JPH03184721A - Thread milling cutter - Google Patents

Abstract

PURPOSE:To eliminate the need for a prepared hole machining as for a prestage and to machine even a female screw of different diameter dimension with a high efficiency, by providing a blade for boring having an outer peripheral edge at the inner peripheral side by the ridge height of the female thread formed from the tip in the diameter direction of a thread cutting edge and having a bottom edge at the end face at the tip side in the axial direction from the thread cutting edge. CONSTITUTION:Boring is executed on the body 44 to be worked by driving tips 16 and 18 with their rotation around a shaft center l, because of the tips 16 and 18 being provided at the tip of a thread milling cutter 10 and made so as to function as an end mill. The prepared hole 46 in a radius R1 is then subjected to cutting by revolving in a radius R2 with the shaft center O of a female thread 42 as the center. The depth of the prepared hole 46 is gradually deepened by advancing in the axial direction simultaneously with the revolution and also the female thread 42 at a pitch P is subjected to cutting in order on the inner peripheral face of the prepared hole 46 by the tip 14. The prepared hole machining as for a prestage becomes unnecessary therefore and also the female threads 42 in various sizes having different diameter dimensions can be subjected to cutting with a high efficiency by using one thread milling cutter, in case of the ridge shape and pitch being the same.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thread milling cutter for cutting internal threads, and particularly to a thread milling cutter that does not require pilot hole drilling as a pre-process.

BACKGROUND OF THE INVENTION A thread milling cutter is a tool for cutting internal threads. This is equipped with a thread cutting blade on the outer periphery that has a shape corresponding to the thread groove of the female thread to be formed, and is attached to, for example, an NC milling machine or machining center, and is rotated around the axis while cutting the inner periphery of the prepared hole of the workpiece. This method cuts a female thread on the inner circumferential surface of the prepared hole by interlocking the two in the circumferential and axial directions of the prepared hole while adding a depth of cut to the prepared hole. There are thread milling cutters and multi-thread milling cutters that have a plurality of thread cutting blades connected in the axial direction.

When cutting a female thread using such a thread milling cutter, it is normal to prepare a pilot hole with the same size as the inner diameter of the female thread to be formed as a pre-process. There has also been proposed a method in which hole drills are connected together and thread cutting is performed continuously after drilling the pilot hole.

Problems to be Solved by the Invention However, in any of the above cases, thread cutting is performed after preparing the hole, which is not necessarily efficient. Particularly, when drilling a prepared hole using a separate drill/hammer, time is wasted in exchanging tools, etc., and there are problems such as a decrease in the operating rate of the apparatus.

In addition, in a thread milling cutter that connects a pilot hole drill, the diameter of the pilot hole is determined by the drill diameter.
Even if the pitch and thread shape are the same, if the diameter dimensions are different, the depth of cut in the side direction of the tool will increase and the cutting resistance will increase, making it necessary to reduce the feed rate and increase the number of cuts, resulting in machining problems. This has the disadvantage of reducing efficiency.

The present invention was made against the background of the above-mentioned circumstances, and its purpose is to provide a thread milling machine that does not require pilot hole machining as a pre-process and is capable of cutting female threads with different diameters with high efficiency. It is about providing.

Means for Solving the Problems In order to achieve the above object, the present invention provides a thread cutting blade having a shape corresponding to the thread groove of the female thread to be formed on the outer periphery, and cuts the workpiece while being rotationally driven around the axis. In a thread milling cutter that cuts the female thread by being moved relative to the thread cutting blade, the outer periphery is located at a position on the inner circumferential side of the tip of the thread cutting blade in the radial direction by approximately the same dimension as the height of the thread of the female thread to be formed. A hole cutter having a blade and a bottom edge on the end face is characterized in that the cutting edge is provided closer to the tip in the axial direction than the thread cutting edge.

Function: This type of thread milling cutter is driven to rotate around its axis, revolves relative to the workpiece around the axial center of the female thread to be formed, and
By relatively moving one lead of the female thread in the axial direction by rotation, the hole-cutting blade cuts the pilot hole while the thread cutting blade cuts the female thread on the inner circumferential surface of the pilot hole. By performing relative movement in the direction by a desired length dimension, a female thread of a predetermined length in a through hole or a blind hole can be obtained.

