more finishing blades. The thread cutting mill shown in FIGS. 1 and 3 shows a case where there is one leading blade and two finishing blades.

  In FIG. 3, θ1 is the thread angle of the finishing blade, and θ2 is the thread angle of the leading blade. In the present invention, the thread angle θ2 of the leading blade is made smaller than the thread angle θ1 of the finishing blade, and as shown in FIG. 5, the shape of the leading blade 5 is based on the root 12 of the thread. When the finish blade 6 is graphically superimposed, the thread of the leading blade 5 is smaller than the thread of the finishing blade 6, that is, the leading blade 5 is formed in a shape included in the finishing blade 6. Furthermore, in the present invention, the angle θ5 of the leading side leading edge of the leading edge, which is the angle formed by the leading side leading edge 5a of the leading edge with respect to a plane perpendicular to the tool axis of the threading milling cutter 1, is set to the tool axis of the threading milling cutter 1. And the angle θ6 of the leading edge of the finishing blade, which is the angle formed by the leading edge 6a of the finishing blade with respect to the plane perpendicular to the angle.

  As shown in FIG. 3, a concave bottom blade 9 is formed at the bottom of the tip of the thread milling cutter 1 of the present invention, and an angle θ3 formed by the bottom blade and a plane perpendicular to the tool axis of the thread milling cutter. Is formed larger than the lead angle of the screw. Further, the angle θ4 formed by the leading edge and the bottom edge of the leading edge is continuously formed with an obtuse angle.

  Next, as one of the structural requirements of the present invention, the cutting action of the threading mill of the present invention configured as described above is as to why the thread angle θ2 of the leading blade is smaller than the thread angle θ1 of the finishing blade. A description will be given with reference to FIG. As shown in FIG. 4, a workpiece P that is a workpiece is fixed, and a gripping portion of a thread cutting mill 1 is mounted on a machining spindle. When helical feeding is performed in the tool axis direction while rotating the thread milling cutter 1, first, the intersection angle portion A between the bottom blade at the tip of the thread milling cutter 1 and the leading cutting edge of the preceding blade is the workpiece P. Next, the pilot hole 10 is made in the workpiece P by cutting the bottom edge 9 and the leading edge 5a of the leading edge.

  Since the intersection angle A between the bottom edge of the tip of the thread milling cutter 1 and the leading edge of the leading edge first hits the workpiece P at the initial stage of cutting, the intersection angle A is at the end of thread cutting. Until the load is continuously applied. In thread cutting of a hard material, a greater load is applied, so that the edge strength near the intersection angle A is important, but the thread angle θ2 of the leading edge is made smaller than the thread angle θ1 of the finished edge. Thereby, the angle θ5 of the leading side cutting edge of the preceding blade can be made smaller than the angle θ6 of the leading side cutting edge of the finishing blade. This makes it possible to make the angle θ4 formed by the leading edge and the bottom edge of the leading edge that determines the edge strength near the intersection angle portion A more obtuse, and as a result, the edge strength is improved. In addition, stable thread cutting can be performed even in thread cutting of high hardness materials.

  In the present invention, it is desirable that the angle θ5 of the leading edge of the leading edge is 2 ° to 5 ° smaller than the angle θ6 of the leading edge of the finishing edge. Thereby, the total cutting edge length combining the lengths of the thread cutting edge 4 and the bottom edge 9 is shortened. As a result, cutting resistance is reduced, and processing with high screw accuracy is performed. If the angle θ5 of the leading edge of the leading edge is made to be smaller than the angle θ6 of the leading edge of the finishing edge by more than 5 °, the processing load of the finishing edge may increase and cutting resistance may increase. is there.

  Furthermore, as another shape of the leading edge in the present invention, as shown in FIG. 6, the leading edge is an angle formed by the trailing edge 5b of the leading edge with respect to a plane perpendicular to the tool axis O of the thread milling cutter 1. The angle θ7 of the trailing edge of the trailing edge is smaller than the angle θ8 of the trailing edge of the finishing edge, which is the angle formed by the trailing edge 6b of the finishing edge with respect to a plane perpendicular to the tool axis O of the thread milling cutter 1. The shape may be sufficient. Further, as shown in FIG. 7, the following angle θ8 of the trailing edge of the finishing blade and the angle θ7 of the trailing edge of the leading edge are the same as shown in FIG. 7, but the trailing edge 5b of the leading edge is finished. The shape provided inside the trailing edge cutting edge 6b of the blade may be used.

  However, in any of the other shapes described above, if the hardness of the work material is further increased, the load when cutting with the finishing blade 6 may be increased. The shape in which the side cutting edge 5b and the trailing edge cutting edge 6b of the finishing edge coincide, that is, as shown in FIGS. 4 and 5, the angle formed by each valley bottom 12 and the trailing edge is the same, that is, the trailing edge of the leading edge. The angle θ7 of the side cutting edge is equal to the angle θ8 of the trailing edge of the finishing edge, and the valley bottom lengths 14 and 15 that are the lengths of the valley bottom when measured in the direction along the tool axis O of the thread cutting mill 1 are An equal shape is desirable.

  In the cutting using the thread cutting mill 1 of the present invention, the thread cutting is performed by the leading blade 5 of the thread cutting blade 4 on the inner peripheral surface of the prepared hole 10 vacated by the bottom blade 9 and the leading cutting edge 5a of the leading blade. Further, when the helical feed of the thread cutting mill 1 proceeds, the thread groove cut by the leading blade 5 is cut by the finishing blades 6 and 7, and a complete thread 11 is formed. In this way, rough cutting of the thread groove to be formed by the leading blade 5 reduces the load on the finishing blades 6 and 7, thereby suppressing wear and cutting with high screw accuracy.

  In the thread cutting mill of the present invention, the edge wear is suppressed by improving the strength of the intersection angle portion A between the bottom edge and the leading edge of the leading edge, and the cutting edge of the finished edge is roughened by rough cutting of the thread groove by the leading edge. Wear is suppressed. As a result of these actions, the cutting force of the tool of the present invention is reduced compared to the conventional threading milling machine, and the bending of the threading tool and the remaining uncut parts, which are peculiar problems in the threading milling machine that performs processing by helical feed, are suppressed. Even when the number of processed holes increases, no offset (adjustment of the cut amount) is required.

  Hereinafter, the present invention will be described in detail by the following examples, but the present invention is not limited thereto.

  In each of the examples in the following table, the present invention, the conventional example and the comparative example are shown as sections, and the sample numbers are described in consecutive serial numbers for each group of the present invention example, the conventional example and the comparative example.

Example 1
In Example 1, the relationship between the thread angle θ2 of the leading blade and the thread angle θ1 of the finishing blade was confirmed.

  In Invention Example 1 and Conventional Examples 1 to 3, the base material of the thread cutting mill was a cemented carbide with a Co content of 8 weight percent and a WC average particle size of 0.8 μm. The number of blades of the milling cutter is 4 blades, the thread cutting blade including the finishing blade and the leading blade is the left blade, the finishing blade diameter is 3.1 mm, the thread cutting blade rake angle is −15 °, and the neck diameter is 2 .2 mm. The pitch of 0.7 mm, the gripping part diameter is 6.0 mm, the total length is 50 mm, the helix angle of the screw cutting blade is 0 °, and the (TiAl) N system is made of Si. A hard film containing selenium was applied to the surface of the thread cutting blade.

  Example 1 of the present invention has one leading edge and two finishing edges, the leading edge has a thread angle of 59 °, the finishing edge has a thread angle of 60 °, and is perpendicular to the bottom edge and the threading milling tool axis. The angle formed by the flat surface is 15 °, and the angle formed by the leading side cutting edge and the bottom edge of the leading edge is 136 °. The thread height of the leading blade was 0.2 mm lower than that of the finishing blade. The leading edge angle of the leading edge is 29 °, the leading edge angle of the finishing edge is 30 °, and the leading edge angle of the leading edge is 1 ° smaller than the leading edge angle of the finishing edge. The angle of the trailing edge of the leading edge was the same as the angle of the trailing edge of the finishing edge, and the valley bottom length 15 was the same as the valley bottom length 14. Further, the shape of the leading blade was a shape that was included in the finishing blade, and a bottom blade that was a cutting blade for forming a pilot hole in the workpiece was provided at the bottom.