Here, the inner diameter dimension of the female thread is, in the case of a -thread thread milling cutter, the above-mentioned hole drilling is defined by the outer peripheral edge of the cutting blade, so the outer peripheral edge has the same dimension as the thread height of the female thread. It is provided at a position on the inner circumferential side from the tip. However, in the case of a multi-thread milling cutter with multiple thread cutting blades arranged in a row in the axial direction, the hole is drilled by the outer peripheral edge of the cutting edge,
Alternatively, when the trough of the thread cutting blade is on the outer side of the outer peripheral edge, the inner diameter of the female thread is determined by the trough of the thread cutting blade, so the outer peripheral blade is moved by a dimension greater than the height of the thread of the female thread at the tip of the thread cutting blade. It is also possible to provide it at a position closer to the inner circumference.

Effects of the Invention As described above, according to the thread milling cutter of the present invention, there is no need to perform pilot hole machining as a pre-process, and since the pilot hole machining and thread cutting are performed simultaneously, there is no need for machining an internal thread. The overall machining efficiency is improved. In addition, even for multi-thread thread milling,
Since only one lead of female thread can be cut in one revolution, the thread cutting time is longer than in the conventional case where multiple threads are machined simultaneously in one revolution, but this requires a separate process. This eliminates the need for time spent drilling pilot holes and changing tools.

In addition, if the thread shape and pitch are the same, the same thread milling cutter can be used to cut female threads of various diameters with high efficiency. Since the directional dimension does not need to be that large, it is also possible to cut the internal thread of the blind hole.

On the other hand, in a multi-thread thread milling cutter, in addition to the above effects, the cutting of the female thread is performed by the most advanced thread cutting blade in the axial direction, so the subsequent thread cutting blades perform a small amount of finishing cutting. Not only does the finished surface roughness improve, but even if the thread cutting blade at the tip wears out, cutting can be performed with the succeeding thread cutting blade, resulting in a longer tool life. In addition, large cutting resistance only acts on the most advanced thread cutting blade, and after cutting one lead worth of female thread with the most advanced thread cutting blade, the +lh bending stress applied to the side of the tool becomes approximately constant. Therefore, compared to conventional multi-thread milling cutters, tool tipping is reduced and the cylindricity of the female thread is improved.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 and FIG. 2 are a front view and a view from the tip side showing an example of the case where the present invention is applied to a single thread milling cutter. This thread milling cutter 1o includes a shank portion 12 that is held by an NC milling machine, etc., and three indexable tips (hereinafter simply referred to as tips) 14.1.
6.18 is composed of a removably attached blade portion 20. The tip I4 is equipped with a triangular thread cutting blade 22 that corresponds to the thread groove of the female thread to be formed, and the thread cutting blade 22 is attached to the tip mounting seat 26 of a straight groove 24 provided in the axial direction from the tip of the blade portion 20. The blade 22 is attached so as to protrude toward the outer circumference.

The tip attachment seat 26 is provided on the rear wall surface of the pair of wall surfaces of the straight groove 24 in the rotational cutting direction A of the thread milling cutter 10, so that the straight groove 24 functions as a chip discharge groove.

The tip 16 also includes a linear outer circumferential cutter 28 and a bottom cutter 30 that intersect at a substantially right angle, and a tip mounting seat 34 of a twisted groove 32 provided at a position spaced apart from the straight groove 24 in the circumferential direction. The outer circumferential blade 28 protrudes toward the outer circumference, and the bottom blade 30 protrudes toward the tip in the axial direction and is attached in a position substantially orthogonal to the axis l. The chip mounting seat 34 is provided on the rear wall surface of the pair of wall surfaces of the helical groove 32 in the rotational cutting direction A, so that the helical groove 32 functions as a chip discharge groove. The twisting direction of the helical groove 32 is opposite to the rotary cutting direction A in FIG. 2, and chips are discharged toward the shank portion 12 as the thread milling cutter 10 rotates.

The outer peripheral blade 28 is located on the inner peripheral side of the radial tip of the thread cutting blade 22 by the height dimension of the thread of the female thread to be formed, and has a positive rake angle in the axial direction. Chips are well discharged. The length in the axial direction of the outer peripheral blade 28 is sufficiently longer than one pitch P of the female thread to be formed, and is longer than one pitch P and shorter than two pitches 2P from the end of the thread cutting blade 22 to the axial tip side. It is possible to cut a range of m.