  Conventional Example 1 is the threading tool of the invention described in Patent Document 1, and the shape of the threading blade and the bottom blade is the same as that of the invention described in Patent Document 1. One leading blade and two finishing blades are provided as thread cutting blades. The thread angle of the leading blade is 62 ° and the thread angle of the finishing blade is 60 °. The thread angle of the leading blade is higher than the thread angle of the finishing blade. The shape was increased. Furthermore, the angle formed by the bottom blade and the plane perpendicular to the tool axis of the thread milling cutter was 15 °, and the angle formed by the leading edge of the leading blade and the bottom blade was 133 °. The thread height of the leading blade was 0.2 mm lower than that of the finishing blade. The leading edge angle of the leading edge is 32 °, the leading edge angle of the finishing edge is 30 °, and the leading edge angle of the leading edge is 2 ° larger than the leading edge angle of the finishing edge. did.

  Conventional Example 2 is an end mill type tap described in Patent Document 2, and a bottom blade having a shape described in FIG. 7B of Patent Document 2 is provided at the tip of the end mill type tap. Two leading blades and one finishing blade are provided at the rear end portion of the bottom blade portion, the thread angle of the two leading blades is 60 °, and the thread angle of the finishing blade is 60 °. The angle was made equal to the thread angle of the leading blade. Furthermore, the angle formed by the bottom blade and the plane perpendicular to the tool axis of the thread milling cutter was 3 °. The height of the thread of the first blade counted from the end of the end mill tap is 0.2 mm lower than the height of the thread of the finished blade, and the second is counted from the tip of the end mill tap. The thread height of the leading edge was 0.1 mm lower than the thread height of the finishing edge. The angle of the leading edge of the leading edge was 30 °, the angle of the leading edge of the finishing edge was 30 °, and the angle of the leading edge of the leading edge was made equal to the angle of the leading edge of the finishing edge.

  Conventional example 3 is the thread cutting mill of the invention described in Patent Document 3, provided with three finishing blades, and the heights of the threads of the three finishing blades were all the same. Further, the thread angles of the three finishing blades were all 60 °, and the angles of the leading edge of the finishing blade were all 30 °. The angle formed between the leading cutting edge of the finishing blade and the bottom blade counted from the tip of the thread milling cutter is 135 °, and the angle between the bottom blade and the plane perpendicular to the tool axis of the thread milling cutter. The angle was 15 °.

  As the work materials subjected to the cutting test using the milling tool of the present invention and the conventional example, blocks each having a width of 250 mm, a depth of 150 mm, and a height of 100 mm were used. As the material of the work material, two materials, SKD11, which is an alloy tool steel having a hardness of HRC58, and SKH51, which is a high speed tool steel having a hardness of HRC62, were used. The cutting conditions were a cutting speed of 45 m / min, a cutting amount per blade of 0.015 mm / tooth, a rotation speed of 4620 min-1, a feed speed of 277 mm / min, an air blow, and M4 with a depth of 7 mm. Without adjusting the depth of cut of the female screw, processing was performed up to 30 holes, which is a standard that can be industrially satisfied as the life of female screw machining on a material hardened with tool steel.

  As an evaluation method, the wear width on the flank face of the bottom blade of the threaded milling machine after cutting was measured with a tool microscope. In addition, as an evaluation of the screw accuracy, the number of holes of the female screw through which the pass-side screw plug gauge passes through the thread using the pass-side screw plug gauge was evaluated. And, when processing 30 holes that can satisfy the life with two kinds of high-hardness work materials, no chipping or breakage occurs, and the wear width on the flank face of the bottom blade is 100 μm or less, In addition, the number of holes in the internal thread through which the pass side thread plug gauge passes was counted, and those having 25 or more holes were evaluated as good. The results are shown in Table 1.

  As a result, the present invention example 1 in which the thread angle of the leading edge is smaller than the thread angle of the finishing edge causes breakage or breakage when 30 holes are machined with two kinds of work materials. Since the wear width on the flank face of the bottom blade is 100 μm or less and the number of holes of the female thread through which the pass-side threaded plug gauge passes is 30, very good results can be obtained.

  In the conventional example 1 in which the thread angle of the leading blade is larger than the thread angle of the finishing blade, the wear width on the flank face of the bottom blade is 153 μm when the SKD 11 is cut, and the number of the female screw holes through which the through-side screw plug gauge passes Was 12 holes. Further, when SKH51 was cut, the wear width on the flank face of the bottom blade was 181 μm, and the number of female screw holes through which the pass-side screw plug gauge passed was 6.

  In the conventional example 2 in which the thread angle of the leading blade is equal to the thread angle of the finishing blade, the wear width on the flank face of the bottom blade could not be measured because the SKD 11 was broken at the fifth hole. The number of holes of the female thread through which the passage-side thread plug gauge passes was 3 holes. Similarly, when the SKH 51 was cut, it was broken at the second hole, so the wear width of the bottom blade could not be measured. The number of holes in the internal thread through which the passing side thread plug gauge passes was one hole.

  In Conventional Example 3 without the leading blade, the wear width on the flank face of the bottom blade was 122 μm when cutting SKD11, and the number of holes in the female thread through which the pass-side screw plug gauge passed was 6. In addition, when SKH51 was cut, the wear width on the flank face of the bottom blade was 157 μm, and the number of holes in the female thread through which the pass-side screw plug gauge passed was 5.

  From these facts, in the milling cutter according to the present invention, the thread angle of the leading edge is smaller than the thread angle of the finishing edge. Therefore, when machining the work material having a work material hardness of HRC50 or more, before the thread cutting, It was confirmed that a good internal thread can be stably formed with a single thread milling cutter without preparing a pilot hole with another tool as a process.

(Example 2)
In the second embodiment, the angle formed by the leading edge of the leading edge with respect to the plane perpendicular to the tool axis of the threading milling cutter 1 and the leading edge of the finishing edge with respect to the plane perpendicular to the tool axis of the threading milling cutter 1 are described. It is an Example for confirming the influence which the difference with the formed angle has on performance.

  In Examples 1 to 7 of the present invention, the base material of the thread cutting mill was a cemented carbide having a Co content of 8 weight percent and a WC average particle size of 0.8 μm. The number of blades of the milling cutter is 4 blades, the thread cutting blade including the finishing blade and the leading blade is the left blade, the finishing blade diameter is 3.1 mm, the thread cutting blade rake angle is −15 °, and the neck diameter is 2 .2 mm, the pitch of each thread provided on the thread cutting blade is 0.7 mm, the gripping part diameter is 6.0 mm, the overall length is 50 mm, and the twist angle of the thread cutting blade is 0 °. The angle of the side cutting edge was the same as the angle of the trailing edge of the finishing edge, and the valley bottom length 15 was the same as the valley bottom length 14. Furthermore, a hard coating containing Si in (TiAl) N system was applied to the surface of the thread cutting blade. In addition, Example 1 of the present invention in Example 2 has the same shape as Example 1 of the present invention in Example 1.

  In Invention Example 2, the angle of the leading edge of the leading edge was made 2 ° smaller than the angle of the leading edge of the finishing edge.

  In Invention Example 3, the angle of the leading edge of the leading edge was made 3 ° smaller than the angle of the leading edge of the finishing edge.

  In Invention Example 4, the angle of the leading edge of the leading edge was made 4 ° smaller than the angle of the leading edge of the finishing edge.

  In Invention Example 5, the angle of the leading edge of the leading edge was made 5 ° smaller than the angle of the leading edge of the finishing edge.

  In Invention Example 6, the angle of the leading edge of the leading edge was made 6 ° smaller than the angle of the leading edge of the finishing edge.

  In Example 7 of the present invention, the angle of the leading edge of the leading edge was made 7 ° smaller than the angle of the leading edge of the finishing edge.