In addition, the length of the bottom blade 30 is shorter than the radius of the outer peripheral blade 28, so that it cuts the part excluding the vicinity of the center of the axis l, and the indentation angle is positive and deeper toward the outer periphery. It is designed to be cut.

The tip 18 has a straight bottom edge 36, and the bottom edge 36 is attached to the tip mounting seat 40 of the straight groove 38 provided between the straight groove 24 and the helical groove 32 in the circumferential direction. It protrudes to the side and is attached in an orientation substantially perpendicular to the axis l. The chip mounting seat 40 is provided on the rear wall surface of the pair of wall surfaces of the straight groove 38 in the rotational cutting direction A, so that the straight groove 38 functions as a chip discharge groove. The bottom blade 36 is located at a portion intersecting the axis l, and cuts a portion on the inner peripheral side of the cutting position by the bottom blade 30 around the axis l, and the bevel angle is When the cutting speed is positive, the cutting becomes deeper toward the outer periphery. In an unembodied example, this tip 18 and the tip 16 constitute a cutting edge portion.

Such a thread milling cutter 10 is used by being attached to an NC milling machine or the like.
As shown in FIGS. 4 and 4, a case in which a female thread 42 with an inner diameter of 2R is cut into a workpiece 44 will be specifically explained.
While rotating in the rotational direction A around the axis l in a substantially vertical posture, the radius dimension of the peripheral blade 28 is set to the dimension R1.
In the case of a right-handed screw, it revolves in the direction of arrow B with the radius R2 subtracted from the axis center 0 of the female screw 42, and in one rotation of the revolution, it moves by the I pitch P of the female screw 42 toward the tip in the axial direction of arrow C. It's good to move forward. In other words, the tips 16 and 18 are provided at the tip of the thread milling cutter 10, and it functions as an end mill, so that it is rotated about the axis RE to drill holes in the workpiece 44. By rotating the female thread 42 around the axial center O with a radius R2, a pilot hole 46 with a radius R1 is cut. Further, by being moved forward in the axial direction in synchronization with the revolution, the depth of the pilot hole 46 is gradually deepened, and the female thread 42 with pitch P is sequentially cut into the inner peripheral surface of the pilot hole 46 by the tip 14. It is processed.

As described above, according to the thread milling cutter 10 of this embodiment, there is no need to prepare a pilot hole as a pre-process, and the cutting of the pilot hole 46 and the threading of the female thread 42 are performed simultaneously, so that the tool The overall processing efficiency for processing the female thread 42 is improved, such as by eliminating wasted time for replacement and the like.

Further, if the thread shape and pitch are the same, female threads 42 of various sizes with different diameters can be cut with high efficiency using one thread milling cutter 10. However, in order to prevent interference due to the lead angle of the female thread 42 and to prevent uncut portions at the center of the shaft, the tool diameter of the thread milling cutter 10 should be approximately 75% to 55% of the inner diameter dimension 21z of the female thread 42. It is desirable to keep it within the range. Note that even if the tool diameter is less than 50%, the female thread 4
If a prepared hole is prepared in advance at the center of the shaft of No. 2 so that no uncut portion is left, the tool can be used satisfactorily.

Furthermore, in this embodiment, the outer circumferential edge 28 of the tip 16 is provided so as to protrude toward the distal end side in the axial direction by a dimension m larger than one pitch P of the female thread 42 than the thread cutting edge 22 of the tip 14. The thread cutting blade 22 does not interfere with a portion other than the inner circumferential surface of the lower flame 46, specifically, a relatively high portion E of the bottom surface of the lower flame 46 as shown by diagonal lines in FIG. This has the advantage that unnecessary thread cutting is prevented and the life of the tip 14 is improved.

Furthermore, since the above-mentioned dimension m is shorter than 2 pitches 2P, as is clear from FIG.
The relatively small depth dimension of 6 prevents unselfish cutting. Note that it is of course possible to cut the female thread 42 of the through hole through the workpiece 44, and in that case, there is no problem even if the above-mentioned dimension m is 2P or more.

In addition, in this embodiment, the depths 14, 16, and 18 are removably attached to each other, making it easy to manufacture the tool, and the cutting edges 22, 28, and 30
．． When the tips 14, 16, 18 are damaged, etc., it is only necessary to replace the tips 14, 16, 18, which is economically advantageous compared to a regular thread milling cutter.

Next, another embodiment of the present invention will be described.