  As a work material in the cutting test, a block having a width of 250 mm, a depth of 150 mm, and a height of 100 mm was used. The materials used were SKD11 which is an alloy tool steel having a hardness of HRC58 and SKH51 which is a high speed tool steel having a hardness of HRC62. The cutting conditions were a cutting speed of 45 m / min, a cutting amount per blade of 0.015 mm / tooth, a rotation speed of 4620 min-1, a feed speed of 277 mm / min, an air blow, and M4 with a depth of 7 mm. 60 holes were machined while adjusting the depth of the female thread. In Example 1, 30 holes, which is an industrially satisfactory standard for the life of female screw machining on tool steel hardened material, was processed. In Example 2, whether or not further long-life processing is possible. In order to confirm this, 60 holes were processed.

  As an evaluation method, the wear width on the flank face of the bottom blade of the threaded milling machine after cutting was measured with a tool microscope. Further, as an evaluation of screw accuracy, the number of times offset (adjustment of cutting amount) necessary until the machining of 60 holes was completed was evaluated. When 60 holes are machined with the SKD11 work material, the wear width on the flank face of the bottom blade is 120 μm or less, and the number of offsets required to complete the machining of the 60 holes is 5 or less. In addition, when 60 holes are machined with the SKH51 work material, the wear width on the flank face of the bottom blade is 150 μm or less, and the number of offsets required to complete the machining of 60 holes is 6 or less. Was good. The results are shown in Table 2.

  As a result, in the inventive examples 1 to 7, when 60 holes are machined with the work material of SKD11, the wear width on the flank face of the bottom blade is 120 μm or less, which is necessary until the machining of 60 holes is completed. The number of offsets is 5 times or less, and when 60 holes are machined with the work material of SKH51, the wear width on the flank of the bottom blade is 150 μm or less, and the machining of 60 holes is completed. Since the required number of offsets was 6 or less, good results were shown.

  Further, the angle of the leading edge of the leading edge with respect to the plane perpendicular to the tool axis of the thread milling cutter is set to be 2 than the angle of the leading edge of the finishing edge with respect to the plane perpendicular to the tool axis of the thread cutter. In Invention Examples 2 to 5, which are reduced by 5 ° to 5 °, the wear width on the flank face of the bottom blade is 108 μm or less when the SKD 11 is cut, and the number of offsets required to complete the machining of the 60 holes is 3 or less. there were. In addition, when SKH51 was cut, the wear width on the flank face of the bottom blade was 138 μm or less, and the number of offsets required to complete the processing of the 60 holes was 5 or less. Therefore, it can be said that Inventive Examples 2 to 5 have obtained better results than Inventive Examples 1 and Inventive Examples 6 to 7.

  Thus, the present invention determines the angle of the leading edge of the leading edge with respect to the plane perpendicular to the tool axis of the thread milling cutter and the leading edge of the finishing edge with respect to the plane perpendicular to the tool axis of the thread milling cutter. It has been found that by making the angle 2 ° to 5 ° smaller than the angle formed by this, the cutting resistance can be reduced more, and the number of offsets can be reduced and machining with high screw accuracy can be performed.

(Example 3)
Example 3 is the difference between the angle of the leading edge of the leading edge and the angle formed by the leading edge of the finishing blade, the angle of the trailing edge of the leading edge and the angle of the trailing edge of the finishing edge. It is an Example for confirming the influence which a difference and the difference of each valley bottom length have on the frequency | count of adjustment of a cutting amount. Inventive Examples 1 and 2 and Conventional Examples 1 to 3 in Example 3 have the same shapes as Inventive Examples 1 and 2 and Inventive Examples 1 to 3 in Examples 1 and 2.

  In Invention Example 1, the angle of the leading edge of the leading edge is made 1 ° smaller than the angle of the leading edge of the finishing edge, and the angle of the trailing edge of the leading edge is set to the trailing edge of the finishing edge. The angle was the same as the blade angle. The valley bottom length 15 was the same as the valley bottom length 14.