5 and 6 are a front view and a view from the tip side showing an example in which the present invention is applied to a single-thread milling cutter. Twisted grooves 54 for chip discharge, respectively
Six thread cutting blades 56 are provided at the same position in the axial direction with the two thread cutting blades 56 in between. The thread cutting blades 56 each have a triangular shape corresponding to the thread groove of the female thread 42.

Further, on the axially distal side of the thread cutting blade 56, there are provided a radial tip of the thread cutting blade 56, and a female thread 42.
3 having an outer circumferential cutter 58 on the inner circumferential side by the height dimension of the screw thread.
The type of hole drilling is the blade part 60a.

Two each of 60b and 60c are provided. Peripheral blade 58
has a length dimension capable of cutting a range m that is longer than 1 pitch P and shorter than 2 pitches 2P from the end of the thread cutting blade 56 to the tip side in the axial direction, and each hole is formed by the cutting edge 60a. , 60b.

Bottom blades 62a, 62b, and 62c are formed on the end face of the outer peripheral blade 58, respectively, from the axial tip end of the peripheral blade 58 toward the axis l. These bottom blades 62a, 62b, 62c
All have positive cutout angles and are oriented to cut deeper toward the outer periphery, but their lengths are different, and the outer periphery is cut by all the bottom blades 62a, 62b, and 62c. , the portion near the axis l is cut only by the bottom blade 62c.

In this thread milling cutter 50 as well, in addition to obtaining the same effects as in the embodiment described above, such as drilling the prepared hole 46 and threading the female thread 42 at the same time and in a delayed manner, the thread cutting blade 56 and Since six peripheral blades 58 are provided, the depth of cut of each cutting blade is smaller than that of the thread milling cutter 10, which reduces cutting resistance and improves machining efficiency.

FIG. 7 and FIG. 8 are a front view and a view from the tip side showing an example of the case where the present invention is applied to a multi-thread milling cutter. This thread cutting fly +t 70
The blade part 72 is provided with four threaded cutting parts 76 in the circumferential direction, each sandwiching a straight groove 74 for discharging chips. A triangular thread cutting blade 78 corresponding to the thread groove of the female thread 42 is formed in the axial direction, and a plurality of the thread cutting blades 78 are provided in series in the axial direction.

Further, on the tip side in the axial direction of the thread cutting portion 76,
Each has an outer circumferential edge 80 on the inner circumferential side of the radial tip of the thread cutting blade 78 by the height dimension of the thread of the female thread 42, in this embodiment, at approximately the same position as the trough of the thread cutting edge 78, and on the tip side. A cutting edge portion 84 is provided in the hole having a bottom edge 82 formed on the end face thereof. The cutout angle of the bottom blade 82 is positive (
(approximately 0 to 10 degrees), and the outer circumference side is designed to cut deeper, and the inner circumference side of the bottom blade 82,
That is, a circular recess 86 is provided in the vicinity of the axis l. In addition, the angle between the straight line connecting the axis l and the outer peripheral edge of the bottom blade 82 and the bottom blade 82 is normally set within a range of about ±15° in consideration of chip evacuation. .

Such a thread milling cutter 70 is used in the same manner as the negative thread milling cutter 10, as shown in FIGS. 9 and 10. In other words, a multi-thread milling cutter is usually inserted into a pre-formed pilot hole and has multiple thread cutting blades simultaneously cut into the inner circumferential surface of the pilot hole, cutting a large number of threads at the same time in one revolution. The thread milling cutter 70 of this embodiment uses the blade part 84 to drill the hole at the tip of the workpiece.
・While drilling is performed in 1, the female thread 42 is thread-cutted by the thread-cutting blade 78 of the thread-cutting part 7G.
It is necessary to perform cutting while advancing one lead at a time during one revolution.

In addition, (a), (b) in FIG. 9 and FIG. 1O above,
(C).

(d) and (e) show the same process; FIG. 9 is a longitudinal sectional view, and FIG. 1O is a plan view. 9 and 10 show the case of machining a female thread 42 in a through hole passed through a workpiece 44, and (e) shows movement to the axial center O of the female thread 42 in order to extract the thread milling cutter 70. It is in a state where it is

Moreover, in such a multi-thread thread milling cutter 70,
By setting the amount of advance in one revolution to an integral multiple of the pitch of the thread cutting blade 78, it is also possible to process a multi-thread thread.

The thread milling cutter 70 of this embodiment also eliminates the need for preparing holes and exchanging tools, which were performed in separate processes, and allows for the production of female threads 42 of various sizes with different diameters and female threads of blind holes. Can be cut.

In addition, since the female thread 42 is cut by the most advanced thread cutting blade 78 in the axial direction, the subsequent thread cutting blade 78 performs a small amount of finishing cutting. Thread milling cutter 10.
Compared to 50 and conventional multi-thread milling cutters, the finished surface roughness of the female thread 42 is improved, and even if the thread cutting blade 78 at the tip wears out, the subsequent thread cutting blade 78 performs the cutting process, resulting in a longer tool life. becomes longer.

In addition, a large cutting resistance only acts on the most advanced thread cutting blade 78, and after cutting one lead of the female thread 42 with the most advanced thread cutting blade 78, the bending stress applied to the side surface of the tool is reduced. Since it is approximately constant, tool tilting is reduced compared to conventional multi-thread milling cutters, and the female thread 42
This has the advantage of improving cylindricity.

Although the embodiments of the present invention have been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, the thread milling cutter 10 of the above embodiment, 50.7
-0 are both integrally equipped with a shank portion, but the present invention can also be applied to thread milling cutters that are not equipped with a shank portion.

In addition, in the above embodiment, the thread milling cutter 10°70 was
Although a case has been described in which a right-handed screw is machined by rotating in the same direction B as the rotational cutting direction A, a left-handed screw can also be machined by rotating in the opposite direction.

Further, in the embodiment described above, the thread milling cutter 10.70 is moved relative to the workpiece 44, but while the thread cutter 10.70 is rotated around the axis, the workpiece 44 is moved relative to the workpiece 44. It is also possible to move it.

Further, it goes without saying that a multi-thread milling cutter can also be produced using an indexable tip in the same way as the thread milling cutter IO.

In addition, the thread milling cutter 1050.7 of each of the above-mentioned embodiments
0 involves machining a female thread into a pre-formed pilot hole or machining a male thread on the outer circumferential surface of a cylindrical workpiece, etc.
It is also possible to use it in the same manner as before.

Further, since the thread milling cutter 70 has a recess 86 at the center of its tip, it is also possible to form an oil hole or the like for supplying cutting fluid or the like in the axis thereof.

Further, in the above embodiment, the case of machining parallel threads was explained, but in the -mount thread milling cutter 10.50, by successively decreasing the diameter of revolution,
In the multi-thread milling cutter 70, each thread cutting portion 7
It is also possible to fabricate a tapered thread for pipes by forming the thread 6 into a tapered shape with a smaller diameter toward the distal end.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example in which the present invention is applied to a single thread milling cutter. FIG. 2 is a night view of the thread milling cutter shown in FIG. 1 from the tip side. FIG. 3 is a diagram illustrating an example of machining a female thread using the thread milling cutter shown in FIG. 1. FIG. 4 is a plan view of FIG. 3. FIG. 5 is a front view showing a thread milling cutter according to another embodiment of the present invention. FIG. 6 is a night view of the thread milling cutter of FIG. 5 from the tip side. FIG. 7 is a front view showing an example in which the present invention is applied to a multi-thread milling cutter. FIG. 8 is a night view of the thread milling cutter of FIG. 7 from the tip side. FIG. 9 is a diagram illustrating the machining process when machining a female thread using the thread milling cutter of FIG. 7. FIG. 10 is a plan view of each processing step in FIG. 9. 10.50. 'yo: Thread milling cutter 16.18 varnished row-away tip (hole drilling is on the cutting edge) 22.56.78: Thread cutting blade 28.58, 80: Peripheral blade 30.36.62a, 62b, 62c, 82: Bottom blade 2: Female thread 44: Workpiece 60a. 60b. Oc. 4 For two-hole drilling, cutting edge: Axial center

Claims (1)

[Claims] A thread cutting blade having a shape corresponding to the thread groove of the female thread to be formed is provided on the outer periphery, and the female thread is cut by being rotated around an axis and moved relative to the workpiece. In the thread milling cutter to be processed, a hole having an outer circumferential cutter at a position on the inner peripheral side by approximately the same dimension as the height of the thread of the female thread to be formed than the tip in the radial direction of the thread cutting blade, and a bottom cutter on the end surface. A thread milling cutter characterized in that a cutting blade portion is provided on the tip end side in the axial direction of the thread cutting blade.