  In Invention Example 2, the angle of the leading edge of the leading edge is made 2 ° smaller than the angle of the leading edge of the finishing edge, and the angle of the trailing edge of the leading edge is equal to the trailing edge of the finishing edge. The angle was the same as the blade angle. The valley bottom length 15 was the same as the valley bottom length 14.

  In Example 8 of the present invention, as shown in FIG. 6, the angle of the leading edge of the leading edge is made 2 ° smaller than the angle of the leading edge of the finishing edge, and the angle of the trailing edge of the leading edge is set. The angle of the bottom edge 15 was made 3 ° smaller than the angle of the trailing edge of the finishing blade, and the valley bottom length 15 was the same as the valley bottom length 14.

  In Example 9 of the present invention, as shown in FIG. 7, the angle of the leading edge of the leading edge is made 2 ° smaller than the angle of the leading edge of the finishing edge, and the angle of the trailing edge of the leading edge is set. The angle of the trailing edge of the finishing blade is the same as that of the finishing edge, and the valley bottom length 15 is 0.02 mm longer than the valley bottom length 14, that is, the trailing edge of the leading edge is 0 than the trailing edge of the finishing edge. .02 mm inside.

  In Conventional Example 1, the angle of the leading edge of the leading edge is 1 ° larger than the angle of the leading edge of the finishing edge, and the angle of the trailing edge of the leading edge is the trailing edge of the finishing edge. The angle was the same. The valley bottom length 15 was the same as the valley bottom length 14.

  In Conventional Example 2, the angle of the leading edge of the finishing blade is the same as the angle of the leading edge of the preceding blade, and the angle of the trailing edge of the leading edge is equal to the angle of the trailing edge of the finishing blade. Identical. The valley bottom length 15 was the same as the valley bottom length 14.

  Conventional example 3 is a thread milling cutter having no leading edge, and the valley bottom length 15 is the same as the valley bottom length 14.

  In each of the cutting tests using the milling cutter of Example 3, a block having a width of 250 mm, a depth of 150 mm, and a height of 100 mm was used as a work material. The materials used were SKD11 which is an alloy tool steel having a hardness of HRC58 and SKH51 which is a high speed tool steel having a hardness of HRC62. The cutting conditions were a cutting speed of 45 m / min, a cutting amount per blade of 0.015 mm / tooth, a rotation speed of 4620 min-1, a feed speed of 277 mm / min, an air blow, and M4 with a depth of 7 mm. 60 holes were machined while offsetting the female screw (adjusting the depth of cut).

  As an evaluation of screw accuracy, the number of times of offset (adjustment of cutting depth) was evaluated. Then, when 60 holes were machined with two kinds of work materials, those having an offset count of 6 or less were evaluated as threaded milling cutters with good screw accuracy. The results are shown in Table 3.

  As a result, Examples 1, 2, 8, and 9 of the present invention have good results because the number of offsets is reduced to 6 or less when 60 holes are machined with two kinds of work materials. It is possible. In particular, as shown in FIG. 5, the angle formed by each valley bottom and the trailing edge is the same, that is, the angle θ7 of the trailing edge of the leading edge is equal to the angle θ8 of the trailing edge of the finishing edge, and the valley bottom length 14 In the present invention example 2, the load of the finishing blade was smaller, and therefore the number of offsets was the smallest and the result was good.

  In Conventional Example 1, the number of offsets when machining 60 holes with two types of work materials was 8 or more. Conventional example 2 was broken at the fifth hole when cutting SKD11, and was broken at the third hole even when cutting SKH51. Therefore, it was impossible to measure the number of offsets. In Conventional Example 3, the number of offsets was 13 or more when machining 60 holes with two kinds of work materials.

  From these facts, in the milling cutter according to the present invention, the angle of the leading edge of the leading edge with respect to a plane in which the angle of the thread of the leading edge is smaller than the angle of the thread of the finishing edge and is perpendicular to the tool axis of the threading miller. Is smaller than the angle formed by the leading edge of the finishing blade with respect to a plane perpendicular to the tool axis of the thread milling cutter, the thread milling machine is used when machining a workpiece having a hardness of HRC50 or higher. As a result, it was found that the bending and the uncut portion of the steel sheet are suppressed, and this effect enables a good internal thread to be formed with a small number of offsets even when the number of processed holes is increased.

  If the thread cutting mill of the present invention is used, the strength of the edge of the intersection between the bottom edge and the leading edge of the leading edge is improved and the wear of the edge is suppressed. Even in the case of a high hardness material having the above hardness, the cutting resistance is reduced, and the screw processing can be performed for stability without the preparation of the pilot hole.

DESCRIPTION OF SYMBOLS 1 Thread milling cutter 2 Gripping part 3 Neck part 4 Thread cutting blade 5 Leading edge 5a Leading edge cutting edge 5b Leading edge trailing edge 6 Finishing edge 6a Finishing edge leading edge 6b Finishing edge trailing edge 7 Finishing blade 8 Chip discharge groove 9 Bottom blade 10 Pilot hole 11 Full thread 12 Valley bottom 13 Tip 14 Valley bottom length 15 Valley bottom length θ1 Finishing blade thread angle θ2 Leading blade thread angle θ3 Bottom blade and thread milling cutter Angle formed by a plane perpendicular to the tool axis of the tool θ4 Angle formed by the leading edge of the leading edge and the bottom edge θ5 Angle of the leading edge of the leading edge θ6 Leading edge of the finishing edge Angle θ7 Angle of the trailing edge of the leading edge θ8 Angle of the trailing edge of the finishing edge A Intersection angle between the bottom edge and the leading edge of the leading edge P Workpiece O Tool axis

Claims (3)

  A threading mill provided with a threading blade on the outer periphery, driven to rotate and helically fed relative to the workpiece, wherein the threading blade has a plurality of screw threads, and among the threading blades, At least one thread on the tip side is a leading blade that performs rough cutting of a screw shape on a workpiece, the other is a finishing blade, and the leading blade is formed with a lower thread height than the finishing blade, The angle of the thread of the leading edge is smaller than the angle of the thread of the finishing edge, and when the shape of the leading edge is graphically superimposed on the finishing edge with respect to the valley bottom, the leading edge is A thread cutting mill for machining a high-hardness material, characterized in that it has a shape that is included in a finishing blade, and a bottom blade that is a cutting blade for forming a pilot hole in a workpiece is provided at the bottom of the thread cutting mill.   A threading mill provided with a threading blade on the outer periphery, driven to rotate and helically fed relative to the workpiece, wherein the threading blade has a plurality of screw threads, and among the threading blades, At least one thread on the tip side is a leading blade that performs rough cutting of a screw shape on a workpiece, the other is a finishing blade, and the leading blade is formed with a lower thread height than the finishing blade, The angle of the leading edge thread is smaller than the angle of the finishing edge thread, and the leading edge angle of the leading edge is 2 ° to 5 ° smaller than the leading edge angle of the finishing edge. And the shape of the leading edge is such that the leading edge is included in the finishing edge when it is graphically superimposed on the finishing edge with respect to the valley bottom, A pilot hole in A threaded milling cutter for machining high-hardness material, characterized in that a bottom blade that is a cutting blade for forming is provided.   A threading mill provided with a threading blade on the outer periphery, driven to rotate and helically fed relative to the workpiece, wherein the threading blade has a plurality of screw threads, and among the threading blades, At least one thread on the tip side is a leading blade that performs rough cutting of a screw shape on a workpiece, the other is a finishing blade, and the leading blade is formed with a lower thread height than the finishing blade, The angle of the leading edge thread is smaller than the angle of the finishing edge thread, and the leading edge angle of the leading edge is 2 ° to 5 ° smaller than the leading edge angle of the finishing edge. The angle between the bottom edge and the trailing edge of the leading edge and the finishing edge is the same, and the shape of the leading edge is graphically superimposed on the finishing edge with respect to the bottom, The leading blade is the finishing blade A threading milling machine for machining high-hardness material, characterized in that a bottom blade that is a cutting blade for forming a pilot hole in a workpiece is provided at the bottom of the threading milling cutter.

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